Gem tourmaline crystals. Greenlaw Quarry, Mount Apatite, Auburn, Maine. Found 1996-1997.
Friday, October 16, 2009
Maine Mineral Photo of the Day
Gem tourmaline crystals. Greenlaw Quarry, Mount Apatite, Auburn, Maine. Found 1996-1997.
Assawompsett Indian Post of the Day
Quartz arrowhead, Titicut, Raynham, Mass. at Pratts' Bridge. Found by Doug Watts, 2004. Yellow bar is 1 cm.
Thursday, October 15, 2009
Maine Mineral Photo of the Day
Smoky Quartz crystal from an extremely radioactive and deadly section of the Wm. Willes #1 Quarry in Topsham, Maine, July 2000.
This quarry was dug in the late 1800s to extract high grade feldspar from the core of a granite pegmatite. The feldspar was ground up and shipped to pottery factories in New Jersey where it was used to make ceramic glazes.
Recent research shows that Topsham, Maine is the root of an exotic chunk of continental crust that slammed into the rest of North America about 350 million years ago.
Jasper Gouge, Sebasticook River, Winslow, Maine.
This rock doesn't look like much else than a rock.
Turned this way, it looks a little more suspect, but not too much.
But held properly in the hand, it is a perfectly fit hand gouge.
From the bottom and side, a crafted, curved blade surface becomes apparent.
This artifact has a funny story. Last Sunday, my brother Tim and I were looking over a Ceramic Period habitation and possible pottery kiln site on the lower Sebasticook River in Winslow, Maine. I found the rock above on the ground, in an area with numerous worked flint flakes, and because it was jasper with bright red flecks (which is uncommon on the Sebasticook), I pocketed it for our rock garden.
Later that Sunday night, I absentmindedly picked up the rock while we were all playing a board game and noticed how perfectly it fit into my hand, and when held in this position an even, curved cutting surface was apparent at the end of the stone, much like a small hand plane for woodworking. I then did a Homer Simpson, "D'Oh !!!!" and realized I had found a prehistoric hand gouge and didn't even know it.
Now, having examined it more carefully, I am convinced it is a hand gouge and was specifically made for this use. What convinced me is not just the shape and its tailor-made fit for the hand, is that it is made out of jasper.
Among Maine geologists, red jasper is a generic term for an extremely hard, tough and dense rock that appears in highly polished cobbles in the bed of the Kennebec River and Androscoggin Rivers and their headwater tributaries. A key diagnostic for this jasper is the presence of deep maroon to blood red swirls and specks within a larger matrix of black, gray and tan.
Robert Doyle (2008) describes the Kennebec jasper variety as a "cryptocrystalline variety of chert, lacking any kind of internal structure. Color is dependent on the content and chemistry of included iron oxide impurities. Red jasper usually forms in association with iron ores, such as those from the Minnesota Iron Range, and occasionally as exhalative deposits of basalt flows ... No local outcrop source for this lithology has been identified. The boulders in the glacial drift are well rounded, suggesting a lengthy journey from the outcrop source. The jasper boulders at New Sharon (Maine) are dark blood red to rusty-red colored, containing black and gray swirling mottles and fracture fillings of dark quartz. Red jasper is very dense, extremely durable and hard."
Close-up of swirling texture in a large jasper cobble from a marine clay deposit along the Kennebec River in Augusta, Maine.
One reason this type of jasper is an uncommon prehistoric tool material is that it is extremely hard and difficult to work, even for skilled prehistoric blade and tool makers. Because it is only found in polished, highly waterworn cobbles, any piece of jasper that has angular, non-rounded edges strongly suggests somebody was actively working it.
Red jasper cobbles from the Kennebec River, Augusta, Maine. These are about the size of golf balls. Dipping the cobbles in water brings out their intense red coloration, which is why I found all these in the shallow parts of the Kennebec River.
A key diagnostic of our Sebasticook River piece of jasper is that about 80 percent of the piece is broken, with just a few remnants of the original, water worn surface of the cobble still showing. Despite this, the angular, worked faces of the jasper are subtle and could be easily mistaken for a river stone cracked and broken by frost action along zones of weakness or structural bedding.
This illustrates the importance of identifying the lithic materials used by prehistoric tool makers and understanding their geological origin and textural character. Because I know from experience that this type of red jasper is almost never found except in very smooth, water worn cobbles, finding a highly angular chunk of this stone is a strong suggestion that it was worked, even if the form is not complete. In contrast, one can be easily fooled by an apparently "worked" surface on bedded rocks like schist or slate when what you are really seeing is the rock naturally splitting along bedding planes from frost or water action. Most of central Maine is underlain by tightly bedded and folded slate and schist, which creates countless thousands of "artifact-looking" rocks that aren't. Even more confusing is that the dominant bedrock in central Maine is a gray phyllite slate, which in small pieces looks almost identical to the dominant prehistoric flint type, the Mt. Kineo-Traveler Mountain rhyolite.
Wetting the jasper gouge shows the diagnostic blood red specks and tendrils. This stone has much more quartz and is coarser than most red jasper cobbles in the Kennebec River valley, which undoubtedly made it easier to make into a gouge. Arrow points to the carefully worked cutting edge.
The area below the yellow arrows has been struck off from the original jasper cobble. The red arrows show two separate strikes to create the inclined plane of the gouge and a hand-holding surface.
The cutting edge of the gouge, viewed from the bottom. All of the surfaces have been created by striking the original waterworn cobble and shearing it off in the intended direction.
Top of gouge showing two parallel struck grooves. All of the surfaces shown here have been struck from the original cobble. Based on some testing, this surface may in fact be the bottom.
This gouge from the Sebasticook is enigmatic because it uses a locally available material, red jasper, that is extremely difficult to work into a usable tool, and for this reason is a lithic material used rarely by prehistoric Maine people. The rock itself is enigmatic because it is an uncommon, but fairly consistent constituent of the glacial rubble within which flows the Kennebec and Androscoggin Rivers and their headwater tributaries, yet nobody knows its actual bedrock source, which Bob Doyle surmises must have been somewhere in far northern Maine or southern Quebec.
Having walked and waded the headwaters of the Kennebec and Androscoggin Rivers for nearly 20 years, fishing for brook trout, panning for gold, swatting black flies, taking photos, and looking for a place to camp, these odd blood red pieces of jasper have been a constant, but uncommon, fixture of the landscape. Viewed in the crystal clear water of the Swift River in Byron, Maine or Nash Stream north of Rangeley Lake, or the Kennebec River in Vassalboro, these nuggets of red jasper leap out at your eye as you look into the water and demand your attention. I am sure they had the same effect on the people living in central Maine 2,000 years ago, who had a much more practical interest in stone than we do today.
I consider this jasper gouge an anomaly in two senses. One, jasper cobbles are extremely uncommon on the Sebasticook River and two, a prehistoric Maine person decided to go against all odds and make a wood plane out of one of them. This jasper is extremely hard to work because, unlike flint and chert, it does not want to break into flat planes and conchoidal surfaces. It either does not break at all or shatters into squarish pieces only if you beat the hell out it.
References Cited:
Doyle, R.G. 2008. Identification of Lithic Artifacts from Central Maine Coastal Archaeological Sites: A Case Study in Regional Lithic Acquisition Strategies. Flying Passage Press. Gardiner, Maine.
Assawompsett Indian Post of the Day
Chert scraper found along shore of Assawompsett Pond, Middleborough, Mass. by Tim Watts. Yellow line is one cm.
Wednesday, October 14, 2009
Prehistoric Stone Fish Weir, West Branch Sebasticook River, Pittsfield, Maine.
This is one of the best preserved prehistoric stone fishing weirs in New England. It is located on the West Branch of the Sebasticook River in Pittsfield, Maine and was discovered by Tim Watts of North Easton, Massachusetts in October 2002. That same month I had walked this entire stretch of the West Branch Sebasticook, taking pictures, and did not even notice the weir's existence. A week later my brother Tim came up to Maine from Massachusetts on a rainy weekend and we drove past this site on our way to Plymouth Pond. As we drove past this spot, Tim slammed the brakes on his truck, and said "Look, a fish weir !!!" I had no idea what he was yammering about. Then we got out of the truck and walked down the river bank and he pointed it out, which you can see here.
This incident shows how hard it can be to identify prehistoric stone fish weir sites unless you are diligently looking for them and are familiar with their structure. The next morning we drove back up to the site and got these photos. We then found a dense concentration of prehistoric flint shards, fire cracked rock and spearhead preforms falling out of the left bank of the river just below the weir site in a grove of silver maples. This artifact concentration helped us confirm that the weir is an actual prehistoric in-river structure.
This spot on the West Branch Sebasticook is the last shallow riffle area before the river deepens and enters a vast swampy area above its junction with the East Branch Sebasticook along Peltoma Road in Pittsfield. The West Branch Sebasticook drains a number of large natural ponds, particularly Great Moose Pond in Hartland and Big and Little Indian Ponds. These ponds were historic alewife and American eel habitat and produced large numbers of both fish (alewife migrating upstream from the ocean, adult eels migrating downstream to the ocean). This weir site was undoubtedly used to catch both species, alewives in the spring and eels in the fall. It has a classic "W" shape which allowed alewives to congregate in the center of the weir as they migrated upstream in the spring and allowed eels to congregate in the two lower points of the "W" as they moved downstream in the fall.
This weir should be included in the National Register of Historic Places because of its uniqueness and outstanding state of preservation.
Assawompsett Indian Post of the Day
Glass Quartz arrowhead preform, found on the shore of Assawompsett Pond, Middleborough, Massachusetts by Timothy Watts.
Tuesday, October 13, 2009
Why no prehistoric Maine pottery cups?
One of the odd things about prehistoric pottery from Maine is that the potters made one form exclusively: large, open mouthed, round-bottomed vessels with a capacity of two to four quarts.
Why no cups? Why no bowls? Why no mugs? Why no plates or platters? Why no sculpture?
Nobody knows. All we know is that based on shards found, with the exception of some tobacco smoking pipes, prehistoric Maine potters appear to have not made any of the above objects from clay. Apparently, they only made tall, open mouthed vessels. There is no question these various forms could have been easily made with the same techniques and materials used to make the large vessel forms that prehistoric potters did make. And there is no question that cups, bowls, mugs, plates etc. made from fired clay would be useful and long-lasting. But from all of the prehistoric pottery shards ever found in Maine, none seem to be from these common types of ware.
So why no cups or bowls?
One possible reason could be that these large open vessels were only made and used for ceremonial and/or religious events and were not made or intended for everyday use. In keeping with special purpose of these vessels it might have been considered a violation of ceremonial tradition to use fired clay for other objects. Given that smoking pipes are the only other object known to be made from clay by prehistoric Maine potters, it is possible that these pipes themselves were only used on ceremonial occasions and everyday use was frowned upon.
Am I satisfied with this explanation? Not really. Without independent evidence, there is no way to falsify it, and unfortunately we know very little about the ceremonial traditions of prehistoric people in Maine several thousand years ago, when many of these pots were made.
A more mundane explanation would be prehistoric Maine people did not make cups, bowls, plates etc. from fired clay because they didn't feel any compelling reason to make them. Perhaps the various non-clay materials prehistoric people used for these items were deemed functional enough to not warrant replacing them with the same objects made from fired clay.
It has been conjectured that large open, mouthed vessels of fired clay of the type made by prehistoric Maine potters would be useful for cooking food on a direct flame, with small burning sticks placed around the base of the vessel where its rounded bottom was buried in sand, gravel or soil. A 1585 painting by John White, a European visitor to North Carolina, depicts a tall open mouthed vessel with a small fire built around its base. The caption of the painting reads: "The seething of their meate in Potts of earth." (Bourque et al. 2001).
The depiction in this painting is questionable because the clay body and firing method used by prehistoric potters would make a large cooking vessel very susceptible to cracking and shattering when exposed to direct flame. This is true even with modern stoneware. Clay vessels that can withstand the thermal shock of heating by direct flame are called "flameware" and require a unique clay body, usually made by including the rare lithium minerals spodumene and petalite which have an extremely low thermal expansion coefficient (Lawrence & West 1982).
Contemporary experience with earthenware clay bodies of the type used by prehistoric Maine potters suggests that heating by direct flame as depicted in the 1585 watercolor painting would have to have been done with very low, slowly applied heat to prevent cracking, especially because prehistoric Maine pots had thin walls for their size. In addition, because earthenware clay is semi-porous and the vessels were filled with water (to make a stew), there would be a high risk of water trapped in the clay turning into steam upon direct heating, expanding and exploding the ware as it tried to escape. Most prehistoric Maine pots use a large amount of coarse, angular crushed quartz temper in the clay. This temper was most likely added to allow the efficient escape of water in the pore spaces of the unfired pot during the early stages of firing, thereby reducing the chance of cracking and shattering. The same tiny fissures and crevices created by the use of rough quartz temper would allow water to infiltrate into the clay body when the vessel was filled with water for cooking. As the pot was heated by direct flame on its outer surface, the water in these tiny fissures would turn to steam and most likely crack the ware.
Given the substantial risk of cracking by exposure to direct flame, it seems more plausible that prehistoric people heated the contents of these pots by dropping superheated stones into the vessel whereby the stone would release its stored heat into the water. This method would eliminate the risk of cracking of the ware due to heat stress.
Alternatively, the same coarse quartz temper may have prevented the shattering of the cooking pot during direct heating by creating a uniform, evenly spaced series of channels and fissures that allowed water absorbed by the pot to quickly escape and evaporate without turning into steam. The best way to test this would be to make a similar clay body with a similar diameter, type and density of temper, fire it, and test it on a small cooking fire. This has not yet been done.
The inability of earthenware pottery to withstand heating by direct flame without cracking and shattering may be one reason why there are no eyewitness observations by European visitors of Indians making and firing clay pots. Bourque (2001) theorizes that the ability of metal cooking pots and kettles to withstand heating by direct flame may have encouraged Contact Period Indians to abandon their use of fired clay vessels as soon as they obtained metal cooking pots from visiting European traders.
Because the number of shards of prehistoric ceramic pots in Maine is fairly low and their time of use extends across two millennia, it is difficult to estimate how often these pots were made and how widely they were used. Were these pots very commonplace items or were they rather scarce, even during the time they were used? Were they "specialty items" or made routinely and often? Did everyone use them or just some people? Did they have cultural or ceremonial significance or were they just a pot you cooked in? Did every family group have a potter and apprentice? Did some family groups not even bother making them? How long did they last before breaking? And why did nobody, apparently, ever make a cup?
References Cited:
Bourque, B., S. Cox, R.L. Whitehead. 2001. 12,000 Years: American Indians in Maine. Univ. of Nebraska Press.
Lawrence, W.G., R.R. West. 1982. Ceramic Science for the Potter. Chilton Book Company, Radnor, Pennsylvania.
Why no cups? Why no bowls? Why no mugs? Why no plates or platters? Why no sculpture?
Nobody knows. All we know is that based on shards found, with the exception of some tobacco smoking pipes, prehistoric Maine potters appear to have not made any of the above objects from clay. Apparently, they only made tall, open mouthed vessels. There is no question these various forms could have been easily made with the same techniques and materials used to make the large vessel forms that prehistoric potters did make. And there is no question that cups, bowls, mugs, plates etc. made from fired clay would be useful and long-lasting. But from all of the prehistoric pottery shards ever found in Maine, none seem to be from these common types of ware.
So why no cups or bowls?
One possible reason could be that these large open vessels were only made and used for ceremonial and/or religious events and were not made or intended for everyday use. In keeping with special purpose of these vessels it might have been considered a violation of ceremonial tradition to use fired clay for other objects. Given that smoking pipes are the only other object known to be made from clay by prehistoric Maine potters, it is possible that these pipes themselves were only used on ceremonial occasions and everyday use was frowned upon.
Am I satisfied with this explanation? Not really. Without independent evidence, there is no way to falsify it, and unfortunately we know very little about the ceremonial traditions of prehistoric people in Maine several thousand years ago, when many of these pots were made.
A more mundane explanation would be prehistoric Maine people did not make cups, bowls, plates etc. from fired clay because they didn't feel any compelling reason to make them. Perhaps the various non-clay materials prehistoric people used for these items were deemed functional enough to not warrant replacing them with the same objects made from fired clay.
It has been conjectured that large open, mouthed vessels of fired clay of the type made by prehistoric Maine potters would be useful for cooking food on a direct flame, with small burning sticks placed around the base of the vessel where its rounded bottom was buried in sand, gravel or soil. A 1585 painting by John White, a European visitor to North Carolina, depicts a tall open mouthed vessel with a small fire built around its base. The caption of the painting reads: "The seething of their meate in Potts of earth." (Bourque et al. 2001).
The depiction in this painting is questionable because the clay body and firing method used by prehistoric potters would make a large cooking vessel very susceptible to cracking and shattering when exposed to direct flame. This is true even with modern stoneware. Clay vessels that can withstand the thermal shock of heating by direct flame are called "flameware" and require a unique clay body, usually made by including the rare lithium minerals spodumene and petalite which have an extremely low thermal expansion coefficient (Lawrence & West 1982).
Contemporary experience with earthenware clay bodies of the type used by prehistoric Maine potters suggests that heating by direct flame as depicted in the 1585 watercolor painting would have to have been done with very low, slowly applied heat to prevent cracking, especially because prehistoric Maine pots had thin walls for their size. In addition, because earthenware clay is semi-porous and the vessels were filled with water (to make a stew), there would be a high risk of water trapped in the clay turning into steam upon direct heating, expanding and exploding the ware as it tried to escape. Most prehistoric Maine pots use a large amount of coarse, angular crushed quartz temper in the clay. This temper was most likely added to allow the efficient escape of water in the pore spaces of the unfired pot during the early stages of firing, thereby reducing the chance of cracking and shattering. The same tiny fissures and crevices created by the use of rough quartz temper would allow water to infiltrate into the clay body when the vessel was filled with water for cooking. As the pot was heated by direct flame on its outer surface, the water in these tiny fissures would turn to steam and most likely crack the ware.
Given the substantial risk of cracking by exposure to direct flame, it seems more plausible that prehistoric people heated the contents of these pots by dropping superheated stones into the vessel whereby the stone would release its stored heat into the water. This method would eliminate the risk of cracking of the ware due to heat stress.
Alternatively, the same coarse quartz temper may have prevented the shattering of the cooking pot during direct heating by creating a uniform, evenly spaced series of channels and fissures that allowed water absorbed by the pot to quickly escape and evaporate without turning into steam. The best way to test this would be to make a similar clay body with a similar diameter, type and density of temper, fire it, and test it on a small cooking fire. This has not yet been done.
The inability of earthenware pottery to withstand heating by direct flame without cracking and shattering may be one reason why there are no eyewitness observations by European visitors of Indians making and firing clay pots. Bourque (2001) theorizes that the ability of metal cooking pots and kettles to withstand heating by direct flame may have encouraged Contact Period Indians to abandon their use of fired clay vessels as soon as they obtained metal cooking pots from visiting European traders.
Because the number of shards of prehistoric ceramic pots in Maine is fairly low and their time of use extends across two millennia, it is difficult to estimate how often these pots were made and how widely they were used. Were these pots very commonplace items or were they rather scarce, even during the time they were used? Were they "specialty items" or made routinely and often? Did everyone use them or just some people? Did they have cultural or ceremonial significance or were they just a pot you cooked in? Did every family group have a potter and apprentice? Did some family groups not even bother making them? How long did they last before breaking? And why did nobody, apparently, ever make a cup?
References Cited:
Bourque, B., S. Cox, R.L. Whitehead. 2001. 12,000 Years: American Indians in Maine. Univ. of Nebraska Press.
Lawrence, W.G., R.R. West. 1982. Ceramic Science for the Potter. Chilton Book Company, Radnor, Pennsylvania.
Tuesday, October 06, 2009
Evidence of a Prehistoric Pottery Kiln, Sebasticook River, Winslow, Maine
View from prehistoric habitation site, lower Sebasticook River, Winslow, Maine. Oct. 2009.
By Douglas Watts
Augusta, Maine
October, 2009
The art of ceramics was well known and widely used by the prehistoric people of Maine as shown by the large numbers of pottery shards found at prehistoric habitation sites in Maine. Independent dating methods show that the "Ceramic Period" in Maine roughly spanned from 2,800 B.P. to the arrival of European traders and settlers after the 1500s (Doyle 2008).
Yet while many shards of completed ceramic pots and vessels are known from Maine, little is known of where and how these pots were fired. It is presumed that the kilns used to fire these pots were "one time" kilns that were assembled for a single firing and then taken apart to gain access to the fired ware inside them. The materials used to make these kilns is not known, nor their shape and design (Bourque et al. 2001).
Because prehistoric people of Maine were frequent travellers, it is logical to assume they took their ceramic pots and vessels with them as they travelled. This means that the site where a pot shard is found may not be the site where it was made and fired. However, we do know that these pots had to be made and fired somewhere. What evidence or diagnostics can we use to identify a potential firing site?
One diagnostic would be a dense collection of shards from pots that failed to fire properly. Even today, potters frequently have pots explode or crack or shatter during the firing process. Once taken out of the kiln, these failed pots are relegated to a "shard pile" and are discarded. This means that a prehistoric kiln site that was used repeatedly would, over time, generate a good number of broken and failed pots. Unfortunately, most of the pottery shards found in Maine prehistoric sites are already very small and quite broken. This makes it very difficult to distinguish between a pottery shard from a finished, successful pot and a shard from a pot that failed during the firing.
A second diagnostic depends on an assumption that at least some prehistoric potters in Maine used clay as a building material in the kiln itself. The challenge in any kiln design is to ensure all of the ware reaches "bisque temperature," which is generally in excess of 1,100 degrees Fahrenheit depending on the character of the clay body. When clay is heated past this minimum temperature, a number of permanent physical and chemical changes occur to the clay body which make it hard, durable, non-porous and incapable of reverting back to a liquid form (Rhodes 1971). If the fired ware (or some areas of the ware) does not reach bisque temperature, the finished piece will dissolve and crumble once exposed to moisture.
Because all prehistoric Maine pottery was wood-fired, we have to consider what type of wood-fired kiln structure would allow for the efficient, reliable heating of pottery to bisque temperature. The simplest firing method is to dig a pit, place the pots in its bottom, fill the pit with firewood on top of the pots, light the firewood and continue feeding the fire until the pots in the bottom of the pit reach bisque temperature. Once the entire pit has burned out and cooled, the pots are dug out of the ashes.
A problem with this method is that the pots are in direct contact with burning wood and coals for the entire firing. This causes some of the carbon in the pieces of burning wood lying in direct contact with the clay surface to migrate into the clay body. This results in "carbonization" of the clay surface which turns the clay surface completely black and/or covered with prominent black scorch marks. Examination of the finished prehistoric pot shards found in Maine shows very little signs of scorching or carbonization. Instead, most outer surfaces of the shards are very clean, uncarbonized, unscorched and carry the natural yellowish tan of the fully bisqued local clay used to make them. Because carbonization and scorching from direct, physical contact with burning wood and the clay surface is unavoidable and permanent (the carbon is actually incorporated into the bisqued clay body), it seems unlikely that most of the shards of prehistoric pottery found in Maine were made with this type of pit firing.
The clean and uncarbonized surface of most (but not all) prehistoric Maine pottery means that the kiln must have been designed in a way that prevented the burning wood from coming in direct, physical contact with the ware. This strongly suggests that prehistoric potters used some version of a "beehive" kiln. A beehive kiln consists of two structures: a sealed chamber which holds the ware with a chimney hole above the chamber, and a firebox attached to the ware chamber with an opening where wood is fed in and air can enter. The secret of a beehive kiln is that it forces the flames and heat from the burning wood to flow around and past the ware in order to exit through the chimney, but does not allow the burning wood to come in direct contact with the ware itself.
For prehistoric potters in Maine, the challenge of building a beehive kiln is finding a suitable material to build the beehive chamber which holds the ware. Stones will not work because they cannot be stacked in the necessary shape without falling apart and breaking the ware (this flaw is exacerbated by the fact that stones tend to shatter and crack when exposed to the intense, prolonged heat necessary to get the clay to reach bisque temperature). A teepee of woven branches and saplings would not work because the fire would quickly consume them. There is only one easily available material that is sufficiently fireproof and capable of being formed into the necessary beehive shape: clay.
One of the easiest ways to make a beehive kiln from clay is to build a teepee structure from woven saplings and to stack rolled coils of clay around the outside of this skeletal structure until it is completely covered with clay coils except for the chimney hole at the top. The stacked coils are then smoothed by hand to join and seal them to one another. Interestingly, because the coil-built technique is exactly how prehistoric Maine potters built their pots, these potters obviously were extremely familiar and well-versed with it. A second technique is to mix the structural clay with straw to give it additional strength. A third technique is to dip large leaves (like maple leaves) into a thick liquid slurry of clay and apply them on the skeletal surface or coils like wallpaper. This method is widely used today with newspaper dipped in clay slurry to make "paper kilns."
A key diagnostic of a prehistoric pottery kiln made as described above would be the presence of bisqued clay fragments from the kiln structure that were discarded when the kiln was dismantled after firing. In a beehive kiln partly or wholly made with clay, some of the clay, especially the clay surfaces directly exposed to the interior of the firing chamber, will reach bisque temperature along with the ware. This clay will survive for as long as the pots themselves. Unlike the finished ware, these clay fragments will not be kept by the potter. They will remain at the kiln firing site (or moved to a "rubble pile" depending on whether the potter is a neatnik). As such, the presence of rough, irregular fragments of bisqued clay at a prehistoric habitation site practically guarantees that a pottery kiln was made and used within a few yards of the site. Such an occurrence seems to exist along the Sebasticook River in Winslow, Maine.
The Sebasticook River Kiln Site
There is a large Ceramic Period habitation site on a flat bench on the south side of the Sebasticook River in Winslow, Maine approx. 1/4 mile below the outlet of China Lake Stream and 3/4 of a mile above the confluence of the Sebasticook River and the Kennebec River. Small shards of decorated prehistoric pottery are fairly common on the surface of the site, which until 2008 was covered by approx. 2 feet of water by the impoundment of the Fort Halifax Dam, located at the mouth of the Sebasticook. At the northern end of this bench is a small, curious array of large (12 inch dia.) stones that were obviously placed there, as the bench is relatively free of large stones. The stones are not arranged in a fire ring with a central pit of soil, as you would expect from a recently made fire pit. Instead they are tightly clustered in a roughly square pavement with no central pit. Recent construction is unlikely because from 1908 to 2008 (the time from when Fort Halifax Dam was built to when it was removed) the site was underwater. And because the stone pavement lacks a central fire pit, it seems unlikely that 19th century residents of Winslow built it (for what possible reason?).
The "stone pavement" site along the Sebasticook River in Winslow, Maine. From 1908 to 2008 this site was under 2-4 feet of water due to the impounding effect of the Fort Halifax Dam, approx. 3/4 mile downstream. The dam was removed in July 2008. The height of the impoundment can be seen as the base of the tree line on the opposite shore.
Flint scraper in between the stone pavement. Photographed as found. The scraper is the size of a nickel.
Highly weathered ceramic shard with small flint flake to the right. Photographed as found. The shard is thumbnail-sized.
Thumbnail sized flint flake, photographed as found. Flakes of this size are common on the surface in the area directly around the stone pavement pictured above, but require very close examination (hands and knees) to see.
Carbonized pottery rim shard with stamped decoration, photographed as found. Approx. 3/4 inch in width.
The most interesting artifact found at the stone pavement area is a two inch long piece of rough, highly irregular bisqued clay. At first when I found this piece I thought it was just a piece of hardened dirt, which is what it looks like. But when I scraped the "dirt clump" with my finger nail, I could not make even the smallest scratch in it. Upon closer examination, it became apparent the "dirt clump" was a piece of bisqued clay. But unlike the decorated pottery shards found nearby, this clump of bisqued clay was far too irregular and rough to have been part of a finished pot. Interestingly one side has a fairly smooth surface while the opposite side is jagged, pitted and extremely irregular.
Rough, irregular side of bisqued clay "blob" found in between rocks of stone pavement. Piece is about 2 inches wide.
Rounded, flattened side of the same bisqued clay "blob." Note the lack of any angular quartz temper in the surface of the clay. All shards of finished, decorated shards of pottery at the site, even pieces 1/2 inch long, show prominent pieces of angular quartz in their cross-section and at their surface.
About two feet away from this piece I noticed a cluster of small blackened lumps embedded in the dirt. Prying them out of the soil, I noticed they were fairly heavy, with a tan colored "rind" and a jet black core. Like the piece described above, the rind of these lumps was extremely hard and could not be scratched, nor could the jet black interiors. After collecting about eight of these tiny, blackened lumps, I noticed several were much lighter than the others. Close examination showed they were fragments of burned wood that had been reduced to charcoal, with a thin rind of bisqued clay on their exteriors. Later, at home, with a 20 power jewelers loupe, I discovered that one of the jet black bisque lumps had the clear impression of a twig in its center.
Small (1 cm) nodule of intensely carbonized bisqued clay. Arrow points to impression of twig or weed stalk encased in center of nodule.
1 cm nodule of charcoal, still showing original wood grain, surrounded by a rind of bisqued clay.
After making these two little discoveries, I spent the rest of the day on my hands and knees examining the soil surface around the stone pavement. Quite quickly I began to find numerous very small shards of prehistoric pottery near the pavement area. These shards were so small (thumbnail-sized) and so weathered and crumbled that they were nearly impossible to see. But a pattern emerged. The shards were all concentrated in an area around the northern side of the "pavement." As I extended my search in concentric circles farther and farther away from the pavement the number of shards fell off sharply.
That I found a concentration of small ceramic shards near a "hearth-like" stone pavement structure could be explained most simply by the fact that ceramic pots were used for food preparation, serving and cooking and the most likely place they would shatter, crack or be dropped is near the cooking area, so that's where the shards would tend to be concentrated, even today.
Red arrow shows location where carbonized nodules of bisqued clay were found, blue arrow is where "blob" of bisqued clay was found, yellow arrow where flint scraper was found.
Overhead view of stone pavement showing what appears to be its original rectangular structure trending from the bottom right to upper left. This is the only surface congregation of large stones in the entire 4-5 acre bench at this habitation site.
Those Weird Lumps of Bisqued Clay
Of all the 30+ tiny pieces of bisque clay that I found on the surface of this habitation site, nearly all were parts of finished, decorated fired pots that had broken at some time in the past and were in a highly weathered and fragile state. The two anomalies were my first two finds directly around the pavement area: the odd two inch irregular lump of bisqued clay and the small "nodules" of bisqued clay with a tan rind and jet black cores. Examination of their fine particle composition with a 20X loupe shows these lumps are made of bisqued local clay of the same type.
What struck me about these lumps is they were made of bisqued clay but were obviously never part of a finished pot. So how and why did they get bisqued? The most logical reason seems to be that these lumps of clay were remnants of the kiln structure itself and reached bisque temperature because of their proximity to the firing chamber. When the kiln was taken apart after firing to retrieve the ware, these lumps were cast aside and ended up on the ground near the kiln. All of the other clay parts of the kiln structure which did not reach bisque temperature quickly dissolved with the first rainstorm after the firing. All of the wooden parts of the kiln were consumed by the heat of firing or were discarded with the lumps of clay.
It then occurred to me that the small nodules of clay with tan rinds and jet black interiors were highly carbonized clay. This was reinforced by the fact that one of the nodules was actually a small piece of carbonized wood, with grain structure still apparent, coated with a very thin but tough rind of bisqued clay. The final hint occurred when at home I split one of the nodules in half with my fingernail and found its cross-section contained a clear, hollow impression of a branched twig. It then seemed obvious that the source of the carbon for the intense jet black core of these bisqued lumps of clay was small tree branches, and the nodules were created when clay was packed around the branches used to support the kiln structure, the heat of the kiln completely burned the wood and its carbon was absorbed into the clay packed around it.
Further examination of the two inch irregular piece of clay showed several things. First, it had an obvious blackened scorch mark on one end. Second, a view along its cross-section showed a clear "rind" about 1/4 inch wide surrounding a much coarser clay body.
Edge on view of bisqued clay "blob" showing rind along the rim with much looser clay in the center. Rolling clay into a loose coil causes the clay molecules at the edge to align themselves in a parallel direction to the direction of pressure with a discontinuity toward the center of the coil. Note the lack of any pieces of angular quartz temper in the clay.
My wife, Lori Watts, who is a professional potter, suggested the overall shape of the fragment resembled a large, loose coil of clay, and that part of the kiln structure was made by stacking thick, long coils of clay. Because clay minerals have a platy, flat crystalline structure, the act of rolling out a coil of clay causes the clay molecules near the surface to align in a parallel structure, while the clay molecules in the core retain a haphazard, random alignment. As such, she hypothesized, the 1/4 inch thick rind could represent the effect of loosely rolling out a coil of clay by hand. And because a clay coil used to build the wall of a kiln chamber would tend to reach bisque temperature only on the side facing the interior the kiln and would not reach bisque temperature on its outer side, the extremely jagged, creviced and "pebbly" nature of the opposite side of the fragment would represent the exact boundary between where the clay in the coil hit bisque temperature and where it did not. And now, after 1,000 or more years of being exposed to the elements, the only part of the coil fragment left is that which was bisqued. The other wall and the rest of the interior of the coil dissolved in the first rainstorm after the firing in which it was used.
Two Kinds of Clay?
Unlike all of the finished pot shards at the site, the intensely carbonized nodules and the "blob" are notable for their lack of large, angular pieces of quartz in the clay body. Examination of the 25+ shards of finished pottery pieces shows they contain a temper of angular quartz of 0.5-2 mm in diameter. Small pieces of feldspar attached to some of the quartz fragments indicate the source rock was granite, which is common in highly weathered cobbles along the riverbank. However, the highly carbonized nodules and the 2 inch "blob" of clay noticeably lack this quartz temper material. This lack of quartz temper suggests these clay nuggets were made from the same body of raw clay as was used to make the finished pots, but quartz temper was not added to it. This suggests the existence of two separate clay preparations at the site: one clay preparation (with added crushed quartz temper) to make the finished pots and a second clay preparation (without quartz temper) to make and seal the kiln itself.
Putting ourselves in the place of the prehistoric potter for a moment, it is clear that a firing operation would use a separate clay preparation than that used for making the ware itself. Finished pots (called "greenware") must be completely dry before firing or they will shatter, crack and explode. If finished greenware is allowed to dry too quickly (such as by leaving it in the direct sun immediately after its completion), it will develop surface cracks before it is fired. Greenware must be dried gradually and slowly to ensure survival during firing. This controlled drying process normally takes several days, or more if the weather is wet and humid. This means there would be a 2-5 day lag between when the pots were made and when they are ready for firing and therefore when the potter would need to make the kiln to fire them. If the prehistoric potters on the Sebasticook used clay to make their "one-time" kilns, as proposed here, the amount necessary to build the kiln would require a second load of fresh clay to be brought from its source. But, unlike the clay gathered for making the pots, this clay is not used for making finished pots. and would not require the addition of crushed quartz temper to make it usable for building and sealing the kiln. Instead, raw clay (with some sand added as temper) would do the job fine.
The Use of Large Quartz Temper
Rhodes (1971) describes the utility of large temper to assist in the successful bisque firing of pots:
"Drying is greatly facilitated by the presence in the clay of any sort of non-plastic particles. Such particles tend to take up much less water than clay and are, therefore, more easily dried out. Non-plastic particles also furnish open pores or channels through which moisture can escape toward the surface. Clays which contain a large percentage of non-clay particles, especially if these particles are relatively large, are called 'open' bodies."
Weathered pottery shard (2 cm wide) with surface spalled off, showing profusion of angular white quartz added by the potter to the raw clay to increase firing success. Photographed as found.
Putting the Pieces Together
From the evidence above, it seems likely the Sebasticook River site where these ceramic fragments were found was the site of a prehistoric pottery kiln; and the very irregular bisqued pieces of clay found at the site are fragments of the kiln. I reach this conclusion because there is no other explanation for the specific character of these bisqued clay fragments. While prehistoric people undoubtedly carried their finished pots with them when they travelled, they certainly did not carry along with them the scorched and broken parts of the kiln. Those were left at the kiln site. And for the same reason, prehistoric potters did not bisque fire rough, irregular oddly shaped lumps and blobs of clay for the fun of it. The highly carbonized lumps of bisqued clay with twig impressions in their core further suggest that the kiln was made with a combination of clay and saplings, twigs, branches, etc., with the wooden elements used to provide a skeletal structure which supported the clay coils stacked outside them.
A particularly pleasing endpoint to this research came when I walked 1/4 mile up the Sebasticook River from the habitation site to the mouth of China Lake Stream. Very near the mouth of the stream I observed its channel cuts through an enormous lens of very pure blue marine clay. This deposit would have provided prehistoric potters at the site with an endless source of clay for pots and for kiln-building in a location that is only a 5 minute ride by canoe. A single canoe load of clay from this bank to the habitation site (downstream, no less) would be enough to build a kiln.
Fifteen foot thick bed of blue marine clay at mouth of China Lake Stream, 1/4 mile upstream of the prehistoric habitation site. Most of the lower 1/2 mile of China Lake Stream flows through this marine clay deposit.
Photo taken at habitation/firing site showing location of marine clay deposit at mouth of China Lake Stream.
Photo taken from marine clay deposit at mouth of China Lake Stream looking downstream to habitation/kiln site.
How big were these kilns?
One of the engineering issues in building a kiln of clay/branch/straw is that the structural integrity of the kiln is inversely proportional to its size, which tends to favor small kilns. Prehistoric Maine potters seem to have made only one size pot: big. Nearly all prehistoric pots found in Maine had capacities of four quarts or more, finished heights of 15-20 inches and mouth diameters of 10-12 inches. Given that bisque fired clay undergoes significant shrinkage during firing (10 percent or more), some of these pots as made and fired were up to 2 feet tall. Three of these vessels, arranged in a triangle, could be fired in a "beehive" kiln of 36 inches in diameter and 36 inches in height. However, for the following reasons, I believe that due to the consistently large size and thin walls of Maine prehistoric pots, each pot was fired singly.
A 30 x 30 inch beehive kiln with a skeleton of saplings and sticks and a coiled and plastered clay exterior would fire one or two pots of the size typically found in Maine, take a skilled potter and assistant a few hours to build and would reach bisque temperature in 5-8 hours. The "one-time" construction of such a kiln (you have to rip it apart to get at the ware) would mean its use would leave very few long-term traces, except fragments of bisqued coils and wall clay. However, because such a kiln construction technique requires lots of clay, they would always be sited very close to a substantial natural clay deposit because nobody likes lugging giant masses of wet, sticky, gooey clay hither and yon if they can avoid it.
My assumption is that the prehistoric Maine potters, after much trial and error and experimentation, devised a happy medium ratio of kiln size to ware capacity. Given the documented size of prehistoric Maine pots, a kiln that could fire one 20 inch tall vessel could only fire one or two additional pots without necessitating a significant increase in kiln width and height (and increasing the risk of kiln collapse and failure). By exceeding this number, you would be required to stack pots on top of each other, increasing the risk of breakage and requiring a much taller kiln. This would create a trend of diminishing returns because it would actually be easier to make two kilns side by side firing one or two pots each rather than one kiln that could fire six pots. The economies of scale do not reward a high capacity kiln design unless the kiln structure itself can be re-used.
Because the success of a firing depends on reaching full bisque temperature on all surfaces of the ware, it is better to fire in smaller amounts and get consistently good pots than fire in one large kiln and risk losing some or all of them due to inadequate temperature or kiln collapse and failure. Or, following this same rule, prehistoric potters may have tended to "play it safe" by firing one large pot at a time. This would minimize the amount of work to make the kiln, increase kiln efficiency, decrease fuel use and decrease firing time. Bisque firing with wood is an "all or nothing" enterprise in the sense that unless the firing process is a complete success, all of the previous work in making and decorating the ware and building the kiln is gone to waste if the pot is not fired properly. The large pots made by Maine potters required great skill to make (especially given their thin walls) and many probably did not even survive the greenware stage (due to unseen flaws and uneven drying) to even make it to the firing stage.
How Long was the Firing Process?
Even thoroughly dried "greenware" contains significant amounts of water trapped in between the particles of clay and temper. Unless this water migrates out of the ware before the firing temperature gets past the boiling point of water, the trapped water will turn to steam and explode and shatter the pot. For this reason, all potters must use a "candling" period where low, steady heat is applied to the ware to drive out and evaporate the pore water from the piece. In a small beehive of the type proposed here for prehistoric Maine potters, this candling would have been done by building a very small fire (with twigs and sticks) just outside the firebox of the kiln and letting the heat move past the ware and out the chimney. If only 1 or 2 pieces were being fired this candling process would take at least 3-4 hours. Because excess candling cannot hurt a pot, but insufficient candling can quickly destroy it, prehistoric potters most likely candled a bit extra, since it requires minimal wood fuel, just to be safe with their ware. [This slow candling process for the ware would also be necessary for the clay components of the kiln itself, which are freshly applied from wet clay on the day of firing and also need a slow, steady increase in heat to maintain their integrity during the firing.]
The ability of a newly made pot to be sufficiently dry to be fired is dependent on the relative humidity of the atmosphere. In 100 percent relative humidity, pots will not dry out. In very low humidity, pots dry quickly. Prehistoric potters in the southwest desert of the United States live in practically ideal conditions for air-drying of newly made pots: high heat, very low relative humidity and little or no chance of rain. In contrast, prehistoric Maine potters were faced with a climate of much higher humidity, frequent rains (even in summer), and high air temperatures in conjunction with high humidity ("muggy" days). All of these factors made the candling process critical for the success of firing a large, thin-walled pot in Maine, and may explain why for a distinct period Maine prehistoric potters deliberately added large amounts of coarse pieces of crushed quartz as temper in their pots, as this would greatly assist in the drying of the ware and fewer explosions in the firing process due to water trapped in pore spaces in the clay.
For the type of small, clay-lined beehive kilns proposed here, the actual firing time required for a well-candled large pot (or two) would be in the range of 4-6 hours. This suggests that the entire firing sequence took 8-12 hours. If the beehive kiln was completed in the morning, candling began at 10-11 a.m., firing began at 4 p.m., the entire process would be done by mid to late evening. Or, as an alternative, kiln construction may have been done the day before, with candling begun in early morning the next day, finished by noon, with firing completed at dusk.
UPDATE: A subsequent visit to the site produced the following oddly shaped lump of bisqued clay about the size of a walnut:
Like the pieces described above, this lump of fired clay has no connection to a piece of completed, fired pottery and contains no quartz temper. What is it and why was it fired to bisque temperature?References Cited
Bourque, B., S. Cox, R.L. Whitehead. 2001. 12,000 Years: American Indians in Maine. Univ. of Nebraska Press.
Doyle, R.G. 2008. Identification of Lithic Artifacts from Central Maine Coastal Archaeological Sites: A Case Study in Regional Lithic Acquisition Strategies. Flying Passage Press. Gardiner, Maine.
Rhodes, D. 1971. Clay and Glazes for the Potter. 14th printing. Chilton Book Company, New York.
Monday, October 05, 2009
Decorative techniques of prehistoric Native American potters of the Sebasticook River, Maine
Upon first looking at a shard of prehistoric Ceramic period pottery from the Sebasticook River in Winslow, Maine, the tiny grid-like patterns impressed in the clay look much like a piece of woven cloth, like burlap, pressed into the wet clay.
However, a close examination of the pieces reveals a very different and much more laborious decorative method. These methods vary widely from shard to shard and it is difficult to figure out exactly what hand tools were made to create these impressions.
One of the most interesting designs is shown below, from a small shard less than one inch square. At first glance this pattern looks like it is part of a large-scale impressed design (ie. from a paddle, knotted string or woven cloth). But close examination shows this design was made row by row by a tiny hand stamping tool. Each of these rows is barely 1 millimeter high and about 1 cm long. As the photos show, the entire pattern is repeated up the shard, with each row staggered slightly to the right.
This one shard is very interesting because it confirms that this patterning was made by the repeated use of a very small stamping tool with regular square notches cut into it. No other design technique could make this type of pattern. What is most bizarre is that a very close examination shows that each row was made by two stamps. This is shown by the clear impression of two tiny squares at the beginning of the row that merge into each other toward the right. That these two tiny squares are not part of one stamp can be seen in how they are slightly offset from each other in some repetitions of the pattern. The photo below shows the same shard tilted vertically:
The next shard shows a similar pattern that is clearly made by a very small (1 mm x 1-2 cm) stamping tool applied horizontally and then repeated vertically on the pot. The key to seeing the application process is that each horizontal row is exactly identical to the one below it. A multi-rowed patterning tool (ie. a paddle with corded string, or wrapped, knotted string) could not have done this because the impressions in each row are exactly identical.
The size and precision of these patterns is shown by the yellow stone in the upper right hand corner of the shard. It is about 1.5 mm in diameter, smaller than a BB. The Sebasticook River prehistoric potters used coarse sand and crushed rock as temper to strengthen the local clay during the working and firing process.
At first examination, I thought this second set of impressions looked less like a stamp and more like it was made with a toothed shell. But the third impression in the row (from the left) is quite tilted and out of parallel. Shells which have finely enough scalloped edges to make an impression like this have perfectly parallel and regular spacing. This does not.
So what on Earth did these prehistoric Sebasticook potters use as tools to make these tiny, sequential, geometric rows of impressions? I don't know. But to make things even more confusing, here's another set:
This is the highly carbonized piece of the rim of a 12 inch wide vase with a similar, but not identical, impression as above. The inside surface of the same piece (ie. the inside surface of the pot rim) shows the same pattern (and tool) used, but in a much more loose and haphazard manner. The aggressive and non-decorative impressions on the inside curve of this rim shows the impression tool was used not so much to make a pattern but to form, define and strengthen the pot rim itself.
What strikes me about all three of these impression patterns is that they are all of the same size (1 mm wide x 1 cm long) but are very different from each other. The first has a pattern which is rigorous geometrical, with tiny squares. The second and third are much looser, rounded and curved. Their tiny size and repetition patterns shows they were made with very small, pre-made tools, about the length of a pencil tip but much narrower, with very regular indentations cut into them.
What Tools Made These Marks?
The very small and precise markings on these pot shards suggests they were pressed into the clay with a tool small enough to contain five to six equally spaced impression in a 1 mm x 1.5 cm row and this row of impressions was the basic unit of design by repetition around the pot surface while the clay was still soft and flexible, but after the overall form was completed and smoothed.
The very small size of the impressions greatly limits the possible materials for the tool that made them. The tool had to be easy to hold and comfortable enough in the hand to allow for great precision in aligning each row of impressions next to each other and above each other. The tool material had to be soft enough to carve geometric notches but hard enough to retain the desired shape of the notch without chipping or cracking. Bone would be one possibility, however the very tiny notches would be difficult to cut into bone with a stone tool without chipping. The bone would have to be very small (much smaller than a deer antler, for example), and notching such a small bone would be difficult without breaking it. At one point I considered as a candidate the edge of a freshwater mussel shell with notches cut into it with flint. However, after experimenting myself with this approach it became obvious that the shell is far too hard to be notched with flint. When you try it, the flint wears away faster than the shell it is supposed to be notching.
While I have no idea if the following idea is true, the best candidate for a tool material for these markings seems to be fired clay. More specifically, the potter created a small button of clay with one flat side and while the clay was in the leather hard stage, cut tiny regular notches or teeth into it with a small, very sharp shard of flint. When complete the tool was allowed to dry and then was fired with the next load of pots. Once fired, the tool would be extremely durable and the geometric shape of the notches would remain exactly as they had been cut. A second benefit of this technique is that these fired clay stamping tools could be made very quickly and in large quantity and once fired they would be as durable as stone. This would be in sharp contrast to other materials (such as bone or stone) which would be much more difficult and time consuming to make in such a small size.
Monday, September 28, 2009
Revenge of the Nerds: The Story of Precocious Atlantic Salmon Parr
Native Atlantic salmon parr, Bond Brook, Kennebec River, Augusta, Maine. Watercolor, gouache and pencil. Douglas Watts, 1999.
By Douglas Watts
Augusta, Maine
September 2009
A fascinating aspect of Atlantic salmon is the existence of precocious parr.
Atlantic salmon live in the streams where they were born until they are two years old. In the spring of their third year, when they are 6-7 inches long, they turn bright silver, their kidneys and other organs undergo a profound change to let them live in saltwater, and they head out to sea for two years, whereupon they return to their natal stream to mate and spawn as 8-15 pound adults.
But some male Atlantic salmon take a different path. In the fall of their second year, they become sexually mature while still only the length of a dollar bill. Because baby salmon in freshwater are called "parr" (a very old Scottish word), these prematurely sexually mature males are called precocious parr.
In any given Atlantic salmon river, only a small number of the baby male salmon become precocious. Most do not develop testes and sperm (fish sperm is called "milt" and looks much like human semen) until they are 4 years old and have spent two years at sea.
The existence of precocious Atlantic salmon parr offers an insightful window into the mechanics of evolutionary biology. To look into this window, we need some background on the basics of the Atlantic salmon's life history.
Atlantic salmon are anadromous fish, which means they are born in freshwater but spend most of their adult life in saltwater, returning only to freshwater to mate and spawn. Atlantic salmon adults have developed an amazing ability to return from their two year stint in the ocean to almost the exact river or stream (or river and stream section) where they were born in order to mate and spawn. How salmon do this is still not known, but smell is considered the most likely candidate. Somehow, salmon can remember the "smell" of their birthplace and unerringly follow it back to where they were once babies. Other anadromous fish such as alewives and shad also share this "homing" ability.
Most Atlantic salmon return to their home rivers in the spring and summer of their fourth year, having spent two years in freshwater and two years in saltwater. In the late fall, the female salmon select nesting sites in the shallow tails of large pools in their natal rivers. These sites are chosen with great care because the fertilized eggs of salmon must remain in the riverbed for 5 months, from late fall to the next spring, before hatching into baby salmon. To build the nest for her eggs (called a "redd," another Scottish word), the female turns on her side and vigorously flaps her tail and body to create a powerful current of water directed at the stream bottom. The force of this jet of water causes the stones on the stream bottom to become momentarily suspended in the water column, whereupon the stream current carries them a short distance downstream. As you can imagine, for this technique to work, the female must choose a nesting site with just the right sized stones (about the size of tennis balls) and with enough current to carry them a small distance downstream once they are dislodged by the shaking of her tail. These sites are invariably located at the end of a pool, just above a small riffle or rapids, where the water becomes shallow and current begins to accelerate before it spills over the riffle just downstream.
This photo shows a 30 inch female Atlantic salmon turning on her side and digging her second redd in Bond Brook, Kennebec RIver, Augusta, Maine. Her first redd is visible at the far right.
After many hours of turning on her side and fanning the water vertically, the female creates a depression in the stream gravel that is roughly 1.5 - 2 feet in diameter and 1 foot deep, with excavated stones in a loose pile just downstream. It is at this point that she selects a male salmon as her partner. The male and female salmon, positioned alongside each other, pointing upstream with their sides touching, then go into a series of brief, quivering mutual orgasms which culminates in the female discharging her eggs into the depression in the gravel and the male simultaneously discharging his milt onto them. Both the eggs (which are the size of small peas) and the milt are somewhat heavier than water, and if everything goes right, the sexual act ends with a kettle-sized depression in the gravel filled with several hundred eggs blanketed and covered in pearlescent milt. This is repeated until the female determines that the depression is sufficiently filled with eggs. She and the male then break off and the female swims a few feet upstream of her nest and repeats the digging process with vigorous beats of her tail. But this time, the female is not trying to dig a nest, she is instead dislodging the stones so that the current will carry them downstream and fill in her egg-filled nest. By repeating this process for several hours, her nest becomes a humped pile of river stones with the eggs safely nestled at the bottom of a sizeable pile of loose, clean gravel. Because most female salmon carry 7-10,000 eggs, far more than one nest can accommodate, the female then digs a second nest and spawns again until she has laid all her eggs.
This photo shows a female Atlantic salmon at left, on her side digging her redd, while a large male (34-36 inches) in the center of the photo "guards" the female and her redd from other males. At the moment this photo was taken, the female had curved her body into a horseshoe and made a powerful downthrust with her tail to dislodge stones from the stream bed. The cloud of sediment from her downthrust can be seen just to the left of the male. Close examination of the male shows his distinctive pink and brick red coloration along his flanks. Large male salmon take on this color only when they are spawning. Just to the right of the male salmon is a 12 inch brown trout, which illustrates how big the male salmon is. Bond Brook, Kennebec River, Augusta, Maine, Nov. 1, 1996.
The 30 inch female salmon fully on her side at the beginning of her digging thrust. A 12 inch male brown trout can be seen in the lower right hand corner of the photo. Brown trout and Atlantic salmon are very closely related species and for this reason, male brown trout respond to the pheromones released by spawning female Atlantic salmon and will try to mate with them.Like many animals, male Atlantic salmon aggressively compete with each other for the right to mate with females. Male salmon compete by "claiming" a female as she is digging her nest and then trying to drive all other interested males away from the nesting site. While male salmon do not bite each other, they will use their heads and snouts (which become curiously enlarged and curved at spawning season) as battering rams to "head butt" a particularly obstinate competitor. As a rule, the larger male tends to win these competitive displays and the smaller male (or simply less aggressive male) moves away to find another available female or to wait on the sidelines for a rematch. In cases where three or more males are vying for one female, these competitive matches are tumultous, with the male salmon chasing each other up and down a pool and in the shallows. This frenzy can continue for several days, especially if additional males arrive in the area after being driven off by other males at nests up or downstream, or as fresh males arrive from the ocean. The male battles only end when all the females in the area have spawned.
Enter stage right our little friends, precocious parr. Precocious parr are sexually mature male Atlantic salmon, but are only the length of a dollar bill. They are only two years old (rather than four), and have never gone to the ocean. Adult male salmon which have gone to sea and back are big fish, anywhere from 28-44 inches long and weighing from eight to 40 pounds. They have swam from their home rivers more than 2,000 miles to their marine feeding grounds near Greenland and back, growing from 7 inches long to nearly 3 foot long in just two years. Most of their compatriots on this long migration did not survive, but were eaten by larger ocean predators at some point in their journey. These large males are the veterans, the survivors, are in the peak of condition, have a tummy full of milt and only one objective: to win a female salmon against all competitors and to pass along their genetic legacy.
So how does a precocious salmon parr that weighs a few ounces and is barely the length of an adult salmon's tail have any chance of competing for and winning a female? Isn't this totally wacky?
Precocious male salmon parr do this by using their tiny size as an asset. Their secret weapon is as comical as it is effective. Here's the secret: during all of the time the big, giant male salmon are chasing each other around, fighting and vying between each other for "possession" of the female salmon and her nest, the precocious parr wait in the wings for the big males to be preoccupied with fighting other and then stealthily swim into the nest itself and sidle up alongside and underneath the female's abdomen, much like how a remora swims underneath the belly of a shark. Then they wait.
The only time I have seen precocious parr mate with a female salmon is when there were also large males around, and a large male with the female. In these cases the precocious parr sidles up underneath the female's belly, waits for the female and large male to simultaneously emit eggs and milt and then the precocious parr emits his (much smaller) package of milt at the same time, which then settles into the nest with the eggs and the large male's milt. Interestingly, even though the tiny parr has a lot less milt to squirt onto the eggs than the large male, his abdomen is much closer to the eggs, because he positions himself underneath the female which places him just a few inches above where the eggs are deposited.
Sunrise on the Kennebec River at Hallowell, Maine.Evolutionary Persistence of Precocious Parr
The reasons why and how precocious salmon parr exist must be viewed from the perspective of the selfish gene (Dawkins 1976) and not to their utility to the species as a whole. From a "selfish gene" perspective, the precocious parr have only one aim: to ensure their genetic legacy is passed onto the next generation.
The most obvious advantage of precocious parr-ness is that they can avoid waiting until they are 4 years old to spawn, and instead spawn when they are only two years old. As important, the male parr does not have to undertake a 2,000 mile journey in the open ocean before it spawns, as must its larger male competitors.
The drawbacks of precocious parr-ness are several. First, the precocious parr is so tiny that it cannot compete for females with the large adults by driving off smaller competitors (although precocious parr will aggressively drive other precocious parr away from a spawning nest). Second is that during the spawning season, precocious parr lose their secretive nature and swim around the stream in the open during the day with wild abandon, exposing them to being eaten by kingfishers and other streamside predators. This is a threat that large males do not face because there are virtually no streamside predators large enough to attack and carry off a full-sized male salmon. A second threat is that to become sexually mature, male 2+ year old salmon parr must devote approx. 20 percent of their body weight to growing testes and developing sperm and spending the fall of their second year attempting to spawn, rather than conserving their body mass and saving their stored "fitness" to survive the oncoming winter in preparation for swimming to the ocean the next spring. Several studies (listed below) show that the over-wintering survival rate of precocious parr is lower than parr of the same age which do not become sexually mature.
We know the trade-offs of precocious parr-ness must outweigh the risks because precocious parr do exist. This means that whatever genetic proclivity toward making some male parr precocious is at least successful enough to persist in the gene pool. If the disadvantages of precocious parr greatly outweighed the benefits, the genetic recipe for making them would long ago have disappeared. By corollary, we can assume there is some sort of ongoing "stalemate" between the advantages and disadvantages of precocious parr-ness because most male salmon are large four year old adults. If the advantages of precociousness greatly outweighed the disadvantages, contemporary salmon populations would be wholly or mostly made up of small males that never went to the ocean.
Two other facets of salmon behavior contribute to the persistence of precocious male parr. First is that female salmon do all of the nest building work. If males had to contribute to the nest-building effort, the precocious parr would be in bad shape, because their tiny body size keeps them from moving even the smallest river stone, while the large males can move stones just as easily as the largest females. Second is that female salmon do not seem to actively select one mate and then drive off all other suitors. Instead, females spend all of their time building their nest, while the males around them are fully occupied with trying to drive one another away from the female. The female is only "ready" to spawn when she decides her nest is finished and is large enough and deep enough to successfully hold her cargo of eggs. It is only at this time she acknowledges or interacts with the jostling males around her.
One-year-old native Atlantic salmon parr, Worromontogus Stream, Kennebec River, Randolph, Maine. Watercolor, gouache and pencil. Douglas Watts, 1999.Why no female precocious parr?
The reason precociousness in male salmon works -- and doesn't work for female salmon -- lies in the enormous difference in size between salmon sperm cells and eggs. Salmon eggs are the size of a small pea. A 7 inch female could only hold in her a dozen or so eggs. A 7 inch male can hold in him thousands of sperm cells. In contrast, a full grown female salmon can hold from 5,000 to 15,000 eggs. From the perspective of the selfish gene, the female has a much better chance of passing along her genetic legacy by going out to sea for two years, feeding in the rich ocean environment, growing to 28-36 inches long and being large enough to carry 10,000 eggs instead of becoming sexually mature at age two, not going out to sea and carrying only 12 eggs. There is also the issue of nest building. The female salmon builds her nest without assistance from males, and it is an arduous task. A 7 inch female could only build a nest the size of a tea cup for her 12 eggs; and few if any males would be willing to use up their sperm supply fertilizing such a tiny amount of eggs. Under the selfish gene concept, the goal of the males is to use their sperm supply to fertilize as many eggs as possible, thus increasing the chance that their genetic legacy will be passed on. The more eggs you fertilize, the greater chance that at least one of the fertilized eggs lives to spawning age itself and passes on part of your legacy. Given that precociousness in male salmon is quite common and precociousness in females is unknown, we can assume that if there ever was a genetic proclivity that created precocious females, it has blinked out of existence every time it arose because it did not "work."
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30 inch long, two sea-winter adult male Atlantic salmon after spawning, Bond Brook, Augusta, Maine, October 1996. Held by Nate Gray, fisheries scientist of Maine Dept. of Marine Resources.
Do females benefit from precocious parr?
In Atlantic salmon, as humans, each fertilized egg gets one half of its chromosomes from its mother and the other half from its father. From a selfish gene perspective, the female's sole interest is in the welfare of her half of the chromosomes in her fertilized eggs. While she needs a male to mate with, this is only because she needs male sperm cells to ensure that her half of the chromosomes is passed on to her children. In this sense, the female doesn't really care whether her eggs are fertilized by a 24 inch, 36 inch, 40 inch or 6 inch male, as long as they all get fertilized. This is shown by the fact that female salmon do not appear to overtly select certain males as mates and refuse to mate with other males. From a purely statistical standpoint, female salmon benefit from having their eggs fertilized by multiple males because it increases the chance that at least some of the eggs will carry beneficial genetic adaptations from the male and have a better chance of living to adulthood and spawning. The idea is the same as betting on 6 numbers on the roulette wheel rather than putting all your money on one.
Second breach of Edwards Dam, Kennebec River, Augusta, Maine, August 12, 1999.
Kennebec River at Augusta, Maine, July 2000, one year after removal of the Edwards Dam. The dam was located in the upper center of the photo.Male vs. Female salmon Imperatives
A large male Atlantic salmon contains millions of sperm cells, enough to fertilize all of the salmon eggs deposited by every female in a salmon river. A female, in contrast, carries between 5-10,000 eggs. From a purely statistical standpoint, it is in the female's interest to have her eggs fertilized by multiple males, which allows her genetic legacy (half of the chromosomes in each egg) to benefit from any potential genetic advantages contained in the various males in the river.
Male salmon have a powerful motivation to prevent other males from spawning with females, because every egg fertilized by another male is one that he did not fertilize. The female, on the other hand, benefits from having multiple males fertilize her eggs. This helps to explain why males devote all their time on the spawning beds to driving away other males from a female; and why females show little interest in selecting one male and spurning others.
This also helps to explain the existence of precocious salmon parr. Under the rules described above, the female benefits from having a precocious parr sneak under her belly just as she emits her eggs and casting his small cargo of milt onto them, even as the large male is next to the female doing the same thing. The large male does not want the precocious parr anywhere near the female when she is releasing her eggs because he wants to make sure that only his milt touches and fertilizes all of her eggs. By hiding underneath (or on the opposite side) of the female as she emits her eggs, the precocious parr stands a good chance of not being noticed by the large male and is able to eject his milt at about the same time as the large male ejects his milt, creating the opportunity that at least some of the parr's milt will reach an egg and fertilize it, thereby thwarting the large male's efforts to fertilize all of the eggs himself.
30 inch Atlantic salmon at mouth of Bond Brook, Kennebec River, Augusta, Maine, July 2005.Species benefits of precocious parr
An important rule of evolutionary behavior is that individuals of a species do not do things to benefit the species as a whole. Each individual is trying to pass on their own individual genetic legacy and that is it. To the extent that one individual's efforts to pass along his or her own genes creates inherited adaptations that are spread through a population, you can (very cautiously) examine how adaptations that help one individual pass on their genetic legacy can ultimately increase the fitness of a larger group of individuals. This is especially true where some type of calamity has caused a drastic reduction in localized population size.
Female Atlantic salmon digging her spawning nest in upper Bond Brook, Kennebec River, Augusta, Maine, October 1998.
This fact was made apparent to me in 1998 in Bond Brook in Augusta, Maine. Bond Brook is a very small (25 square mile) watershed which enters the Kennebec River just below the site of the Edwards Dam, an impassable structure built in 1837 that almost completely wiped out the Kennebec River's Atlantic salmon population. The dam was removed in 1999. For several decades prior to 1999, Bond Brook was one of the only places below the Edwards Dam that contained quality Atlantic salmon spawning and nursery habitat, and for this reason, a dozen to several dozen adult salmon would swim up the brook each fall and spawn. These few salmon represented the last, tiny struggling remnant of the Kennebec's original salmon population, which exceeded 100,000 adults prior to the construction of the Edwards Dam in 1837.
In 1996 I located a previously unknown Atlantic salmon spawning area several miles up Bond Brook in a remote, roadless area that required a long, muddy walk to reach. In this reach, the habitat was nearly pristine and ideal for spawning salmon and their young. In late October 1998 I hiked into this habitat and was very pleased to find a large female digging her nest, accompanied by two large males, who fought and chased each other constantly for control of the lone female. Hiding in the tall grass next to the brook bank, I was able to spend several hours observing the stream and the salmon without being noticed, even though the salmon were only 15 feet away from me. During this time, I noticed a dozen precocious male salmon parr swimming all around the female's nest, constantly chasing each other away from the nest and vying for "ownership" of it, even as the two large males did the same thing to each other. The precocious parr behaved exactly toward each other as the two large males toward each other. They all viewed each other as competitors and rivals for possession of the nest and the female salmon building it.
What struck me was that in such a depauperate, remnant salmon population (with only one female and two large males in this stretch of brook and a total population of perhaps 30 adults), the addition of the dozen precocious parr I saw darting about greatly increased the effective breeding population of the brook. From the female's perspective, a fertile male is a fertile male, even if one is 30 inches long and the other is only 6 inches long. It is in the female's interest to have her eggs fertilized by as many different males as possible. If there were no precocious parr in the stream reach I observed in 1998, the female's eggs would at best be fertilized by two males, and perhaps only one, if the larger male was successful at driving the smaller male away and fertilizing all of the female's eggs. With the dozen precocious parr present, and because of their sneaky way of swimming underneath the female's belly without being noticed by the large males, the female's eggs had the opportunity of being fertilized by as many as 14 different males. While each baby salmon that hatched in spring 1999 from this site would have the same mother, they would have perhaps as many as 14 different fathers.
Large male and female Atlantic salmon just above the female's spawning redd in Cobbosseecontee Stream, downtown Gardiner, Maine, November 1997. I took this photo 25 feet up in a red maple tree. On this same afternoon, I observed several precocious male salmon parr occupying the redd below.
Precocious Parr, Genetic Drift and Bottlenecking
Animal populations reduced to extremely small sizes must mate with closely related members of the population or go extinct. They have no choice. This fact is especially pronounced in Atlantic salmon, which display a tightly focussed homing instinct to the stream and river of their birth and in doing so increase the chance of mating with close relatives. In a large, healthy salmon population with hundreds of fertile males and females in a short reach of river, the chance of a full sibling mating is quite small because it requires, by pure chance, a male salmon selecting his sister even in the presence of dozens or hundreds of other females who are more distantly related. But in a very small, impoverished salmon population, where only a handful of males and females spawned, there is a very high likelihood that many of the males and females returning four years later are full or half siblings. Given the choice of spawning with a sibling or not spawning at all (and not passing on their genetic legacy), the salmon must spawn with "who they brought." Over time, such a pattern of repeated sibling mating can have a very negative effect, which is well known in humans via cases of human incest. Sibling mating is bad because many diseases and birth defects are caused by the mother and father sharing the same rare, debilitating gene which is only activated when an offspring inherits it from both its mother and its father. When distantly related males and females mate, the chances of both having this debilitating gene are very low. But if the mating pair are siblings, the chance that both have the defective gene can be quite high.
Large Atlantic salmon trying leap over an impassable 1850s dam on Cobbosseecontee Stream, Gardiner, Maine, Nov. 11, 1996. The dam is still impassable.
An analogy is a deck of cards. Let's say you play a card game where each player draws a card and places it on the table. If the cards match exactly, both players "die." If the cards don't match both players "live." In such a game the risk of living and dying is dependent on the number of cards in the deck. With a 52-card deck, the players might have to go through many full decks to each throw down the same card at the same time. But now add a variation. Each time the players go through a full deck without getting a match, each has to remove some cards from their deck (say, remove all the kings, then the queens, then the jacks, and then all the 10s, etc.) With every round of the game, the chance that the players will throw down the exact same card increases because they always share the same set of cards but the total number of cards decreases. As the deck grows smaller and smaller, the chance that both players will throw down the same card approaches unity. This is a rough analogy to the effects of genetic "bottlenecking" due to a greatly reduced population size where genetic variation is sharply reduced because of the need for close relatives to mate with each other or not mate at all.
Now let's add precocious parr to our card game. Let's assume that each time a male and female "player" goes through a full deck without losing (ie. throwing down a matching card) is equal to one spawning season for Atlantic salmon. Because our game assumes a rapidly declining population of adult salmon (due to losses of adults and juveniles at dams, from human capture), we invoke a penalty after each game where each player removes all of the cards of one number before starting the next round, leaving them with fewer cards, and fewer chances of a mismatch (and their offspring living) and a greater chance of an exact match (and their offspring having a genetic defect and dying). Because an adult female having her eggs fertilized by a precocious male parr eliminates the chance of sibling mating (by definition a 2 year old precocious parr is not a sibling of a mature 4 year old female), the addition of precocious parr to the spawning stream decreases the chance of a female mating with a sibling male.
We can approximate this change in our card game by reducing (by some number) the amount of cards each side loses after each round of the game from what it would be if precocious parr were not present and available to mate with adult females. This is because, without precocious salmon parr, the chance that a 4 year old female and 4 year old male being siblings in a very depressed salmon population approaches one, and the increase in the chance of deleterious genetic defects and diseases due to sibling mating increases dramatically.
Using our card game as an analogy for the genetic shuffling between male and female Atlantic salmon, precocious parr are an important buffer against the tendency of a declining salmon population to enter a genetic bottleneck where siblings increasingly tend to mate with direct siblings, resulting in a continued reduction in genetic variation and an increase in harmful defects caused by the mother and father each having copies of the same harmful gene.
Precocious parr cannot mate with their siblings
Due to the two-year separation between precocious male parr and their 4-year-old female mates, it is impossible for precocious parr to ever mate with their sisters. This is because only male salmon are precocious and all of their sisters must reach age 4 before they reach spawning age. When the precocious males are trying to spawn at age 2, their sisters are nearby in the same stream, still two years away from reaching sexual maturity. In contrast, nonprecocious male parr and their sister parr each spend two years in the ocean before returning together to spawn at age 4. This creates a fairly high chance (especially in small, impoverished populations) that brothers and sisters will mate. In a large, healthy population the chance of direct sibling mating is greatly reduced by the large number of available, unrelated male and females in any river reach. While sibling mating in a large river population is statistically possible (and undoubtedly happens), the number of matings between unrelated salmon is much larger. In a very depressed salmon population where most of the juveniles arise from a handful of closely related adults, sibling mating becomes the rule rather than the exception.
Precocious parr and newly established salmon populations
Precocious parr should assist the establishment of persistent Atlantic salmon populations in unoccupied habitat (in contrast to the "the last survivors model" described above, this model would be the "first pioneers" model). While Atlantic salmon have an acute homing instinct which causes them to return to the river reach where they were born, some Atlantic salmon break from this instinct and explore and colonize suitable habitat where few, if any, salmon are present. This "straying" instinct is well documented in Atlantic salmon, although it is adopted by only a small (1-5 percent) of salmon, with most (95 percent) returning to the same river, stream and even gravel bar where they were born (Baum 1997).
A pioneer group of Atlantic salmon colonizing an uninhabited stream is comprised of just a few spawning males and females. The success of this colonization effort depends on the progeny of the first pioneers surviving in the stream to adulthood and returning to the same stream to spawn. In such a nascent population, sibling and half sibling mating is practically guaranteed.
Precocious salmon parr provide a unique opportunity for newly established salmon populations to "mix-up" their mating combinations by allowing cross-generational spawning between 4 year old females and 2 year old males. This greatly reduces the chance that all of the offspring in an early spawning generation are produced by the mating of siblings or half siblings.
Close-up of male two sea-winter Atlantic salmon, approx. 30 inches long, Bond Brook, Augusta, Maine. You can tell this male has completed spawning because his coloration has started to become greyish. During the height of spawning the males have a ruddy pink coloration along their sides.
The needs of the "selfish genes" of Atlantic salmon
In this era of Atlantic salmon populations approaching extinction, the primary focus of Atlantic salmon biologists and conservationists is on the preservation of Atlantic salmon populations rather than the welfare of any one individual Atlantic salmon (although obviously the former is completely dependent on the latter). Evolutionary biology requires us to examine Atlantic salmon strictly through the lens of individual salmon trying to preserve their legacy by surviving to spawning age, mating, and giving birth to salmon that also spawn. This is especially true in the case of precocious male salmon parr. While we can theorize or surmise that precocious parr increase the fitness of a local population, stave off the extirpation of depressed populations, and increase the chance that newly established populations will persist, we cannot forget that the genetic adaptations which allow 2+ male salmon parr to be sexually mature two years earlier than most of their cohorts was not "designed" for these purposes. A more appropriate way of characterizing this genetic adaptation is that it has persisted in Atlantic salmon populations because in some statistical way it confers a neutral or positive survival advantage to those salmon who are born with it; and that the "success" of this peculiar life history strategy can be estimated by its prevalence or absence in the gene pool of Atlantic salmon today. Presumably, in Atlantic salmon populations decimated by long-term anthropogenic effects (as in the U.S.), if precocious parr provided a neutral or negative benefit to survival of their offspring, it would have disappeared from the remaining gene pool of U.S. salmon. By an admittedly speculative analytical basis, the adaptation of precocious parr seems to provide individual Atlantic salmon in highly depressed remnant populations an important hedge against the environmental and genetic forces which conspire to drive remnant populations to increased dimunition and extirpation.
Precocious parr mitigate against harmful environmental effects face by young salmon as they try to migrate downstream as smolts and live in marine waters for two years before they return to spawn. This is accomplished by allowing some male 2+ parr reaching sexual maturity in their own natal stream without having to live to age 4 or survive a perilous 2 year journey back and forth across the Atlantic Ocean to their feeding grounds near Greenland.
The adaptation of precocious parr mitigates against the harmful effects of genetic bottlenecking and genetic drift in small, declining, remnant Atlantic salmon populations by reducing the chance that most or all returning adult salmon are forced to mate with their sisters and brothers or not mate at all. Precocious male salmon parr have a unique life history because they mate at age two with females that are age four or older. This guarantees that they will not mate with their siblings or close relatives. The presence of numerous precocious parr in an impoverished Atlantic salmon spawning stream greatly increases the effective population size of the stream by greatly increasing the number of potential fathers for the available females' egg cargo. Due to their young age, precocious parr have different mothers than the females they try to mate with and the adult males they compete with. This means precocious parr increase the effective population size of mothers in a given stream because they do not share a mother with any of the adult males and females. In contrast, in a very depressed and small population, it is possible that most of the adult male and female salmon have the same mother.
Wild Atlantic salmon parr, Worromontogus Stream, Randolph, Maine, October 1996. This is an "0+ parr" meaning it has had one summer of growth after emerging from the gravel that spring. This parr would overwinter, spend the next summer in the stream as a "1+ parr", overwinter again and become a smolt the next spring and head out to sea.
A Theory Explaining Precocious Male Atlantic Salmon Parr
It is likely that all male Atlantic salmon carry the necessary genes to allow them to become precocious, ie. to become sexually mature prior to migrating to sea as smolts. It is also possible that this gene for precociousness tends to be triggered by the relative presence or absence of male salmon testosterone in a salmon spawning stream. A spawning stream occupied by a large number of adult males carries a much higher "signal" of male salmon testosterone than a stream with very few adult males. If the presence of salmon testosterone inhibits the genetic expression of precociousness in 2+ male salmon parr, the number of male parr in the stream displaying precociousness would be higher if there were few adult males.
Such an environmental triggering would explain why recent field research shows a higher incidence of precociousness in small, depressed Atlantic salmon population lacking adult males and a lower (observed) incidence of precociousness in salmon populations with a large number of adult males. Support for this theory is shown by the fact that male brown trout (Salmo trutta) and brook trout (Salvelinus fontinalis) typically become sexually mature at age 2-3. Two sea-winter Atlantic salmon become sexually mature at age 4, three sea-winter salmon at age 5 and male grilse at age 3. In contrast, sexually mature female anadromous Atlantic salmon less than age 4 are extremely rare. Among brook trout and brown trout, its closest cousin species, sexual maturity for male Atlantic salmon at age 2 is the norm, ie. the age at which precocious salmon parr become sexually mature. Only in healthy anadromous Atlantic salmon populations do males tend to delay their sexual maturation until age 3, 4 or 5. This suggests an environmental inhibiting factor keeps most anadromous male Atlantic salmon from exhibiting their "normal" sexual maturity at age 2 and delays it until age 3, 4 or 5; the existence of precocious parr suggests a relaxing of this inhibition; and this relaxation is expressed most prominently when a local population lacks adult males. From this we can deduce an inverse relationship between the number of precocious parr in a spawning stream and healthy survival conditions for those male Atlantic salmon which go to sea before spawning.
Large Atlantic salmon, Cobbosseecontee Stream, Kennebec River, Gardiner, Maine. Nov. 11, 1996.
UPDATE: A recent research study of southern European salmon populations (Garcia-Vazquez et al. 2001) seems to confirm the above theories of species benefits in depressed Atlantic salmon populations from the presence of precocious male parr. The study states in part:
"Mature juvenile males may have saved south European Atlantic populations from extinction, given the depressed size of populations for a number of decades. This point suggests that these populations may be under intense selection for maturation of juvenile males, and hence that the relative preponderance of mature juvenile males in the southern populations may be an adaptive response to anthropogenic depletion of anadromous salmon numbers .... In conclusion, precocious Atlantic salmon parr contribute to balance the sex ratio, enlarge the effective population size, and increase outbreeding. In addition, they fertilize most eggs in the interspecific matings between Atlantic salmon and brown trout. Sneaking behavior has not been evidenced in small maturing brown trout, this being the main reproductive difference between brown trout and Atlantic salmon in wild southern European populations."
Works Cited:
Baum, E.T. 1997. Maine Atlantic Salmon: A National Treasure. Atlantic Salmon Unlimited. Hermon, Maine.
Dawkins, R. 1976. The Selfish Gene. Oxford University Press. London, England.
Garcia-Vazquez, E., P. Moran, J. L. Martinez, J. Perez, B. de Gaudemar, and E. Beall. 2001. Alternative Mating Strategies in Atlantic Salmon and Brown Trout. The Journal of Heredity 2001:92(2).
Myers, R.A, J.A. Hutchings. 1987. Mating of Anadromous Atlantic salmon, Salmo Salar L., with mature male parr. J. Fish Biol. (1987) 31, 143-146. PDF here.
Saura, M. et al. 2008. Impact of precocious male parr on the effective size of a wild population of Atlantic salmon. Freshwater Biology. Vol. 3 No. 12. pp. 2375-2384. Blackwell Science, Oxford.
Mark Kemezys (1961-2009) at the ledges and falls at the head of tide of Bond Brook, Kennebec River, Augusta, Maine in spring 2005. For more than 150 years, Bond Brook provided the only accessible habitat for Kennebec River salmon below the impassable Edwards Dam. A native of Norridgewock, Maine, Mark spent many hours cleaning up trash and debris along the Kennebec River at the "yellow stairs" in downtown Augusta.
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