Wednesday, December 02, 2009

Sturgeon at Norridgewock, Maine, on the Kennebec River and Sandy Rivers.

A "scute" or skin plate of an Atlantic sturgeon, recovered from a 2,000 year old shell midden near Bristol, Maine, July 2005.

Art Spiess, senior archaeologist with the Maine Historical Preservation Commission, sends along some more details of a recent archaeological dig at the Norridgewock Mission site, dated 1695-1724. Feature 15 at the site, a straight sided, flat bottomed storage cache, contained 469 fish bones, of which 77 could be identified to species. The breakdown is 1 sturgeon, 24 American eel, 3 alewife/shad, 22 white sucker, 1 striped bass, 4 yellow perch, 1 Atlantic salmon, 21 hornpout (bullhead). The data are from a 2002 Ph.D. thesis by Ellen Cowie. [Note: the numbers refer to individual bones identified to species, not the number of individual fish.]

What is striking about this find is the wide variety of fish species present, including most of the above-tidal migratory fish species native to the Kennebec, as well as three non-migratory species, white sucker, yellow perch and hornpout. The only native migrating fish not present in the cache are sea lamprey, rainbow smelt and tomcod.

Most surprising is the presence of sturgeon, which according to conventional wisdom, did not migrate up the Kennebec past Ticonic Falls in Waterville, Maine, 30 river miles downstream from Norridgewock. The find of a sturgeon raises the "carried there or caught there" conundrum. In order for the sturgeon to have been caught 30-50 miles downriver, it would have to have been smoked hard at the capture site to keep it from spoiling and then transported back upriver for 30-50 miles and then, finally, eaten.

Locations of sturgeon remains from Kennebec River Native American habitation sites.

This raises the obvious question of why someone would go through all of this effort to catch a sturgeon at tidewater, smoke it, and then paddle 30-50 miles against the current up to Norridgewock before eating it. Why not just eat where it was caught? Why not eat it at some point during the long, hard 50 mile canoe trip back upriver?

The great variety and number of fish in the cache shows there was no shortage of fish to be caught at or nearby the Norridgewock mission site. Why make such an effort to catch, smoke and transport a single fish from 30-50 miles downriver when there was an abundance of fish to be caught on-site?

And why do we even need to question whether the sturgeon was caught at the site or not?

The reason is that conventional wisdom holds that sturgeon did not migrate up the Kennebec past Waterville, 30 miles below Norridgewock. This belief is not based on information and evidence, but on a lack of information and evidence. Up until now there are no documented records of sturgeon above Waterville. There may be some, and only diligent search can turn them up, but to date, they have not. A problem with estimating a fishes' natural range by this method is that it violates the general evidence rule of science: absence of evidence is not evidence of absence, ie. you can't draw a positive conclusion from a negative finding.

In contrast with sturgeon, there are independent lines of evidence which confidently rule out such hypotheticals as swordfish or bluefish swimming up to Norridgewock, since they cannot survive in freshwater. If a swordfish bone were found at Norridgewock we could say with confidence that it had to have been carried there from saltwater. As Thoreau said, "sometimes circumstantial evidence can be quite strong, as when you find a trout in the milk." But unlike a swordfish or whale bone, there is no reason a sturgeon at Norridgewock would be like "a trout in the milk."

Five foot long Atlantic sturgeon leaping in the Kennebec River in Augusta, Maine. The entire photo sequence is here.

Looking at the documented migrational range of sturgeon in other Atlantic coast rivers, we find that the distance from Norridgewock to tidewater on the Kennebec (approx. 50 miles) is well within the migrational range that sturgeon are known to travel. A sturgeon swimming 50 miles above tidewater is not an unusual behavior or occurrence. It is quite normal.

The discrepancy between archaeological evidence and the 'conventional wisdom' of the range of sturgeon is not confined to the Kennebec River. On the Penobscot, the 'conventional wisdom' holds that sturgeon did not migrate past the ledge drops at Indian Island in Old Town. Yet there is a well-known record of burned, calcined shortnosed sturgeon bone from the Hirundo site in Alton, Maine on Pushaw Stream, a number of miles upstream from Indian Island. This aerial view shows the rapids at the Hirundo site, Pushaw Stream, Alton, Maine. Pushaw Stream drains Pushaw Lake, which historically held a very large alewife population. Shortnosed sturgeon conduct their spawning runs in early to mid-May, at the same time as alewives. A weir fishery for alewives at this site would intercept shortnosed sturgeon present.
This map shows the location of sturgeon bones found at the Hirundo site on Pushaw Stream in Alton as compared with the location of the alleged 'impassable' barrier for sturgeon at Old Town and Milford.
The risk associated with an over-reliance on 'conventional wisdoms' is shown at the State of Maine and University of Maine's official 'scientific synthesis' website for the Penobscot River. This resource cites the Hirundo archaeological site as one of three places on the Penobscot River where sturgeon bones have been found, but goes on to say in the next sentence, "Most likely, sturgeon historically ranged as far up the Penobscot as Milford, where natural falls and ledges prevented them from migrating any farther upstream." A small problem is that the Hirundo site, on Pushaw Stream, is located well above the ledge drops in Milford. The same page states the Penobscot River is the "northern limit" for Atlantic sturgeon, even though the supporting scientific link for this statement correctly states that Atlantic sturgeon live as far north as the Gulf of St. Lawrence and southern Labrador. This resource is further contradicted by an 1825 eyewitness description of 20-40 pound striped bass in the middle and lower Piscataquis River, 30 miles above Milford. These basic errors of fact show why sources relying on a 'conventional wisdom' approach require careful scrutiny.

Steve Fernandes with a medium sized shortnosed sturgeon from the Penobscot River.

Junction of Kennebec and Sandy Rivers near Norridgewock Mission Settlement, Norridgewock, Maine. The Sandy enters from the opposite side.

On the Kennebec, in contrast to the Penobscot, the archaeological record prior to 2000 agrees with the "best conservative guess" of an upstream limit of sturgeon somewhere near Ticonic Falls in Waterville. Prior to the Norridgewock find, the farthest upstream prehistoric records of sturgeon were at the junction of the Kennebec and Sebasticook Rivers in Winslow and one mile up the Sebasticook at the outlet of China Lake Stream. With the Norridgewock find, the migration limit of sturgeon shifts upstream by at least 30 miles to the falls on the Kennebec at Madison and the Sandy River up to Farmington Falls. While this more than doubles the natural range of sturgeon in the Kennebec River, this revised range is well within the normal migrational range of the species documented in other U.S. and Canadian rivers.

Additional supporting evidence is provided by the recent capture of adult shortnosed sturgeon at the very top of Ticonic Falls by the dam owner, FPL Energy, during spring flashboard replacement. Due to the configuration of the low dam spillway at the top of the ledges at Ticonic Falls, it is apparent that if the concrete dam spillway were not present at the site, the shortnosed sturgeon captured by FPL at the toe of the spillway would have been able to continue swimming upstream.

Unlike statements in old historical records, the remains of sturgeon bones in an archaeological site are direct, physical evidence of presence. Their existence at a site must have an explanation. In this instance, there are only two possible. The sturgeon either swam to Norridgewock or was caught 30-50 miles downriver, smoked to prevent spoiling, and then carried to Norridgewock and eaten. Occam's Razor favors the former, as it requires far less special pleading than the latter.

If and when funding becomes available to conduct additional archaeological surveys of prehistoric habitation sites along the Kennebec and Penobscot Rivers, faunal remains found at these sites should provide us with additional illumination on the natural range of all of the migratory fish native to these rivers.

Are sturgeon weak swimmers? You decide:

No comments: