Quoddy Nature Notes ~ Atlantic Sturgeon

Atlantic Sturgeon

Walking with the Pathfinders on Friar’s Beach a few weeks ago I found a dead sturgeon.  I hadn’t seen a sturgeon up here before, and the last one I had seen was probably over 50 years ago in the Connecticut River below the Turners Falls dam.  I was tempted to sneak it home in amongst the junk, like buckets, buoys and beach glass that I usually collect on the beach, but I decriminalized the situation and only brought home its picture.

Atlantic Sturgeon. It looked freshly killed. Probably got caught in a tide pool and the birds got him through the gills, as the rest of him looks heavily armored.

There are lots of interesting and confusing stuff about our sturgeons.  I first went to the Audubon Field guide.  Hmm “…anadromous and freshwater fishes, 7 species in North America…Atlantic Sturgeon page 365…” and there it was,  gone(?).  I next went to the bible, ‘Fishes of the Gulf of Maine’, by Bigelow and Schroeder.  Unfortunately this book is pretty dated (1950’s), and the sea sturgeon found there was the European sturgeon Acipensersturio, not our Atlantic sturgeon Acipenseroxyrhynchus subspecies oxyrhynchus, so most of my research was done online.

Apparently both the caviar and the meat of sturgeon are prized, although I have never tasted either.  In colonial times the export of these items was a lucrative trade, and the histories of the St John River in New Brunswick noted that prior to the Revolutionary war great quantities of sturgeon were shipped, and that there were more sturgeon there than anywhere else on the continent.  This trade was almost non-existent  by 1900 and also along the whole east coast, but developed again in the later 1940’s, probably due to more formidable equipment.  This fishery peaked in the early 1970’s, but is a minor industry now, and the Atlantic sturgeon is classified as Threatened in the Gulf of Maine and some populations elsewhere are listed as Endangered.

The Atlantic sturgeon can live for over 60 years and get to be a huge fish.  The heaviest sturgeon caught in the Gulf of Maine was a 12 foot 600 pound lunker landed by a trawler in Portland in 1932, but 18 foot monsters had been reported in colonial times.  For some reason Atlantic sturgeons at times tend to leap high out of the water, and, when they were plentiful, were noted as a hazard to small boatsmen.  In our area the Atlantic sturgeon takes upwards of 20 years to reach maturity, and, being anadromous, they spawn in the fall line of large rivers a little before the alewives migrate, or when the water temperature is somewhere between 13.3 and 17.8 deg C.  The number of eggs produced is related to body size, and a large female can lay up to 8 million eggs.

Apparently there had been some reverse colonization of the North American sturgeon on their counterpart, the European sturgeon (A. sturio) in the Baltic Sea.  Mitochondrial DNA testing on the extinct Baltic sturgeon indicated a strong correlation to A.oxyrhynchus.  One hypothesis on this mystery is that about 800 years ago the temperature of the Baltic Sea dropped below 20 degC, which is the minimum spawning temperature for the European sturgeon, but was within range of the North American sturgeon.  Thus, the theory goes, the American lady sturgeons had the field open to lay their eggs and these were happily fertilized by the more abundant European males.  The resulting sturgeons, however, were eventually fished to extinction.  To further muddy up the story, apparently some A.oxyrhynchus were caught in the St. John river and stocked in the Baltic Sea.  I have no confirmation of this.  I was told that no sturgeon have been noted spawning in the St Croix River, but it seems that they would spawn pretty close to Calais/St Stephen.  I don’t know very much about the Atlantic sturgeon in Passamaquoddy Bay.  I’m pretty sure I found one on Friar’s beach.