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Dinosaur Fish

October 5, 2019

 

Bayou-Diversity (5 October 2019)  For a very long time, 70 million years or so, a strange sort of fish has been swimming along the sandy bottoms of North America’s largest rivers.  They have neither bones nor scales.  Instead they have a cartilaginous skeleton and rows of boney scutes for protection.  An elongated snout, asymmetrical, scimitar-shaped tail, and whisker-like barbels add to their bizarre appearance and reputation as living fossils.  More people are familiar with their eggs than the fish themselves.  Eight species of sturgeons inhabit this continent and three are found in Louisiana, if only barely.  They are among the rarest of our aquatic fauna.

 

Of the three types of sturgeons in Louisiana, perhaps more is known about pallid sturgeons due to a recent flurry of research after it was placed on the federal endangered species list in 1990.  Named for its pale coloration, pallid sturgeons are found in the Missouri and lower Mississippi River basins.  In Louisiana they inhabit the Mississippi, Atchafalaya and Red rivers.  Attaining five feet in length and weighing up to 85 pounds, pallid sturgeons are long lived but slow growing, only reaching maturity after 15 years.  They are opportunistic bottom-feeders of invertebrates and small fish.

 

Doubtless, pallid sturgeons were once more common in suitable habitat throughout their range.  In Louisiana and elsewhere they were sought commercially for their flesh.  One record indicates that in 1914 a single fisherman had 150,000 pounds of sturgeon iced down at Melville on the Atchafalaya River.  However, they were most prized for their eggs from which valuable caviar is made.

 

Although commercial fishing may have reduced local stocks, levee building and lock construction on major rivers decimated the species everywhere by reducing turbidity and flow velocities beyond those parameters necessary for its survival.  For decades biologists observed no natural reproduction in the species, and the remaining fish seemed to be aging out.  In Louisiana at least, pallid sturgeons are hanging on but barely so.  As it isn’t likely the forces that caused the decline will be reversed anytime soon, the prognosis for this species is not good even after a showing that has lasted 70 million years.  Such is the heart-rending dominance of our own species.  (Adapted from Bayou-Diversity: Nature & People in the Louisiana Bayou Country; LSU Press) Photo by USFWS

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