Sturgeon and Lamprey

The destruction of the sturgeon population mirrors the devastation of southeastern primeval forests.  Both of these astonishing natural resources have been utterly obliterated.  In a previous blog entry from about a year ago, I excerpted William Bartram’s 18th century description of a magnificent forest in Georgia consisting of trees with diameters 8-12 feet thick.  I drove through the same area last summer and was hard pressed to find a single tree greater than 1 foot in diameter.  The story of Georgia’s most impressive river fish follows the same plotline.

 

 

 

 

 

Man Alive!  Look at the size of this Atlantic sturgeon.  There used to be so many of these fish in our southeastern rivers that they posed a navigational hazard.  Now, they are almost extinct.

The sturgeon run in southeastern rivers began in mid-May.  For the first month of the run most of the spawning sturgeon averaged 3-4 feet in length, but beginning in mid-June and lasting until mid-September sturgeon averaging 6-9 feet in length were common.  Captain John Smith, founder of the Jamestown colony, caught 62 sturgeon in 1 haul of a net, though that take was extraordinary, even for that time.  More often, netting would yield 7 or 8 large sturgeon in a few hours.  The schools of sturgeon “clogged” the river and made for a dangerous navigational hazard that could upturn boats.  Occasionally, the giant fish even jumped into a boat.  John Lawson, an early naturalist who traveled and settled in North and South Carolina circa 1704, wrote that he saw hundreds of sturgeon every day. (He also mentioned pulling 300 chain pickerel from 1 fish trap in a single day.)  Now, sturgeon are almost extinct.  There is a tiny breeding population in Georgia’s rivers but none of the rare sturgeon found in mid-Atlantic rivers breed there.  About 1850  men began overfishing sturgeon which formerly were considered trash fish.  This decimated the population, but dams and muddy erosion from agriculture blocked and smothered much of their former spawning grounds–perhaps the final death blow.  Sturgeon need shallow water with gravel bottoms for spawning, but instead, if the spawning fish themselves are not blocked by dams, the gravel bottoms have become covered in mud, making them unsuitable.  The sturgeon eggs need to adhere to gravel.

Three species of sturgeon, all endangered, live in Georgia.  The Atlantic sturgeon (Acipenser oxyrhincus) reaches the most spectacular size, obtaining a maximum length of 9 feet and a weight exceeding 800 pounds.  The adults live in the lower stretches of the river and near offshore ocean water, but they used to spawn as far as 300 miles up the river.  The juveniles stay in the river until they’re about 7 or 8 years old before they migrate to the ocean.  They return when they reach breeding age which isn’t until they’re between 10-30 years old, explaining why it’s so difficult to bring back sustainable population levels.  They feed on the bottom by scooping out depressions and lying in ambush nearby.  Smaller fish and invertebrates carried by the current fall into these saucer-shaped traps next to where the hungry sturgeon awaits.  The short-nosed sturgeon (Acipenser brevirostrum) is similar in habit to the Atlantic sturgeon, but it is smaller in size reaching 4-5 feet in length and just 50 lbs in weight.  A landlocked population of lake sturgeon (Acipenser fluvescens) lived in the Coosa River  until 1965.  In 2003 biologists reintroduced them to the Etowah River.  The Coosa River lake sturgeon must have been a relic population that some how made their way from the Mississippi River system, perhaps from a chain of wetlands that existed during the Pleistocene in northern Alabama.  Floods between river basins must have facilitated the spread of this species.

Sturgeon piccatta, broccoli, and stuffed squash blossoms.  I’ve never eaten fresh sturgeon.  I think I’ve had smoked but it’s been so long I can’t remember for sure.  I’ve had caviar…tastes like fish guts.

It’s hard to believe the early settlers considered sturgeon a trash fish and fed the flesh and caviar to the hogs and dogs.  Sturgeon flesh when dressed correctly is reportedly supposed to be mild and durable and an acceptable substituted for boneless chicken breasts or veal in recipes.  Caviar, of course, is considered a delicacy but in my opinion tastes like fish guts.  Mixed with cream cheese, it’s palatable.  In my fantasy Pleistocene world, I’d definitely be harvesting and eating the sturgeon.

Sea lampreys parasitize fish, latching on and ingesting blood.  Sea lampreys no longer occur in the Savannah River, but they used to.  They must have been dependent on the large sturgeon population.

Sea lampreys (Petromyzon marinus) are no longer recorded from the Savannah River, but there is a historical record of 1 from the upper part of this river where Clark Hill Reservoir now inundates.  John Lawson mentions sea lampreys as a fish the Indians refused to eat (though the French consider them a delicacy).  This anectodal evidence suggests sea lampreys used to be fairly common in southeastern rivers.  They’ve likely disappeared from the Savannah River because they depended upon sturgeon for sustenance and now that the sturgeon are all but gone, so are the lampreys.  It’s no coincidence that sea lamprey spawn in the same habitat as sturgeon–shallow water with gravel bottoms.  The larva move downstream after hatching, then burrow into sandy or muddy bottoms and become filter feeders, living on detritus and algae until they grow into their parasitic phase.  When they reach this stage they actively attack fish as depicted in the figure above.  I suspect sturgeon were their primary prey/host in southeastern rivers.  Striped bass and swordfish have been recorded as preying on sea lampreys, but probably any large predatory fish will eat them.

At least 3 other species of lampreys inhabit Georgia’s rivers–the southern brook lamprey (Ichthyomyzon gagei), the American brook lamprey (Lampetra appendic), and the least brook lamprey (Lampetra aegypidtra).  The former occurs in the Chattahoochee River, and the latter 2 live in north Georgia rivers.  None of these have a parasitic phase and they live as filter feeders burrowed in mud for most of their lives, except when they spawn.  They all have rasping mouths, however.  This is evidence they evolved from parasitic species.

Sturgeon are an ancient family of fish.  Fossils of sturgeon dating to the Cretaceous prove they swam when dinosaurs roamed the earth.  Lampreys long ago evolved to exploit this once abundant food source.  It’s a shame both of these remarkable fish have nearly vanished in the last 150 years in the wake of man’s environmental destruction after they’d successfully survived natural ecological changes for over 100 million years.

Tags: Atlantic sturgeon. early American sturgeon populations, brook lamprey, John Lawson, land locked lake sturgeon, Savannah River, sea lamprey, short-nosed sturgeon, William Bartram