Sturgeon research begins on South Dakota lake
PIERRE, S.D. — Something prehistoric thrashed against the boat.
It made a dull thump against the aluminum hull as Conservation Technician Jeremy Pasbrig grabbed its spiny tail and lifted it from the waters of Lake Sharpe on a Tuesday morning in 2017. The same basic fish, a shovelnose sturgeon, could have been pulled from a river 70 million years ago.
It looked the part, too. Exaggerated, bony plates called scutes formed a sharp ridge down its spine and made a sort of armored triangle down its back. The scutes developed spikes the closer they got to the tail. The fish’s head was triangle-shaped and resembled a spearhead or shovel.
It wasn’t hard to imagine the fish that Jeremy Pasbrig was holding swimming in the same rivers regularly crossed by such prehistoric North American titans as the tyrannosaurus rex. The shovelnose sturgeon, as well as the roughly 26 other sturgeon species around the globe, haven’t changed terribly much since the time of the dinosaurs.
Jeremy Pasbrig was pulling the sturgeon out of Lake Sharpe as part of a South Dakota Game, Fish and Parks Department research project. The project is being helmed by Chelsea Pasbrig, a fisheries biologist whose work focuses on non-game fish species.
“Nobody’s ever looked at the population here,” Pasbrig said.
U.S. Fish and Wildlife Service lists shovelnose sturgeon as a threatened species, partially because they look much like pallid sturgeon. Pallid sturgeon are critically endangered and the USFWS didn’t want any anglers mistaking them for shovelnose sturgeon. If an angler were to catch a member of either species, they’d have to throw it back.
Both pallid sturgeon and shovelnose sturgeon are native to the Missouri River. They long ago adapted to living in riverine environments and, for the pallid sturgeon, that became something of an Achilles heel with the damming of the Missouri River. Pallid sturgeon can’t reproduce without lots of moving water.
Shovelnose sturgeon, on the other hand, appear able to spawn in Lake Sharpe. At least, the GF&P crew out traut-lining for sturgeon this spring has been able to catch plenty of them. In the first two days of trying to catch sturgeon, Chelsea Pasbrig said, biologists caught 64 and 78 respectively. Between her boat’s first two traut lines on March 21, seven sturgeon were boated.
Shovelnose sturgeon, unlike some sturgeon species which can live for 50 years or more, only live to be about 20.
“We know there’s been recruitment here because it’s been more than 50 years since the dams were built,” Chelsea Pasbrig said.
Getting a good idea of just how well shovelnose sturgeon are faring in Lake Sharpe is one of the study’s goals. So is figuring out a way to estimate the size of the population, Chelsea Pasbrig said.
To that end, GF&P has been setting twenty 110-foot lines, each with 20 hooks baited with large nightcrawlers. The lines were set to sit overnight on the bottom of the lake. March is a good time to traut-line for sturgeon, Chelsea Pasbrig said, because sturgeon are easier to target exclusively. On March 21, for example, three catfish and a carp were the only fish besides sturgeon that the biologists caught.
Once in the boat, each sturgeon was placed in a large tank to await being weighed, measured and marked. Each fish was implanted with a numbered tag, then had it’s left pectoral and tail fins clipped as additional markers. The pectoral fin clip will be used to help age the fish. Both fins eventually will regrow, Chelsea Pasbrig said.
Once all the vital statistics were recorded, each sturgeon was sent on its way. As of March 21, none of the already-marked fish had been recaught, Chelsea Pasbrig said.
Another piece of the sturgeon study is looking at the species’ movements in Lake Sharpe. In May, 25 sturgeon will be implanted with radio telemetry tags. A series of passive receivers already has been placed throughout Lake Sharpe for similar studies on other species.
Chelsea Pasbrig and her fellow GF&P biologists will collect data through the rest of 2017 and repeat the tagging process again next year. The goal is to gather data over several years and present results from the study to the public in about five years.
There is potential that anglers might get the chance to harvest shovelnose sturgeon in the future, Chelsea Pasbrig said.