Adopt-A-Fish update – May 15, 2008
for pallid sturgeon
By DAVE FULLER
Montana Fish, Wildlife and Parks
FORT PECK -- It was a tough week of fishing for pallid sturgeon brood stock as Missouri-Yellowstone Adopt-A-Fish program biologists gathered near the confluence of the Missouri and Yellowstone rivers.
These fish are caught by putting out trammel nets and letting them drift down the river. But after roughly 500 drifted trammel net drifts, we only caught two adult pallid sturgeon for the Garrison Dam National Fish Hatchery.
Those nets covered a lot of river, but the fish were just scattered. At least that’s what we’re hoping, since these fish have not produced young that survived to adulthood in decades and they are most likely reaching the end of their age limits.
Take our Adopt-a-Fish for example. Pallid #1 (Wolfe or Cabingbang) is up the Yellowstone River, #2 (Roosevelt or LaserRed) is remaining below the confluence, and #3 (Lucky sturgeon) is about 20 miles up the Missouri River. The fish are behaving differently than they normally would with cooler water temps, low Yellowstone flows and higher Missouri flows than normal.
Fortunately, the two fish that were caught were very large females; both over 60 pounds and they should have 200,000 to 250,000 eggs each. Other males that were collected in prior weeks and sperm that has been cryopreserved from past years will fertilize those eggs. Next spring, their young will be will be stocked back into the Missouri and Yellowstone rivers as juveniles.
A few weeks ago, we talked about how implanting radios in some of these juvenile fish will give us an idea of habitat selection and how we can adjust our stocking locations from this information. These implanted hatchery-reared fish will also help us learn about over-winter survival during their first year in the wild.
These are long-lived fish and we’re not too sure how many fish we need to stock to get a sufficient number to adulthood if we don’t know how many are surviving.
We also don’t know how old the remaining 150 or so adults are in the wild population. Aging techniques are difficult. Normally, you can age fish by cross-sectioning a hard structure of the fish and counting annual growth rings – called annuli – which is very similar to counting rings on a tree.
However, many of these fish haven’t been growing for over 15 years.
For example, one of those 60-pound females was 60 pounds back in 1995, so there is potential that those annuli would be laid right on top of one another resulting in very underestimated age. To put their old age in another perspective, we just captured two fish that were stocked in 1997 and they weighed a whopping 2 pounds. These fish have a long way to go to catch up to their parents.
One thing is for sure, the hatchery program is needed to preserve the species and to protect the genetics of the remaining individuals. However, this is just a band-aid until habitat alterations can be made for pallid sturgeon to achieve a self-sustaining population. And time is running out!
Weekly updates on our radio-implanted fish can be found on the Missouri-Yellowstone Adopt-A-Fish home page with updates posted Thursday mornings in April and May. Just click on the Find your Fish button on the home page. The program is sponsored by Montana Fish, Wildlife and Parks, The Billings Gazette, Walleyes Forever, Montana PikeMasters, U.S. Army Corps of Engineers, U.S. Geological Survey, Bureau of Reclamation and the U.S. Fish and Wildlife Service. The program is free.
School classrooms, youth fishing clubs and home schoolers can sign up for the program and adopt and name two fish. Just go to the Web site and click on the How To Adopt Button or send us an e-mail at Missouri-Yellowstone Adopt-A-Fish.
Adopt-A-Fish correspondents are fisheries biologists with Montana Fish, Wildlife and Parks. They’ll post weekly updates every Thursday throughout April and May on this site and in the Outdoors section of The Billings Gazette.