Researchers study early life cycle of Black Lake sturgeon
Editors Note: This is the first of a three-part series on the sturgeon population in Black Lake. This article describes some of the unique research that is taking place under the auspices of Michigan State University to determine how best to manage the resource.
The high banks of the Black River cast a shadow over the water in the early morning sunlight. Dave Sanborn is watching for poachers and waiting for the shift change.
Sanborn is with the Cheboygan chapter of the Vietnam Vets of America on the sturgeon watch. It is about eight o’clock in the morning and the sunlight is beginning to drift down the riverbank and shine on the surface of the river.
The rocky river bottom is clearly visible now. A few mullet jump in the middle of the river as a dark shadow makes its way upstream.
AS THE SHADOW swims closer the distinctive shape of a sturgeon becomes clear in the shallow water along the riverbank.
The sound of an approaching pickup truck can be heard up the sandy two-track road leading to the watch areas.
The location is ideal for sturgeon watching. There is a bend in the river and a deep pool of 13 to 15 feet swirls in the elbow of the bend. Sanborn explains researchers from Michigan State University have been dipping sturgeon out of the pool to measure, clip and tag the fish.
Sanborn’s group is responsible for keeping vigil during the night. The VVA volunteers coordinate with DNR personnel who man the river 24/7 and hand over to the volunteers who arrive in the morning to cover the daylight hours.
THE GREEN PICKUP truck drives into the campsite and four MSU researchers get out. They start sorting their gear and surveying the riverbank for a spot. Once they have donned their waders and unraveled their gear they are ready to climb down into the chilly 50-degree water.
Patrick Forsythe is working on his doctorate in zoology from MSU and is studying the early life cycle of the sturgeon. He explains that little is known about the survival rates of fertilized eggs or larval sturgeon.
Recent MSU science graduates Allison Ethridge of Kansas, Holly Wellard of Lewiston, and Christin Davis of Toronto, Ontario assist Forsythe.
Another MSU doctoral student in Fisheries and Wildlife, Jamie Crossman, is working at one of the other five surveillance sites along the river. Crossman’s research is to develop better stocking strategies for the successful placement of young larval fish in their environment.
BECA– USE OF the long life span of these creatures and their infrequent spawning cycles, it may take 15-20 years to see if these young larval fish that were tagged and released live to become breeding specimens.
Forsythe explains the best times to see the sturgeon are at dawn and dusk. They tend to be inactive during the day, sticking to pools and deeper water. He says the latest estimate (1997) indicates there are between 450 and 550 mature breeder sturgeon in Black Lake.
It is not actually known if this number is sufficient to maintain the population. That is one of the goals of Forsythe’s research. Female sturgeon usually breed only once every six years while the males will breed every other year.
“This means we see a lot more males than females,” he explained. This is the third year Forsythe has been tagging sturgeon in the Black River. He explained that MSU started doing biological studies of Black Lake sturgeon in 2000.
THE MATURE MALE sturgeon are noticeably smaller than the female specimens. The Black Lake sturgeon tend to run up the river to spawn in two waves during the spring.
The males get some signals from the females that say they are ready to spawn and the males swim along side, releasing sperm in the water with the eggs.
Forsythe noted that sturgeon are “broadcast” spawning fish, meaning they release their eggs in the open water to travel freely down stream. After some time the eggs develop a sticky surface that allows them to adhere to rocks and other structures in the river.
Beginning around April 30 the first wave of spawning fish start swimming upriver. The second wave of fish comes through from mid-May to the end of the month.
Forsythe and his colleagues have netted about 100 specimens so far this spring. About half of these were tagged before. He says the majority of the males have been tagged but fewer of the females have been tagged.
This is because of the f
Forsythe has designed some special platforms in the river that contain sturgeon eggs and are surrounded by different gauges of mesh wire to determine the size and type of predators feeding on the roe. His fieldwork will continue until the end of August.
Next: A look at the work the DNR is doing.