Menominee Indian Tribe of Wisconsin and USFWS
Juvenile Lake Sturgeon Survey
BY KEVIN MANN GREEN BAY FWCO
Indian Tribe of Wisconsin Reservation. Credit: Rob Elliott, USFWS
On August 13th, biologists Kevin Mann and Rob Elliott from the U.S Fish and Wildlife Service’s Green Bay Fish and Wildlife Conservation Office (FWCO) traveled to Keshena, Wisconsin to help the Menominee Indian Tribe of Wisconsin (MITW) search for young-of-year lake sturgeon in the upper Wolf River. For the last three years MITW and the Wisconsin Department of Natural Resources (DNR) have transported adult sturgeon above the Shawano and Balsam Row dams to reestablish spawning at Keshena Falls, the historic spawning grounds within the reservation boundaries. This spring, MITW biologists did observe spawning by the transported adults at Keshena Falls. USFWS and Wisconsin DNR then assisted MITW in setting D-framed larval drift nets below the spawning area to document any successful reproduction. Drift nets collect larvae after they hatch and float downstream during nighttime hours. This was the first year larval drift sampling was attempted on the reservation and it proved successful in capturing fish, confirming that successful spawning had occurred.
Credit: Rob Elliott, USFWS
Now that successful spawning had been documented, biologists were interested in verifying if any of the larvae might have survived and stayed in the short section of river below Keshena Falls and the Balsam Row dam. One way to do this is to conduct nighttime spotlight surveys where the survey crew travels slowly upstream in the river and uses bright spot-lights to shine for young-of-year sturgeon (YOY) that typically reside on the bottom of shallow river sections. If fish are found, dip nets are used capture them. When successful, location, length and weight are collected and each fish is given a passive integrated transponder (PIT) tag which has a unique identification number. In this manner, if any of those fish are captured again, the unique PIT tag number will allow biologists to track the fish’s growth and location history.
On this particular night biologists did not find any YOY lake sturgeon which wasn’t terribly surprising. The limited amount of spawning this spring, the typical low survival of larvae, and the close proximity of the dam are all factors that likely limit large production of YOY fish in this section of river at this early stage in rehabilitation efforts. The survey crew did however capture a one year old lake sturgeon that had been released many miles further upstream during a 2012 stocking event, and they also observed 2 of the adult transfer sturgeon during the evening survey. As the population of spawning adults continues to grow above the Balsam Row dam, nighttime spotlight surveys for YOY fish will be an effective way to monitor the survival and residency of larval fish and potential production of YOY fish within this section of river.