NEAFWA 2018

AUTHORS: Lisa K. Izzo, Vermont Cooperative Fish & Wildlife Research Unit, Rubenstein School of Environment and Natural Resources, University of Vermont; Donna L. Parrish, U.S. Geological Survey, Vermont Cooperative Fish & Wildlife Research Unit, Rubenstein School of Environment and Natural Resources, University of Vermont; Gayle B. Zydlewski, School of Marine Sciences, University of Maine; Chet Mackenzie, Vermont Fish & Wildlife Department

ABSTRACT. Lake sturgeon (Acipenser fulvescens) in Vermont are only found in Lake Champlain, and the species was listed as endangered in the state in 1972 following declines in commercial harvest. Whereas monitoring efforts have confirmed that spawning still occurs in three of the four historic spawning tributaries, there are no abundance estimates for any life stage of lake sturgeon in Lake Champlain. The goal of this study is to develop a hydroacoustic sampling protocol to estimate the abundance of spawning adult lake sturgeon in one historic spawning tributary. In 2017, a fixed-location dual-frequency identification sonar (DIDSON) was deployed downstream of the lake sturgeon spawning site in the Winooski River, VT to count upstream migrating lake sturgeon. Data were collected in low-frequency mode (1.1 MHz, 48 beams). During the 2017 spawning season, hydroacoustic data were paired with data from an array of five stationary acoustic receivers that monitored the movements of tagged adult lake sturgeon that entered the river (n=10, tagged in 2015 and 2016). From May 10 to June 21, 1000 hours of DIDSON footage were collected and 271 sturgeon targets (fish > 1 m) were observed moving upstream. Acoustic receiver data indicated that 6 of 10 tagged sturgeon made multiple movements upstream during the spawning run, suggesting that sturgeon behavior during this period had the potential to inflate abundance estimates obtained from fixed-location hydroacoustic equipment. To estimate overall spawning abundance, counts from the DIDSON will be combined with acoustic telemetry data to account for repeat movement past the DIDSON throughout the spawning season. Results of this work, which will continue through 2019, will provide managers with an estimate of spawning adult abundance without the need to handle pre-spawn fish. In addition, the methods developed during this study can be used to track progress towards lake sturgeon recovery in Lake Champlain.