Site fidelity, depth-habitat use, and reproductive behavior of ciscoes in Grand Traverse Bay, Lake Michigan

Darryl Hondorp (USGS, dhondorp@usgs.gov), Jason Smith (Sault Ste Marie Tribe of Chippewa Indians), Jory Jonas (MIDNR), Ben Turschak (MIDNR), Erik Olsen (GTB), Nathan Barton (USFWS), Kevin Donner (Little Traverse Bay Band of Odawa Indians), Andrew Muir (GLFC)

Our study of the movement ecology of Grand Traverse Bay Cisco commenced in late November 2019 with the deployment of 40 acoustic receivers and tagging of 85 adult-sized individuals sampled from spawning shoals near Elk Rapids, MI, and Ingalls Pt. near Omena, MI (Figures 1, 2). No tagging occurred in 2020 due to the pandemic, but 76 Cisco from the Ingalls Pt. shoal were tagged in December 2021, and an additional 20 individuals were sampled from Lake Charlevoix during January 2022. Information on Cisco movement is current through mid June 2022 when receivers in the Grand Traverse Bay (GTB) array were last recovered and downloaded. Acoustic tags implanted in fish during 2019 ceased transmitting by December 2021, so detection histories for the 2019 release group now are complete. Tags in the fall/winter 2021/22 release groups will continue to transmit until fall/winter 2023. Survival of Cisco tagged in 2019 was lower than expected due to high mortality of individuals sampled in gill nets (~ 70%) vs. trap nets (< 30%). Of the 85 individuals tagged in 2019, only 38 likely survived. Therefore, subsequent sampling was conducted using trap nets (Grand Traverse Bay) or angling (Lake Charlevoix), and surgery/handling procedures were adjusted to improve fish condition at release (refer to 2022 report for details). Survival of the 2021/22 release group is currently estimated at about 80%, which suggests that modifications to capture and handling procedures significantly reduced tagging mortality.