Target strength estimates of Mysis diluviana across the Great Lakes and Finger Lakes

Session: Spatial Dynamics in the Pelagia of Large Lakes – Technological Advances and Applications

Toby Holda, Cornell Biological Field Station, [email protected]
Lars Rudstam, Cornell University Bio Field Station, Dept. of Natural Resources, [email protected]
David Warner, USGS, [email protected]
Joseph Warren, Stony Brook University School of Marine and Atmospheric Sciences, [email protected]
Patrick Sullivan, Cornell University, [email protected]

Abstract

The mysid shrimp, Mysis diluviana, is an abundant and important migratory macroinvertebrate in the Laurentian Great Lakes and surrounding lakes. The carapace of M. diluviana reflects high frequency sound, and the animal often suspends in the water column at night. Fisheries acoustics can thus collect spatially fine-scale data on M. diluviana spanning entire lakes in relatively short time intervals. While estimates and theoretical models of M. diluviana target strength (TS) estimates are available, a substantial degree of variability in estimates of M. diluviana TS remains unaccounted for. We analyzed the influence of size structure, lake, year, and vessel on 141 field-based estimates of M. diluviana TS (120 kHz transducers) from 3 Great Lakes and 2 Finger Lakes. We also compared field TS estimates to TS predictions of a published theoretical scattering model for M. diluviana. Preliminary results suggest a mean TS per M. diluviana of -89.5 dB (sd: 3.9 dB, range: -106.4 dB to -79.1 dB, n: 141). Preliminary results also indicated lake and vessel operations can be important. TS predictions of previously published model were significantly higher than field estimates (1.3 dB). A re-parametrized model is currently in development.