This study provides species-specific catch and baseline mortality estimates of non-target species (bycatch) for the Saginaw Bay, Lake Huron commercial trap net fishery. Bycatch can represent a significant mortality source that is often unknown or unaccounted for. Bycatch and bycatch mortality rates in the Saginaw Bay commercial trap net fishery, which primarily targets lake whitefish (Coregonus clupeaformis), yellow perch (Perca flavescens), and channel catfish (Ictalurus punctatus), are currently unknown. Throughout the 2010 fishing season, I observed onboard commercial trap net vessels and took species-specific counts of bycatch and bycatch mortality. The high levels of walleye (Sander vitreus) catch and mortality observed within inner Saginaw Bay have not been previously documented in the Great Lakes. The levels of lake trout (Salvelinus namaycush) catch observed in outer Saginaw Bay were within the range observed in previous studies, but mortality (percent) was higher than has been previously observed. Through the use of generalized linear models, this analysis also indicates factors that most influenced catch of non-target species including time of year and soak time (i.e., time interval between trap net lifts). Surface water temperature, trap net depth, and magnitude of target catch most influenced mortality. As evidenced by this and other studies that evaluate Great Lakes fisheries, the variable nature of bycatch abundance and mortality precludes generalizations across regions and years. This highlights the need for comprehensive bycatch monitoring throughout the Great Lakes.
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