Barotrauma in Lake Erie Yellow Perch and Implications of Bycatch Mortality in Commercial and Recreational Fisheries

In Lake Erie, yellow perch are managed via an interagency quota system and separated into four management units.  Stock assessment models within each unit were reviewed by a Technical Review Panel which had concerns regarding the impact of unmeasured harvest or bycatch of yellow perch.  We enumerated yellow perch with barotrauma from bottom trawl surveys and developed a sigmoidal logistic model using depth as the independent variable.  We also investigated the effects of size, sex, month, and their interactions and found that 92% of the variability in barotrauma was explained by depth.  Different models also occurred when we broke size distributions into adult and juveniles.  Using just adults greater than 170m, we applied our model to bycatch from commercial and sport fisheries to examine impacts of bycatch mortality.  Data were collected from commercial fishers in 2015 to compare observed values to the model projections.  We found bycatch mortality to be less than 5% for both fisheries using model projections whereas observed data indicated about a15% bycatch mortality.  Estimating bycatch mortality may be a critical component of mortality that is not accounted for in current population projections and quota management strategies.