Variation in the catchability of yellow perch (Perca flavescens) in the fisheries of Lake Erie using a Bayesian error-in-variable approach

Catch per unit effort (cpue) from fisheries, and abundance or biomass indices from fisheryindependent surveys are often used to infer the dynamics of exploited populations. To do this, cpues and survey indices are usually assumed to be proportional to population size or biomass. Four sources of data on the cpue of yellow perch (Perca flavescens) in Lake Erie were available to evaluate this assumption: commercial gillnet and trapnet fisheries, an angling fishery, and a fishery-independent gillnet survey. The relationships between fisheries cpue and population biomass (estimated from an age-structured model), and between fisheries and survey cpues were analysed by error-in-variable (EIV) models because of the absence of independent estimates of population size. Cpues were not proportional to population size, estimated by biomass. Catchabilities varied widely among fisheries (gear types), time period, and areas (management units) within Lake Erie. A spatial EIV model showed that the migrations among management units were considerable. The whole-lake spatial EIV model showed that cpues were not proportional to population size.