Variability in Haul Seine Retention Rates and its Effects on Abundance and Size Structure Estimates of Black Crappie and Sunfish Populations

Gear catch efficiencies have a large effect on data collected to describe fish populations and communities used by managers to make informed decisions. We measured the retention rate of black crappie (Pomoxis nigromaculatus) and sunfish (Lepomis spp.) from a seeding experiment composed of 10 haul seines pulled at three lakes. Approximately 50 individuals of each group were marked and placed into closed haul seines, and fish recovery rates were measured. Retention rates ranged between 0.34 and 0.94 for black crappie and 0.38 and 0.89 for sunfish. Akaike's Information Criterion was used to select between alternative generalized linear models of recapture probability using site-specific environmental and sampling measurements as covariates. Our top ranked model for black crappie incorporated heterogeneity in fish retention across lakes with different sample area sizes, while the best model for sunfish included covariates for lake, size of sample area, and sample effort. Nonparametric bootstrap (with replacement) estimates of mean retention rate across sites were 0.57 (90% confidence interval [CI]=0.48 - 0.66) for black crappie and 0.63 (90% CI=0.55 - 0.71) for sunfish. We observed increased retention rates of larger fish for both groups, indicating higher capture probabilities. This information may be useful for adjusting haul seine catches used to estimate absolute abundance and size structure on black crappie and sunfish populations.

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