Investigation of the Catch Efficiency of Different Traps Used in Blue Crab (Callinectes sapidus) Fisheries along the Seferihisar Coast of İzmir.
Project no. 29601 · Status: Kapanmış · 2023
Summary
<p>This study aims to evaluate the efficiency of trap types and bait combinations in the population control of the invasive Callinectes sapidus, based on fishing trials conducted in the Azmak Stream of Seferihisar (İzmir) between 2023 and 2025. As a result of using two different trap types and three bait combinations, 197 crabs were caught, and morphological measurements were obtained. Carapace width (CW) changed between 81–195 mm, while weights (W) were between 39.8–357.6 g. The classical OLS model showed a strong fit for the CW–W relationship (R² = 0.70; p < 0.001), estimating a slope coefficient of b = 2.2 (95% CI: 2.01–2.41) and a scale coefficient of a = 0.00268, confirming negative allometry in the population. Among the Bayesian models assessing the effect of sex, the M3 model provided the best fit, estimating slopes of bₘ = 2.70 (95% CrI: 2.40–3.00) for males and bₓ ≈ 2.18 (95% CrI: 2.01–2.35) for females, thereby revealing significant sex-specific differences in both level and slope. In CPUEN analyses, the best fit was achieved with the Negative Binomial model (AIC = 236.80). It was determined that umbrella traps reduced CPUEN by approximately 35% compared to double-entry traps (IRR = 0.65; p = 0.021). A clear difference was observed among bait types: chicken bait increased CPUEN by 62% (IRR = 1.62; p = 0.014), whereas rumen bait decreased by 62% (IRR = 0.38; p < 0.001). Emmeans estimates were 1.209 individuals·hour⁻¹ for chicken, 0.745 individuals·hour⁻¹ for fish, and 0.282 individuals·hour⁻¹ for rumen bait. The results show that the bait efficiency ranking follows Chicken > Fish ≫ Rumen and that double-entry traps yield higher catch efficiency. These findings highlight the critical importance of appropriate trap and bait selection in the fishery-based control of invasive blue crab populations.</p><p>Keywords: Callinectes sapidus, CPUE,pot, trap efficiency, Bayesian models, invasive species management.</p>