Pot type and bait selection shape catch rates of the invasive blue crab (Callinectes sapidus): evidence from a model-based comparative analysis

Abstract

Context The Atlantic blue crab (Callinectes sapidus) is among the most ecologically and economically damaging invaders in the Mediterranean, and commercial removal is increasingly promoted for population control. Yet, existing gear comparisons often confound pot design with bait, leaving managers without clear guidance on efficient configurations. Aims We tested whether pot design and bait type influence catch per unit effort (CPUE) when their effects are disentangled, and identified the most efficient combination for removal-oriented trapping. Methods Two pot designs (umbrella type, double entrance) were factorially crossed with three baits (chicken, fish, tripe) in standardised trials in Azmak Stream, Türkiye (2023–25). An effort-offset negative binomial model, selected by AIC, yielded estimated marginal means and Tukey-adjusted contrasts. Key results Double-entrance pots achieved 1.54-fold higher CPUE than did umbrella-type pots (95% CI 1.06–2.22). Chicken increased CPUE by 62% relative to fish (IRR = 1.62), whereas tripe reduced it (IRR = 0.38). CPUE peaked in early summer, declining towards autumn. Conclusions Pot design and, especially, bait selection, are decisive operational levers; double-entrance pots baited with chicken were most efficient (~1.49 individuals pot−1 h−1). Implications These standardised benchmarks can optimise control-oriented removals, provided scaled trap use is paired with gear-loss mitigation.