Fisheries assessment of Callinectes arcuatus (Brachyura, Portunidae) in the Gulf of Nicoya, Costa Rica

The Callinectes arcuatus population of the Gulf of Nicoya and its current level of exploitation were investigated based on size frequency analysis of trap and trawl catches. Von Bertalanffy growth parameters (K = 0.89; CW∞ = 142 mm for males) are in the range reported for other species of this family and suggest that the male size at first maturity (CWmat = 94.3 mm) is reached in about a year. Total and natural mortality (Zyr = 2.49; Myr = 1.32) were derived from catch curve analysis and age at first maturity, respectively, and indicate that the stock is below full exploitation (E = 0.47). A yield per recruit analysis suggests that yield could be maximised, if E was increased to 0.7 under the precondition that recruitment was independent of stock size. Until this has been verified, the use of a precautionary exploitation rate (E0.1) of 0.57 is advised allowing for a 20% increase in fishing effort (from 300 traps currently being fished to around 360 traps). A maximum effort of 1600 traps, as recommended by the Instituto Costarricense de Pesca y Acuicultura (INCOPESCA), is unlikely to be sustained by the population, since a decrease in the proportion of large males in the catches has already been observed over the past years under the current fishing regime. This resource is as yet only sold locally, but present catches of around 145 t seem to already cause market saturation. A greatly increased catch (at E > 0.57) would thus not only be detrimental to the stock but also to the market price of the resource. Future developments of the fishery should be based on a co-management approach and should involve the exploration of new market opportunities such as the “soft crab market”.