Catch dynamics, species diversity, and community composition of small-scale fisheries in Pagasitikos Gulf, Greece

Small-scale fisheries (SSF) in semi-enclosed Mediterranean gulfs are ecologically and socioeconomically significant yet remain poorly characterized due to chronic data limitations. This study presents an integrated analysis of catch dynamics, species diversity, and community composition of SSF in Pagasitikos Gulf, central Greece, a trawl-restricted semi-enclosed system in the Aegean Sea. Fishery-dependent data were collected across 97 fishing trips between 2023 and 2025, encompassing two gear types (trammel nets, GTR; gillnets, GNS), 71 recorded taxa, and 14 distinct fishing areas. Catch per unit effort (CPUE) was modelled spatially using a Stochastic Partial Differential Equation (SPDE) framework and analyzed in relation to depth, season, gear type, and fishing area. The central finding is a depth-mediated quantity-versus-quality trade-off: the 0–20 m stratum yielded the highest CPUE but simultaneously the lowest target species success rate (63.6%) and highest discard rate (68.2%), while intermediate depths (20–40 m) offered a more favorable balance between productivity and selectivity. Gear type functioned as an ecological filter, with six pelagic and benthopelagic species significantly associated with GNS and none with GTR. PERMANOVA confirmed that depth, season, and gear independently structured community composition. Species-resolved, depth-by-gear optimization was identified for five principal target species. Significant inter-fisher CPUE variability underscores the value of participatory monitoring designs. These findings provide a locally grounded, methodologically transferable evidence base for ecosystem-based co-management of SSF in data-poor Mediterranean systems.