Underwater visual census-derived fish biomass as a proxy for small-scale fisheries catch and revenue indicators

Abstract

Empirical data about small-scale fishery indicators, such as catches and revenues, are generally scarce and scattered. In this study, we examined for the first time the relationships between fish biomass estimated through underwater visual census (UVC) and small-scale fishery indicators, namely catch per unit effort (CPUE) and revenue per unit effort (RPUE). Significant correlations could provide a practical and useful means to estimate CPUE and RPUE from UVC data, particularly in situations where fishery surveys are logistically challenging or where catch data are unavailable. Using a comprehensive dataset from 10 coastal Marine Protected Areas (MPAs) and adjacent areas across the Northern Mediterranean Sea, our results show that: i) total fish biomass of the assemblage assessed via UVC, and ii) the biomass of the most frequently recorded species in both UVC and small-scale fisheries catches (the two-banded seabream Diplodus vulgaris), are positively and significantly correlated with total CPUE and RPUE. These findings highlight that UVC-derived fish biomass data can serve to reliably estimate SSF metrics, such as CPUE and RPUE, that are key socio-ecological variables for assessing the effectiveness of MPAs. This study underscores the potential of UVC as a valuable tool for integrating ecological and socio-economic assessments in marine conservation efforts.

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