Survival rates of commercial elasmobranch species: exploring post-capture release at early life stages as a fishery management measure

Developing conservation approaches for elasmobranchs in the Mediterranean Sea is an urgent matter. Within Italy's monitoring program under the European Union's Marine Strategy Framework Directive (Directive, 2008/56/EC), we investigated the release of juvenile commercial species (e.g., minimum conservation reference size, MCRS) as a management strategy. From 2020 to 2023, we evaluated the vitality, At-Vessel Mortality (AVM; 4940 individuals, 22 species) and Short-Term post-capture Mortality (STM; 2 h after capture, 1099 individuals, 17 species) of elasmobranch species caught during commercial operations (trawlers and static nets) in three areas (northern Adriatic Sea, Ligurian Sea, Strait of Sicily). AVM averaged 21.3 %, while STM averaged 8 %, indicating overall high survival. To evaluate the effect of abiotic and biotic variables associated with capture mortality, data were assessed by species, gear, and area. Temperature (sea bottom and air) and time on deck were positively related to mortality and worsening vitality, and emerged as the most common and strong influences across models. While the odds of survival and physical condition decreased with body size, even smaller fish showed high survival if unfavourable deck conditions, e.g., duration and temperature, were minimized. Using only commercially collected data, this study represents the first of its kind in the area in terms of scale and scope. These data can contribute directly to the development of feasible and effective practices for managing and conserving elasmobranchs in the Mediterranean Sea.