Fish dispersal from a sabotage-mediated massive escape event

Abstract

Farm sabotage can cause massive fish escape events with significant ecological and socio-economic risks. This study examined the fate of Mediterranean seabass Dicentrarchus labrax escapees following a large-scale escape event caused by sabotage in the Western Mediterranean Sea. We monitored the escapee density and size structure over 3 mo after the escape at increasing distances from the escape point, up to 45 km away. Fish density adjacent to the escape location 5 d after the sabotage was, on average, 114 ± 44.7 (SE) fish per 100 m2. Our analyses showed that fish density decreased by 17% for every km away from the location, dropping to 2 and 1% after 1 and 2 mo, respectively, following the escape event. As escapee density declined throughout time and space, the size distribution of seabass shifted towards larger sizes. The rapid decrease in fish densities highlights the need for contingency plans focusing on fishing efforts in the coastal areas near the escape location (<20 km) within the first 24 h. These results are paramount to mitigating the risks associated with escape events cost-effectively. We emphasise the importance of sabotage prevention measures, such as security systems that can quickly detect intruders and trigger an immediate response to deter them. Additionally, enforcing appropriate sanctions based on the severity of the damage caused could help to discourage future sabotage attempts.