A condition assessment and handling guideline for skate (Rajiforms) by-catch in longline fisheries: Lessons from the Southern Indian Ocean

Elasmobranchs (sharks, skates and rays) are among the least productive fish species, which make their populations vulnerable to increased mortality. Although skates exhibit elevated vulnerability to fishing, they are commonly caught as incidental bycatch in demersal fisheries. Management measures to prevent the decline of skate populations often includes the release of captured individuals which are still alive. Once a skate is brought onboard, handling by crew members will influence its survival and animal condition will have to be assessed to avoid discard of dead individuals. In this paper, we analyzed skate handling practices and condition assessment methods in the toothfish longline fisheries operating in the Southern Indian Ocean. Images of skate taken onboard were examined by veterinarians to determine the physical and physiological consequences of injuries. In total, 13 different types of injuries were identified including 10 that are caused by the capture process. Among these injuries, only two were considered to be irreversible and led to a recommendation to retain the individual at any time. Most of the injuries examined occurred over a gradient from superficial to severe, particularly in case of mouth damage which was the most frequent injury. Posters describing recommended handling practices and condition assessment were developed, as well as a video tutorial. They provide clear guidelines for crew members operating on longline vessels to maximize survival of skates released at sea. We welcome feedback to improve these communication tools developed specifically for fishing vessel crew and would be willing to share them with the wider CCAMLR fishing fleet if deemed relevant by all members.