Investigating conflict between threatened marine megavertebrates and Mediterranean small-scale fisheries
Date: 25 March 2019
University of Exeter
Doctor of Philosophy in Biological Sciences
Most fish stocks are being extracted at unsustainable rates and through bycatch, many marine megavertebrate species have unfavourable conservation status. The sheer number and diversity of small-scale fishing vessels worldwide presents a challenge to monitoring and research, therefore compared to industrialised fisheries, little is ...
Most fish stocks are being extracted at unsustainable rates and through bycatch, many marine megavertebrate species have unfavourable conservation status. The sheer number and diversity of small-scale fishing vessels worldwide presents a challenge to monitoring and research, therefore compared to industrialised fisheries, little is known about their activities or their sustainability. This thesis addresses this information gap by examining motorised polyvalent vessels <12 m length in the Mediterranean, which make up over 80 % of the fleet. We take North Cyprus as a case example to scrutinise interactions with marine turtles and dolphins. Marine turtle mortalities were found to be common (of the order of 1000 turtles caught annually; 60 % mortality), with trammel nets targeting Siganidae likely the greatest source of mortality. During the nesting season, breeding loggerhead turtles (Caretta caretta) were poorly protected from fishing pressure by a proposed Marine Protected Area, while both green (Chelonia mydas) and loggerhead turtles under-used areas within the reserve. After nesting in Cyprus, loggerhead turtles used foraging areas across the eastern Mediterranean, where they were impacted by a range of fisheries with small-scale fisheries likely leading to the mortality of three study animals. Dolphins frequented 28 % of set nets and small numbers were present in fishing areas year-round. Although infrequent, dolphin bycatch was considered to have population level impacts. A pinger was trialled but had no effect on interactions. Dolphin depredation cost fishers thousands of euro annually, while landings were estimated to be far beyond those previously reported. A tool was developed to provide spatiotemporal activity data on small-scale fisheries and this tool was used to demonstrate potential conflict between seabirds, sea turtles and protected habitats in MPAs and in a Marine IBA. The results presented using anthropological surveys, strand monitoring, onboard observation, telemetry, vessel tracking and acoustic monitoring, will be useful in developing fisheries policy for North Cyprus and in directing Marine Spatial Planning. Novel techniques developed will be relevant in addressing fisheries interactions with marine megavertebrates in small-scale fisheries globally.
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