Review of Loggerhead Turtle (Caretta caretta) Bycatch and Technical Mitigation Measures in the Mediterranean Sea

Incidental catch by fishing gear is one of the major threats to the survival of the loggerhead turtle (Caretta caretta) in the Mediterranean Sea. The current paper reviews the turtle bycatch assessment and the gear parameters responsible for turtle capture and mortality, taking into account the possible mitigation measures tested in the Mediterranean Sea. Drifting longlines, bottom trawls and set nets (without considering illegal drift nets) are demonstrated to have the greatest impact on Mediterranean turtles. Nevertheless the type of impact strongly depends on fishing gear characteristics. Different types of fishing gear may induce different mortality rates and may affect different sea turtle ecological phases (pelagic or demersal). The bycatch assessment in different Mediterranean areas was reviewed evidencing the need of a method for homogenising the estimates of turtle bycatch. Most information available is focused on drift longlines but for some mitigation measures, Authors obtained different results in different areas: circle hooks have the potential to reduce turtle mortality only in certain fisheries and areas larger hooks are less likely to be swallowed by turtles due to physical constraints of the mouth, reducing the mortality rate and the catch of juveniles branchlines, once ingested, appear to be one of the major causes of sea turtle mortality; squid bait, which consistently catches more turtles than mackerel, and lightsticks, which strongly attract turtles, should be banned, at least in some areas and seasons. Only two studies were carried out in the bottom trawl where the Turtle Excluder Devices (TEDs) were tested with very good preliminary results. For set nets no practical solutions are available at this time.