Bycatch records of marine turtles are examined from the waters surrounding the UK and Eire. The primary sources of data for this region are records held in the database 'TURTLE' (Pierpoint & Penrose 1999). Additional data have been gathered from marine mammal and discard monitoring programmes. Fishery interactions in other regions are reviewed and mitigation measures taken to reduce bycatch are also discussed.

 

TURTLE currently holds 712 records of marine turtles in UK and Irish waters and includes 154 records of turtle bycatch. Most bycatch records involve the leatherback turtle (94% of records identified to species), the species most frequently reported from UK and Irish waters. There are a small number of records of loggerhead, Kemp's ridley and hawksbill turtles. The most common method of incidental capture for leatherback turtles is entanglement in rope, particularly those used in pot fisheries targeting crustaceans and whelk. Rope entanglement occurs predominantly between July and October, on the north, west and south-west coasts of the UK and the south and west coasts of Eire. Of 83 capture records since 1980, entanglement in rope accounts for 36 records, 62% of leatherback bycatch for which the method of capture was specified. Recorded mortality was 61%; 11 turtles are known to have been released alive (30.5%). There are no data on injury or post-release mortality.

 

The database also includes records of leatherback capture in driftnets, trawls, set gill nets, purse seines and in longline fisheries. Data from marine mammal and fisheries monitoring programmes suggest that turtle bycatch in pelagic and demersal trawls, and in set gill nets in UK and Irish waters is uncommon. Bycatch of leatherback and loggerhead turtles is reported from pelagic driftnet fisheries however. The number of animals captured by the French tuna driftnet fleet in 1993 was estimated at 100 turtles (Gougon et al. 1993; SMRU 1996), most of which were leatherbacks. Turtle bycatch was also recorded by observers in the smaller Irish and UK driftnet fleets (E Rogan pers. comm.; SMRU, 1996). All turtles taken by French vessels in 1992 and 1993 were reported to have been released alive; recorded mortality on UK and Irish vessels was 25% and 17% respectively. No data are available for vessels of pelagic longline fleets that target tuna Thunnas spp. and swordfish Xiphias gladius in approximately the same area as French, Irish and UK driftnetters. High capture rates are reported from longline fisheries elsewhere in the North Atlantic and in the Mediterranean Sea (e.g. Witzell 1984, Aguilar et al. 1992; Camiñas et al. 1992; Johnson et al. 1999; Ferreira et al. in prep.).

 

Hence, marine turtles are prone to accidental capture by a wide variety of fishing methods. The highest known incidence of bycatch in UK and Irish waters is recorded for leatherback turtles in inshore pot fisheries and pelagic driftnets. The significance of marine turtle bycatch in the region is not known. Leatherback turtles are globally endangered however, and Spotila et al (1996) suggest that the impact of bycatch on Atlantic leatherback populations may be unsustainable.

 

Recommendations are made to further monitor and address the impact of fishery interactions in this region.