Estimated catch and mortality of sea turtles from the East Coast Otter Trawl Fishery of Queensland, Australia

Abstract

Trawling for penaeid prawns has been suggested to have major effects on the size of sea turtle populations in Australia and overseas. The numbers of turtles caught and killed in the Queensland East Coast Otter Trawl Fishery were estimated from a 2-year programme monitoring turtle captures in this commercial prawn trawl fishery. A sample of about 50 commercial fishers participated and reported an average catch rate of 0·068 turtles per day fished. Loggerhead Caretta caretta (50·4%), green Chelonia mydas (30·1%) and flatback Natator depressus (10·9%) turtles comprised the main species caught. An estimated 5295 ± 1231 turtles were caught annually by the Queensland East Coast Otter Trawl Fishery, which had an annual fishing effort of 80,558 days. About 1·1% of captured turtles were reported dead when landed. This mortality rate is lower than those reported for other trawl fisheries because in the Queensland East Coast Otter Trawl Fishery tow durations are short (<80 min) where turtles are commonly caught. Potentially, if all comatose turtles are assumed to die, the mortality rate of trawl caught turtles could be as high as 6·8%. However, the true mortality rate is probably somewhere between 1·1% and 6·8% of turtles landed because some commercial fishers resuscitate trawl-caught turtles.