Sea Turtles Study: The Impact of Pelagic Longlines on Loggerhead and Leatherback Sea Turtles

  • April 01, 2004
  • By Rebecca L. Lewison, Sloan A. Freeman, and Larry B. Crowder

The depletion of fish stocks from global fisheries has been a long-standing concern. More recently, incidental catch of non-target (termed bycatch) vertebrates also has been proposed as a serious conservation issue.

This paper presents a bycatch assessment for loggerhead and leatherback sea turtles that are incidentally caught by global pelagic longlines. It integrates catch data from over 40 nations and bycatch data from 13 international observer programs.

Despite infrequent rates of encounter, the analyses show that more than 200 000 loggerheads and 50 000 leatherbacks were likely taken as pelagic longline bycatch in 2000. The analyses suggest that thousands of these turtles die each year from longline gear in the Pacific Ocean alone. Given 80–95% declines for Pacific loggerhead and leatherback populations over the last 20 years, this bycatch level is not sustainable.

Adopting a large-scale, synthetic approach is critical to accurately characterize the influence of global fisheries bycatch on globally distributed and imperilled pelagic vertebrates.