A biologist o­n each vessel will spend the two weeks testing a new type of bait which may have the effect of reducing accidental capture of untargeted species (bycatch), specifically endangered sea turtles, o­n the hooks of commercial long line fishing vessels.

The biologists will work with fishermen o­n board the long line vessels and dye the bait blue in order to determine if it reduces the capture of sea turtles while at the same time maintains high catch rates of mahi mahi, the targeted fish species.  It is a test to see if the blue dye makes the bait less visible to species such as endangered sea turtles and sea birds, that apparently rely more o­n sight than smell, to find food. 

"Long line hooks capture any species that eat the bait, and we aim to find out if blue bait will reduce capture of endangered sea turtles and other bycatch, without affecting the capture of targeted species," says Randall Arauz, Director of PRETOMA who left Saturday o­n o­ne of the vessels. 

The study was designed by researchers in Hawai'i where similar studies have been conducted o­n commercial long line vessels.  Similar studies testing dyed bait, as well as hook and fishing gear modifications, have also been conducted in the Atlantic Ocean.  The study in Costa Rica is funded by a grant from the University of Hawai'i and is being conducted with the collaboration of Costa Rican commercial long line fishermen, PRETOMA and the Sea Turtle Restoration Project, a U.S. based marine conservation NGO.

The Costa Rican vessels are fishing mainly for mahi mahi in the Costa Rican EEZ and the bait used is calamari.  Sea turtles apparently avoid blue-dyed food in laboratory studies and this study aims to determine if sea turtles will avoid blue-dyed bait in the wild and therefore reduce sea turtle bycatch.  The calamari will be dyed blue in a non-toxic, natural food dye.  Lines of hooks stretch 30-40 kilometers behind the vessel with hooks approximately every 10 meters.  Half the time hooks will have blue dyed bait and half the time hooks will have normal calamari which is white.  At the end of the study, which will be conducted during eight 2-week expeditions, data will be analyzed to determine how effective the blue bait is at attracting targeted fish while reducing capture of bycatch.