Study on the methods to mitigate the bycatch of juvenile bigeye tuna by introducing Double-FADs with light stimulus for tuna purse seine fishery in the Western and Central Pacific Ocean

A double-fish aggregating device (FAD) design was tested for its ability to mitigate the incidental capture of juvenile bigeye tuna (Thunnus obesus) in purse seine fisheries in the Western and Central Pacific Ocean. The design consisted of two separate FADs with underwater light stimuli attached. The number of animals caught was not large enough to conduct statistical analyses, but based on the weight of fish, the size proportion of skipjack (Katsuwonus pelamis), yellowfin (Thunnus albacares), and bigeye was bigger using the Double-FAD design compared to the standard design. The bycatch rate (proportion of total catch) of bigeye tuna was 6.1% and 7.2% using Double-FADs and 8.9% and 14.2% using standard FADs for numbers and weight respectively.  The proportion of skipjack tuna caught using the Double-FADs was 58.6% (number) and 29.1% (weight) compared to 72.4% (number) and 39% (weight) with the standard FAD.  The proportion of yellowfin tuna using the Double-FADs was 35.4% (number) and 63.7% (weight), while with the standard FAD, the proportion was 18.7% (number) and 46.8% (weight).  It appears this design has some effect on reducing bigeye tuna bycatch, despite the low sample size.