Longline sampling off Destin, Florida between May 20 and June 3, 2017 revealed that the entangling leader performed as expected, reducing shark bycatch by 85% over control leaders (see Figure below). The blue bar is the number of leaders broken or sharks captured on entangling leaders and the orange bar is the number of sharks captured on control leaders. Although preliminary, when compared with experimental leaders, shark captures were over 700% greater on controls.
RECENT DEVELOPMENTS IN SHARK BYCATCH RESEARCH
Our work to produce an entangling leader has progressed nicely. Longlining and hook and line sampling during 2016 off of Destin, FL, Dauphin Island, AL and Ocean Springs, MS resulted in a number of sharks captured on control leaders with a number of break-offs on experimental. Tensile testing of monofilament versus polyethylene line (PE, also known as spectra, see Figure below) revealed that whereas monofilament required 5000 strokes of a simulated shark tooth to achieve failure of 300 lb (227 kg) test line, the same 300 lb test monofilament required no more than 20 strokes. With increasing load, PE line performance deteriorated rapidly (see Figure below). This was important to document and suggests that a simple change from monofilament to PE (spectra) during commercial fishing would significanty reduce the capture of sharks. With the help of our design engineer (who happens to be my son T.J., recently graduated with his mechanical engineering degree and now looking for a position) we now have a leader clip (see picture) that holds the loops of leader in place. Whereas we have been using a small strip of duct tape, which actually worked quite well, the adhesive on the tape tended to weaken over time and had to be replaced after a few sets of the longline. The new leader clip will allow fishers to rapidly re-spool the leader to continue fishing.