There are four approaches to solving the shark bycatch problem: (1.) Reduce or eliminate commercial fishing, (2.) prevent the shark from taking the hook at all, (3.) facilitate release of the shark as soon after hooking as possible, and (4.) reduce stress of the shark while it is hooked thereby increasing survivorship of the animal upon release.
Approach #1 is likely unattainable (or even desirable for some) and approach #2 has been met with poor success (i.e. repellents to make fishing baits unpalatable for sharks have not worked well). We have taken the approach that a leader that will effect immediate release of a hooked shark (#3) has the highest probability of success and/or a hook/leader that reduces stress (#4) to the captured animal could be developed.
The Entangling Leader:
We have researched the application of a leader that simply "spools out" when the bait is taken by a typical fish such as a tuna or swordfish. However, when a shark takes the hook, the leader entangles on the sharks blade-like teeth, which compromises the integrity of the line and encourages the line to break. In this way the shark swims away unharmed (a steel hook will quickly rust away and disappear from a sharks mouth). Preliminary testing has been promising but we need to conduct additional research to determine the best configuration and demonstrate the efficacy of this leader.
Sedation to Lessen Stress:
Aside from the above entangling leader we are also investigating the use of a mild, cheap sedative to lessen the stress of capture such that released sharks will enjoy increased survivorship after capture.