The effect of hook type and trailing gear on hook shedding and fate of pelagic stingray (Pteroplatytrygon violacea): New insights to develop effective mitigation approaches
The pelagic stingray (Pteroplatytrygon violacea) in the French Atlantic bluefin tuna makes up almost half of the catch in numbers, ranking first of the five major species caught. Given the high levels of catches, more attention was given to the impact of this fishery in order to avoid future conservation issues. The effects of the hook shape (circle versus J-type hooks) and trailing gear on hook retention has been investigated on 10 individuals kept in captivity during 125 days. Experiments showed that the J-type hook used commonly by fishers had a fast self-shedding rate which will allow for a quick resumption of feeding and minimal injury which means quicker wound healing and better chance for survival. J-type hooks were all expelled within 6 days while circle hook shedding rates were much longer, taking 44.5 ± 54.4 days (mean ± SD). The mechanism of expulsion of the hook has been clearly described and the impact of the trailing line assessed. Appropriate handling practices maximizing the crew safety and the post-release survival were identified. Other effective mitigation approaches for the fishery are proposed and discussed.