Policy simulations showed that retention bans could reduce shark mortality three-fold, on average, but that this wasn’t enough to reduce mortality to sustainable fishing levels for already heavily fished species, like mako and silky sharks. “Retention bans are a beneficial first step towards addressing shark overfishing,” said Bradley, “but they need to be complemented with other strategies, such as area-based fishing restrictions, catch quotas and fishing gear requirements to sustain populations for many shark species.”
Bans are most likely to benefit species with faster reproductive rates — like blue sharks, bonnetheads and angel sharks — because their populations tend to recover faster. The blue shark is actually the most heavily fished species worldwide. “While it is highly unlikely that retention bans will ever be implemented for such a commercially important species,” Feitosa said, “our results show that this could be a relatively simple and impactful strategy if it becomes necessary to sustain populations.”
For other sharks, maintaining healthy populations will require additional strategies. Methods to reduce catch rates to begin with — such as banning the use of steel wire on longlines — could complement retention bans. Spatial regulations could also help bolster shark populations, such as closing off shark nurseries and pupping grounds.