Is restricting catch to young sharks only more sustainable? Exploring a controversial management strategy for bull, tiger, blue and bonnethead sharks

Proper management of shark populations is an immediate concern due to their high vulnerability. In this study, we applied stochastic demographic models for four shark species (bull shark Carcharhinus leucas, tiger shark Galeocerdo cuvier, blue shark Prionace glauca and bonnethead Sphyrna tiburo) to test how population growth behaved under different exploitation scenarios, such as the exclusion of older sharks from fisheries. Populations grew at considerably slow rates when unfished, except for P. glauca. When fisheries targeted all individuals, populations started to decline at generally very low fishing mortality and harvest rates. Conversely, when adult individuals were excluded from fisheries, population resiliency increased despite higher fishing pressures, with no negative growth rates even if harvest levels were doubled. This study indicates that conservation of these species may benefit from protecting adult stocks.