Thirty-five years of tiger shark Galeocerdo cuvier relative abundance near Bimini, Bahamas

Thirty-five years of tiger shark Galeocerdo cuvier relative abundance near Bimini, Bahamas, and the Southeastern United States with a comparison across jurisdictional bounds

Matthew J. Smukall, John Carlson, Steven T. Kessel, Tristan L. Guttridge, Félicie Dhellemmes, Andrew C. Seitz, Samuel Gruber

ABSTRACT:

Abundances of large sharks are reported to have declined worldwide, and in response various levels of fisheries management and conservation efforts have been established. For example, Marine Protected Areas have been suggested as means to protect large expanses of ocean from fishing and other industrial activities (e.g., habitat destruction), and in 2011 The Commonwealth of The Bahamas established The Bahamas Shark Sanctuary. However, assessing the effectiveness of conservation efforts is challenging because consistent long-term datasets of shark abundances are often lacking, especially throughout the Caribbean and The Bahamas. Here, we investigated the catch rates and demographics of tiger sharks Galeocerdo cuvier caught in a fishery-independent survey near Bimini, The Bahamas, from 1984 to 2019 to assess relative abundance trends following the banning of longline fishing in 1993 and the subsequent establishment of the shark sanctuary. To contextualize the relative abundance trends near Bimini, we compared this to the relative abundance of tiger sharks in a fishery-dependent survey from the Southeastern USA (SE USA), conducted from 1994 to 2019. Our data suggest that local abundance of tiger sharks has been stable near Bimini since the 1980s, including after the banning of longline fishing and the implementation of the shark sanctuary. In comparison, the abundance near the SE USA has slowly increased in the last decade, following potential declines in the decade preceding the USA Shark Management Plan. The results of this study provide some optimism that current conservation efforts in The Bahamas have been effective to maintain local tiger shark abundance within the protected area. Additionally, current fisheries management in the SE USA is allowing this species to recover within those waters.

Journal of Fish Biology, DOI: 10.1111/jfb.15067

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