Fisheries Ecology of Threatened Sharks in the Western Central Atlantic Ocean

Authors

Brendan Suneel Talwar, Florida International UniversityFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Biology

First Advisor's Name

Michael Heithaus

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

R. Dean Grubbs

Second Advisor's Committee Title

Committee Member

Third Advisor's Name

Jeremy Kiszka

Third Advisor's Committee Title

Committee Member

Fourth Advisor's Name

Alastair Harborne

Fourth Advisor's Committee Title

Committee Member

Fifth Advisor's Name

William Anderson

Fifth Advisor's Committee Title

Committee Member

Keywords

Sharks, fisheries, Caribbean, longline, silky shark

Date of Defense

11-10-2022

Abstract

In the western central Atlantic Ocean, fisheries threaten many sharks and rays through targeted and incidental capture. More information on their extinction risk, movements, abundance, and capture behavior is required to set management priorities, appropriately scale management efforts, and evaluate the effectiveness of management measures.

Thirty-six percent of shark and ray species in this region are threatened with extinction, primarily due to overfishing. The United States, Mexico, and Venezuela lead the region in historical catches and in conservation responsibility, yet only the United States is highly engaged with shark and ray management. In The Bahamas, longlining and shark fishing were banned. Long-term trends in the abundance of two coastal shark species, the tiger shark and Caribbean reef shark, suggested that these management decisions contributed to the stability and slight increase in catch rates of these species, respectively, since the late 1970s. Other fisheries-independent surveys in The Bahamas identified aggregation sites for threatened oceanic sharks, such as the silky shark and oceanic whitetip shark, suggesting some sites in The Bahamas offer them valuable refuge from fishing.

Still, these sharks are considered migratory, making them susceptible to fisheries outside of protected waters. For example, satellite tag data from silky sharks suggested that, although some individuals exhibit limited displacement, others travel thousands of kilometers through multiple jurisdictions. Large silky sharks tagged off eastern Florida, for example, traversed Bahamian, Cuban, and American waters, highlighting the need for multinational cooperation in managing their populations.

Where longline fishing occurs, these and other sharks can suffer at-vessel or post-release mortality despite retention bans. Mortality may be tied to on-hook behaviors that lead to stress and exhaustion, and these behaviors may be linked to distinct evolutionary traits, such as respiratory mode. Generally, fight intensity of longline-captured sharks over time was best described by a negative linear and positive quadratic response, with buccal pumpers exhibiting lower fight intensity than mixed-ventilators and obligate ram ventilators.

Taken together, these data improve our understanding of the fisheries ecology of sharks and highlight the need for improved fisheries landings data and regional collaboration to effectively manage sharks in the western central Atlantic Ocean.

Identifier

FIDC010870

ORCID

0000-0001-6014-5007

Previously Published In

Talwar, B.S., Anderson, B., Avalos-Castillo, C.G., Blanco-Parra, M.D.P., Briones, A., Cardeñosa, D., Carlson, J.K., Charvet, P., Cotton, C.F., Crysler, Z., Derrick, D.H., Heithaus, M.R., Herman, K.B., Koubrak, O., Kulka, D.W., Kyne, P.M., Lasso-Alcalá, O.M., Mejía-Falla, P.A., Morales-Saldaña, J.M., Naranjo-Elizondo, B., Navia, A.F., Pacoureau, N., Peréz-Jiménez, J.C., Pollom, R.A., Rigby, C.L., Schneider, E.V.C., Simpson, N., and Dulvy, N.K. (2022). Extinction risk, reconstructed catches, and management of chondrichthyan fishes in the Western Central Atlantic Ocean. Fish and Fisheries, 23 (5):1150-1179.

Talwar, B.S., Stein, J.A., Connett, S.M.H., Brooks, E.J. (2020). Results of a fishery-independent longline survey targeting coastal sharks in the eastern Bahamas between 1979 and 2013. Fisheries Research, 230:105683.

Talwar, B.S., Bouyoucos, I.A., Brooks, E.J., Brownscombe, J.W., Suski, C.D., Cooke, S.J., Grubbs, R.D., Mandelman, J.W. Variation in behavioral responses of sub-tropical marine fishes to experimental longline capture. ICES Journal of Marine Science. 2020. 77 (7-8):2763–2775. https://doi.org/10.1093/icesjms/fsaa146

Recommended Citation

Talwar, Brendan Suneel, "Fisheries Ecology of Threatened Sharks in the Western Central Atlantic Ocean" (2022). FIU Electronic Theses and Dissertations. 5208.
https://digitalcommons.fiu.edu/etd/5208