Defense Date

4-3-2017

Document Type

Capstone

Degree Name

M.S. Marine Biology

Second Degree Name

M.S. Coastal Zone Management

First Advisor

Mahmood Shivji

Second Advisor

Tracey Sutton

Abstract

The shortfin mako (Isurus oxyrinchus) is a regionally endothermic lamnid shark with a circumglobal distribution in temperate and tropical waters. This species has special adaptations for a highly migratory, apex predator lifestyle, including specialized anatomical structures, the retia mirabilia, that allows maintenance of a higher than ambient internal body temperature, a higher percentage of red muscle fibers located closer to its body core compared to ectothermic sharks, and specialized dermal denticles to help achieve the remarkable swimming speeds for efficient predation. However, many parts of the life history of the shortfin mako are still unknown, and difficult to study due to the highly migratory nature and large size of these sharks.

Shortfin mako populations have declined in many areas of the world’s oceans as a result of a combination of exploitation pressures, including both directed fisheries and bycatch in teleost fisheries. Given these declines and conservation concerns, the shortfin mako is currently categorized as Vulnerable to extinction on the International Union for Conservation of Nature (IUCN) Red List. Although international agreements to protect the shortfin mako exist in the Atlantic, they lack the strength of punitive measures if signatory countries fail to comply with their responsibilities. Additionally, insufficient catch data from many nations prevent accurate population assessments, and in many areas the stock status of the shortfin mako is incompletely known or unknown.

Current national and international management efforts are insufficient to halt or reverse this declining population trend, in part due to a lack of knowledge about the sharks’ behaviors. Little is definitively known about feeding, movement, mating, or habitat use behaviors of these sharks. The relatively new scientific discipline of conservation behavior can inform fisheries management and conservation planning for this species. Increased research is needed to better understand the movement ecology of shortfin makos, including how they interact with each other, with other species, with the physical environment, and spatial fishing effort. This information, along with more accurate population assessments, will form the basis for future ecosystem-based management plans to conserve the shortfin mako throughout its range.

This capstone reviews the existing literature on the biology and behavior of the shortfin mako shark, and makes recommendations about how research on conservation behavior can potentially improve the population and conservation status of this key, marine apex predator.

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