Defense Date

8-9-2023

Document Type

Thesis

Degree Type

Master of Science

Degree Name

Marine Science

First Advisor

Dave Kerstetter, Ph.D.

Second Advisor

Joshua Feingold, Ph.D.

Third Advisor

Michael Schirripa, Ph.D.

Fourth Advisor

Eric Orbesen

Keywords

Juvenile swordfish, Post-release Mortality, Gulf of Mexico, Florida East Coast, Buoy Gear, Highly Migratory Species (HMS), Vertical Habitat Utilization

Abstract

Buoy gear used to target swordfish (Xiphias gladius) has become an increasingly popular commercial gear type throughout the United States fisheries in both the Atlantic and Pacific oceans. Buoy gear can be defined as a series of independent free-floating gear where each rig consists of at least one floatation device, a vertical mainline, and no more than two hooks. Because of the potential modifications to the component parts and deployment strategies, buoy gear has been hypothesized to decrease bycatch interaction and dead discard numbers by targeting specific depths of swordfish habitat throughout various times of the day. Under the Deepwater Horizon (DWH) Oceanic Fish Restoration Project (OFRP), commercial buoy gear fishing was analyzed through ecological and economic data collection. The DWH OFRP aimed to reduce fishing mortality of catch and bycatch of pelagic fish, through a six-month repose of pelagic longline (PLL) fishing by a portion of the Gulf of Mexico (GOM) PLL fleet. Although there have been studies evaluating swordfish post-release mortality (PRM) rates after commercial fishing gear interaction, little has been done to assess juvenile swordfish (<49in/119 cm LJFL) mortality rates after release from commercial buoy gear. Data collected by pop-off satellite archival tags (PSATs) was analyzed for PRM rates and vertical habitat utilization from 45 swordfish captured on buoy gear in the GOM and Florida East Coast (FEC). A suggested PRM from commercial buoy gear of 42.1% was found with a mortality rate of 60.5% of individuals who did not survive to the full 30-day tag expression. This suggest a survival rate of 57.9% of juvenile swordfish after post-release from commercial buoy gear. Management suggestions of potential gear modification is then suggested in order to increase the post-release survival rate of juvenile swordfish for the current regulations of the commercial buoy gear fishery in the Florida Straits.

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