Graduation Year

2009

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Marine Science

Major Professor

David A. Mann, Ph.D.

Keywords

Lutjanus campechanus, Epinephelus morio, Undersized bycatch, Management implications, Ecomorphology

Abstract

Although closed seasons, bag limits and quotas are used to manage fishes within the Grouper/Snapper Complex off the southeastern United States, size limits are the cornerstone of fisheries management. Because fishers must release all undersized fishes despite fish condition, this regulation has created a mandatory catch and release system. Inherent in this management strategy is the supposition that these undersized fish survive in sufficient numbers so as to justify this regulation. To satisfy this criteria fish mortality must be low and released fish must also experience minimal sub-lethal effects. Determination of sublethal effects and evaluation of their potential impairment and duration of injury are required to develop effective physiology-based criteria to evaluate the efficacy of the minimum size rule. The goal of this research was to evaluate some aspects of the efficacy of the minimum size rule in the red grouper and red snapper fisheries off Florida by collecting traditional fisheries data and analyzing it in light of fish physiology, ecomorphology and behavior.

Study objectives included 1) determination of the causes for the differences of hook mortality for red grouper and red snapper in the recreational and recreational-for-hire fisheries by necropsy of acute and latent mortalities, analysis of tag and recapture data for both J and circle hooks, determination of fish dentition and any differences in feeding behavior, 2) examination of the effects of rapid depression from depth on fish survival by inspection and comparison of the red grouper and red snapper swim bladders in both healthy and swim bladder ruptured fish from various water depths, comparison of tag and recapture data, investigation of the effects of fish venting, and laboratory simulations using fish hyperbaric chambers to determine healing and survival from rapid depression trauma, 3) analysis of movement patterns of tagged fish and 4) evaluation of some of the consequences imposed by the minimum size limit based on study results.

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