Date Awarded

2018

Document Type

Thesis

Degree Name

Master of Science (M.Sc.)

Department

Virginia Institute of Marine Science

Advisor

John E Graves

Committee Member

Richard W Brill

Committee Member

Christopher J Hein

Committee Member

Andrij Z Horodysky

Abstract

Cobia (Rachycentron canadum) is a cosmopolitan marine fish inhabiting tropical, sub-tropical, and temperate marine and estuarine waters. Recent changes in U.S. cobia management have sparked controversy and highlighted limitations in our understanding of seasonal movement patterns and problems with estimating recreational harvests. Consecutive years (2015 and 2016) of estimated overharvests from the Atlantic Migratory Group stock triggered accountability measures to prevent overfishing by recreational anglers. My project employed pop-up satellite archival tags (PSATs) to study cobia movements, habitat utilization, and post-release survival. It was, therefore, designed to enhance knowledge of cobia biology and aid sustainable management. We deployed 36 PSATs on cobia caught in Virginia state waters using standard recreational techniques in August 2016 and August – September 2017. All fish larger than 37- inches total length were tagged, and several of these were deep-hooked. No mortalities were inferred from the 24 cobia whose PSATs reported. Only five PSATs remained attached until the 180-day programmed release date. This made it difficult to accurately describe cobia seasonal movement patterns, although it appears that areas near North Carolina's continental shelf break may be important overwintering habitat. Other overwintering areas may exist, however, as some fish made longer migrations, and one PSAT reported in Florida waters (beyond the current stock demarcation boundary). Cobia have a strong affinity for waters ≥20°C, even in the coldest months. They also display distinct seasonal differences in vertical movement patterns which make them more susceptible to capture in the summer when Virginia recreational anglers often employ sight-fishing techniques.

DOI

http://dx.doi.org/10.25773/v5-ega0-mp97

Rights

© The Author

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