Publication Date



Open access

Degree Type


Degree Name

Master of Science (MS)


Marine Biology and Fisheries (Marine)

Date of Defense


First Committee Member

Gary Thomas

Second Committee Member

Liana McManus

Third Committee Member

David Kerstetter

Fourth Committee Member

Eric Prince

Fifth Committee Member

Maria Villanueva


This thesis is composed of two studies: (1) an assessment of the vertical habitat use of swordfish Xiphias gladius in the Florida Straits; and (2) a systematic description of the southeast Florida recreational swordfish fishery. First, the vertical distribution of swordfish (Xiphias gladius) was assessed in relation to diel cycles and lunar phase from data gathered utilizing popup satellite archival tags (PSATs). Seven tags were deployed in the Florida Straits during this study from recreational and commercial fishing vessels; two fish died shortly after deployment, and the remaining five were included in the analysis. Tags were deployed for periods ranging from 120 to 151 days and recorded data on temperature, depth, and light level every ten seconds. Transmitted data was summarized into one hour histograms. Swordfish vertical distribution in response to diel cycles was characterized by typically spending daytime hours below 500 m and nighttime hours in waters less than 75 m. Swordfish distribution differed significantly in response to lunar phase, with animals occupying successively deeper depths in response to increasing lunar illumination. This study is consistent with the widely accepted hypothesis that the swordfish vertical distribution is a function of ambient light levels. However, in contradiction to this hypothesis was the observation of a number of daytime surfacing events recorded by the tags. This less pronounced but frequent behavior is hypothesized as a mechanism to warm the fish's body after extended daytime feeding dives to great depths. A recreational fishery targeting swordfish in southeast Florida has gained popularity in recent years. However, little data is currently available on the fishery and its participants. A survey was distributed to recreational swordfish anglers at local swordfish fishing club meetings and a swordfish fishing tournament to describe the fishery and its participants. Questions were organized into four sections: demographics, fishing habits, cost, and views on regulations. A total of 38 surveys were completed by anglers and included in the study. Recreational swordfish fishermen in southeast Florida were mainly Caucasian, with the largest group by percentage ranging from 41-50 years of age. Most fishers surveyed had over 20 years recreational fishing experience, with less than 10 years experience targeting swordfish. Anglers typically fished out of center console boats ranging from 21-35 feet, and usually made less than 50 trips per year. Costs associated with the fishery typically exceed those associated with general recreational saltwater fisheries by thousands of dollars (USFWS, 2006). Fishers were divided in their views on the current recreational swordfish regulations. Forty percent of anglers surveyed were unsatisfied, 37% were satisfied, and 23% remained neutral.


Big Game Fishery; Broadbill