Marine & Environmental Sciences Faculty Proceedings, Presentations, Speeches, Lectures

Post-Release Survival and Habitat Utilization of Juvenile Swordfish in the Florida Straits

Event Name/Location

63rd Annual Tuna and Billfish Conference, Los Angeles, California, May 21-24, 2012

Presentation Date


Document Type

Conference Proceeding




The use of pop-up satellite archival tags (PSATs) eliminates many of the limitations associated with acoustic and conventional tags by using fishery-independent data collection and retrieval. Previous research techniques have provided information on longer-term movements, migrations, and behavior patterns, but there is still a need for additional tagging studies with “second generation” tags with depth and light data and increased memory that will further define the short-duration activity patterns and habitat utilization of juvenile swordfish in the western North Atlantic. PSATs have been successfully used on other large pelagic fishes, but have yet to be used on juvenile swordfish.

This project investigates two topics: a) the post-release survival rates of juvenile swordfish after being released from the recreational rod-and-reel fishery and commercial swordfish buoy gear fishery in the Florida Straits, and b) the habitat utilization of juvenile swordfish following release. High-resolution PSAT technology is being used to estimate the post-release survival of 20 individual juvenile swordfish captured with standard recreational or buoy fishing gear and techniques in the southeast Florida swordfish fishery. To date, 16 of the 20 tags have been deployed. Analysis of release mortality estimates is being done using the “Release Mortality” Program. A deterministic, periodic model is being developed to fit to the data and describe the fishes’ habitat utilization. This model has four amplitude parameters, two each for the daily and lunar cycle, and a mean depth value. This model will aid in identifying any diurnal and lunar signals in the data as well as any patterns in the residual data. Data gathered by the PSATs will also be used to analyze behavioral interactions with the fishing gear, such as habitat utilization patterns, and compared with other descriptions of swordfish behavior.

This study is a collaborative effort with the local recreational and buoy swordfish fisheries, utilizing local fishermen to conduct the field work. Data from this study will help to identify habitats most used by juvenile swordfish and their movement patterns. The data from the tags will also provide experimentallygenerated estimates of fishing mortality. Data from this study will also aid in determining better management practices in terms of the efficacy of mandatory release of undersized fish.

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