Part 1: Permit Spawning Aggregation Dynamics & Predator Ecology Research

Program Overview

The purpose of this research is to monitor permit spawning aggregations on natural and artificial reefs in the Florida Keys, collecting data on aggregation size and distribution, fishing pressure, and depredation mortality.

Expedition Summary

From March 16-28, 2024, The International SeaKeepers Society assisted researchers from Florida International University and Carleton University in conducting research on permit (Trachinotus falcatus) spawning aggregations and associated predators in the Lower and Middle Florida Keys. Permit aggregate on natural and artificial reefs in the Keys surrounding the full moons from March through June each year. Catch-and-release angling for permit during their spawning season has become a popular sport fishery for many anglers, and, although not inherently detrimental to the fishery since permit harvest is prohibited between April 1 and July 31 throughout the Florida Keys, depredation (i.e., the removal of hooked fish by a predator) has produced a high level of concern regarding the sustainability of this practice. As a result, Florida Fish and Wildlife Conservation Commission implemented a seasonal fishing closure from April 1 – July 31 each year at Western Dry Rocks (WDR), where depredation mortality has been historically high, to protect permit and other species that aggregate here.

To evaluate the size and ecology of permit aggregations, monitor fishing pressure and depredation mortality, and assess predator foraging ecology of these aggregations in the Florida Keys we use a combination of methods. Video (unbaited and hemispherical cameras and line-mounted cameras) and hook-and-line fishing surveys are conducted to gather data on predator occurrence, permit abundance, individual fish size, diet and genetics. The movement and residency of permit are monitored using acoustic telemetry, where individual fish are tagged and underwater receivers are deployed at known aggregation sites. Observational data on fishing pressure (i.e. number of fishing boats, time spent fishing) and depredation rates (i.e. number of angled permit lost to sharks) at openly fished sites is also collected. Lastly, we assess shark movements and foraging ecology through acoustic tagging and biological sampling methods.

Some highlights from data collected on this trip:
• Our initial results from the video data suggest that permit abundance ranged from several hundred to over one thousand individuals at WDR in the Lower Keys.
• The range of permit sizes (57-73 cm fork length) was similar to previous seasons in the Lower Keys (average 66 cm fork length).
• We collected 10 cloacal swabs, which will be used to analyze permit fecal DNA and assess their diet during the spawning season, and 10 fin clips from permit, which will contribute to an assessment of permit genetic connectivity throughout Florida.
• Observed fishing pressure in the Middle Keys was not focused on permit and instead targeted other bottom fish (i.e. mutton snapper). In the Lower Keys, we observed 1 boat/day targeting permit, which occurred at pre-closure Western Dry Rocks (WDR).
• We observed several shark species, including great hammerhead (Sphyrna mokarran; min. 2 individuals), Caribbean reef (Carcharhinus perezi; min. 4 individuals), bull (C. leucas; min. 1 individual), lemon (Negaprion brevirostris; min. 1 individual), and nurse sharks (Ginglymostoma cirratum; min. 1 individual).