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NCCOS Project

Location and Status of Reef Fish Spawning Aggregations in the Florida Keys

This project began in January 2009 and is Ongoing

We are identifying and surveying historical and recently reported reef fish spawning aggregations in the Florida Keys National Marine Sanctuary. Spawning aggregations are critical to sustaining fish population and healthy reef ecosystems. This research is supporting zoning and regulatory review by the Florida Keys National Marine Sanctuary.

Why We Care
Many types of reef fish, like snapper and grouper, gather in large groups to reproduce. These groups are called fish spawning aggregations (FSAs). These aggregations attract anglers, making aggregating species particularly vulnerable to overfishing. Many aggregations in the Florida Keys (and worldwide) have been reportedly overfished or “fished out.”  Only a few of the known FSAs in the Florida Keys are within protected no-take areas or reserves. The identification of FSA locations, along with assessment and monitoring of FSAs, are critical steps toward enabling the sustainable management of commercially important species that aggregate to spawn, not only for the economies they support through fishing and ecotourism, but also for the sustainability and health of the coral reef ecosystem.

What We Did
In partnership with National Marine Fisheries Service’s (NMFS) Southeast Fisheries Science Center, the Florida Keys National Marine Sanctuary (FKNMS), and the state of Florida, we:

  1. Collected locations and descriptions of historical FSAs (some reported as “fished out” by anglers decades ago) from previous research and interviews of recreational and commercial anglers.
  2. Surveyed these locations using splitbeam and fishery multibeam sonars (akin to “fish finders”) to characterize geomorphological signatures of the seafloor and remotely detect large aggregations of fish in the water column during the predicted lunar period (e.g., full moons) and season for the species of interest.
  3. Deployed science divers at each location to record fish species observed, fish sizes, and fish behavior indicative of spawning activity.

What We Found

  • We have observed large aggregations of a variety of species throughout the Florida Keys.
  • At several reefs near Key West, Florida, we repeatedly observed hundreds to thousands of gray snappers aggregating on consecutive full moons during summer spawning periods.
  • Although we have not directly observed spawning by any species, we have found fish aggregating in great numbers and exhibiting several behaviors and colorations only shown during spawning events.
  • Our data have also shown that these large aggregations of commercially important species (such as mutton and cubera snappers) are under extreme fishing pressure, with as many as 40 fishing vessels angling at a single aggregation site.
  • There seem to be similar bottom features or “habitat signatures” for several FSAs that are not described by current habitat maps or bathymetric/nautical charts.

Next Steps
The interest in this research continues to grow in the Florida Keys (and elsewhere) as we interact with more anglers that are concerned about the high exploitation of aggregating reef fish species. We are continually updating our database of reported FSAs in the Florida Keys through interviews with anglers and our own observations. Our geospatial data and database of field observations are being shared with our partners at FKNMS and their Advisory Council for use in the review of their management zone (e.g., special protected areas) and regulatory process. The South Atlantic Fishery Management Council is also using our observations in management options to reduce overfishing of mutton snappers in the Florida Keys region. We are testing new applications of acoustic technologies like splitbeam and multibeam sonar for detecting and assessing the abundance and distribution of fish aggregations and the habitats in which they reside.

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