14 - USA: Protecting Mutton

Protecting Mutton Spawning Aggregations in the Dry Tortugas

In June 2009, the National Oceanic and The muton snapper, Lutjanus analis, migrates to specifics sites to form annual transient spawning aggregations in the tropical western Atlantic (Domeier et al. 1996; Lindeman et al. 2000; Heyman and Kjerfve 2008). Regrettably, previous fishery management strategies have not always considered the susceptible nature of reef fish spawning aggregations (FSAs), allowing them to be rapidly depleted by unregulated fishing activities (Aguilar-Perera 2006). In 2001 the Tortugas South Ecological Reserve (TSER) was established to alleviate pressure on a historical mutton spawning aggregation site. This area is considered a critical source of recruits to southeast Florida and the Florida Keys (Domeier 2004). Re-formation of the mutton spawning aggregation has been documented since the closure of the TSER (Burton et al. 2005) but little is known about adult fish movements within the Dry Tortugas region.

In May 2008, a study was initiated by Florida Fish and Wildlife Conservation Commission's Fish and Wildlife Research Institute (FWC) to determine movement patterns and spatial range of adult mutton snapper using telemetry. An array of 64 acoustic receivers was deployed throughout the Dry Tortugas region. This array covers approximately 800 square km2 and is designed to measure both small-scale movement and long-range migrations of tagged mutton snapper through a variety of benthic habitats. To date, 48 mutton snappers have been surgically implanted with coded transmitters. Some individuals have been documented making repeated migratory round trips of up to 50 km to the spawning grounds during the spawning season (maximum of 4 trips per individual). The greatest distance recorded, to date, of a tagged fish away from the aggregation site is 55 km. Preliminary results also indicate that FSA residency times by individual fish may span up to 16 days around the full moon from May to August. 

Thousands of mutton snapper are estimated to be present on the spawning grounds around the full moon, although smaller subgroups of 20 - 60 fish will break away from the main FSA during a spawning event. For the first time in Florida, subgroups of mutton snapper were observed spawning within the TSER in the late afternoon, 5 days after the full moon (see cover, top figure, a subgroup of mutton snapper spawning in Florida).

Information from this study will help establish the degree of connectivity between different management areas of the Dry Tortugas and determine the efficacy of those management areas for providing adequate habitat to encompass home ranges and migratory pathways of reef fish species. Future work will expand to other ecologically and economically valuable species, such as black grouper, Mycteroperca bonaci, that may also utilize this and possibly other sites yet to be discovered.

Danielle Morley
Florida Fish and Wildlife Conservation Commission
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Reference

Aguilar-Perer A. (2006). Disappearance of a Nassau grouper spawning aggregation off the southern Mexican Caribbean coast. Marine Ecology Progress Series, 327: 289-296.

Burton M.L., K.J. Brennan, R.C. Muñoz and R.O. Parker J. (2005). Preliminary evidence of increased spawning aggregations of mutton snapper (Lutjanus analis) at Riley's Hump two years after establishment of the Tortugas South Ecological Reserve. Fisheries Bulletin, 103: 404-410.

Domeiere M.L. (2004). A potential larval recruitment pathway originating from a Florida marine protected area. Fisheries Oceanography, 13: 287-294.

Domeier M.L., C. Koenig and F. Coleman. (1996) Reproductive biology of gray snapper (Lutjanus griseus) with notes on spawning for other western Atlantic snappers (Lutjanidae). In: Biology and culture of tropical groupers and snappers. F. Arreguin-Sanchez et al., (eds), p. 189-201. ICLARM Conference Proceedings 48, Makati City, Philippines.

Heyman W.D., B. Kjerfve. (2008). Characterization of transient multi-species reef fish spawning aggregations at Gladden Spit, Belize. Bulletin of Marine Science, 83: 531-551.

Lindeman K. C., R. Pugliese, G.T. Waugh, J.S. Ault. (2000). Developmental patterns within a multispecies reef fishery: management applications for essential fish habitats and protected areas. Bulletin of Marine Science, 66: 929-956.