404 



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 



Michael L. Burton 



Kenneth J. Brennan 



Roldan C. Munoz 



Richard. O. Parker Jr. 



Center for Coastal Fisheries and Habitat Research 



National Marine Fisheries Service 



National Oceanic and Atmospheric Administration 



101 Pivers Island Rd 



Beaufort. North Carolina 28516-9722 



E-mail address Michael.BurtoniSnoaa.gov 



In this note we describe the re-for- 

 mation of a spawning aggregation of 

 mutton snapper {Lutjanus analis). A 

 review of four consecutive years of 

 survey data indicates that the aggre- 

 gation may be increasing in size. 

 Mutton snapper are distributed in 

 the temperate and tropical waters of 

 the western Atlantic Ocean from Flor- 

 ida to southeastern Brazil (Burton, 

 2002). Juveniles and subadults are 

 found in a variety of habitats such 

 as vegetated sand bottoms, bays, and 

 mangrove estuaries (Allen, 1985). 

 Adults are found offshore on coral 

 reefs and other complex hardbottom 

 habitat. They are solitary and wary 

 fish, rarely found in groups or schools 

 except during spawning aggrega- 

 tions (Domeier et al., 1996). Spawn- 

 ing occurs from May through July at 

 Riley's Hump (Domeier et al., 1996) 

 and peaks in June, as indicated by 

 gonadosomatic indices (M. Burton, 

 unpubl. data). Mutton snapper are 

 highly prized by Florida fishermen 

 for their size and fighting ability, and 

 the majority of landings occur from 

 Cape Canaveral, , through the Flor- 

 ida Keys, including the Dry Tortugas 

 (Burton, 2002). 



Reports of spawning aggregations 

 of tropical reef fishes are abundant 

 in the fisheries literature. Most docu- 

 mented aggregations of commercially 

 important fishes are attributed to 



members of the grouper family, Ser- 

 ranidae, including observations of 

 spawning Nassau grouper iEpineph- 

 elus striatus), red hind (E. guttatus), 

 and tiger grouper {Mycteroperca ti- 

 gris) in the Caribbean (see review in 

 Domeier and Colin, 1997, and refer- 

 ences therein). Eklund et al. (2000) 

 observed black grouper (M. bonaci) 

 aggregating during their spawning 

 season just outside no-take zones 

 along the Florida Keys reef tract. 

 Samoilys and Squire (1994) and 

 Samoilys (1997) documented spawn- 

 ing aggregations of coral trout (Plec- 

 tropomus leopardus) from the Great 

 Barrier Reef, and Johannes (1988) 

 described the aggregating behavior 

 of squaretail coralgrouper (P. areola- 

 tus) from the Solomon Islands. Most 

 recently, Sala et al. (2003) observed 

 aggregating behavior in two species 

 of serranids — the sawtail grouper 

 (M. prionura) and the leopard grou- 

 per (M. rosacea) from the Gulf of 

 California. 



There are fewer descriptions of 

 spawning aggregations of the com- 

 mercially important snappers (Lut- 

 janidae) in the literature. Wicklund 

 (1969) described spawning behavior 

 of lane snapper {Lutjanus synagris) 

 from southeast Florida, Carter and 

 Perrine (1994) described a spawning 

 aggregation of dog snapper (L. jocu) 

 from Belize, and Sala et al. (2003) 



described spawning behavior in two 

 lutjanids from the Gulf of California 

 (yellow snapper, L. argentiventris; Pa- 

 cific dog snapper, L. novemfasciatus). 

 Mutton snapper (L. analis) are per- 

 haps the best known snapper to form 

 spawning aggregations. Craig (1966) 

 observed concentrated commercial 

 fishing on an apparent "spawning 

 run" of mutton snapper in August at 

 Long Cay, Belize. Domeier and Colin 

 (1997) described an aggregation of 

 L. analis in the Turks and Caicos 

 Islands in April 1992, and Domeier 

 et al (1996) identified a spawning ag- 

 gregation at Riley's Hump. 



Because of their predictable nature 

 with respect to location and time, 

 spawning aggregations become ex- 

 tremely vulnerable to heavy exploi- 

 tation once discovered by fishermen. 

 The majority of annual catches of 

 Nassau grouper in some areas comes 

 from annual spawning aggregations 

 (Colin, 1992; Aguilar-Perera and 

 Aguilar-Davila, 1996), whereas other 

 aggregations have been completely 

 extirpated (Olsen and LaPlace, 1978; 

 Sadovy and Eklund, 1999; Heyman, 

 2003). Russ (1991) observed that 

 uncontrolled fishing on spawning 

 aggregations could lead to recruit- 

 ment overfishing. During a May 1991 

 survey of Riley's Hump, a site of a 

 known mutton snapper spawning ag- 

 gregation in the Dry Tortugas, Flor- 

 ida, Domeier and Colin (1997) noted 

 that fish were more scattered and far 

 less abundant than they were at the 

 Turks and Caicos site. The authors 

 suggested that this difference was at- 

 tributable to heavy commercial fish- 

 ing pressure at Riley's Hump during 

 the several years prior to 1991. 



Although recent literature indi- 

 cates that fishing pressure on Riley's 

 Hump has been intensive for several 

 years prior to 1991 (Domeier and 

 Colin, 1997), anecdotal information 

 indicates otherwise. According to a 

 commercial hook-and-line fisherman 

 who fished on Riley's Hump from 

 1978 through 2001, the first known 



Mansucript submitted 20 December 2003 

 to the Scientific Editor's Office. 



Manuscript approved for publication 



29 December 2004 by the Scientific Editor. 



Fish. Bull. 103:404-410 (2005). 



