642 



Long-distance movement of a Nassau grouper 

 {Epinephelus stria tus) to a spawning 

 aggregation in the central Bahamas 



Stephania K. Bolden 



Southeast Fishery Science Center 



National Marine Fisheries Service, NOAA 



75 Virginia Beach Drive 



Miami, Flonda 33133 



E-mail address: slephania bolden a noaa gov 



Long Island, Fig. 1) to correlate with 

 spawning season. Mean monthly water 

 temperature was calculated for the 

 months of February 1998 (this inves- 

 tigation) and February 1989 (Colin, 

 1992). February 1988 data (Colin, 1992 1 

 were not available. 



Fish were continuously tracked by 

 their individual acoustic frequency 24 

 hours a day for a 3-week period. Sub- 

 sequent daily diver observations iden- 

 tified individual fish by their external 

 tags. 



Smith (1972) first reported Epinephe- 

 lus striatus (Nassau grouper) spawn- 

 ing aggregations. Since then, spawning 

 aggi'egations from a few dozen indi- 

 viduals to perhaps 100,000 individuals 

 have been reported from the Baha- 

 mas, Jamaica, Cayman Islands, Belize, 

 the Virgin Islands, and Mexico (Olson 

 and LaPlace, 1979; Colin et al., 1987; 

 Carter, 1988; Colin, 1992; Aguilar-Per- 

 era and Aguilar-Davila, 1996). Colin 

 (1992) investigated and documented 

 actual spawning of £. striatus off Long 

 Island, Bahamas. Colin et al. (1987) 

 and Sadovy et al. ( 1994) have provided 

 the only other observations of spawn- 

 ing aggregations of western Atlantic 

 serranid species (£. guttatus and Myc- 

 teropercci tigrist. 



Epinephelus. striatus spawning ag- 

 gregation sites are transient, site spe- 

 cific, and are usually known by local 

 fishermen who fish them intensely 

 during the spawning period. Epineph- 

 elus striatus spawn in the southern 

 Caribbean during the full moon of 

 December and January (Smith, 1972; 

 Olsen and LaPlace, 1979; Colin et al., 

 1987; Colin, 1992), and at more north- 

 ern locales (i.e. Bermuda) from May to 

 July (Bardach et al., 19.58). Jo hanne s 

 (1978) sugg ested that the period and 

 loc ation o f reef fi sh spaw ning is selecte d 

 to favor lar\'al survival: m o re recen tly 

 Colin (1996) has suggested that aggre- 

 gation sites may be "learned." Differing 

 densities of E. striatus at spawning 

 sites prior to, during, and following full 

 moon periods indicate that individuals 

 move to an aggregation site for a lim- 

 ited period oftime( Colin. 1992). Timing, 

 size, and sex composition of moving pre- 

 spawning individuals are unknown. 



Knowledge of the distance and direc- 

 tion of E. striatus movement to historic 

 spawning sites is based on Colin ( 1992) 

 where a single tagged specimen was 

 recaptured by a fisherman at a known 

 spawning site east of Long Island, Baha- 

 mas, after travelling approximately 110 

 km in two months. This contribution doc- 

 uments long-distance movement (220 

 km) of a tagged E. str-iatus to a spawn- 

 ing aggregation. 



Materials and methods 



The Exuma Cay Land and Sea Park 

 ( ECLSP. Fig. 1 ) was the study site for 

 an investigation of the home range of 

 E. striatus. The 456-km- ECLSP was 

 established in the central Bahamas in 

 19.58 and fishing was banned in 1986. 

 A total of eleven individuals were cap- 

 tured by traditional Bahamian fish 

 traps, tagged, and released for the home 

 range study during summer 1997. An 

 E. striatus (58.1 cm TL) captured on 24 

 June 1997, tagged on 25 June, held in 

 a fish trap and released at 24°18.8'N 

 and 76°33.6'W on 2 July 1997 was later 

 recaptured by a fisherman. 



Each fish had a unique Floy dart tag 

 (Floy Tag & Manufacturing. Inc., Seat- 

 tle, Washington) inserted below the 

 anterior dorsal-fin rays, between the 

 second and third scale rows. 



Each fish also had an acoustic trans- 

 mitter (VEMCO Limited, Nova Scotia, 

 Canada) surgically implanted into its 

 body cavity. 



Daily water temperature data were 

 obtained from Caribbean Marine Re- 

 search Center i CMRC ) at Lee Stocking 

 Island I approximately 120 km NW of 



Results 



The recaptured Nassau grouper was 

 tracked by ultrasound at its presumed 

 "home reef" from 2 to 31 July 1997. 

 Daily visual observations I by divers) 

 from 9 to 15 August confirmed the pres- 

 ence of the Nassau grouper at its home 

 reef The last observation was recorded 

 at the tagging locale on 16 August 1997 

 at the end of the field season. 



Three other individuals tagged dur- 

 ing the summer 1997 investigation 

 were observed at the exact patch reef 

 where they were tagged in summer 

 1998. Two of these tagged individuals 

 were considered to be mature adults 

 when tagged (47.1 cm TL and 44.1 

 cm TL). and the third was deemed a 

 juvenile (25.2 cm TL). Measurement 

 of two individuals indicated an annual 

 growth rate of 3-4 cm: from 47. 1 to 50. 1 

 cm TL, and from 25.2 to 29.0 cm TL. 

 Seven other E. striatus tagged during 

 summer 1997 were not observed during 

 summer 1998. 



A fisherman caught the tagged 

 individual on 16 February 1998 in a 

 fish trap at the Long Island, Baha- 

 mas, spawning location described by 

 Colin (1992) as the "south point aggre- 

 gation site" at 22''51.0'N and 74°51.5'W, 

 approximately 220 km (in a straight 

 ESE route) from the release point (Fig. 

 1). Physical features of the aggregation 

 site are described by Colin ( 1992). The 

 fish was at large for 185 days and was 

 caught in 18-21 m of water Because 

 fishing was limited during the period 

 "due to high seas and strong wind,"' 

 the exact date the fish entered the trap 

 or the soak time is unknown. 



Manuscript accepted 16 February 2000. 

 Fish. Bull. 98:642-64.5 (2000). 



