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Fishery Bulletin 103(2) 



senior author completed over 115 dives on Riley's Hump 

 from 1995 through 2004, and the typical mutton snap- 

 per sighting during dives made outside the spawning 

 season (February, 5 dives; August, 5 dives; October, 7 

 dives) was a single fish. In these instances, the closest 

 approach allowed by the fish was 3 m, and when an 

 attempt was made to approach, the fish would swim 

 away, maintaining separation. The only exceptions to 

 this behavior were the four sightings in which groups 

 of fish were apparently unconcerned with the presence 

 of divers (Table 1). Johannes (1981) described a condi- 

 tion he termed "spawning stupor" in P. areolatus from 

 Palau. He took this term from the Palauan fishermen's 

 description of the fish as "stupid." We do not believe 

 that "stupid" in this context means unaware, but more 

 closely approximates Johannes et al.'s (1999) modified 

 description of spawning stupor as more of a lack of 

 concern about divers. Mutton snapper in the spawning 

 aggregation we observed seemed aware of our presence 

 because they approached and retreated from the divers 

 many times. Domeier and Colin (1997) asserted that 

 spawning or courtship behavior is easily broken off by 

 a diver's close approach or SCUBA exhalation, although 

 Johannes et al. (1999) offered evidence showing that this 

 is not always the case. We conducted our dive operations 

 primarily in the day and thus did not witness spawning, 

 which is thought to occur at dusk or later (Domeier and 

 Colin, 1997). Courtship behavior has not been described 

 for mutton snapper except by Domeier and Colin (1997) 

 who observed that fish in the Turks and Caicos aggrega- 

 tion "milled in a dense school from the bottom to within 

 a few meters of the surface." The mutton snapper we 

 observed exhibited this milling behavior and did not 

 change it because of our presence. 



Consistent timing of spawning with respect to a spe- 

 cific lunar phase has long been thought to be a char- 

 acteristic of many spawning aggregations. Johannes 

 (1978) noted that the majority of fishes with known 

 lunar-associated spawning rhythms spawned near the 

 full or new moon. However, the published literature 

 does not provide strong support for a correlation be- 

 tween spawning of most lutjanid species and any single 

 lunar phase. The lane snapper aggregation observed by 

 Wicklund (1969) occurred just after the new moon but 

 has not been corroborated since this single observa- 

 tion. Spawning of dog snapper in Belize was variable, 

 however, occurring three days after the new moon on 

 Cay Glory (Carter and Perrine, 1994) and just after the 

 full moon on English Cay (Domeier and Colin, 1997). 

 Spawning peaks for gray snapper off Key West, Florida, 

 were also variable, occurring on the new and full moons 

 of June-August, although the strongest spawning peak 

 was associated with the last quarter moon of August, 

 half way between the new and full moons (Domeier et 

 al., 1996). Back-calculated spawning dates of gray snap- 

 per collected in ichthyoplankton samples near Beaufort 

 Inlet, North Carolina, have indicated that spawning 

 takes place primarily at the time of the new moon and 

 secondarily at the time of the full moon (Tzeng et al., 

 2003). 



Evidence of mutton snapper spawning tends to sup- 

 port the argument that the species spawns during a 

 full moon, in contrast to the examples of other lutjanids 

 above. Mutton snapper aggregations off Gladden Spit, 

 Belize, peaked during the April and May full moons 

 and were heavily exploited by fishermen (Heyman et 

 al., 2001). Domeier and Colin's (1997) observation of a 

 mutton snapper aggregation off West Caicos occurred 

 on the April 1992 full moon, and Domeier collected 

 specimens with hydrated oocytes from the Riley's Hump 

 location within one day of the full moon in May 1991 

 (Domeier and Colin, 1997). Our observation of a small 

 group of about 10 mutton snapper at Riley's Hump in 

 July 2001 occurred three days before the new moon. 

 Our observations of groups of approximately 100, 200, 

 and 300 fish, however, occurred one day after the full 

 moons of May 2002 and June 2003, and two days after 

 the full moon of July 2004, respectively. In contrast, 

 the back-calculated spawning dates of mutton snapper 

 collected in icthyoplankton samples near Beaufort Inlet, 

 NC, indicated that spawning occurred from two days 

 after the full moon to three days before the new moon 

 and that peak spawning occurred between the full moon 

 and last quarter moon phase (Hare 3 ). These data are 

 not inconsistent, however, with our observations of fish 

 beginning to aggregate on or around the full moon for 

 spawning. Our sightings of such large groups of mutton 

 snapper around the full moon indicate activity associ- 

 ated with a spawning aggregation. 



Finally, many species of reef fishes consistently aggre- 

 gate to spawn at specific locations at regular intervals 

 (e.g., daily, annually). The two main hypotheses as to 

 why reef fishes do this are to offer increased chances 

 of 1) immediate survival of eggs and larvae, and 2) en- 

 trapment of larvae in favorable currents for transport 

 to suitable nursery habitat (Johannes, 1978; Lobel, 

 1978; Gladstone, 1994), although the former hypothesis 

 currently has more support (Hensley et al., 1994; Peter- 

 son and Warner, 2002). Without invoking the hypothesis 

 of local adaptation to the aggregation sites on Riley's 

 Hump, several studies have indicated that the physical 

 oceanography of the region is favorable for transporting 

 larvae spawned at Riley's Hump up the Florida Keys 

 reef tract (Lee et al., 1994; Lee and Williams, 1999) 

 and even as far north as Vero Beach, Florida (Domeier, 

 2004), presumably to suitable habitat. We believe that 

 the specific location on Riley's Hump where we observed 

 aggregations supports our conclusion that these were 

 spawning aggregations. 



In describing lutjanid behavior Thresher (1984) 

 said, "A key feature of reproduction ... is an extensive 

 spawning migration to select areas along the outer 

 reef." Observations in the literature of reef fish spawn- 

 ing aggregations occurring on the outer reef edge, on 

 seaward extensions or promontories, near the shelf-edge 



3 Hare, J. 2002. Personal commun. Center for Coastal 

 Fisheries and Habitat Research, National Ocean Service, 

 NOAA, 101 Pivers Island Rd., Beaufort, NC 28516-9722. 



