COLIN: VARIATION IN MASS SPAWNING OF STRIPED PARROTFISH 



outer face of this pinnacle, the reef drops away 

 steeply and at a depth of 50-70 m becomes nearly 

 vertical in profile. 



In Jamaica S. croicensis occurred in foraging 

 groups similar to those described by Ogden and 

 Buckman ( 1973) in Panama. In the vicinity of the 

 spawning site only one sizeable foraging group 

 occurred. Although no tagging experiments were 

 carried out, this group almost surely constituted 

 the major portion of the spawning population 

 studied. During morning hours this group ranged 

 as much as 300 m inshore from the spawning area 

 onto the shallow reefs to depths of as little as 7 m. 

 They also ranged only about 100 m in either direc- 

 tion parallel to shore along the reef. 



These foraging groups consisted of several 

 hundred S. croicensis (the exact number being 

 impossible to determine in most cases) plus a few 

 other fishes. In one instance at least 410 individu- 

 als of S. croicensis were visible in photos taken of 

 the entire group. Only a few terminal phase males 

 were seen in these groups. The group swam about 

 1 m above the substrate in the A. cervicornis zone 

 and descended en masse at intervals to feed. Algae 

 were scraped from rock surfaces of the reef, par- 

 ticularly from the dead lower portions of the 

 branches of A. cervicornis. 



Mixed foraging groups consisting largely of S. 

 croicensis have been reported by Buckman and 

 Ogden (1973) and Itzkowitz (1974). In the former 

 two species of acanthurids (Acanthiirus chirurgus 

 dLXidi A . coeruleus); aham\et,Hypoplectruspuella; a 

 goatfish; and a few other parrotfishes were typi- 

 cally found associated with the foraging groups. 

 Similar composition of associated species was ob- 

 served in the present study. Only A. coeruleus 

 among the surgeonfishes occurred with the forag- 

 ing group. However, A. chirurgus is relatively 

 rare in the study area. A different species of ham- 

 let, H. indigo, also occurred with the foraging 

 group rather than H. puella. Among fishes ob- 

 served occasionally joining foraging groups and 

 not mentioned by Buckman and Ogden ( 1973 ) was 

 Halichoeres maculipinna. 



The functionality of such schooling behavior has 

 been commented on before. Various Indo-Pacific 

 surgeonfishes form schooling groups which be- 

 have much like the foraging groups of S. croicensis 

 (Jones 1968; Randall 1970; Barlow 1974). Randall 

 (1970), Barlow (1974), and Vine (1974) believed 

 this foraging herd was a method for the sur- 

 geonfishes to swamp the defenses of territorial 

 food competitors, in the former instance an acan- 



FlGURE 3. — Striped phase individuals of Scarus croicensis at 

 Discovery Bay, Jamaica, in the "contrast" color form (A) and 

 "gray" form (B). Standard length is approximately 100 mm. 



thurid and in the latter a pomacentrid. This also 

 seems to be the case in the present study. When 

 the foraging group entered the territory of Eupo- 

 macentrus planifrons, attacks were quickly di- 

 rected at a few members causing an escape reac- 

 tion in the few individuals near the center of 

 attack. The group was largely undisturbed by the 

 actions of the damselfish. 



Two color forms of striped phase S. croicensis 

 were seen in both foraging and spawning groups. 

 The first had two broad dark stripes separated by 

 thinner pale stripes, the dorsal surface dark and 

 the snout yellowish. This form is termed the "con- 

 trast" (Figures 1,3). The second color form, termed 

 the "gray" form does not have the sharp contrast 

 between dark and pale stripes (Figure 3). The 

 stripes are apparent on the head, but posteriorly 

 they become much less distinct. The scales near 

 the caudal peduncle, even in the center of the dark 

 stripe, are pale-edged and resemble a checker- 

 board pattern. In foraging groups one-fourth to 

 one-half of the indivuals had the gray color pat- 

 tern and the remainder were of the contrast pat- 

 tern. No functional role could be assigned to these 

 color forms. The possibility does exist that they 

 represent male and female, but this could not be 

 established. 



MASS SPAWNING BEHAVIOR 



Spawning occurred on the deep coral pinnacle 

 (Figure 2) of Dancing Lady Reef at 24 m depth. 

 This pinnacle is the feature with the greatest re- 



119 



