FISHERY BULLETIN: VOL. 76, NO. 1 



lief for a distance of several hundred meters along 

 the outer face of the reef. Transects were swum 

 along the sloping face for 200-300 m each direction 

 from the study area while spawning was under- 

 way at that site and no other spawning aggrega- 

 tions were encountered. In one instance a group of 

 several S. croicensis were observed spawning on 

 the seaward face of a shallow reef immediately 

 west of Dancing Lady Reef at 18 m depth. 



The spawning population did not arrive en 

 masse at the spawning site, but rather appeared in 

 small groups over a lengthy period of time. 

 Whether the foraging group breaks up on the shal- 

 low reef before the individuals move to the spawn- 

 ing site is not known. The behavior of the striped 

 parrotfish after arrival at the spawning area con- 

 sists of swimming in small groups around the area 

 within a few meters of the bottom ("milling") and 

 bouts of feeding (from the substrate). 



The size of eight individuals speared from the 

 spawning aggregations varied between 80 and 100 

 mm SL, relatively small for mature specimens. 

 These are deposited in the University of Puerto 

 Rico fish collection (UPR 3452). This sample is 

 biased for small individuals since these were most 

 easily approached and the mean size of specimens 

 in the aggregation was certainly near or over 100 

 mm SL. 



The numbers engaged in milling and the speed 

 and frequency of turns gradually increased. Often 

 groups of 20 or more individuals broke away from 

 the main group and swam as a school farther 

 above the substrate than the milling individuals 

 (Figure 4A, B). The separated group swam in- 

 creasingly rapidly making abrupt lateral turns 

 ("weaving"). The entire group or a portion of it 

 rushed upward extremely rapidly a distance of 

 several meters (Figure 4C, D) releasing eggs and 

 sperm at the peak of the "rush." They returned to 

 the substrate nearly as rapidly (Figure 4E). Be- 

 cause of the large numbers of individuals present 

 in the spawning aggregation, several separate 

 weaving groups could be present and rush at near 

 the same time. Rushes by some weaving groups 

 began at the level of at least 3 m above the sub- 

 strate as they were level with the observers' line of 

 sight. 



From analysis of motion pictures of spawning 

 behavior the number of fish engaged in a rush 

 varied between 5 and 30 with the mean number 

 about 15 individuals. Generally only about one- 

 half of the group engaged in weaving actually 

 participated in the rush and often a few individu- 



als starting the upward rush were left behind. The 

 entire upward rush and return to the level of the 

 weaving group took <1 s. Of seven rushes which 

 were filmed in their entirety the time for the up- 

 ward movement varied between 0.21 and 0.40 s 

 and for the return 0.20 and 0.40 s. One rush with 

 return occupied only 0.45 s total. Assuming a dis- 

 tance of 3 m was covered during the upward rush 

 (probably a conservative estimate), the average 

 speed from leaving the weaving group until turn- 

 ing at the point where the gametes are released 

 was around 40 km/h. 



The sexual composition of the rushing groups 

 has not been determined. Randall and Randall 

 (1963) believed that the spawning groups of 

 Sparisoma rubripinne were predominantly males 

 and that a single female participated in the 

 spawning rush with 3 to 12 males. 



A single terminal phase male Scarus croicensis 

 was present at the spawning site. This fish vigor- 

 ously defended a territory near the outer edge of 

 the coral pinnacle and patrolled the area in the 

 "bob-swim" manner with the caudal fin upturned 

 as described by Barlow ( 1975). No attempts at pair 

 spawning with striped phase females by this fish 

 were observed. The only other parrotfish observed 

 on the deep coral pinnacle was Sparisoma viride 

 with only a few present. 



SPAWNING FREQUENCY 



The frequency of rushes during the daily periods 

 for both January and June is presented in Figure 

 5. The summer spawning begins earlier in the day, 

 continues later, and has a higher frequency of 

 rushes than during the winter. It is impossible to 

 determine the number of eggs released per rush 

 and whether differences exist between summer 

 and winter. No data are available concerning the 

 number of fish participating in rushes during 

 winter, but observations suggest this was also 

 lower. 



Considering an equal number of eggs are expel- 

 led on each rush, it appears that the production of 

 eggs by this population of Scarus croicensis is 

 about six times greater during a summer day than 

 winter on the basis of the area beneath the curves 

 derived from Figure 5. It is likely that S. croicen- 

 sis, at least in the Caribbean, spawns year round, 

 but the warm months are the most important 

 period of egg production. 



During the summer the occurrence of spawning 

 rushes might be referred to as epidemic. When the 



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