FISHERY BULLETIN: VOL. 87, NO. 4, 1989 



as 650 mm FL for uku and 450 mm FL for onaga 

 in the main Hawaiian Islands, indicating that, 

 for onaga, the present fishery is capturing indi- 

 viduals that have not yet reached sexual matur- 

 ity. Continuing this practice could lead to a ser- 

 ious decline in spawning stock biomass (Polovina 

 1987). 



Sex ratio also differed between the two 

 species. The ratio of male to female uku was 

 judged not significantly different from the ex- 

 pected ratio of 1:1. In contrast, the onaga sex 

 ratio was significantly different from unity in 

 favor of males. Females dominated in the larger 

 size classes for both species. The preponderance 

 of large females has also been reported for other 

 snapper species, including Lutjanus synagris 

 (Reshetnikov and Claro 1976), R. aurorubens 

 (Grimes and Huntsman 1980), and E. carbun- 

 culus (Everson 1984). This phenomenon is 

 thought to be due to differential mortality of the 

 sexes rather than to growth (Wenner 1972; 

 Grimes and Huntsman 1980). The preponder- 

 ance of male onaga in the smaller size ranges is 

 more difficult to explain and may reflect inter- 

 sexual behavioral differences. If smaller males 

 feed more aggressively, they would be overly 

 abundant in the catch. Differences in feeding 

 behavior may also explain monthly variations in 

 sex ratio reported for both species. The ratio of 

 female uku increased markedly at the close of 

 the spawning season, suggesting a heightened 

 vulnerability to the fishing gear owing to what 

 may be greater nutritional demands of post- 

 spawning females. Seasonally, the largest catch 

 of uku occurs in summer (May-October), when 

 fish are thought to form spawning aggi-egations 

 (Ralston, fn. 2). 



Numerous investigators have suggested that 

 snappers are multiple spawners, based upon the 

 presence of multiple size modes of developing 

 oocytes (Min et al. 1977; Grimes and Huntsman 

 1980; Everson 1984; Kikkawa 1984; Grimes 

 1987). Other evidence reported as substantiating 

 this phenomenon has been the wide variations 

 exhibited in GSI's of L. griseus (Starck and 

 Schroeder 1970) and R. aurorubens (Grimes and 

 Huntsman 1980) during the spawning season. 

 Ralston (1981) suggested that P. filamentosus is 

 a multiple spawner because the ovaries of ripe 

 females make up only about 4% of the total body 

 weight, a relatively small percentage compared 

 with that of a single spawning temperate 

 species. These observations, the presence of 

 multiple size modes of developing oocytes and 

 the wide variations in GSI's, were noted for uku 



and onaga and suggested that these species also 

 spawn repeatedly during the spawning season. 

 Although it has been documented that the oocyte 

 size-frequency distribution of many snapper 

 species contains two or three distinct modes, the 

 exact number of batches spawned per season is 

 rarely reported. This is because the process of 

 recruitment from the undifferentiated oocyte 

 pool is dynamic and difficult to characterize 

 (Grimes 1987). 



Much of the above evidence is largely con- 

 tingent on the assumption that multiple oocyte 

 modes continue to develop and are successively 

 spawned. Foucher and Beamish (1980) observed 

 that, for Pacific hake, Merluccius productus, 

 from the Strait of Georgia, oocyte development 

 was multimodal during the spawning season, 

 suggesting multiple spawning for this species. 

 Histological examination of the ovaries revealed, 

 however, that only the largest batch became 

 hydrated and was spawned and all remaining 

 residual yolked oocytes were resorbed. More 

 direct evidence for this mode of spawning, as 

 well as the delineation of the number of batches 

 spawned, has been obtained through the process 

 of identifying and ageing postovulatory follicles 

 in species that exhibit these multiple modes of 

 oocyte development. This method has been used 

 to estimate spawning frequency in several en- 

 graulid species (Hunter and Goldberg 1980; 

 Hunter and Macewicz 1980, 1985; Albeit et al. 

 1984; Parrish et al. 1986; Clarke 1987) and also 

 for the skipjack tuna, Katsuwomis pelamis 

 (Hunter et al. 1986). Ageing postovulatory fol- 

 hcles seems to work well for species normally 

 found in large aggregations or schools but has 

 yet to be applied to snappers. The ageing 

 method using postovulatory foUicles may be 

 more difficult to apply to such species as snap- 

 pers, which are known to occur in fewer num- 

 bers. Although our study attempted to identify 

 postovulatory follicles in natural populations of 

 uku and onaga, they could not be positively iden- 

 tified or aged. Future studies will have to 

 address this problem, since the delineation of 

 spawning frequency is important for accurate 

 fecundity estimates. 



ACKNOWLEDGMENTS 



This study would not have been possible with- 

 out the assistance of the staff at United Fishing 

 Agency; Wing Sing, Inc. ; Tropic Fish and Vege- 

 table Center, Inc.; Fishland Market, Ltd.; Slow 

 Poke Fishmarket; Star Markets, Ltd.; M. Q. 



886 



