EVERSON ET AL.: MATURATION AND REPRODUCTION IN TWO HAWAIIAN SNAPPERS 



temperature and photoperiod are much less pro- 

 nounced at these depths. In Vanuatu, Brouard 

 and Grandperrin (1985) found that seasonal 

 changes in gonad maturation based on GSI 

 values differed among species inhabiting dis- 

 crete depths. 



Grimes (1987) has suggested two distinct 

 spawning patterns for snappers. One is a re- 

 stricted pattern with spawning centered around 

 the summer months, typical of species associated 

 with continental habitats where peaks in produc- 

 tion cycles occur because of nutrient run-off re- 

 sulting from high rainfall. The opposing pattern 

 is characterized by year-round spawning with 

 peaks occurring in spring and fall, a pattern 

 thought to be typical of less productive insular 

 populations. Grimes (1987) has noted that Cuba 

 and New Caledonia are large islands that follow 

 the continental pattern, with spawning peaks 

 arising during periods of high rainfall. Etelis car- 

 bunculus (Everson 1984) and P. filamentosus 

 (Kikkawa 1984) have also been reported to follow 

 a restricted spawning pattern in the North- 

 western Hawaiian Islands. Both uku and onaga 

 in our study also followed the restricted 

 spawning pattern associated with continental 

 habitats. Spawning took place over a protracted 

 period centered around the summer months. 

 Neither species was found in spawning condition 

 at any other time of the year. Since temporal 

 primary production cycles e.xhibit little seasonal 

 variation throughout the Hawaiian Archipelago 

 (Bienfang and Szy per 1981; Bienfang et al. 1984), 

 the basis for this restricted pattern observed for 

 uku and onaga is unclear. Apparently, the 

 seasonal changes in day length and water tem- 

 perature in Hawaii provide adequate spawning 

 stimuH. 



Interspecies differences in size at se.xual 

 maturity also were noted. The slope of the lo- 

 gistic curve fitted to the size at sexual maturity 

 data was considerably steeper for uku compared 

 with onaga (Fig. 6). Uku matui-ed at 450-500 

 mm FL, wath nearly 100% mature above 550 

 mm FL, and onaga matured at 550-800 mm FL, 

 with 100% mature at 850 mm FL. Size at sexual 

 maturity differed between species in terms of 

 the percentage of MAXLEN at which matmnty 

 occurred. Uku began maturing at about 429 mm 

 FL or 42% of their MAXLEN, whereas onaga 

 began maturing at about 522 mm FL or 54% of 

 their MAXLEN. Talbot (1960) reported that 

 male and female A. virescens of East Africa 

 reached maturity at 410 mm SL (51%) and 465 



mm SL (58%), respectively. Aprion virescens 

 off Vanuatu matured at 440 mm FL, a figure 

 that Brouard and Grandperrin (1985) calculated 

 from a MAXLEN coefficient of 57.6%, which 

 was based upon the average values obtained 

 from 34 tropical fish species from the west coast 

 of Africa. The same coefficient, applied to 

 Vanuatu populations of E. coruscans, indicated 

 that sexual maturity was reached at 470 mm 

 FL, although developmental staging data ob- 

 tained for this species revealed that mature fish 

 were first sampled at 330-380 mm FL. The 

 actual size at which maturity commenced in all 

 of these locations agreed closely with our data 

 for uku in Hawaii, while the percentage of 

 MAXLEN values differed considerably. How- 

 ever, Hawaii and Vanuatu populations of onaga 

 matured at substantially different sizes. 



Disparities in size at sexual maturity between 

 areas may reflect differences in resource utiliza- 

 tion and gi'owth allocation. Grimes (1987) calcu- 

 lated the average percentage of MAXLEN at 

 which sexual maturity occurred for lutjanid pop- 

 ulations occupying similar zoogeographic loca- 

 tions and habitats. Insular and continental popu- 

 lations had average MAXLEN values of 51 and 

 43%, respectively, while the deep (> 91 m) and 

 shallow (< 91 m) species were calculated at 49 

 and 43%'. The MAXLEN value of 42% calculated 

 for the study population of uku indicates that 

 this species fits the shallow, continental pattern. 

 As previously mentioned, onaga- are found at 

 much greater depths and therefore seem to be 

 less influenced by continental effects than uku. 

 These observations are substantiated by the fact 

 that the MAXLEN value of 54% calculated for 

 onaga conforms closest to the deep, insular pat- 

 tern reported in Grimes (1987). He reasoned that 

 these anomalies may result from regional differ- 

 ences in food production. Fish fi'om a relatively 

 resource-rich environment may mature at a pro- 

 portionally smaller size than fish in less produc- 

 tive habitats. He further speculated that selec- 

 tion may favor maturation at a larger maturing 

 size in insular regions because the cost of year- 

 round spawning may be higher in these areas. 



Estimates of von Bertalanffy growth param- 

 eters, derived from weight-frequency distribu- 

 tions for uku and onaga landed in Hawaii in 

 1984-86, indicate that uku mature at about ages 

 4-5 (429 mm FL), while onaga begin maturing at 

 ages 5-6 (522 mm FL) (Ralston and Kawamoto, 

 fn. 1). In the same study, Ralston and Kawamoto 

 (fn. 1) calculated the size at entry to the fishery 



885 



