232 



Fishery Bulletin 89(2). 1991 



low zooplankton biomass, and recent rain explained 

 66% of the variation in spawning periodicity at Tulagi 

 (P<0.01). Cloudy conditions, light winds, and waning 

 moon phases were the variables most correlated with 

 spawning in S. lewisi at Vona Vona (Table 4). However, 

 the combined data showed that temperature and zoo- 

 plankton biomass were the most significant stimuli. 

 These conflicting results were reflected in the second 

 analysis, where the stimuli chosen could not explain a 

 significant amount of the variation in spawning at any 

 site (Table 5). 



Correlations between environmental stimuli and the 

 spawning periodicity of S. gracilis could only be ana- 

 lysed for fish from Vona Vona. Most variation could 

 be explained by moon phase, temperature, tide, and 

 zooplankton biomass (Tables 4, 5). Most fish spawned 

 at full moon and when temperature, tidal range, and 

 prey biomass were high. 



Archamia zosterophora This species was most fre- 

 quently caught at Munda and Vona Vona where it 



spawned most often during periods of high rainfall (at 

 Munda), and when zooplankton biomass was high (at 

 Vona Vona) (Table 4). These variables were also the 

 most significant when all data were combined. When 

 these variables were excluded from the analysis (Table 

 5), lower tidal range and higher temperatures (Vona 

 Vona) were the only significant stimuli. 



Discussion 



Size-at-sexual-maturity of some Encrasicholina and 

 Spratelloides species from the Solomon Islands varied 

 both locally and compared with other studies elsewhere 

 in the South Pacific. 



Encrasicholina heterolobus and S. gracilis reached 

 sexual maturity at smaller lengths than previously 

 reported (Tham 1965; Tiews et al. 1971; Dalzell and 

 Wankowski 1980; Conand 1985; Dalzell 1985, 1987b). 

 Such differences may be partly an artifact of the dif- 

 ferent sexual maturity criteria used. The present study, 



