FECUNDITY AND EGG-PRODUCTION OF 4 SPECIES OF SHORT-LIVED CLUPEOID FROM SOLOMON-ISLANDS, TROPICAL SOUTH-PACIFIC

The fecundity and egg production of four species of small clupeoid, th e anchovies Encrasicholina devisi, E. heterolobus, and the sprats Spra telloides delicatulus and S. lewisi, were examined at three sites in t he Solomon Islands, tropical South Pacific. All species are multiple s pawners and batch fecundity ranged between 500 and 1900 eggs per spawn ing, being significantly lower in the two sprat species than in the co -occurring anchovies. The fecundity of all species varied between site s, but not markedly between seasons. In Encrasicholina, fecundity was positively correlated with water temperature and zooplankton density, whereas in Spratelloides it was correlated with the hepatosomatic inde x. These results suggest that the fecundity of Encrasicholina is direc tly related to food intake, but Spratelloides probably depend on energ y reserves in the liver for spawning. Egg volume differed between spec ies and between sites for each species. Egg volume was inversely relat ed to fecundity. Both species of Spratelloides had fewer, larger eggs than the similar-sized Encrasicholina species, which had much higher b atch fecundity. This may be a consequence of lower or more predictable egg mortality that results from their benthic-spawning habits. Egg dr y weight varied between sites for all species except E. devisi, but th e pattern differed for each species. For Spratelloides, egg weight var ied in a similar manner to egg volume. However, at any site the egg we ights of all species were similar and showed little seasonal variation . These species are fast growing and short-lived (4-8 months); they sp awn at 2 to 4 months of age and spawn, on average, every 2 to 8 days d uring their reproductive lifespan of up to 4 months. Differences withi n species in these reproductive parameters made monthly reproductive o utput highly variable, but with a similar mean life-time egg productio n at each site. The estimated daily population egg production of popul ations of each species varied with stock size (estimated from catch pe r unit effort). Daily egg production was correlated in E. devisi and E . heterolobus at Munda and Vona Vona, which suggests that similar fact ors affected egg production at these sites. However, there was no dire ct relationship between egg production and subsequent recruitment, exc ept for S. lewisi at Tulagi. These results indicate that even for shor t-lived, fast-growing tropical species that recruit within 2 months of hatching, recruitment is more strongly influenced by factors such as variation in egg and larval survival than parental stock size.