CLARKE: FECUNDITY AND SPAWNING FREQUENCY OF NEHU 



weight with each spawning and must depend on 

 bodily reserves and assimilation of food, rather than 

 ovarian reserves, to continue spawning. As men- 

 tioned above, Hunter and Leong (1981) showed that 

 about 65% of the caloric cost of spawning is supplied 

 by fat reserves. Even if the same were true for nehu, 

 the additional requirements for continued spawn- 

 ing would have to come from food assimilated and 

 available for reproductive processes over a period 

 of only 2 d rather than 7 d in £". mordax. Assuming 

 cost per batch is 4% of dry bodily weight and that 

 65% of this comes from bodily reserves in both E. 

 mordax and summer nehu, the average additional 

 requirements per day would be 0.2% and 0.7%, 

 respectively. 



The above suggests that all aspects of reproduc- 

 tive output in nehu— batch fecundity, spawning fre- 

 quency, and duration of spawning— would be very 

 sensitive to any factors affecting availability of 

 resources for reproduction. Parasite load, which has 

 been shown to affect batch fecundity in cod (Hislop 

 and Shanks 1981), apparently has only an insignifi- 

 cant effect on nehu, but since a batch is formed only 

 2 or 3 days before spawning and the ova to be 

 spawned on a given evening do not attain maximum 

 size until just a few hours before spawning, even re- 

 cent events could affect the number or the growth 

 rate of oocytes in a batch. Some of the great varia- 

 tion in fecundity and the indications that some fish 

 spawn more or less often than normal could result 

 from individual differences in recent feeding suc- 

 cess, injury or stress from predators or the fishery, 

 or perhaps the extent of inshore-offshore move- 

 ments over the diel cycle. Unfortunately, none of 

 these putative factors (except for serious injury) 

 would leave any detectable trace on individual fish 

 that might explain why fecundity or spawning fre- 

 quency was higher or lower than average. 



ACKNOWLEDGMENTS 



I thank L. R. Johnson and K. C. Landgraf for 

 assistance in different phases of this study. The re- 

 search was supported by the University of Hawaii 

 Sea Grant Program, PM/M-20 and PM/M-lBBl; by 

 the University of Hawaii Research Council; and by 

 the Hawaii Institute of Marine Biology. 



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