FISHERY BULLETIN: VOL. 80, NO. 3 



Table 6.— Average daily ration of 3-4 mm Pacific hake larvae (data 

 from Sumida and Moser 1980, table 1). Number prey/stomach in- 

 cludes those with empty guts. 



001025 



Calories per stomach = 0.01025 mg X 5.2519 cal/mg-dry wt 4 = 0.05383 cal 

 Calories in stomach x Feeding period (FeJgenbaum 1979; 



Daily ration 



Digestion time 



Laurence 1977) 



0538 X 12 



0.129 cal/d. 



'From Brodskii 1967, Fulton 1968 



2 From Total length = 1.16 x prosome length f 0.34; Fulton 1968 



3 From Vidal 1978; Feigenbaum 1979. 



"5.2519 cal/mg-dry weight conversion for copepods (Laurence 1976). 



gain of laboratory-reared larvae and metabolic 

 rates at 19°C. As they note this must be a lower 

 limit. Assuming the same assimilation coeffi- 

 cient that I used for hake, 0.7, mackerel would 

 need to ingest 0.204 cal/d to satisfy this ration 

 requirement. First-feeding hake larvae have 

 very large mouths compared with either mack- 

 erel or anchovy (Fig. 10), so they may feed on a 

 wide size range of planktonic animals (including 

 adult copepods); hake larvae could satisfy daily 

 rations by capturing 25 nauplii or 15 small cope- 

 podites or 6 small calanoid adults or 1 Calanus 

 adult. In contrast, both first-feeding mackerel 

 and anchovy require a smaller size range of food 

 particles (Hunter 1980). At least for anchovy, 

 their survival depends on finding patches of 

 small food organisms, such as the dinoflagellate, 

 Gymnodinium (Lasker 1975). To satisfy its ration 

 requirement a first-feeding Pacific mackerel 

 larva would have to capture 4,000 Gymnodinium 

 cells, 240 rotifers, or 39 copepod nauplii. It seems 

 evident that they require high density patches of 

 prey for successful feeding, whereas hake larvae 

 may not require such dense patches of food for 

 successful first-feeding. 



From the results of this study, I infer that the 

 first feeding of Pacific hake larvae is not as im- 

 portant to their survival as it is for Pacific mack- 



erel and also for northern anchovy. This concept 

 is supported by 1) the lower daily ration of hake 

 larvae due to temperature-dependent activity 

 and growth, 2) larger food items in the diet of 

 hake larvae which provide more calories per prey 

 item, 3) the relatively longer starvation time for 

 hake larvae, i.e., they take 6-12 d to starve after 

 complete yolk utilization, whereas anchovy take 

 only about 4 d (Lasker et al. 1970), and 4) the abil- 

 ity of hake larvae to feed while still having yolk 

 reserves (Sumida and Moser 1980). In addition, 

 there is evidence of high energy wax esters in 

 eggs of Merluccius (Mori and Saito 1966); thus 

 larvae may have a longer safety period to find 

 food. This concept does not exclude the possibil- 

 ity of a critical starvation period occurring later 

 in larval or postlarval life, when stored energy 

 reserves are exhausted and energetic demands 

 are greater. 



Predation may be relatively important as a 

 factor influencing survival of Pacific hake lar- 

 vae. Egg and yolk-sac stages of marine fish 

 appear to be the stages most vulnerable to preda- 

 tion (Theilacker and Lasker 1974; Hunter 1980). 

 Because of the colder temperatures that Pacific 

 hake eggs and larvae inhabit, and resulting 

 growth and development rates that are slow 

 compared with Pacific mackerel (Hunter and 



596 



