HUNTER: CULTURE AND GROWTH OF ENGRAULIS MORDAX 



Fat was removed by Soxhlet extraction with 

 chloroform-methanol (Krvaric and Muzinic 1950) 

 from batches of 5 to 9 fish each. One such sample 

 was taken at the beginning of the experiment, 

 one from each group just before food was added, 

 and one from each group when the experiment 

 ended after 5 to 8 days of feeding. 



A marked initial mortality occurred on the day 

 following the transfer of the two groups (Figure 5) 

 which was probably caused by handling. For this 

 reason the first day's mortality is excluded from 

 the analysis presented below, but the survival is 

 given for all days in the figure. 



Table 4. — Lengths of fish in starvation groups and lengths 

 of fish that died during starvation. 



= FOOD ADDED 



Figure 5. — Percent survival of metamorphosed larvae reared 

 in experiment 5 during starvation periods of 12 and 15 days. 

 Arrow indicates end of starvation period. 



After 12 days of starvation, 50% of the fish were 

 alive in group 1 (excluding the first day mortal- 

 ity) and 58% were alive in group 2 after 15 days of 

 starvation. One fish in group 1 died the day after 

 the first feeding. This was the only fish to die 

 after feeding began. Thus for fish averaging 35 

 mm in length, about 50% mortality is reached 

 after about 15 days of starvation and nearly all 

 surviving fish are able to recover from a starva- 

 tion period of that duration. Mortality during 

 starvation appeared to be dependent on size or 

 state of maturity, however. Metamorphosis is 

 completed in the northern anchovy when they 

 reach 35 mm standard length (E. H. Ahlstrom, 

 Southwest Fisheries Center La Jolla Laboratory, 

 pers. commun.). Eighty-three percent of the fish 

 that died were less than 35 mm whereas only 17% 

 of those longer than 35 mm died (Table 4). About 

 45% of the fish were less than 35 mm long at the 

 beginning of the experiment. These results are 

 similar to those obtained for herring larvae, 

 Clupea harengus. The number of days to irrevers- 

 ible starvation for herring larvae increased from 



'Fish that died on first day of starvation in groups 1 and 2 not included. 

 ^Surviving fish measured at end of experiment after 5- to 8-day feed- 

 ing period. 



6 days at the end of the yolk-sac stage to 15 days 

 at age 88 days (Blaxter and Ehrlich 1974). 



Lipid content offish declined during the starva- 

 tion period from about 30% of dry weight to about 

 12% (Table 5). Recovery for the surviving fish was 

 rapid, as they returned to the 30% level after 5 to 

 8 days of feeding. Water content was inversely 

 related to fat as expected (lies and Wood 1965). 

 Fat content of muscle of adult anchovy is about 30 

 to 40% of dry weight during late summer and fall 

 when gonadal fat is low (Lasker, Southwest 

 Fisheries Center La Jolla Laboratory, unpubl. 

 data). Thus, fat levels of these newly metamor- 

 phosed larvae appeared to be about the same as 

 that of adult fish. 



Table 5. — Total lipid and water content of anchovy at meta- 

 morphosis before, during, and after starvation. 



Extreme vulnerability to starvation appears to 

 be characteristic of only the larval phase of the 

 northern anchovy and it is over by the time the 

 fish completes metamorphosis. There is a danger 

 in interpreting these data beyond these general 

 conclusions because reared fish may have more 

 fat than wild ones and this could alter the results 

 (Balbontin et al. 1973). 



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