FISHERY BULLETIN: VOL. 74, NO. 3 



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10 20 30 40 60 60 70 80 90 



LENGTH OF LARVAE AND JUVENILES (mm) 



100 



Figure 9.-Relative body depth of ocean caught northern 

 anchovy larvae and juveniles calculated from Ahlstrom et al. (see 

 text footnote 4). 



larvae generally decrease until they are 17 to 18 

 mm long. Figure 10 compares relative body depth, 

 averaged per millimeter of length, of the above 

 ocean-caught anchovy larvae to that of larvae 

 grown in the laboratory. These are larvae grown 

 by Kramer and Zweifel (1970, experiment 17-11) at 

 17°C on a diet of wild plankton and with a feeding 

 incidence described as "high." At the 10-mm length 

 the two curves are different at the 0.05 sig- 



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.080 



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2 4 6 8 10 12 14 16 IB 20 



LENGTH OF LARVAE (mm) 



Figure lO.-Comparison of relative body depth of ocean caught 

 and laboratory grown northern anchovy larvae. Each point 

 represents an average of at least four larvae. 



nificance level (Ntest) and they differ with greater 

 significance at increasing lengths. 



Condition factor (weight -^ length^) for labora- 

 tory-grown anchovies increases throughout the 

 larval period as calculated from weight-length 

 relationships presented by Lasker et al. (1970) and 

 Hunter (1976). 



Condition factor for ocean-caught E. anchoita 

 larvae as calculated from wet weight data record- 

 ed by Ciechomski (1965) is at its lowest value 

 between 15 and 20 mm. 



The available data, therefore, indicate that 

 relative body depths and weights of well-fed 

 laboratory-grown anchovy larvae increase allo- 

 metrically throughout the larval period, whereas 

 these values for average ocean-caught larvae are 

 at a low value at some midlarval period, followed 

 by an increase through metamorphosis. This in- 

 crease is probably related to the start of transfor- 

 mation to the juvenile stage but may also be 

 accelerated by improving nutrition. 



A relationship between gut thickness and feed- 

 ing conditions was reported for ocean-caught 

 larval sardine Sardinops melanosticta (Nakai 

 1960, 1962). The relationship of body depth to the 

 nutritional level of fish larvae has been recorded 

 for E. ja panic Hs (Honjo et al. 1959; Nakai et al. 

 1969) together with relative body weight for 

 herring larvae (Blaxter 1965, 1971). Blaxter at- 

 tributed the low value of body weight for ocean- 

 caught herring larvae to scarce plankton and to 

 few feeding hours in the Clyde area at the time of 

 sampling. The 14- to 15-mm long laboratory- 

 grown herring larvae when deprived of food died 

 at relative body weights that were higher than 

 those of living ocean-caught individuals. This may 

 be a result of the ocean-caught larvae having 

 survived on suboptimal rations most of their 

 existence whereas the laboratory-grown larvae 

 had ample rations until the time they were sud- 

 denly deprived of food. The observed decrease in 

 condition with size might also be an index of the 

 increasing ability to resist starvation. The rich 

 feeding conditions of successful laboratory-rear- 

 ing experiments probably seldom obtain in the 

 ocean (Lasker 1975; Hunter in press), and this may 

 be reflected in the condition of the average 

 ocean-caught larva. 



The sardine larva initiates its first feeding 

 activities in a nutritional deficit (Lasker 1962). 

 This may also be indicated by the increasing 

 thinness of the average ocean-caught E. mordax 



526 



