THEILACKER: MORTALITY OF SEA-CAUGHT JACK MACKEREL 



< 



Q 



OC 

 LU 



LU 

 O 

 OC 

 LU 

 CL 



OFFSHORE 



100 r- r 



AROUND ISLANDS 



50 





 100 



YOLK-SAC 



< 3.2mm 



N=15 



FIRST FEEDING 

 < 3.5mm 

 N=200 



FIRST FEEDING 

 < 3.5mm 

 N=20 



50 



3.5- < 4.0mm 

 N=112 



100 i- 



^ 4.0mm 

 N=59 



Figure 16.— Comparison of the nutritional condition of young Trachurus symmetricus collected from offshore and 

 nearshore habitats. Daily percents taken from Tables 2 and 3. 



been assessed using histological criteria. O'Connell 

 examined 318 northern anchovy larvae from 64 sta- 

 tions that extended over a large area, 20-350 km off 

 the coast of California. lb compare the mortality of 

 northern anchovy with the daily rates I found for 

 jack mackerel, I calculated size-specific daily mor- 



tality of northern anchovy by using 1) O'Connell's 

 (1980) histological evaluation, 2) information on time 

 to irreversible starvation to determine durations 

 (Lasker et al. 1970; Hunter 1981; Theilacker and 

 Dorsey 1981), 3) information on shrinkage of ocean- 

 caught northern anchovy to determine size at first 



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