FISHERY BULLETIN: VOL. 72, NO. 2 



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18 JUNE '70 

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14 JULY '70 

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12 MAR. 71 

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31 JULY '70 

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2 4 6 8 10 12 



WHOLE YEAR 

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2 4 6 8 10 12 



MEAN DIAMETER, mm 



Figure 16. — Seasonal variations in the size frequency distribu- 

 tions of Pleurobrachia bachei captured by the 0.363-mm mesh 

 0.5-m net, expressed as the percentage in each size class of total 

 numbers of all sizes on each sampling date. Each histogram is 

 based on all sample data from each respective sampling date. 

 The date and number of individuals measured are given with 

 each histogram. 



and 6, whose difference should be less influenced 

 by tidal currents and represents the order of true 

 spatial variation within the first 10 km from 

 shore. 



The size-frequency distributions of postlarvae 

 for the 8 March 1970-2 June 1971 period indicate 

 that most of the year the 1- to 2-mm size classes 

 made up the highest proportion of all postlarvae 

 (Figure 16). The lower abundance of the 0.25-mm 

 class relative to the 1-mm class is the result of 

 sampling gear mesh selectivity caused by the ina- 



bility of the 0.363-mm mesh to retain larvae 

 quantitatively. At sporadic intervals the 

 size-frequency distributions show drastic 

 changes, and these are attributed to immigration 

 of individuals in advected water. Between 14 July 

 and 21 August 1971 note the decline in proportion 

 of 1 and 2 mm sizes and a shift in modal class from 

 1 to 7 mm. During this same period the occur- 

 rences of eggs and larvae showed that while up to 

 9,000 eggs/m^ were present in the water, seven of 

 eight samples for larvae indicated none present 

 (Figure 14). Assuming that these changes in 

 size-frequency distribution over the 4-wk period 

 are the result of biological activity rather than 

 sampling error and advective change, it is con- 



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 1970 1971 



Figure 17. — Seasonal variations in standing stocks of postlar- 

 vae, larvae, and eggs at station 5. Each type of line connects the 

 respective mean values for the replicate samples at each sam- 

 pling date. The vertical bar represents the range of values for the 

 replicate samples, and solid symbols indicate that the range is 

 less than the size of the symbol; the open symbols without any 

 vertical bar are single observations. 



312 



