SMITH: SPAWNING BIOMASS OF NORTHERN ANCHOVY 



20 



10 



y 2 



, 1 I I I I I I I I I 1 1 L ^L J^ 



'2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 



LENGTH (mm) 



Figure 3. — The size frequency of sardine larvae caught 

 in the CalCOFI standard silk net (0.55 mm). The tri- 

 angle dot-dash curve represents the 1951-60 catch from 

 the selected stations in all eleven regions; the black 

 dot-dash curve represents the 1940 catch from selected 

 stations in the southern California inshore and offshore 

 region and the clear dot solid line represents the 1941 

 catch from the same two regions. Relative catch refers 

 to the catch at a standard size group (3.00, 3.25 (1940- 

 41), 4.75, 5.75 ... 15.75 mm), divided by the average 

 catch from size groups 8.75 to 15.75. 



ESCAPEMENT AND AVOIDANCE BY 

 ANCHOVY AND SARDINE LARVAE 



The chief errors causing underestimates of 

 C for both anchovy and sardine larvae are those 

 attributable to larvae "escaping" through the 

 meshes of the standard plankton net (see Lenarz, 

 1972, p. 839) and larvae "avoiding" the mouth of 

 the net (Silliman, 1943; Ahlstrom, 1954, 1959; 

 Clutter and Anraku, 1968). While "escape- 

 ment" and "avoidance" are important biases to 

 consider in the study of larva growth and mor- 

 tality, I consider them beyond the scope of this 

 paper. The estimate of anchovy biomass is 

 based on a relative estimate of the number of 

 anchovy larvae and sardine larvae. I must treat 

 escapement and avoidance briefly, since they act 

 differently on the anchovy and sardine and vary 

 from season to season and with changes in sam- 

 pling gear. 



Lenarz (1972) found no appreciable difference 

 in size-specific escapement of sardine and an- 

 chovy through net apertures. However, newly 

 hatched anchovy larvae are considerably smaller 

 than sardine larvae. This leads to a variation 

 in the degree of bias (Murphy, 1966) to such 

 escapement. In Figure 3 the catch of all stan- 

 dard sizes of sardine is related to the average 

 catch between 8.75 and 15.75 mm, a size range 

 I assume to be completely retained on 0.55-mm 

 mesh width silk. The primary line is the aver- 

 age size composition for the period 1951-60 for 

 the sardine. The size composition of the 1940 



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