SMITH: SPAWNING BIOMASS OF NORTHERN ANCHOVY 



INSHORE 



-« OFFSHORE 



6 SEAWARD 



61 62 63 64 65 66 



Figure 11. — A time-series comparison of the annual total regional census estimates 

 of anchovy larvae as grouped by distance from shore within the southern California 

 section. Lines connecting open triangles represent the southern California inshore, 

 closed circles, the southern California offshore, and open circles, the southern California 

 seaward. For relative areas of the regions refer to Table 3 and Figure 2. 



the early sixties and becoming largely unused 

 by the mid-1960's. The incidence of larvae has 

 continued at less than 10% of the 1962 peak 

 year in the southern California seaward region 

 (Table 9). 



THE CURRENT ESTIMATE OF 

 ANCHOVY SPAWNING BIOMASS 



The practice adopted in this paper for esti- 

 mating anchovy spawning biomass consists of 

 1) regression estimates of the relationship be- 

 tween sardine larval abundance and Murphy's 

 estimate (1966) of sardine biomass; 2) the ratio 

 of anchovy: sardine larva abundance until 1958; 

 3) the regression estimate of the relationship 

 between anchovy larva abundance between 1951 

 and 1958 and the sardine-derived anchovy bio- 



mass; and 4) the use of regression estimates 

 to calculate anchovy and sardine biomass esti- 

 mates outside the regression period. This differs 

 from Murphy's (1966) method of using an an- 

 chovy: sardine ratio for each anchovy estimate. 

 It also differs from Ahlstrom's (1968) method 

 of tying each estimate to the biomass of sardine 

 adults in 1958. Since regressions between two 

 variables with time trends are influenced by the 

 degree of temporal coherence of each variable, 

 caution is warranted in their use. Confidence 

 intervals may be calculated but their meaning 

 is not clear due to the violation of the assumption 

 of independence among the values used to calcu- 

 late the regression. The regression estimates 

 are used here as a simple shorthand method of 

 reporting an apparent relationship. 



The spawner biomass estimates of anchovy 

 and sardine which result from this and previous 



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