80 

 60 : 

 40 ■ 



PROGRUi 

 l-UPINCeUENT 



L-LARVAE 

 T-TRAVW. 



20 



lELT lELT lELT lELT lELT lELT PROGRAU 

 I — 5 —i 1 — 6—1 I — 7 —i 1—8 — I I— SH 1-10H UONTH 



Figure 9. The monthly percent distribution of anchovies collected in impingement plankton and trawl samples. 



the high abundance of a planktivorous ctenophore that occurred during the summer of 1984 (see tautog 

 subsection for a further discussion of this phenomenon). As expected, the catch of adults in impingement 

 samples and the density of eggs decreased the following year. However, later in 1985, a large increase 

 occurred in larval density (compared to 1984), which was followed by the largest annual catch of young- 

 of-the-year in trawls (Fig. 11). Because the 9. 1-m trawl does not sample anchovies well, due to their small 

 size and patchy distribution, year to year comparisons based on these data are generally not useful. 

 Nevertheless, the 1985 increase was probably real because the mean annual trawl catch for that year was 

 nearly an order of magnitude larger than in any other year, and was significantly larger than the mean in 

 any of the previous three years. These fluctuations did not appear to be related to MNPS operations nor 

 to the abundance of adults and eggs, but rather caused by density-dependent mechanisms as other re- 

 searchers have reported (Lasker 1974). 



The seasonality of anchovy catches in plankton and impingement programs was described by the 

 periodic components in the time-series models (Appendices XV, XVI, and XVII). The models of egg and 

 larval abundance explained the data better (R values larger than 0.84) than the impingement model did 

 (R =0.69). The 1984 decline in larval abundance is now a feature of the two-unit operational series 

 described by the model (Appendix XVII). The lower R value of the impingement model was probably 

 the result of the unusually high 1983 catches (NlJSCo 1984a). Summaries of these baseline models are 

 presented in Appendices XV, XVI, and XVII. 



34 



