Hernandez and Castro Lan/al growth of Engraulis nngens 



709 



entire sampling season. In fact, obsen'ed larval food 

 concentrations may be considered high compared with 

 concentrations reported for the same species in lower 

 latitudes (Walsh et al., 1980). Differences in seawater 

 temperature experienced by both groups of cohorts 

 spawned during winter, however, may have accounted 

 for the apparent differences in larval gi'owth rates. 

 An increase in water temperature occurred during the 

 last weeks of sampling owing to an intrusion of off- 

 shore warmer waters into the coastal zone (Castro et 

 al., 2000). Response to changes in seawater tempera- 

 ture as the spawning seasons progress is known for 

 other anchovy species (A. mitchilli. Leak and Hode. 

 1987; Rilling and Houde, 1999). However, earlier evi- 

 dence may have not been so conclusive for lai-val 

 anchovy at upwelling areas (i.e. E. inordax, Methot 

 and Kramer, 1979; Butler, 1989), probably because 

 of the difficulties of determining the temperature of 

 the water where the lai"vae actually developed, espe- 

 cially given the frequent changes in hydrographic con- 

 ditions common in coastal upwelling areas. 



Because growth may be dependent on environmen- 

 tal factors (Pepin, 1991), seasonal variations in growth 

 rates were expected among the cohorts spawned during 

 the year In our study, we documented potential differences 

 in growth rates of groups of cohorts spawned a few weeks 

 apart during the main spawning season. For coastal species 

 living in upwelling areas, changes in growth rates among 

 cohorts may be beneficial because environmental condi- 

 tions may change markedly in short time scales (from days 

 to a few weeks). With this scenario, increases in growth 

 rates in some cohorts (given the right conditions during a 

 few weeks) may be advantageous because the main spawn- 

 ing season for E. ringens occurs in winter. At the end of 

 the season we expected a large pool of late larvae and 

 early juveniles within a similar size range that had grown 

 at different rates because they were exposed to different 

 conditions. Given the relationship between environmental 

 conditions and larval development, and the wide distri- 

 bution range of the anchoveta (from 4°S to 40°S). differ- 

 ences in gi'owth rates are to be expected in lar\'al anchovies 

 growing in different latitudes. Future studies should eval- 

 uate whether the models and gi-owth rate changes deter- 

 mined off Talcahuano (37°S). close to the southern limit of 

 distribution for the anchoveta, also apply for lai-vae grow- 

 ing in lower latitudes, such as spawning areas off northern 

 Chile (18-24°S) and Peru (4-14°S) . 



Acknowledgments 



The authors of this paper wish to thank G. Salinas, for 

 helping in the collection of samples and in processing 

 these samples, and C. Maturana for helping in the larval 

 rearing experiments in the laboratory An early version 

 of this manuscript was reviewed by J. Butler. Funds for 

 the field work were provided by FONDECYT and Funda- 

 cion Andes through gi'ant numbers 3950024 and 12999-8. 

 respectively, to L. R. Castro. During the writing of the 

 manuscripts, L. R. Castro was also supported by FONDAP: 



Subprogram Advanced studies on the Humboldt Current 

 System. 



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