LENARZ: MESH RETENTION OF LARVAE 



50r 



Lj (mm) 



Figure 7. — Catches of northern anchovy by standard 

 length (Lj) taken by type 3 (0.505-mm mesh) net. 



changes in the slopes of the catch curves. How- 

 ever, since the catches are plotted with size 

 rather than age, a faster rate of growth at small 

 sizes relative to large sizes could cause small 

 size larvae to be relatively undersampled. If 

 this were the case, a critical period could occur 

 but not be indicated by catches plotted with size. 

 Kramer and Zweifel (1970) indicated that the 

 growth rate of anchovy larvae increases rather 

 than decreases with size during the first few 

 millimeters of growth. Another factor that 

 could influence the catch rate of larvae diflfer- 

 ently with size is avoidance of the net. How- 

 ever, experience indicates that avoidance in- 

 creases with size (Lenarz, in press). Thus, the 

 large larvae should be relatively undersampled. 

 I conclude, therefore, that available data does not 

 provide any evidence of the critical period for 

 sardine or anchovy larvae. This conclusion is 



in agreement with other authors that have ex- 

 amined catch curves of fish larvae, e.g., Marr 

 (1956). 



ACKNOWLEDGMENTS 



I owe considerable thanks to Drs. Paul E. 

 Smith and Elbert H. Ahlstrom for encouraging 

 this study and for providing many constructive 

 comments. Thanks are also due to Sharron G. 

 Cramer, Biological Aid, for processing many of 

 the samples and for her comments on the tech- 

 nique of measuring fish larvae, and to Bradley 

 W. Cowell, NOAA Jr. Fellow, for performing 

 many of the calculations. 



LITERATURE CITED 



Ahlstrom, E. H. 



1954. Distribution and abundance of egg and larval 

 populations of the Pacific sardine. U.S. Fish 

 Wildl. Serv., Fish. Bull. 56:83-140. 

 1966. Distribution and abundance of sardine and 

 anchovy larvae in the California Current region 

 off California and Baja California, 1951-1964: A 

 summary. U.S. Fish Wildl. Serv., Spec. Sci. Rep. 

 Fish. 534, 71 p. 

 1968. An evaluation of the fishery resources avail- 

 able to California fishermen. In D. Gilbert (ed- 

 itor) , The future of the fishing industry of the 

 United States, p. 65-80. Univ. Wash. Publ. Fish., 

 New Ser. 4. 

 Cochran, W. G. 



1963. Sampling techniques. 2d ed. Wiley, N.Y., 

 413 p. 

 Heron, A. C. 



1968. Plankton gauze. In D. J. Tranter (editor). 

 Part I, Reviews on zooplankton sampling methods, 

 p. 19-25. UNESCO Monogr. Oceanogr. Methodol. 

 2, Zooplankton sampling. 

 Hjort, J. 



1926. Fluctuation in the year classes of important 

 food fishes. J. Cons. 1:5-38. 

 Hunter, J. R. 



1972. Swimming and feeding behavior of larval 

 anchovy, Engraulis mordax. Fish. Bull., U.S. 70: 

 821-838. 

 Isaacs, J. D. 



1965. Larval sardine and anchovy interrelation- 

 ships. Calif. Coop. Oceanic Fish. Invest. Rep. 10 : 

 102-140. 

 Kramer, D., and J. R. Zweifel. 



1970. Growth of anchovy larvae (Engraulis mor- 

 dax Girard) in the laboratory as influenced by 

 temperature. Calif. Coop. Oceanic Fish. Invest. 

 Rep. 14:84-87. 



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