SMITH: SPAWNING BIOMASS OF NORTHERN ANCHOVY 



Figure 13 contains all the estimates resulting 

 from this study. Murphy's sardine biomass esti- 

 mates are plotted from 1940 to 1959. The an- 

 chovy biomass estimates derived from the an- 

 chovy sardine ratio and the anchovy larva re- 

 gional census in 1940, 1941, and 1950 through 

 1959. The regression estimates are reproduced 

 from 1951 to 1959 for comparison with the 

 Murphy sardine biomass and ratio-derived an- 

 chovy biomass. The regression estimates of both 

 sardine and anchovy spawner biomass are ex- 

 tended through 1966 and a tentative estimate for 

 1969 is placed for comparison. 



DISCUSSION 



Important changes in the size of the anchovy 

 population have occurred in the California Cur- 

 rent area over the past two decades. The in- 

 crease of anchovy has coincided with the contin- 

 uing decrease of sardine in the same area. All 

 available evidence indicates that the anchovy 

 and sardine populations declined between 1941 

 and 1951, and thereafter the anchovy underwent 

 a sustained increase reaching a plateau of 5-8 

 million metric tons between 1962 and 1966. This 

 population size may be between 2 and 3 times the 

 anchovy spawning population of 1940-41 and be- 

 tween 5 and 10 times the anchovy population 

 in 1950-51. Changes of this magnitude in the 

 absence of a fishery underscore the importance 

 of natural fluctuations in the population size of 

 a fish species. Fishery management of such a 

 species must be responsive to changes of this 

 magnitude and rapidity. 



Murphy (1966, 1967) speculated on the effect 

 of the anchovy population on the recovery of 

 the sardine population. Neither the feeding of 

 anchovy and sardine nor the population dynam- 

 ics of the food organisms is well enough under- 

 stood in the California Current. Since the size 

 frequency curves of larvae are relatively invar- 

 iable (Ahlstrom, 1965; Lenarz, in press) one 

 would expect competition, if any, to occur in the 

 juveniles and pre-recruits of either species. 



One interesting fact may be the decline of 

 sardine spawning in the spring and summer has 

 coincided with an increase of spawning in spring 



by the anchovy. In the estimates of spawner 

 biomass of sardine and anchovy, no attention 

 has been given the possibility that fecundity in 

 numbers of eggs per batch and number of batches 

 per unit time is plastic. 



The numbers of anchovy and sardine larvae 

 have been used here exclusively to describe 

 changes in the adult biomass which spawned 

 them. Since this process seems so effective, one 

 might wonder what is required to refine tech- 

 niques so that spawning, and larval and juvenile 

 survival, may be used to predict the recruitment 

 of year classes to the fishery. I believe the two 

 major barriers are that 1) the size composition 

 of the larvae of both species is so dependent 

 on the sampling gear that mortality rates will 

 remain too crude to project survival and 2) the 

 effect of transport of larvae, particularly off- 

 shore to "unfavorable" areas, is neither well 

 enough measured nor understood to effect pre- 

 dictive sampling systems. 



ACKNOWLEDGMENTS 



I would like to acknowledge the impact on my 

 personal research and the effect on the overall 

 study of environmentally induced natural vari- 

 ability that Dr. 0. Elton Sette has had. The 

 preparation of this paper would not have been 

 possible without the aid and discussions of Dr. 

 E. H. Ahlstrom. I would like also to acknowledge 

 the assistance of my colleagues Dr. William 

 Lenarz, David Kramer, and James Zweifel in 

 compiling and editing this paper. Drawings and 

 mathematical tables were prepared by James 

 Thrailkill, Esther Barker, and Nancy Wiley. All 

 biological specimens used were sorted and identi- 

 fied since 1940 by Dr. E. H. Ahlstrom and his 

 staff. 



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. 

 1959. Vertical distribution of pelagic fish eggs and 



larvae off California and Baja California. U.S. 



Fish Wildl. Serv., Fish. Bull. 60:107-146. 



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