THE INCREASE IN SPAWNING BIOMASS OF NORTHERN ANCHOVY, 



ENGRAULIS MORDAX 



Paul E. Smith'^ 



ABSTRACT 



The northern anchovy, Engraulis mordax, is a common fish off the west coast of North 

 America. Its biomass has increased markedly since 1951. The various methods of de- 

 riving anchovy spawner biomass from the sardine spawner biomass and analogous census 

 estimates of sardine and anchovy larvae are reviewed. A new compilation of anchovy and 

 sardine larval data is presented for 1940, 1941, 1949, 1950, and 1951-69. The effect of 

 several errors of estimate are examined and it is concluded that none is important 

 enough to affect measurably the trend of increase between 1951 and 1966. Lastly, a 

 current interpretation of the larval survey data is used to estimate the spawning bio- 

 mass of both sardine and anchovy. 



The northern anchovy (Engraulis mordax Gi- 

 rard) is a common pelagic schooling fish off the 

 west coast of North America between British 

 Columbia and Baja California (lat 53 °N to 

 22°N). The fishery for northern anchovy has 

 usually been small relative to the Pacific sardine 

 (Sardinops caerulea (Girard)) ofl' California 

 but the anchovy catch has been increasing since 

 the late 1930's (Figure 1). Following the col- 

 lapse of the sardine fishery in the early 1950's, 

 the catch of anchovy exceeded that of sardine. 

 The further decline of sardine catch and the 

 eventual moratorium on sardine, combined with 

 a limited reduction fishery on anchovy, have 

 again allowed the anchovy fishery to exceed that 

 of sardine since the mid-1960's (Messersmith 

 and Associates, 1969). 



Routine planktonic larva sampling since 1951 

 shows an increase in the number of anchovy lar- 

 vae (Murphy, 1966; Ahlstrom, 1966, 1968) and 

 the present consensus estimate of the spawning 

 population of northern anchovy is about 5 mil- 

 lion tons for 1966, the last year for which com- 

 plete data are available. The same sample data 

 for the Pacific sardine now indicate an extremely 

 small number of larvae and the spawning bio- 



^ National Marine Fisheries Service, Southwest Fish- 

 eries Center, La Jolla, CA 92037. 



mass of the northern subpopulation of the sar- 

 dine may now be less than 5,000 tons. All an- 

 chovy biomass estimates must now be referred 

 to analogous sardine biomass estimates based on 

 the sardine fishery and on sardine and anchovy 

 egg and larva surveys because no fishery-based 

 estimate of anchovy biomass has yet been made: 

 this becomes increasingly difl^cult and imprecise 

 as the sardine "reference" population diminishes. 

 The purposes of this paper are to: 



1) review the estimates of spawner biomass 

 of the anchovy; 



2) present a summary of the incidence of 

 larval anchovy by region and season since 

 1951; 



3) examine the effects of three spawning be- 

 havior models on the estimates of spawn- 

 ing biomass; 



4) establish a standard reference period for 

 the determination of anchovy biomass 

 without further consideration of the cur- 

 rent size of the sardine population. 



PREVIOUS ESTIMATES OF 

 ANCHOVY BIOMASS 



Messersmith and Associates (1969, p. 9) tab- 

 ulated all the estimates of anchovy spawning bio- 

 mass for the years 1940-66. Ahlstrom (MRC, 



Manuscript accepted April 1972. 



FISHERY BULLETIN: VOL. 70. NO. 3, 1972. 



849 



