AGE DEPENDENT FECUNDITY, NUMBER OF SPAWNINGS PER YEAR, 



SEX RATIO, AND MATURATION STAGES IN 



NORTHERN ANCHOVY, ENGRAULIS MORDAX 



Richard H. Parrish, 1 Donna L. Mallicoate, 1 and 

 Richard A. Klingbeil 2 



ABSTRACT 



Maturity stage data from fishery sampling programs and ovarian histological data from research cruises 

 were used to develop a method for determining the age-specific number of spawnings per year and annual 

 fecundity of the central stock of northern anchovy, Engraulis mordax. 



The sex ratio was found to be size and age dependent in both the fishery and trawl surveys with 

 females increasingly dominant in the larger and older size and age classes. The overall sex ratio in trawl 

 surveys was nearly 1:1; the fishery data favored females 1.48:1. The magnitude and duration of maturity 

 stages were size and age dependent with peak spawning occurring earlier in the season in younger fish. 

 Maturity stages and histological classes with hydrated eggs showed essentially the same diurnal pattern 

 for nightly spawning activity indicating that the presence of hydrated eggs could be used as an index 

 of daily spawning. The daily spawning incidence and total annual fecundity were found to be heavily 

 age dependent. Females in their first spawning season had an average of 5.3 spawnings, while those 

 in their fourth had an average of 23.5 spawnings. When combined with the higher batch fecundity of 

 larger fish this results in 4 + year-old females producing nearly 5 times as many eggs per unit of weight 

 as 1-year-olds. When the age-specific fecundity and sex ratio in the fishery are combined it is apparent 

 that the catch of a ton of 4 + year-old northern anchovy reduces the reproductive potential of the stock 

 7.3 times as much as the catch of a ton of 1-year-olds. 



It was concluded that age-specific fecundity in multiple spawning fishes is of greater significance 

 for management than previously thought. It is also significant that much of the observed variance in 

 stock-recruitment relationships for multiple-spawning fishes may be due to the fact that spawning biomass 

 is a poor index of the egg production and reproductive potential of the stock. 



Age-specific variation in life history rates is a major 

 factor in population and management models of ex- 

 ploited fishes, and variation in reproductive effort 

 is of great significance in such models. Size and age- 

 specific batch fecundity estimates have been avail- 

 able for many species for decades, and for species 

 which spawn only once per spawning season these 

 are readily incorporated into models. However it has 

 been impossible to determine the age-specific repro- 

 ductive effort of species which spawn many times 

 during a spawning season because there has been 

 no way to determine the number of spawnings per 

 year. 



Recent research on the histology of the ovaries 

 of northern anchovy, Engraulis mordax, and an- 

 choveta, Engraulis ringens, suggest that they 

 spawn approximately once a week during peak 

 spawning months (Hunter and Goldberg 1980; 



'Southwest Fisheries Center, Pacific Fisheries Environmental 

 Group, National Marine Fisheries Service, NOAA, P.O. Box 831, 

 Monterey, CA 93942. 



California Department of Fish and Game, 245 W. Broadway 

 Street, Long Beach, CA 90802. 



Hunter and Macewicz 1980; Alheit et al. 1983; Alheit 

 et al. 1984). Hunter and Leong (1981), in their study 

 of the spawning energetics of the northern anchovy, 

 found that northern anchovy spawn about 20 times 

 per year. Hunter and Leong (1981) and Alheit et al. 

 (1983) suggested that annual fecundity per unit of 

 parental biomass may be highly variable and depen- 

 dent upon the nutritional state and size structure 

 of the stock. 



Potentially the recently developed histological 

 techniques could be utilized to determine age-specific 

 annual fecundity; however, this would be very ex- 

 pensive as it would require a very large data set 

 which would necessarily be stratified by age and 

 time of year. The objectives of this report are 1) to 

 demonstrate a method for combining the high 

 resolution reproductive information from the 

 histology of the ovaries with inexpensive, lower 

 resolution reproductive information derived from 

 resource surveys and fishery sampling programs to 

 determine the age-specific reproductive potential of 

 a multiple spawning species, and 2) to evaluate the 

 gross anatomical maturity stages which have been 



Manuscript accepted January 1986. 

 FISHERY BULLETIN: VOL. 84, NO. 3, 1986. 



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