THE SPAWNING ENERGETICS OF 

 FEMALE NORTHERN ANCHOVY, ENGRAVLIS MORDAX 



J. Roe Hunter and Roderick Leong^ 



ABSTRACT 



The seasonal pattern in incidence of postovulatory follicles in northern anchovy females indicated that 

 they spawn about 20 times per year. The maturation rates of females in the laboratory indicated that 

 they were capable of maturing a spawning batch of eggs at weekly intervals. Examination of the egg 

 size frequency distributions in sea-caught specimens indicated that vitellogenesis and egg maturation 

 continued until the last spawning. We evaluated for northern anchovy the fat-water balance, caloric 

 values of tissues, annual fat cycle, seasonal changes in egg weight, total calories present in a mature 

 ovary, batch fecundity; and determined in the laboratory the gross caloric conversion efficiency 

 (12.8*7^). These measurements indicated that the caloric equivalent of only two spawning batches are 

 present in a mature ovary at any time and that two-thirds of the annual cost of 20 spawTiings could be 

 supplied by fat stores. Estimates of ainnual reproductive effort (egg calories/ration calories x 100) 

 ranged from 8% for 1 year to 11% for 3-year-old females. A daily ration of copepods equivalent to 4-5'^ of 

 female wet weight per day is required to support the annual cost of growth and reproduction. 



Histological evidence indicated that female north- 

 ern anchovy, Engraulis mordax, spawned about 

 once a week in February 1978 (Hunter and Gold- 

 berg 1980) and at 7-10 d intervals from late 

 January through the middle of April 1979 ( Hunter 

 and Macewicz 1980). Egg and larva survey data 

 indicate that some spawning occurs throughout 

 the year, although about 50% of the annual 

 production of northern anchovy larvae occurs 

 during the peak months of spawning (February to 

 April) (Lasker and Smith 1977). These findings 

 indicate that northern anchovy females spawn 

 many times per year. Thus, the annual fecundity 

 of northern anchovy is higher than originally 

 suspected by MacGregor (1968) and may be regu- 

 lated by availability of food. Energy regulation 

 of fecundity has been suggested for other marine 

 fish stocks and could be important as a density- 

 dependent population regulation mechanism 

 (Bagenal 1973). 



The objectives of this study were: to validate 

 recent work on northern anchovy spawning by 

 determining if such a high frequency of spawning 

 is developmentally and energetically possible; to 

 estimate the annual energy cost of reproduction; 

 and to discuss the sources of variation. We esti- 

 mated the average number of spawnings by north- 

 ern anchovy females in a year and tested the 



'Southwest Fisheries Center La Jolia Laboratory, National 

 Marine Fisheries Service, NOAA, La Jolla, CA 92038. 



Meinuscript accepted October 1980. 

 FISHERY BULLETIN; VOL. 79, NO. 2, 1981. 



hypothesis that they are capable of maturing eggs 

 at the required rate. We considered the energy 

 cost of reproduction, factors that affected varia- 

 tion in costs, and related reproductive costs to 

 fat stores. Finally we estimated the annual repro- 

 ductive effort (egg cal /ration cal). In addition to 

 data collected specifically for this study, we used 

 data available at the Southwest Fisheries Center 

 (SWFC), La Jolla, Calif., including many unpub- 

 lished sources. 



METHODS 



Field Data 



To estimate the annual number of spawnings 

 by northern anchovy, we used the data of Hunter 

 and Goldberg (1980) and Hunter and Macewicz 

 (1980) on the incidence of 24-h-old postovulatory 

 follicles. The proportion of mature females with 

 24-h-old postovulatory follicles was considered 

 equivalent to the fraction of females spawning per 

 day during a cruise (Hunter and Goldberg 1980). 

 All samples were taken in the Southern California 

 Bight in 1977-79; the number of females analyzed 

 per cruise was 148 from March 1977; 14 from 

 September 1977; 295 from February 1978; 395 

 from January-February 1979; 557 from March- 

 April 1979; and 33 from June 1979. Data were 

 plotted at the mid-date for the cruises which were 

 10-22 d long. 



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