FISHERY BULLETIN: VOL. 84, NO. 3 



utilized in field sampling programs for northern an- 

 chovy and to use the historical data from these pro- 

 grams in conjunction with ovarian histological data 

 to describe age-dependent annual fecundity in the 

 central stock of northern anchovy. 



DATA SOURCES 



There are three major sources of biological data 

 for adult northern anchovy in California: samples 

 taken from the commercial fishery (Collins and 

 Spratt 1969), samples taken from midwater trawl 

 hauls carried out by the Sea Survey Program (Mais 

 1974), and samples taken primarily by midwater 

 trawl during egg production cruises (Picquelle and 

 Hewitt 1983). The first two sources are the result 

 of long-term research and monitoring programs 

 carried out by the California Department of Fish and 

 Game, and the third is the result of research cruises 

 carried out by the National Marine Fisheries Ser- 

 vice. The fishery data used in this analysis consist 

 of biological information for 60,661 northern an- 

 chovy sampled from the San Pedro purse seine fleet 

 during the period of 1966-80 and 4,904 northern an- 

 chovy sampled from the Monterey fleet during 

 1966-78. All northern anchovy in the fishery samples 

 were aged and nearly all were assigned maturity 

 stages. We used a geographically restricted subset 

 of the 1966-83 sea survey data (lat. 29.5°-34.5°N; 

 54,457 northern anchovy). Maturity stages were not 

 recorded for males in the sea survey data and age 

 determinations were made on only a portion (19,031) 

 of the fish sampled. In both data sets age determina- 

 tions were made from otoliths with methods 

 described by Collins and Spratt (1969). The third 

 source of data, provided to us by B. Macewicz 3 , con- 

 sists of histological information for the gonads of 

 8,672 females sampled during the months of 

 February to April from 1977 to 1984. Age deter- 

 minations were not made and maturity stages were 

 not taken on these fish. 



The gross anatomical maturity stage description 

 used for northern anchovy is a slightly modified 

 version of the system developed by Bowers and 

 Holliday (1961) for herring. The system has seven 

 maturity stages which are primarily based on the 

 portion of the body cavity occupied by the gonads 

 and, in the later stages, by the appearance of trans- 

 lucent eggs or milt (Table 1). Herring are consider- 

 ably larger than anchovy, and they are generally not 



3 B. Macewicz, Southwest Fisheries Center La Jolla Laboratory, 

 National Marine Fisheries Service, NOAA, 8604 La Jolla Shores 

 Drive, La Jolla, CA 92038, pers. commun. August 1984. 



considered to be multiple spawners; therefore, there 

 are some difficulties in applying the maturity stages 

 to anchovy. The most obvious problem is that a con- 

 siderable proportion of the anchovy sampled had 

 gonads so small that sex determinations were not 

 made as they would have required magnification. 

 There was also a small proportion of fish in which 

 physical deterioration made sex determination im- 

 possible. The California anchovy fishery is primar- 

 ily for reduction to fish meal, and the quality of the 

 fish was occasionally very poor when the fish were 

 sampled. Another major difficulty is that it is not 

 possible to distinguish between anchovy gonads that 

 are resting (i.e., stage 2) between multiple spawn- 

 ings in the same season and those resting between 

 spawning seasons. A comparable problem exists 

 with spent fish (stage 7). 



Table 1 .—The international (Hjort) scale of maturity stages of the 

 gonad. From Bowers and Holliday (1961). 



Stage 1 : Virgin individuals: very small sexual organs close under 

 vertebral column; ovaries wine-colored, torpedo-shaped, 

 about 2-3 cm long and 2-3 cm thick, eggs invisible to 

 naked eye; testes whitish or greyish-brown, knife- 

 shaped, 2-3 cm long and 2-3 cm broad. 



Stage 2: Maturing virgins or recovering spents: ovaries some- 

 what longer than half the length of ventral cavity, about 

 1 cm diameter, eggs small but visible to naked eye; milt 

 whitish, somewhat bloodshot, of same size as ovaries, 

 but still thin and knife-shaped. 



Stage 3: Sexual organs more swollen, occupying about half of 

 ventral cavity. 



Stage 4: Ovaries and testes occupying almost two thirds of ven- 

 tral cavity; eggs not transparent, milt whitish, swollen. 



Stage 5: Sexual organs filling ventral cavity; ovaries with some 

 large transparent eggs; milt white, not yet running. 



Stage 6: Roe and milt running (spawning). 

 Stage 7: Spents: ovaries slack with residual eggs; testes baggy, 

 bloodshot. 



SEX RATIO 



Description of the sex ratio in northern anchovy 

 was confounded by the presence of fish for which 

 the sex could not be determined. The relationship 

 between size and the percentage of these unsexed 

 fish is similar for both the commercial purse seine 

 and midwater trawl data. In both data sets, a large 

 percentage of the fish smaller than 100 mm stand- 

 ard length (SL) are of unknown sex, about 10% of 

 the 101-110 mm fish are of unknown sex, and only 

 a small percentage of the fish larger than 110 mm 

 are of unknown sex (Table 2). The percentages of 

 fish with unknown sex at sizes larger than 110 mm 

 in the purse seine data are somewhat higher than 

 those in the midwater trawl data. This is probably 

 due to the occasional occurrences of fish in which 



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