FISHERY BULLETIN: VOL. 74, NO. 2 



Table 3. — Estimated growth for the first 24 mo of life of the 

 northern anchovy reared in the laboratory. Estimates are based 

 on a two-phase Gompertz growth curve (see text). 



General Remarks 



The steplike growth pattern is commonly found 

 in fishes. Gerking (1967) reviewed the literature 

 on this subject and noted that many temperate 

 species have seasonal, sigmoid growth curves. 

 Lockwood (1974) recognized this feature in the 

 growth of plaice and brown trout and applied a 

 multiphase von Bertalanffy growth model to de- 

 scribe the data mathematically. His results were 

 satisfactory but because the von Bertalanffy 

 growth equation does not describe a sigmoid 

 curve, his analysis was confined to growth for part 

 of the season only. 



In this study we used the Gompertz growth equa- 

 tion to describe the sigmoid curve. The two-phase 

 model satisfactorily described our data for 

 laboratory-reared anchovy, and a cycle that occurs 

 at 12-mo intervals is evident in our results. This is 

 quite similar to the seasonal growth patterns de- 

 scribed by Gerking (1967), Mann (1971), Kroger et 

 al. (1974), and others. The cycle indicates that for 

 the northern anchovy, about 95% of the first year's 

 growth is completed by the 8th month of life and 

 about 9 1% of the second year's growth is completed 

 by the 20th month of life. 



If this cyclic pattern in growth also occurs in 

 anchovies in the wild, then it may have a consid- 

 erable impact on yield models, such as yield-per- 

 recruit models, and on management decisions. It 

 might be that the best harvesting strategy in 

 terms of maximum yield-per-recruit is during the 

 period of the cycle when growth is relatively slow, 

 i.e., period of plateau. It seems important, there- 

 fore, that a multiphase growth function be 

 considered for use in yield models for northern 

 anchovy. 



We point out the possibility that the cyclic pat- 



tern could have been artificially created because 

 our data were from three cohorts that were reared 

 under different laboratory conditions during dif- 

 ferent periods of the year and the ages of fish 

 reared by Leong (pers. commun.) were estimated. 

 However, we discount that possibility because the 

 cyclic pattern persists even if our age estimates of 

 Leong's fish were off by 1 or 2 mo. Rearing condi- 

 tions, on the other hand, could have produced the 

 cyclic pattern if the pattern is influenced primar- 

 ily by environmental factors, e.g., temperature, 

 length of day, and food density and quality 



WEIGHT-LENGTH RELATION 



Weight-length relations for the northern an- 

 chovy were reported by several investigators (Ta- 

 ble 4). OnlyLaskeretal. (1970), however, reported 

 on estimates for laboratory-reared anchovies, and 

 their estimates were for anchovy larvae. 



Length and weight data were collected by Leong 

 (pers. commun.) and Paloma^ from fish reared in 

 their experiments. We used their data from 757 

 fish to estimate the weight-length relation of 

 laboratory-reared anchovies of 70 to 131 mm long. 

 Data from Paloma were only from fish in their first 

 year of life, in which growth was somewhat simi- 

 lar to that of fish reared by Leong. Separate esti- 

 mates were made for males and females (Table 4), 

 and the results subjected to covariance analysis 

 (with log transformed data) to test whether the 

 relation could be represented by a single line. The 

 analysis indicated that the separate lines were 

 parallel and not significantly different from a 

 common line. The data were, therefore, pooled and 

 a weight-length relation estimated for the com- 

 bined (all sexes) data (Table 4). 



Our estimates are compared with those of Col- 

 lins (1969) for anchovies from southern California 

 (Figure 4). Collins based his estimates on data 

 from anchovies caught in the reduction fishery off 

 southern California. For a given length, fish 

 examined by Collins were lighter than the 

 laboratory-reared fish. This phenomenon appears 

 common for fishes (Kramer 1969; Kimura and 

 Sakagawa 1972). Kimura and Sakagawa (1972) 

 mentioned that for Pacific sardines, differences in 

 diet and reduced amount of exercise because of 

 confinement were some possible causes for 



^Paloma, P. 1971. Annulus formation in the scale of marked 

 anchovy Engraulis mordax Girard. Unpubl. manuscr. Southwest 

 Fisheries Center, La Jolla, CA 92038. 



276 



