FISHERY BULLETIN; VOL. 73, NO. 2 



trends associated with latitude. Generally, the 

 relative abundance of 4- and 5-yr-olds tended to 

 decrease as sampling progressed from south to 

 north while the relative abundance of 7- to 10-yr- 

 olds tended to increase. This is consistent with 

 obsen'ations over a larger sampling area. 



In summary, 1-, 2-, and 3-yr-old Pacific hake are 

 rarely encountered north of California and, as 

 sampling progresses northward along the 

 Washington coast, the younger age groups (4- and 

 5-yr-olds) contribute less to the population while 

 the relative abundance of the older age groups (7- 

 to 10-yr-olds) increases. 



Such latitudinal stratification of age groups, 

 apparently occurring to some extent even within 3 

 degrees of latitude, compounds the problem of 

 representatively sampling the age composition of 

 not only the entire hake population, but also the 

 com.mercially available portion of the population. 

 This spatial variation should be considered when 

 comparing annual changes in age composition. 



Sexual Variation 



Pacific hake samples taken off Washington in 

 1965-69 were used to examine the variation in age 

 composition between male and female com- 

 ponents. The percentage of each sex by age group 

 was calculated (Table 2) and plotted in Figure 9. 

 The age compositions for males and females are 

 similar in all years. The greatest difference oc- 

 curred in 1965 when females contributed a larger 

 proportion of the 4-yr-old group. In all years, a 

 greater percentage of the females occurred in the 

 older age groups (8 yr and older). These results 

 correspond well with earlier observations (Best 

 1963; Tillman 1968) that females live longer and 

 may be the sole survivors by age 11 and 12. 

 Therefore sampling that is highly selective for sex 

 would provide biased estimates of the relative 

 abundance of older age groups. 



GROWTH OF PACIFIC HAKE 



Growth in Length 



To determine the general shape of the growth 

 curve for Pacific hake, average lengths-at-age by 

 sex were computed using combined data from 

 samples taken off Washington, Oregon, and 

 California during 1965-69 (Table 3). 



Growth of both sexes is quite rapid during the 

 first 3 yr, then slows abruptly (Figure 10). 



Deceleration of the growth rate probably is not as 

 pronounced as indicated. Latitudinal stratification 

 of ages discussed previously is probably a result of 

 stratification by size; therefore, mainly the larger 

 members of the younger age groups would be 

 recruited to the Washington-Oregon area where 

 most samples were collected. Best (1963), for ins- 

 tance, computed the average lengths for small 

 samples of hake (age groups 4-13 consisted of 

 females only) taken off northern California and 

 the 3- to 6-yr-olds were somewhat shorter than 

 those in the Washington-Oregon samples (Figure 

 10). The most accurate growth curve for 2- to 6- 

 yr-olds would probably fall somewhere between 

 that based on Best's (1963) data and the curves 

 generated from my data. Asymptotic growth has 

 been shown for Cape hake, M. capeiisis (Botha 

 1969); silver hake (Fritz 1962); and Pacific hake in 

 Puget Sound (see footnote 3). For the purpose of 

 this study it is assumed that the growth curve for 

 the length of coastal Pacific hake is also asympto- 

 tic. 



Sexual differences in the size at age occur in 

 most hake species (Hickling 1933; Hart 1948; Fritz 

 1962; Botha 1969), and the Pacific hake is no ex- 

 ception (Figure 10). Females are noticeably longer 

 by age 4, but may be longer even at an earlier age. 

 Larkins et al. (see footnote 3) reported that female 

 Pacific hake of the Puget Sound population are 

 slightly longer than males even as 1-yr-olds. This 

 cannot be demonstrated for coastal hake because 

 sex information was not available for 1-yr-olds 

 and so few 2- to 3-yr-olds were collected that one 

 cannot accept the estimated mean lengths by sex 

 with confidence. Although sexual differences in 

 growth exist, these differences are not large. The 

 maximum difference in mean lengths is 3.12 cm 

 occurring at 11 yr of age (Table 3). 



Year class variation with respect to growth was 

 examined by two means: 1) the comparison of 

 age-length data collected in 1965-69, and 2) the 

 back-calculation and comparison of growth rates 

 for five year classes. 



Mean body lengths by age for the 1956-62 year 

 classes are found in Table 4 and compared in 

 Figure 11. Only samples taken off the Washington 

 coast were used so that successive year classes 

 could be compared while minimizing any spatial 

 effects. These growth curves generally fall into 

 two sets. Individuals of the 1956-59 year classes 

 were considerably larger at age than the members 

 of the 1961-()4 year classes. The growth curve for 

 the 1960 year class falls between the two sets. 



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