FISHERY BULLETIN: VOL. 70, NO. 3 



90r 



80 



70 



60- 



50 



40 



30 



20 



10 



0^M_ 



/ — CLARK (1928) 



30 



50 



70 90 110 130 



STANDARD LENGTH (mm) 



150 



170 



190 



Figure 3.— Weight-length relation for the Pacific sardine, 



(Figure 3) and found to be significantly differ- 

 ent based on analysis of covariance (F = 18.02, 

 df = 1, 237). The laboratory-reared fish were 

 appreciably heavier for a given length than sar- 

 dines caught in the 1920's. This may be attrib- 

 uted to several causes, among them diff'erence in 

 diet, in amount of exercise, and in the range of 

 sizes sampled. 



SEASONAL GROWTH PATTERN 



Growth of the Pacific sardine has been well 

 documented by several investigators (e.g., Wal- 

 ford and Mosher, 1943; Phillips, 1948; Felin, 

 1954; Clark and Marr, 1955) . Most of the stud- 

 ies have concentrated on estimating growth 

 based on scale readings of fish caught by the 

 commercial fishery. 



Another method of estimating growth is by 

 rearing experiments. Although we recognize 

 the limitation of laboratory vs. natural condi- 

 tions, we believe that estimates of growth of lab- 

 oratory-reared sardines can indicate the general 

 trend in growth in the wild. We therefore esti- 

 mated growth of our laboratory-reared sardines. 



As shown in Figure 4, growth in length was 

 rapid from the start of the experiment to the 

 fourth month, after which the increase was more 

 gradual. The average instantaneous rate of 

 growth was about 0.47/month during the first 

 4 months and about 0.03/month during the fifth 

 to 24th month. In contrast, growth in weight 

 increased somewhat exponentially during two 

 phases: during the first 4 months and again dur- 

 ing the fifth to 14th month (Figure 5). 



Walford and Mosher (1943) reported the 

 standard lengths of juvenile sardines caught in 

 monthly samples in the late 1930's. Although 

 the date of birth, and hence the exact age, of 



ANNULUS 

 -I * 



ACCESSORY 



MAY J 

 I 



M A M J J 



10 II 12 13 14 



AGE (MONTH) 



Figure 4. — Growth in length of Pacific 

 sardines reared in the laboratory for 24 

 months. Mean length is represented by 

 a circle, and one standard deviation is 

 shown on each side of the mean. The 

 sample size is also indicated. The first 

 accessory mark occurred in August-Oc- 

 tober, and the second in May-August. The 

 first annulus formed in November-March, 

 and the second apparently in December. 



1048 



