212 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Fish in the northern part of the range of the 

 fishery are perhaps distinguishable as large, long- 

 ranging individuals, while southern stocks may 

 be characterized by smaller size and more limited 

 migration routes. These stocks appear to overlap 

 in their distribution on fishing grounds as evi- 

 denced from the length-frequency data accumu- 

 lated over a long period of years by the California 

 Department of Fish and Game and later by the 

 State agency in cooperation with the United 

 Slates Fish and Wildlife Service. Over the period 

 of study of age composition of the catch for which 

 length composition by age is also available, it is 

 evident that the smaller sizes of each year class 

 are rarely caught north of central California. 



Ronquillo (1949, p. 29) foimd that the sizes of 

 pilchard in the Pacific Northwest during most 

 months of fishing did not differ significantly from 

 those caught off central California, but that fish 

 from both these regions showed significant dif- 

 ferences from those taken off San Pedro. Over 

 three seasons, from 1945-46 through 1947^48, 

 in all age groups there was a significant difference 

 in size between fish landed at San Pedro and 

 Monterey. During the first 2 years of life sardines 

 taken at San Pedro were significantly larger; in 

 older age groups those landed at Monterey were 

 larger than those at San Pedro. Ronquillo (op. 

 cit ., p. 25) also found that the coefficient of variation 

 fluctuated more at San Pedro than at other 

 localities which indicated greater heterogeneity 

 in those samples. He found this measure rel- 

 atively constant in the Pacific Northwest and 

 therefore indicative of homogeneity within the 

 samples. 



The tendency for smaller sizes to remain in the 

 southern part of the range of the species is il- 

 lustrated also by tagging results (Clark and 

 Janssen 1945, p. 22). They found a southward 

 migration of some of the sardines released in 

 central California and note — 



a greater proportion of the smaller sizes have made this 

 southward migration. For the group tagged in 1940, 72 

 percent of the recoveries in southern California during the 

 first season after tagging were less than 19 cm. when 

 tagged. For the same season in central California only 

 50 percent of the recoveries were of these smaller sizes. 

 During the second season after tagging, 74 percent of the 

 southern California recoveries were less than 19 cm. when 

 tagged but only 43 percent of the central California 

 recoveries were composed of these smaller sizes. 



Recoveries of sardines tagged off central Lower 



California have been almost entirely in California. 

 Approximately 78 percent were recovered in 

 southern California, 15 percent in Monterey, 7 

 percent in San Francisco and less than half of 1 

 percent (represented by one tag) in Washington 

 (Janssen 1948). Concerning the absence of 

 recoveries in Lower California, Janssen (p. 7) 

 states as follows: 



Xo tag recoveries have been reported from reduction 

 plants in Lower California. Facilities for recovering t ags 

 were in operation there for only a brief period and the 

 quantity of sardines processed in Mexico is small in com- 

 parison with other localities along the coast. 



Considering the total number of tags recovered 

 without regard to area of recovery, only 10 per- 

 cent of tags put out off Mexico were recovered, 

 while off southern California 2.'i percent and oil' 

 central California 25 percent were recovered 

 (according to Janssen's adjusted percentage re- 

 covery figures, p. 9). The Mexican laggings 

 further indicate the tendency for the southern fish 

 to remain in southern waters. 



The larger pilchard of a year class, on the other 

 hand, commonly are caught on any of the usual 

 fishing grounds from the Pacific Northwest to 

 southern California. Whether the significant 

 difference in attained ultimate size, l„, of south- 

 ern as opposed to northern growth types arises by 

 reason of primary difference either in location of 

 spawning centers or in location of nursery grounds, 

 or both, and whether in turn difference in origin 

 of stocks also represents genetic difference await 

 further data from spawning studies and determi- 

 nation of how discrete are the areas of spawning 

 and of spawning stocks. 



The apparent differences in growth characteris- 

 tics in populations along the coast suggest the 

 desirability of study of population dynamics not 

 only for the coast as a whole but also for geo- 

 graphic areas, e. g., for the Pacific Northwest, 

 central California, southern California, and further 

 subdivisions of areas off Lower California not yet 

 clearly delineated. 



SCALE AND GROWTH PATTERNS OF 

 INDIVIDUAL FISH 



That the fished stocks of the Pacific Northwest 

 and southern California have, for practical pur- 

 poses, some independence seems indicated from 

 further lines of evidence. 



