222 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



T\ble 4 — Calculated mean first growth increments (Ti) for pilchard year classes from 1- to 5-ring caught at San Pedro and 



Monterey, 1936-48 



appear, the observed Length a I 0-ring is comparable 



to the calculated length at 1-ring, and observed 

 length of 1-ring fish is comparable to the calculated 

 length at 2-ring. 



Tagging and growth data thus both appear to 

 indicate a tendency for larger fish to migrate 

 farther north, but there is apparently not a great 

 deal of emigration of the large 1- and 2-ring sar- 

 dines from the southern California grounds so that 

 these early ages may he used as reasonably good 

 indices of early year-class strength in one geo- 

 graphical area. 



ANOMALIES IN YEAR-CLASS CATCH 

 CURVES 



Vital statistics of I he fishery show that, new 

 sources of fish were unexpectedly available in 

 season 1949-50 (Felin, Daugherty, and Pinkas, 

 1950 and 1951). The overavailability of certain 

 ages is reflected in certain anomalies in year-class 

 catch curves at all California ports. At all three 

 ports there was a marked deviation from the 

 previous trend of total mortality rate for 1944 and 

 1945 year classes, as 4- and 5-ring fish. In central 

 California ports, the 194.3 and 1946 year classes 

 also showed increase in availability (as defined by 

 Marr 1951). 



BIMODALITY IN LENGTH-FREQUENCY 

 COMPOSITION 



There are also indications of bimodality in 

 length-frequency composition of the 1944 year 

 class caught during the 1949-50 season in Cali- 



fornia ports (Felin, Daugherty, and Pinkas, 1950). 



Study of growth transformations from calculated 

 lengths of individual fish of the 1944 year class 

 showed that coincident with the unexpectedly 

 large catches of this year class as 5-ring fish in 

 1949-50 there were many small-sized individuals 

 of this age caught in San Pedro and Monterey. 

 Some of these 5-ring fish were smaller than sar- 

 dines of the same year class as 4-ring so that their 

 presence in the catches could not be accounted 

 for as small fish remaining after the exodus of 

 larger migrants going north. Their presence must 

 rather he explained as an influx, probably from the 

 south, of small fish into the southern and central 

 California fishing areas. Thai this appears to he 

 a st rongly southern year class is indicated in figure 

 9. The average observed lengths of the 1944 year 

 class as 5-ring at San Pedro and Monterey also 

 show a decrease as compared with the same year 

 class caught as 4-ring fish in I he previous season. 



An appearance of bimodality has also been 

 observed in the length composition of other year 

 classes in previous seasons (cf. Felin and Phillips 

 1948), and is further evidence from growth that 

 pilchard caught along the Pacific coast do not 

 constitute a single homogeneous population. 



SUMMARY AND CONCLUSIONS 



1. The question whether the fished stocks of 

 the Pacific pilchard, or sardine, along the Pacific 

 coast are homogeneous is considered in the light 

 of evidence from growth studies and other vital 

 statistics. 



