FECUNDITi^ OF THE PACIFIC SARDINE 



445 



(resting) and L (spent) fish in the next hiiiar period. 

 This would indicate a short peak spawning period 

 in the Monterey region during tliese two years. 

 Clark shows a decrease in ratios in 1930 at Mon- 

 terey from 3.88 in the January-February 

 lunar period (1:15-11:13) to 2.22 in the April- 

 May lunar period (IV:14-V:12). Assuming that 

 the values adequately represent the ratios during 

 the two periods (the higher is based on 2 speci- 

 mens), the decrease in ratios amounts to 1.66, 

 hence the average number of batches spawned 

 per female could approximate 2.66 batches. 



The situation at San Pedro is more difficult to 

 interpret. In 1929 Clark shows a high ratio of 

 3.80 (based on 18 G stage fish sampled between 

 11:24-111:25), a low of 2.07 (based on 5 stage G 

 fish sampled between VII:22-VIII:20) for a total 

 decrease in ratios of 1.73; this approximates the 

 decrease given above for Monterey in 1930. It 

 should be noted that most of the decrease in ratios 

 in 1929 at San Pedro also occurred during a two- 

 montli period. The ratio of 3.80 had decreased 

 to 2.38 by lunar period IV:24-V:23 for a drop in 

 ratios of 1.4. During the four succeeding lunar 

 months the further drop in ratios amounted to 

 only 0.3. The 1930 data show no real change in 

 ratios during the season. A drop in ratios from 

 3.06 to 2.02 occurred between two lunar periods 

 (between 11:14-111:14 and III:15-IV:13), but the 

 ratios again jumped to 2.92 and 2.84 in the two 

 following lunar periods. 



At the end of the spawning period at both ports 

 spawning females still contained several modes 

 that had not been spawned. These yolked ova 

 must have degenerated and been resorbed. In 

 fact, it may be characteristic of fish wliich mature 

 several modes of ova, that one or more of the 

 modes will be resorbed eventually rather tlian 

 spawned. 



LENGTH AT FIRST MATURITY 



To facilitate handling of the data, the samples 

 have been grouped by lunar periods ^ in table 14. 



Clark (1934) considered as maturing all those 

 fish having a group of ovarian eggs with a modal 

 diameter of .22 mm. or larger (i. e., yolked ova). 



' The Pacific sardine fishery in California Is carried on at night, when the 

 fish schools can he located by inmlne.scence. There is generally no flshing 

 (luring the full-moon period. Lunar periods are assigned inirnbers in con- 

 nection with the sampling program of the California Cooperative Oceanic 

 Fisheries Investigations. 



Using this critcriDii, the 250 fish taken in lunar 

 periods 325 and 326 are compared in table 15 with 

 Clark's data for the months of February, March, 

 April, and May of the years 1929, 1930, and 1931. 



Table 14. — Samples grouped by lunar periods 



Maximum ovum diameter, the measurement 

 used to describe the stage of maturity for the 

 1946 material, is the diameter of the largest ova- 

 rian ovum present in a sample of the ovary. An 

 average value (mode, mean, or median) of the 

 group of developing ova cannot be determined ac- 

 curately for early developmental stages when the 

 developing ova are not completely dift'erentiated 

 from the mass of immature, non-yolked ova that 

 are always present in the ovary. For developing 

 groups of ova that have differentiated enough from 

 these immature ova to form a distinct size group, 

 the maximum ovum diameter is about .07 mm. 

 greater than the median ovum diameter of that 

 size group. This difference is probably less for 

 developing groups of smaller ova than for groups 

 of larger ova. 



Table 15. — Numbers of sardines and percentages containing 

 developing ova 

 |San Pedro, Calif.) 



