FISHERY BULLETIN: VOL. 75, NO. 4 



100 r 



80 



E 



^ GO 



X 

 h- 

 tD 



LU 



|5 40 



o 



h- 



20 



10 20 



JAN 



10 20 



FEB 



1974 



28 



10 20 



MAR 



30 



FIGURE 8. — Scatterplot of lengths of fetuses and neonates (open 

 dots) of the eastern spinner dolphin on day of capture, 

 January-March 1974. 



fetal modes is not apparent in the data. For exam- 

 ple, in the large samples of fetuses collected in 

 January-March 1974 (Figure 8), a sharp mode at 

 60 to 75 cm in January is not apparent in Feb- 

 ruary, even as neonates, and the diffuse mode at 

 30 to 60 cm in February is not accounted for in the 

 January sample. A probable reason for these dis- 

 crepancies is the existence of area-related differ- 

 ences in the timing of calving peaks or in the 

 degree of synchrony of breeding. The tuna fleet, 

 our source of samples, moves around from month 

 to month. The January 1974 samples came for the 

 most part from more easterly, offshore localities 

 than did the February samples (Figure 9). In other 

 words, in 1974, calving in the more offshore region 

 may have been sharply synchronized, with a peak 

 in February-March, while in the more onshore 

 region, calving may have been spread over most of 

 the year. This hypothesis is reinforced by the data 

 for January- April 1975, when sizeable samples of 

 fetuses were collected in the more onshore region 

 during both January and February and smaller 

 samples through April (Figure 10) were from more 

 offshore (around Clipperton Island), northerly 



30° 



25° 



20° 



- 10° 



-0° 



125° 120° 115° 110° 105° 100° 95° 90° 85° 80 



125° 120° 115° 110° 105° 100° 95° 90° 85° 80° 



FIGURE 9. — Localities at which fetuses of the eastern spinner dolphin were collected in January (a) and February (b) 1974. 



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