Table 3. — Combined ovary weights, maximum follicle diameter, and 

 corpora counts in "non-atrophic" (normal) ovaries with no corpus 

 lutem (n = 3,455) and atrophic ovaries (n = 9) of sexually mature 

 female spotted dolphins collected in 1973-82. 



FISHERY BULLETIN: VOL. 84, NO. 2 



lacked macroscopic follicles. Such specimens have 

 in common: 1) the absence of CLs and Type 1 cor- 

 pora, 2) a large number of total corpora, 3) a high 

 frequency of atresia (a relatively large proportion of 

 the total corpora), and 4) a maximum follicle 

 diameter of 0.5 mm or less. The incidence of obvious 

 senescence in the sample of spotted dolphins (0.4%) 

 is much less than that in pilot whale samples studied 

 (5% in Globicephala melaena from the northern 

 Atlantic Ocean [Sergeant 1962] and 25% in G. 

 macrorhynchus from the western Pacific [Marsh and 

 Kasuya 1984]). This may be indicative of inherent dif- 

 ferences in the social structure or longevity between 

 pilot whales and spotted dolphins. 



Table 4.— Mean age, maximum follicle diameter, ovary weight, corpora counts, and reproductive states 

 for female spotted dolphins. Type 1 and Type 2 corpora defined by Perrin et al. (1976). 



includes atretica. 



specimens were pregnant or lactating. All 14 of the 

 second group were pregnant or lactating. Thus, the 

 first group shows reduced fertility when compared 

 with the second group. Marsh and Kasuya (1984) 

 described an age-related decline in follicle abundance 

 in pilot whales, stating that when follicles are 

 "depleted" the animals become senescent. The reduc- 

 tion in fertility indicated in our sample of spotted 

 dolphins is not strictly age-related; it is more depen- 

 dent on the number of corpora (including corpora 

 atretica) already present in the ovaries. This has been 

 shown to be true in western Pacific spotted dolphins 

 (Kasuya et al. 1974) and in sperm whales (Best 1967). 



In addition to the postreproductive females with 

 atrophic ovaries, four mature females with normal- 

 appearing ovaries had no macroscopic follicles (one 

 of the atrophic ovaries contained no macroscopic 

 follicles). This is similar to the condition described 

 by Marsh and Kasuya (1984). The ovaries of these 

 specimens weighed from 2.2 to 5.9 g, had no CLs 

 or Type 1 or Type 2 corpora, and contained 8-22 total 

 corpora, 12% of which were atretic None were lac- 

 tating. They are considered to have been postrepro- 

 ductive also. 



Spotted dolphin specimens were judged to have 

 been senescent when they had atrophic ovaries or 



CONCLUSIONS 



Several of our analyses have yielded results similar 

 to those reported previously for spotted dolphins by 

 others, notably Perrin et al. (1976) and Kasuya et 

 al. (1974). We found ovulation rates to have high in- 

 dividual variability with a markedly higher rate of 

 corpus formation in the earlier reproductive years 

 that decreases after a fixed number of ovulations has 

 occurred. 



The conclusions reached by Perrin (1969b) and par- 

 ticularly by Kasuya et al. (1974) with regard to the 

 close correlation between color pattern and sexual 

 maturity in spotted dolphins are also supported by 

 our study. Ninety-six percent of the fused, 50% of 

 the mottled, and only 4% of the speckled specimens 

 were sexually mature Fused specimens had more 

 corpora and appeared to have been sexually mature 

 longer than mottled specimens of the same age or 

 length. 



Our estimated length of the calving interval (3.03 

 yr) is within the range of earlier estimates calculated 

 for this stock by Perrin and Reilly (1984). It is also 

 within the range of estimates for two other spotted 

 dolphin stocks. 



Some of our analyses, however, produced results 



256 



