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6961186 
Journal Article 
GROWTH AND REPRODUCTION OF THE COMMON DOLPHIN, DELPHINUS-DELPHIS LINNAEUS, IN THE OFFSHORE WATERS OF THE NORTH PACIFIC-OCEAN 
Ferrero, RC; Walker, WA; , 
1995 
1 
Fishery Bulletin
ISSN: 0090-0656 
NATL MARINE FISHERIES SERVICE SCIENTIFIC PUBL OFFICE 
SEATTLE 
483-494 
WOS:A1995RG19000005 
A total of 707 common dolphins, Delphinus delphis Linnaeus, (376 males and 331 females) taken in Japanese, Korean, and Taiwanese drift nets in the central North Pacific Ocean from February to November 1990 and 1991 were examined. Sex, total length, date, and location of capture were recorded. Biological samples were collected from 152 of the dolphins examined (93 males and 59 females). Ages were determined by counting dentinal layers. Female reproductive status was determined by macroscopic examination of ovaries (n=43). Eight females were mature, two were pregnant, three were resting, two were lactating, and one was of unknown condition. Testes and epididymes were examined for evidence of spermatogenesis (n=70); 21 males were mature. A preliminary estimate of gestation period was 11.1 months. The sex ratio appeared to favor males; segregation during the sampling period may be responsible for differences from 1.0. Male average age at sexual maturation was estimated to be 10.5 years. The largest sexually immature male was 179 cm; the smallest sexually mature was 182 cm. Mature testis weights ranged from 273.2 g to 1,190 g. Females reached sexual maturation at about 8.0 years; estimates of length at sexual maturation were 172.8 and 170.7 cm. Predicted asymptotic lengths for males and females were 188.1 cm and 179.4 cm, respectively. Calving appeared to peak in May and June. Sampling effort moved northward through September; infrequent sampling of parturient females and neonates during the projected calving mode suggests they were segregated outside the fishing area at that time.