Differences in reproductive strategies between obscure puffer Takifugu obscurus and ocellated puffer Takifugu ocellatus during their spawning migration

Reproductive strategies were compared between obscure puffer Takifugu obscurus and ocellated puffer Takifugu ocellatus captured in waters near Yangzhong Island in the lower reaches of the Yangtze River during the spawning migration season from February to June in two consecutive years (1995 and 1996). Results showed that obscure puffer and ocellated puffer have adopted different reproductive strategies, including different spawning times, different size at maturity, and different number and size of oocytes, resulting in two different larval sizes. In detail, the timing of the spawning migration and status of gonad development of obscure puffer was about 1 month earlier than that of ocellated puffer; the obscure puffer was obviously longer and heavier than ocellated puffer in both mature male and female fish; mean GSI of obscure puffer females (15.8%) was significantly higher than that of ocellated puffer females (14.6%); the average diameter of ocellated puffer eggs (1.49 +/- 0.12 mm) was significantly larger than that of the obscure puffer (1.22 +/- 0.08 mm); and obscure puffer females (320.8 oocytes mg(-1) somatic wet weight) had significantly higher relative fecundity than ocellated puffer females (125.2 oocytes mg(-1) somatic wet weight). These differences in reproductive strategies between two closely related species of the Takifugu genus indicate that both obscure puffer and ocellated puffer fit the r/K dichotomy. Obscure puffer shows K-selected characters with maturity at relatively large size and r-selected characters with relatively many and small offspring, whereas ocellated puffer shows r-selected characters with maturity at a relatively small size and K-selected characters with relatively few and large offspring.