Energy Storage and Utilization in Wild Pacific Oysters (Crassostrea gigas) in an Annual Reproductive Cycle in Uihangri Tidal Flat on the West Coast of Korea, 4 Years After the Hebei Spirit Oil Spill (HSOS) Accident

초록

This study investigated reproduction and related changes in reserve levels in a wild population of the Pacific oyster, Crassostrea gigas, in the Uihangri tidal flat on the west coast of Korea, 4 years after the Hebei Spirit Oil Spill (HSOS) accident. Histology showed a clear yearly pattern of gametogenesis and spawning aligned with seasonal changes in sea surface temperature (SST). Gonad-somatic index (GSI), a ratio of the egg mass to the somatic tissue, dropped dramatically from August (27.1%) to September (8.2%), suggesting a massive spawning during this period. The glycogen content, a proxy for the energy reserve, showed its annual peak in May (68.3 mg/g tissue) and the second-highest in October (64.5 mg/g tissue). The condition index (CI) also showed a clear seasonal pattern, with an annual maximum when the wild oysters were in the ripe stage, and an annual minimum after the massive spawning. Digestive gland atrophy, a proxy for oyster nutritional condition, remained higher during the winter (December-March), suggesting that the oysters are in a state of starvation. The observed high synchronization of the annual reproductive cycle and the significant spring recovery of nutritional health indicated that the physiological and reproductive parameters of wild Pacific oysters at Uihangri were within the range previously reported for populations from this and nearby sites, suggesting no clear evidence of persistent impairment during the study period.

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