Quantitative assessment of reproductive effort of the Manila clam Ruditapes philippinarum in a lagoon on Jeju Island (Korea) using enzyme-linked immunosorbent assay

Abstract

We investigated gonad development and reproductive effort (RE) of the Manila clam Ruditapes philippinarum at Jeju Island, Korea. Gonad maturation and RE were determined using histology and an indirect enzyme-linked immunosorbent assay (ELISA). In June 2006, most of the clams (80%) in the lagoon were in the resting stage. Spawning clams first appeared in late July, and most clams spawned from early August to mid-September. The condition index increased gradually from early July to late August, then declined from early to mid-September, suggesting that spawning occurred during this period. The gonadosomatic index assessed by ELISA also increased dramatically from June (0.9), peaked in early August (19.7) then declined from late August to mid-September, indicating that clams at the study site had only one spawning pulse during the spawning period. Spawning at Jeju Island was one month later than Manila clams on the west coast of Korea. The delayed spawning and low RE of the clams could be in part, be explained by lower food availability, as the level of chlorophyll-a recorded in this study was much lower than that found in water from the west and south coast.

Keywords:

• Manila clam
• fecundity
• quantification
• GSI
• food availability

Acknowledgements

The authors thank the staff of Shellfish Research and Aquaculture Laboratory at Jeju National University for the field and laboratory work. This study was conducted as a part of the project titled “Assessment of the Impact of Climate Change on Marine Ecosystems in the South Sea of Korea “(PM57090)”, funded by the Ministry of Oceans and Fisheries, Republic of Korea.

Notes

Present adress: Department of Fisheries Management, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh