Reproductive Ecology of the Freshwater Bivalve, Unio douglasiae (Unionidae) in Lake Uiam
Mi-Young Song, Jire Im, Wan-Ok Lee, Sung Tae Kim and Dae-Hee Kim
Inland Fisheries Research Institute, National Fisheries Research and Development Institute, Gyeonggi-do 477-815, Korea Fisheries Resources Research Division, National Fisheries Research and Development Institute, Busan 619-705, Korea

The reproductive ecology of freshwater bivalve, Unio douglasiae in Lake Uiam were examined from March 2014 to February 2015. The gonads distributed in reticular connective tissue, the dioecious clams take an internal fertilization and fertilized eggs are stored in the foster-sack in the gills, then the hatched juveniles are released outside after an ovoviviparous process. The gonad index (GI) began to increase in April, reached the maximum value in July and to decrease in August. The reproductive cycle of U. douglasiae can be divided into five successive stages: multiplicative stage (November to January), growing stage (February to March), mature stage (February to May), spawning stage (April to September), recovery stage (August to December). The spawning periods were from April to September, and the main spawning occurred between April and July. The shell length at 50% group maturity was estimated to be 29.4 mm.

  
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