Nursery Grounds for Round Crucian Carp, Carassius auratus grandoculis , in Rice Paddies Around Lake Biwa

摘要: Since the turn of twenty-first century, two means promoting use rice paddies as fish nursery ground have been implemented around Lake Biwa in Japan. One involves culture: newly hatched or pre-flexion larvae are released into after transplantation, and then reared to juveniles before mid-season drainage. The other installation passes enhance entry adult encourage their natural reproduction there. These efforts mainly aim round crucian carp (nigorobuna), Carassius auratus grandoculis, an endangered endemic subspecies inhabiting Biwa, which is also principal ingredient funa-zushi, a specialty food Shiga Prefecture. Both methods regarded environment-friendly thus well supported by local people. Our studies on paddy chain revealed, however, that impact larvae/juveniles aquatic biota profound. Fish predation results extreme reduction Cladocera, concomitant increase species competitors cladocerans. Through benthic foraging, juvenile cause rise total phosphorus concentration phytoplankton water. In addition, scarce predators contribute rapid growth low mortality larvae/juveniles. Although employment may be effective for conservation carp, approaches needed overall biodiversity areas Biwa.