Abstract
Longitudinal distribution of the fish fauna of the 20 main channel and tributary sites in the Nakdong River was investigated from July 1999 to December 2000. A total of 4,791 individuals of fisHes were collected from three to seven sampling programs of all study sites and 48 species of 17 families were collected. Dominant family was Cyprinidae (25 species, relative abundance (RA): 91.8%). Zacco platypus (RA: 18.0%) was found to be the most abundant inhabitant. Subdominant species were Opsariichthys bidens (17,1%), Squalidus chankaensis tsuchigae (13.2%), Hemibarbus labeo (9.9%), and Z. temmincki (8.2%). Among the total species, 12 species were identified as endemic species (4 families, 24.5% of 1,172 individuals). Four exotic fishes were collected (Carassius cuvieri, 25 indv.; Micropterus salmoides, 214 indv.; Lipomis macrochirus, 14 indv.; Oreochromis niloticus, 6 indv.). M. salmoides was distributed in mid to lower part of the Nakdong River. As the result of cluster analysis, sampling sites were divided into three groups (upper, middle and lowerpart). Site below Gumi (St. 10) were considered as the lower part of the Nakdong River. Combined with previous surveys, about 80 species are present in the main channel and tributaries of the Nakdong River. Since the middle of 1990s, population density of the M. salmoides rapidly increased in the stagnant lower part of the river(RA 8.8% in lower 5 sites). The feeding strategy of M. salmoides was "generalized" on Daphnia sp. (<100 mm), and "specialization" about Cladocera (<150 mm) and Insecta(<200 mm).
낙동강 본류 및 지천을 중심으로 20개 지점에서 1999년 7월부터 2000년 12월까지 지점별 3${\sim}$7회에 걸쳐 어류상을 조사한 결과 총 17과 48종 4,791개체가 채집되었다. 잉어과 (25종: 상대풍부도 (RA), 91.8%)가 우점하였으며, Zacco platypus (RA: 18.0%)는 우점종으로 나타났으며, 아우점종은 Opsariichthys bidens (17.1%), Squalidus chankaensis tsuchigae (13.2%), Hemibarbus lab대 (9.9%), Z. temmincki (8.2%) 순으로 나타났다. 채집된 종중 한국고유종은 모두 12종으로 나타났다(4과, 1,172개체 , 24.5%). 외래도입종은 Carassius cuvieri (25개체), Micropterus salmoides (214개 체), Lepomis macrochirus (14개 체), Oreochromis niloticus (6개체) 등 4종이 채집되었다. M. salmoides는 낙동강의 중류와 하류부에 고루 분포하는 것으로 나타났다. 집괴분석 결과 세집단으로 나뉘었으며, St. 10(구미)부터 하류집단에 포함되었다. 1990년대 후반 낙동강에 유입된 M. salmoides는 하류부에서 급격히 그 수가 증가하였다(하류 RA 8.8%). M. salmoides의 섭식은 Daphnia sp.가 일반적이었으며 (<100 mm), Cladocera (< 150 mm)와 Insecta (< 200 mm)는 특별한 것으로 나타났다.