Population Ecology of Endangered Fish Gobiobotia naktongensis Inhabiting the Gamcheon Stream, Nakdonggang River (Pisces: Gobioninae)

낙동강 수계 감천에 서식하는 멸종위기어류 흰수마자 Gobiobotia naktongensis (Pisces: Gobioninae)의 개체군 생태

Population ecology of Gobiobotia naktongensis was investigated at the Gamcheon stream, Nakdonggang River in Korea from March to November in 2010 and June in 2012. It mainly inhabited on the slow-flowing waters 0.11~0.44 m/s (mean: 0.32) and shallow depth 11~69 cm (mean: 28). As a result of the sieve analysis, size of the particles in the stream bottom beds consisted of 1.71% (>3.35 mm), 71.3% (>0.500 mm) and 26.9% (>0.106 mm). The standard length of the population indicated that the age for 25~30 mm group is one 31~41 mm group is two and longer than 42 mm group over three (May in 2010). The spawning period was from June to July with water temperatures ranging from 28.0 to $31.0^{\circ}C$. The sex ratio of female to male was 1 : 0.64 while the number of eggs in the ovaries was 1,067~7,298 (mean: 2,827). The number of matured eggs size in ovaries was 0.71~1.04 mm (mean: 0.79) and the stomach contents were mainly Chironomidae. The individual number of stomach contents was increased at noon and showed the highest rate from noon to 3 pm.

2010년 3월부터 11월, 2012년 6월에 낙동강 수계 감천일대에서 흰수마자의 서식지 환경특성 및 개체군 생태를 조사하였다. 흰수마자의 미소서식처의 환경조건은 유속 0.11~0.44 ($0.32{\pm}0.06$) m/s, 수심 11~69 ($28{\pm}14.4$) cm 내외인 곳이었고, 하상입자크기의 구성비율은 1.71% (>3.35 mm), 71.3% (>0.500 mm), 26.9% (>0.106 mm)이었다. 1년생은 체장 25~30 mm, 2년생이 31~41 mm, 3년생이 42mm 이상으로 추정되었다 (5월 기준). 산란기는 6월과 7월 사이(수온 $28.0{\sim}31.0^{\circ}C$)였고 성비는 1 : 0.64로서 암컷이 우세하였다. 포란수는 1,067~7,298 (평균 2,827)개였고 난경은 0.71~1.04 ($0.79{\pm}0.051$) mm였다. 흰수마자의 주요 먹이생물은 깔다구과였고, 먹이생물 개체수는 정오인 12:00시부터 증가하기 시작하여 0:00~03:00 사이에 가장 많았다.