River estuaries are dynamic and productive ecosystems with high regional biodiversity. Environmental DNA (eDNA) has become a useful approach to assessing biodiversity in aquatic ecosystems. This study was conducted to investigate fish community characteristics and species diversity in two river estuary ecosystems, the Taehwa River and Changwon Stream. We further compared conventional and eDNA metabarcoding analyses of the fish communities. The conventional survey was performed in May, July, and October 2022, while the eDNA analysis was conducted only in May. We observed various fish species with different life histories, including carp, goby, and marine fish. We also found that migratory fish, such as dace Tribolodon hakonensis, sweetfish Plecoglossus altivelis, and eel Auguilla japonica, occurred in the Taehwa River, suggesting high river connectivity. Marine fish species were predominant in the Changwon Stream, as this river is located close to the sea. The diversity indices showed that the Taehwa River generally had higher species richness, evenness, and diversity values than the Changwon Stream. A total of 9-19 species were detected in the conventional survey for the three sites, whereas 11-18 species were found from eDNA analysis. The findings indicate that the sensitivity of eDNA was similar to or higher than that of the conventional method. Our study findings suggest the efficiency and efficacy of eDNA-based fish community monitoring, although with some shortcomings in applying the genetic marker to Korean fish, including no clear-cut distinction for Korean endemic species and/or genetically closely related species groups.

본 연구는 울산광역시의 태화강을 포함한 하구역에 서식하는 대형저서동물의 군집구조를 파악하기 위하여 2012년 2월부터 동년 11월까지 총 4회에 걸쳐 현장조사를 실시하였다. 태화강 하구역에서는 총 176종/9.6㎡ 과 1,992개체/㎡ 의 대형저서동물이 출현하였고, 가장 우점한 동물군은 다모류로 출현 종수와 평균 서식밀도는 각각 91종과 1,463개체/㎡ 이었다. 태화강 하구역의 주요 우점종은 다모류의 Minuspio japonica(609±1,221개체/㎡ ), 참갯지렁이(Hediste japonica, 174±318개체/㎡ ), Tharyx sp.1(106±283개체/㎡ ), 긴자락송곳갯지렁이(Lumbrineris longifolia, 79±207개체/㎡ ), 이매패류의 아기반투명조개(Theora fragilis, 114±272개체/㎡ ) 및 단각류의 발성육질꼬리옆새우(Grandidierella japonica, 88±223개체/㎡ )등이었다. 출현 종과 개체수의 자료를 근거로 대형저서동물의 군집구조를 파악한 결과, 대형저서동물 군집은 크게 3개로 구분되었다. 그룹 Ⅰ (조립질 퇴적물)과 Ⅲ (세립질 퇴적물)은 각각 담수 및 해수우세 환경의 군집으로, 그룹 Ⅱ (혼합질 퇴적물)는 2개 환경이 혼합되는 추이대로 고려할 수 있었다. 결국 태화강 하구역에 서식하는 대형저서동물 군집은 염분농도의 구배와 퇴적상에 따라 구조를 달리함을 알 수 있었다.