This study analyzed the structural characteristics and influencing factors of fish assemblages according to lake size (small, medium, large) based on fish survey data from 90 lakes designated under the National Aquatic Ecosystem Health Monitoring Program in Korea. From surveys conducted between 2022 and 2024, a total of 107 fish species belonging to 32 families were recorded. The dominant species was the bluegill (Lepomis macrochirus, relative abundance [RA]: 21.2%), followed by Hemiculter eigenmanni as the subdominant species (RA: 13.6%). Statistical analysis based on lake size revealed significant differences across eight ecological indicators including species richness, abundance, diversity, evenness, richness, dominance, number of endemic species, and number of exotic species according to lake size. These indicators tended to increase with lake size. While this pattern may be initially attributed to positive factors associated with larger lakes, such as greater habitat heterogeneity and food resource diversity, it is considered that the primary factor influencing these results is the difference in the number of sampling sites per lake. Since sampling sites were designated based on the national water quality monitoring network, they are considered representative of each lake’s environmental conditions. Bray-Curtis similarity and SIMPER analyses identified patterns in assemblage similarity and the key contributing species for each size group. This study provides empirical evidence that demonstrates the influence of lake size on fish assemblage composition and structure and highlights the necessity of incorporating lake size and typology into fish-based assessments of lentic ecosystem health.

옥정호로 유입되는 37km의 추령천에는 육봉화된 은어의 이동을 가로막는 많은 보가 설치되어 있었으나 2006년 12월 옥정호 추령천 하류에는 은어가 성숙하기 위해 추령천 상류로 이동하도록 어도가 설치되었다. 따라서 2007년 4월부터 10월까지 13개 지점에서 어도와 은어의 성장률을 조사하였다. 그 결과 어도의 설치 후, 치어들은 강수량이 풍부했던 시기에만 소상할 수 있는 상류를 새로 설치된 어도를 통해서 자유롭게 상류로 이동할 수 있었다. 2007년 9월 산란시기 동안 성숙된 은어는 163±21.5mm로 어도가 설치되기 전인 2006년에 비해 약 13mm, 2004년 약 20mm, 2005년 약 57mm정도 더 크게 나타났다. 따라서 하천에서 어도는 육봉형 은어집단의 평균 크기와 생존력에 중요한 역할을 하는 것으로 확인되었다.