• Korean Journal of Environmental Biology
• /
• v.33 no.1
• /
• pp.34-44
• /
• 2015

Fish fauna, difference of stable isotope ratio between freshwater and seawater, and trophic guilds of freshwater fishes were investigated in the lower Geum River. The study was conducted in 2011, and total study area was about 30 km of 20 km upstream and 10 km downstream from the Geum River estuary barrage. Only freshwater fishes were used for analyzing trophic guilds, and discriminant function analysis (DFA) was utilized to reclassify trophic guilds based on stable isotope ratio. Fish fauna in freshwater and seawater areas were entirely different each other, but small number of migratory species such as Coilia nasus and Chelon haematocheilus occurred both areas. Other species were not collected in the different areas because they did not have physiological ability to adapt different salinity concentrations. Stable isotope ration of two areas were different considerably due to food sources. Estuary and seawater fishes uptake food sources originated from marine, and freshwater fishes were from freshwater and terrestrial. Some migratory species showed reverse stable isotope ratio. Even though they collected in freshwater, they showed stable isotope ratio of seawater. This is because ecological characteristics of each species. Trophic guilds of freshwater fishes were reclassified by DFA, and showed slight difference with literatures. However, because this result is related with ontogenetic shift of species, more studies are needed to explain exact and correct trophic guilds. Stable isotope ratio can be changed among regions, seasons and ontogenetic stage, thus we always consider these aspects when analyzing results to get a right answer.