Spatial distribution and migration pattern analysis of Erythroculter erythropterus utilizing a telemetry approach in relation to water quality in the Nakdong River basin

The fish Erythroculter erythropterus has been introduced to the Nakdong River. It is a top carnivore (growing to up to 1.5 m long) but is inedible. The population of Erythroculter erythropterus tends to increase in areas where mainstream flow is slowed by weirs, likely due to the creation of more favorable habitat conditions. Erythroculter erythropterus dominates the fish community, reducing the number of endemic and commercial fish. The South Korean government sought to eliminate the species, but the spread was too rapid, resulting in top-down biological disturbance. The species distributions and movement patterns of Erythroculter erythropterus are not well known and no management strategy is available. Here, we determined the distribution and migration patterns of Erythroculter erythropterus in the tributaries and mainstream of the Nakdong River and analyzed how the water chemistry and physical habitat affected these variables. We used a submersible ultrasonic receiver to collect signals from transmitters attached to fish and analyzed the migration pattern. Massive aggregations of this species were evident at depth. Erythroculter erythropterus dominated all study sites but was significantly (p < 0.05) more common in the mainstream (relative abundance [RA] = 12.2