Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Assessing the invasion history and contemporary diet of nonnative redear sunfish (Lepomis microlophus Günther, 1859) in an ecotonal riverscape.

Abstract

The redear sunfish (Lepomis microlophus Günther, 1859) is widely-introduced as a sportfish in the United States and globally. The redear sunfish can become invasive when introduced to lentic waterbodies, but the outcome of lotic introductions has received less attention. As such, we evaluated trends in the distribution and abundance of introduced redear sunfish throughout the Spring River subbasin (SRS) of southeastern Kansas during 1962-2019 using five separate datasets. We also examined contemporary diet of the redear sunfish in the SRS during 2018 at sites where it was most abundant to determine if its diet differed from the native range. The SRS included low-velocity, turbid streams draining the Cherokee Lowlands and Osage Cuestas physiographic regions and high-velocity, clear streams flowing through the Ozark Plateau. Streams across all physiographic regions in the SRS are ill-suited to the Redear Sunfish, which prefers low water velocity coupled with high water clarity. We found that the redear sunfish exhibited a restricted distribution with low relative abundance in the SRS throughout the entire study period. Furthermore, its contemporary diet was dominated by non-biting midge larvae (Chironomidae), seed shrimp (Ostracoda), fingernail clams (Sphaeriidae), and snails (Gastropoda), similar to its diet in the native range. The inability of redear sunfish to achieve widespread prevalence in the SRS at least 50 years after introduction likely stems from habitat in the SRS being a poor match to its niche requirements. However, future environmental alterations resulting from human activity and climate change (e.g., dewatering and lentification in streams of the Ozark Plateau) could make conditions in the SRS more suitable for redear sunfish. As such, continued monitoring will be necessary to determine if the prevalence of the redear sunfish in the SRS of Kansas changes in the future.