Factors Influencing Successful Mechanical Removal of Green Sunfish

Authors: Brian Hickerson, Anthony Robinson, David Partridge, Matthew Rinker

Year: 2018

Abstract

Green Sunfish Lepomis cyanellus are exceptional invaders and have become widespread throughout watersheds of the Southwest, largely due to their ability to tolerate the extreme physical and biological conditions characteristic of desert aquatic systems. Green Sunfish are frequently linked to declining native fish populations as a result of competitive and predatory interactions. Consequently, managers of desert fishes have put substantial resources into mechanical removal efforts intended to eradicate nonnative Green Sunfish, with varying degrees of success. We sought to evaluate factors that contributed to the success of mechanical removal of Green Sunfish across eradication efforts in Arizona. We compared six Green Sunfish removal efforts in Arizona that occurred between 2012 and 2018. We considered a number of factors that likely influence success of removal efforts including whether removal reaches were isolated from invasion, watershed size, removal reach length, and initial relative abundance. We used logistic regression to evaluate which factors contributed to removal success. We found that successful removals were characterized by low initial relative abundance and isolation from an invasion source. By identifying factors contributing to successful outcomes for removal efforts, we can focus our limited resources for nonnative fish control on systems where mechanical removals are likely to be successful.