Potential of behavioral and morphological bias in invasive brook trout capture methods

Abstract

Invasive species in aquatic systems can result in numerous adverse effects such as reduced native populations, loses in biodiversity, and degraded ecological services. When these effects become too great to ignore management techniques available for invasive fish programs vary greatly. Selective manual methods of species removal such as electrofishing and trapping have been shown to be part of successful removal programs but typically require extensive effort and multiple treatments. Electrofishing requires specialized equipment and training to actively capture invasives whereas trapping uses commonly available traps and after installation is more passive. Due to differences between capture method it was theorized by this study that capture method may be biased for different behavioral and morphological characteristics of invasive brook trout (Salvelinus fontinalis) in Swedish streams. It was theorized that bolder brook trout would be selected for by trapping as the method requires trout to investigate and enter the new and foreign traps while electrofishing would select for less bold individuals that would remain stationary upon disturbance. Morphological differences could occur as salmonids such as brook trout demonstrate high phenotypical plasticity as potentially part of dietary niche exploitation which has been linked to personality. Behavioral analysis consisted of startle response field boldness testing at the study location, group feeding boldness, and individual feeding behavior in a simulated stream. Morphological analysis was performed using facial digitization and principal component analysis. Results showed that capture method did not select for size, weight or individual feeding or in-group boldness. Morphological analysis showed that while two facial morphs made up 47% of facial morphological differences there was no significant difference in facial morphology. Trapping did select for more bold than shy trout. This study’s findings suggest that using only trapping will select for more bold trout, but further studies are needed to understand the population impacts.