Effects of Smallmouth Bass on Atlantic Salmon Habitat Use and Diel Movements in an Artificial Stream

Abstract

Invasive smallmouth bass Micropterus dolomieu have been introduced to some of the last remaining watersheds that contain wild anadromous Atlantic salmon Salmo salar, yet little is known about the interactions between these species. We used an artificial stream equipped with passive integrated transponder tag antenna arrays to monitor habitat use and movements of age‐0 Atlantic salmon and age‐0 smallmouth bass in sympatry and allopatry. We used additive and substitutive designs to test for changes in habitat use, diel movements, and diel activity patterns of prior‐resident Atlantic salmon or smallmouth bass resulting from the addition of conspecifics or heterospecifics. Atlantic salmon prior residents did not change their habitat use in the presence of conspecific or heterospecific invaders. However, Atlantic salmon invaders did lessen riffle habitat use by smallmouth bass prior residents during daytime. Atlantic salmon and smallmouth bass displayed different diel activity patterns of movement (Atlantic salmon were more nocturnal; smallmouth bass were more diurnal), which were affected by heterospecific introductions. Because the two species tended to favor different habitat types and displayed different diel activity patterns, we suggest that under the conditions tested, the level of interspecific competition for habitat was low. Age‐0 Atlantic salmon and smallmouth bass may be able to avoid intense interspecific competition through spatial and temporal habitat partitioning. These data do not, however, predict the potential for competition under different seasonal or ontogenetic circumstances.

Smallmouth bass (Micropterus dolomieu) suppress Atlantic salmon (Salmo salar) feeding activity and increase aggressive behaviours at warmer temperatures

“…Although Wathen et al (2012) suggests that ATS were inferior competitors, their results offer some potential for these two species to co-exist as juveniles in Maine streams.…”

“…It is possible that spatial portioning between ATS and non‐native species could influence competitive interactions in complex natural streams; however, empirical evidence is limited (Fausch, 1998). Wathen et al (2012) examined habitat use between ATS and SMB and found that when occupying the same habitat, these species may distribute spatially to prevent high levels of direct competition. Although Wathen et al (2012) suggests that ATS were inferior competitors, their results offer some potential for these two species to co‐exist as juveniles in Maine streams.…”

“…Wathen et al (2012) examined habitat use between ATS and SMB and found that when occupying the same habitat, these species may distribute spatially to prevent high levels of direct competition. Although Wathen et al (2012) suggests that ATS were inferior competitors, their results offer some potential for these two species to co‐exist as juveniles in Maine streams.…”