Water flow and temperature interact to determine oxidative status, swimming performance, and dispersal of mosquitofish (Gambusia holbrooki)

Abstract

The health of running freshwater systems depends to a large extent on flow rates, which can co‐vary with other environmental variables such as temperature. Water flow and temperature can influence oxidative status of individual animals, thereby impacting muscle function and locomotion. Consequently, ecologically important behaviours such as dispersal may be disrupted. Our aim was to determine whether the interactions between acclimation to flowing water (3 weeks at 0.06 m/s or still water), thermal acclimation (3 weeks at 18 and 28°C), and acute test temperatures (18–32°C) determine oxidative status, locomotor performance, and dispersal in mosquitofish (Gambusia holbrooki). We show that swimming capacity was greater in fish living in flowing water compared to those in still water, and that this difference was greater in warm acclimated fish. However, dispersal was not dependent on maximal locomotor capacities. Fish initiated dispersal to a greater extent when acclimated to flowing water and cool temperature, although there were interactions with acute test temperature. Dispersal speed was not affected by flow acclimation, but it was greater at cool test temperatures in cool acclimated fish, and vice versa for warm acclimated fish. Also, fish acclimated to flowing and cool water made a greater number of dispersal decisions. Oxidative damage to membranes and proteins did not change with flow or temperature treatments, but antioxidant capacities were greater in animals acclimated to flow and cool temperatures. Trait‐specific approaches used to assess fish responses to altered flow regimes typically consider a range of morphological and life‐history traits to characterise species and predict the impact of environmental change. Physiological traits and responses such as those we describe here can be a useful addition to life‐history traits in predicting the impact of environmental change on movement. Consideration of the impacts of physiological traits on dispersal can increase the efficacy of management and restoration projects.

Simplified environmental flow metrics and environmental water requirements for Mediterranean seasonal rivers

“…Promotes resilience leading into the low flow/cease to flow period (eWater, 2022) Promotes fish recruitment success (Green et al, 2014) Migration of obligate aquatic fauna (Lucas and Baras, 2008) Discourages exotic fish species (Seebacher and Kazerouni-Ghanizadeh, 2021)…”