Can pikeperch colonise new freshwater systems via estuaries? Evidence from behavioural salinity tests

Abstract

Pikeperch (Sander lucioperca) are non-native in the United Kingdom. It is important to understand how environmental factors, such as salinity, influence the behaviour and activity of introduced fish species to identify their dispersal potential. Previous studies have shown that pikeperch, traditionally recognised as a freshwater fish, can tolerate brackish waters and demonstrate physiological acclimation. However, their behavioural responses to brackish waters are unknown. The aim of the present study was therefore to investigate the activity and swimming behaviour of pikeperch obtained from freshwater canals in southern England. In the laboratory, fish were exposed to a 12-h simulated tidal cycle and a 12-day stepped salinity challenge where salinity was increased by 4 every 2 days, up to a salinity of 20. In both regimes, fish showed increased swimming activity in response to increasing salinity, which may represent an avoidance response. The most dramatic changes, including vertical movements, occurred at salinities above ~16. At these higher salinities, head shaking and coughing behaviours were also observed, suggesting significant stress and respiratory impairment. However, during the simulated tidal cycle, normal behaviour was rapidly restored once salinity was reduced. The results of this study may have implications in understanding the dispersal of non-native fish in the wild.