Behavioural and metabolic responses of Unionida mussels to stress

Abstract The aim of this study was to assess the extent to which the behavioural traits of freshwater mussels provide suitable indicators of stress in individuals, towards the advancement of non‐invasive, remote monitoring techniques to examine population condition. Variation in the expression of particular behavioural metrics was examined in accordance with measurements of oxygen consumption, across environmental stressors (aerial exposure and high concentrations of total suspended solids), and between two freshwater mussel species (Margaritifera margaritifera and Anodonta anatina) Aerobic metabolic rate was quantified using intermittent respirometry, and behaviour was observed using time‐lapse footage. Comparisons of metabolic response and the occurrence of behavioural traits, across the two stressors, focused on differences between the 24 h pre‐exposure period (pre‐exposure), the first 3 h of post‐exposure (immediate post‐exposure), and the time following the initial 3 h of post‐exposure until the end of the experimental run (extended post‐exposure). The results of this study demonstrated a relationship between the frequency of occurrence of behavioural responses to stress exposure, associated with valve activity, and significant changes in the metabolic functioning of A. anatina and M. margaritifera mussels. The findings from the study also highlighted substantial intraspecific variation across species and stressors. Data from this research could assist in the development of novel biosensors that track mussel valve activity remotely in their natural environment. When coupled with real‐time data examining alterations in environmental metrics, this technology could assist in the monitoring of population condition and aid conservation management.