Investigating the impacts of environmental change on social behaviour in fish

Social behaviours occur between individuals across the animal kingdom and mediate a variety of essential fitness related processes. The interactions between individuals can change depending on differences between individuals (e.g. in physiological state or personality) and ecological context. Anthropogenic impacts are rapidly changing the environment through climate change, pollution and habitat fragmentation. Individuals will alter their behaviour as a result of these changes, which can have consequences for social interactions and the maintenance of animal groups. The aim of this research is to investigate the impacts of environmental conditions on social associations in fish shoals. Using two distinct approaches and measuring social interactions at different scales, I consider how environmental conditions can alter the dynamics of these groups. Presenting a novel field method, I explore the impact of several environmental conditions on social behaviour in populations of three-spined sticklebacks (Gasterosteus aculeatus). Temperature, season, light intensity and dissolved oxygen were found to alter the numbers of fish caught. The only variable affecting aggregation of sticklebacks was their reproductive state, where populations were less aggregated during the breeding season. Under controlled laboratory conditions I investigate how acoustic noise can alter group dynamics in groups of Trinidadian guppies (Poecilia reticulata), analysing behaviour with video tracking software. Added noise had no effect on the activity or exploration behaviour of individuals, nor the cohesion of groups. Guppies displayed more following behaviour in the control versus the noise treatment, providing evidence that noise can alter decision-making dynamics in shoals of guppies. Together, these studies provide a broader insight into how social dynamics in fish shoals can change under different environmental contexts and at different scales. This work establishes areas that require more attention in future considerations of how, and the extent to which, environmental change may impact social species at a broader scale