Novel quantification of the reactions of a cypriniform fish to acoustic stimuli

Anthropogenic structures in the aquatic environment can cause mortality, damage and ecological exclusion of fish. These anthropogenic threats are traditionally mitigated for by physical means of excluding, diverting and deterring fish. These methods are not entirely effective for all species and all life stages of fish. Increasingly, fisheries managers are turning to behavioural deterrents to supplement and replace these traditional technologies; however, quite often these devices are deployed with little scientific basis. Current understanding of fish behaviour in the presence of acoustic stimuli focuses on, often large-scale, experiments that aim to manipulate the placement of fish within a system. This management-led, deterrent-concentrated research misses many of the complex, and important, parts of the behaviour being displayed by these animals. The fundamental based approach of the research investigates the difference in reaction of individuals and groups of small cypriniform fish. Using finely measured acoustic treatments and high-definition video recording in an experimental flume, the European minnow (Phoxinus phoxinus) was exposed to differing acoustic treatments and the resultant footage was analysed. Results indicate that groups of fish are more uniformly impacted by sound than individuals and that they return to normal behaviour more slowly. The data also demonstrates that individuals within a group behave in a more coherent manner when initially exposed to sound. Where individuals did demonstrate changes in their behaviour, groups of fish did not demonstrate changes in the same metrics, namely swimming speed and persistence of swim paths. The research presented within this thesis has contributed to scientific understanding of how the placement of fish can be influenced by sound and also the fine scale behaviours that they present when exposed to an acoustic stimulus. Reactions of individual fish are compared with reactions of groups of fish and the significant differences between them are discussed. The information brought about by conducting this research will go towards furthering knowledge of the complex nature of animal behaviour and also the complexities of experimental acoustic work within water tanks