Inferring individual behavioral strategies within group-living drift-feeding fish, using fine-scale, three-dimensional analysis.
Group-living is widespread in fish, and mono- or multi-specific assemblages can be found in a variety of environmental contexts. In streams, drift-feeding fish either display territorial behaviour or form shoals. They inhabit dynamic and heterogeneous three-dimensional environments, where micro-scale hydraulic features and food patchiness make spatial positioning critical for individual fitness. In this con- text, the spatial structure displayed by such groups is likely to have high ecological significance, as it would reflect mechanisms underlying intra-specific competition and resource distribution. In territorial fish such as salmonids, there is still an on- going debate about how intra-specific competition is underlying density-dependent growth and mortality. On another hand, empirical studies on intra-specific competition within non-territorial (or shoaling) species are very scarce, as the accurate description of such dynamic systems is challenging, in terms of collecting and analysing data. Here, I used a digital imaging technique (VidSync) to manually monitor movements and behaviour of individual fish, in 3-D, and at a high spatiotemporal level of resolution. I developed tools to study the statistical property of space-use of each individual, enabling the description and quantification of key features of the spatial structure of drift-feeding fish. I studied links between individual space-use strategy, feeding and social behaviour in order to investigate how the spatial structure of group-living drift-feeding fish could be related to its social organisation. This study was carried out on free-ranging shoals of juvenile drift-feeding fish (Galaxias anomalus) and on juvenile brown trout (Salmo trutta). The aim of this study was to investigate mechanisms underlying patterns of intra-specific competition within groups of territorial and non-territorial species, under different environmental contexts. Results highlights interspecific differences in competition regulation, but also provide unique insights on the economic underlying the spatial and social structure of these species.
Advisor: Closs, Gerard; Tentelier, Cédric; Crow, Shannan; Paulin, Michael
Degree Name: Doctor of Philosophy
Degree Discipline: Zoology
Publisher: University of Otago
Keywords: Behaviour; space-use; 3D; drift-feeding fish; intra-specific competition
Research Type: Thesis