An artificial stream tank was constructed at the SOAFD Smolt Rearing Station at Almondbank, for investigations into the effects of substrate diversity on the behaviour of juvenile Atlantic salmon. The tank incorporated 2 experimental arenas and the environmental parameters water depth, water velocity, light and substrate arrangement could be altered independently. Wild juvenile Atlantic salmon from a nearby river system were used in this study. The fish were tagged using a custom designed, fingerling-type tap to allow for individual identification and detailed analysis of fish location within an overhead video image. The fish were found to spend more time among the experimental substrates than outwith the substrate arena irrespective of substrate arrangement. When among the experimental substrates, salmon parr were found to vary time budgets depending upon the diversity of the substrate within the experimental arena, with more time spent moving and less time stationary within a uniform over a diverse substrate. This difference in the time spent moving was accounted for by a difference in the frequency of events while the difference in time spent stationary was a result of differences in the duration of individual events. Within a diverse substrate fewer agonistic encounters occurred among the fish, which was linked with an increase in the frequency of hiding behaviour and an increase in the carrying capacity of the experimental arena, when compared with a uniform substrate arena. Occupied sites were highly clumped in distribution in both diverse and uniform substrates. The population utilisation distributions of the substrate arenas contained more core areas, which were smaller in area, for a diverse substrate compared with a uniform substrate. This indicated the highly localised nature of the preferred sites within a diverse arena.