Publication Abstract

The migratory behaviour of juvenileand adult salmonids in relation to an estuarine barrage

I.C. Russell, A. Moore, S. Ives, L.T. Kell, M.J. Ives and R.O. Stonehewer

There is wide concern regarding the effects that estuarine barragesmay have on estuarine environments and the species which utilise them. Of particularconcern are the possible effects on diadromous fish which move between fresh and saltwater. This paper presents results from a 3-year investigation (1993-95) of the migratorybehaviour of both juvenile and adult salmonids undertaken in the vicinity of a barrage onthe River Tawe in South Wales, which was completed in 1992. The localised upstreammovements of acoustically tagged returning adult salmonids (n = 28) were investigated inthe immediate vicinity of the barrage and associated fish pass using a High Resolution(HiRes) tracking system. The behaviour of salmonid smolts (n = 52), tagged with miniatureacoustic transmitters, were also monitored during their spring seaward emigration withinthe impounded estuary. The upstream movement of adult salmonids appeared to be delayed bythe presence of the barrage with many fish holding station close to the barrage structure.Of these, about half were clearly attracted by the plume of water from the fish pass, butfew fish ascended the barrage by this route. Approximately one third of those fishdetected below the barrage were subsequently detected upstream in the impoundment, mostmoving past when the barrage was over-topped.

Reference:

I.C. Russell, A. Moore, S. Ives, L.T. Kell, M.J. Ives and R.O. Stonehewer, 1998. Themigratory behaviour of juvenile and adult salmonids in relation to an estuarine barrage.Hydrobiologia, 371/372: 321-333.