ISSN:
1573-5117
Keywords:
Atlantic salmon
;
sea trout
;
migration
;
adult
;
smolt
;
telemetry
;
barrage
;
estuary
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract There is wide concern regarding the effects that estuarine barrages may have on estuarine environments and the species which utilise them. Of particular concern are the possible effects on diadromous fish which move between fresh and salt water. This paper presents results from a 3 year investigation (1993–95) of the migratory behaviour of both juvenile and adult salmonids undertaken in the vicinity of a barrage on the River Tawe in South Wales, which was completed in 1992. The localised upstream movements of acoustically tagged returning adult salmonids (n = 28) were investigated in the 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 miniature acoustic transmitters, were also monitored during their spring seaward emigration within the impounded estuary. The upstream movement of adult salmonids appeared to be delayed by the 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, but few fish ascended the barrage by this route. Approximately one third of those fish detected below the barrage were subsequently detected upstream in the impoundment, most moving past when the barrage was over-topped. The movement of fish over the barrage was significantly unimodal with respect to the tidal cycle with a mean passage time of 4 minutes after high water. Once in the impoundment fish often remained close to the barrage (〈 100 m) for several hours or days during which time movements appeared largely random. The movement of salmonid smolts through the impounded estuary and into the lower estuary, downstream of the barrage, was not continuous. Smolts held position within the impoundment immediately upstream of the barrage. The movement of smolts upstream of the barrage was predominantly random, and fish that successfully negotiated the structure did so by migrating through the ship lock or over the weir during an over-topping flood tide. The migratory behaviour patterns of juvenile and adult salmonids are compared with previous studies in unmodified river estuaries, and discussed in relation to the possible impact of barrages on salmonid migration.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1017043726512
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