Fisheries enhancement of the Rye Water, a lowland river in Ireland

Abstract

1. The Rye Water is the major salmon spawning tributary of the River Liffey. It is an example of a lowland river which lost much of its productivity as a salmonid fiver following an arterial drainage scheme which extended over 2 years (1955-1957). The scheme introduced a series of hydraulically uniform continuous glides of abnormal length and a reduction in the diversity of the natural riverine habitats. To rectify this, a fisheries enhancement programme was initiated in 1994 on a 2.4 km stretch of the river. 2. The aims of the programme were to optimize the capacity of the channel to function as a brown trout (Salmo trutta L.) fishery, to improve the angling value of the river and to ensure that its role as a salmonid spawning and nursery area would be enhanced. 3. The enhancement project was designed to narrow and deepen the channel, create meanders, pools, cover, and to stabilize eroding stream banks. Habitat improvement structures included deflectors, riprap and boulder placements. Work was carried out by the Office of Public works in conjunction with the Central Fisheries Board and the Zoology Department, University College Dublin, Ireland. 4. Detailed monitoring of physical characteristics is continuing. Salmonid populations have been monitored by electrofishing before and after enhancement at control (unaltered areas) and experimental sections. Initial results (i.e. 1 year post-works) indicate that salmon densities have significantly increased. Brown trout, on the other hand, were slower to recover.