Long-term effects of hydropower installations and associated river regulation on River Shannon eel populations: mitigation and management

Abstract

The Shannon, Ireland's largest river, is used for hydroelectricity generation since 1929. Subsequently, the Electricity Supply Board assumed responsibility for management of its eel stocks, due to the impact of the hydro-dam on recruitment to the commercial fishery. In order to negate a decline in juvenile recruitment resulting from the installation of hydroelectric facilities, management was focused on stocking lakes with elvers and fingerling eels. These were trapped at the hydropower facilities and in estuarine tributaries during their up-stream migrations. Due to the decline of natural recruitment in more recent times, attempts have also been made to develop an estuarine glass eel fishery. Stock levels are then monitored through annual surveys of the population trends of juvenile (glass eel, elver), growing phase (yellow eel) and downstream migrating pre-spawners (silver eels). Survey results and fishery management programmes are reviewed in this article. In addition to the long-term effects the hydroelectric facilities have had on the stock levels, there is also an annual effect on the migratory patterns of downstream migratory silver eels. In the lower reaches of the river system flow rates are regulated by the hydroelectric stations. We review previous work that had highlighted the importance of flow in determining the timing of the silver eels migrations, and assess the relationship between flow and migration in more detail through the use of hydroacoustic and telemetric studies. Current research on seaward migrating silver eel populations, suggests that spawner escapement rates can most effectively be increased by trapping migrating eels at fishing weirs located up-stream of the power station and transporting them towards the estuary.

Forecasting animal migration using SARIMAX: an efficient means of reducing silver eel mortality caused by turbines

“…Several studies have shown the negative impacts of hydropower on adult silver eels, with mortalities ranging from 5 to 100% in the case of old turbines (see review by McCarthy et al 2008). Because European eels are classified as an Endangered species, conservation measures have been recommended by the European Union.…”

Multi-GCM ensembles performance for climate projection on a GIS platform

“…It has been estimated that there are more than 1600 lakes in the river basin district. The area includes about 73 % agricultural land and 12 % wetland, mostly peatland habitat (McCarthy et al 2008, Gharbia et al 2016Assessment 2012Assessment , 2013.…”

“…1) drains an area of approximately 11,700 km 2 , before flowing into the sea at Limerick. The gradient is remarkably low, with the river rising at about 152 m above sea level and then flowing southwards with only a 12-m drop in altitude over 185 km, before finally descending more rapidly to sea level (Gharbia et al 2016;Assessment 2012Assessment , 2013McCarthy et al 2008). The potential impacts of climate change are of most concern where water resources are either heavily allocated or particularly vulnerable to changes in rainfall (Kulkarni et al 2011), in addition to risks due to extreme events (Engler and Werner 2015).…”

Using GIS based algorithms for GCMs' performance evaluation

“…The various phases of the CMIP have grown steadily as testified both in terms of participants' number and scientific impacts [16]. In this study, climate change projections for the Shannon River [17,18] catchment are presented for several temperature and precipitation from multi-GCM ensembles for three future time intervals using a range of different Representative Concentration Pathways (RCPs). The projection process used a statistical downscaling procedure based on statistical relationships linking a set of large-scale atmospheric variables to regional climate variables in an observational calibration period.…”