Fishing in Ireland

近年、まちを流れる農業用水路は農地の都市化によりその役割を終えようとしている。そこで本稿は、大阪府八尾市内を流れる玉串川を対象とし、農業用水路再生における課題や改善点、住民の意識構造を考察した。主に玉串川沿線の３校区において三回にわたりワークショップを開催し意見交換およびアンケート調査を行った。調査の結果、今後の都市に残る農業用水路を住民の憩いの場として再生させるためには、農業用水路としての機能に加え、景観・生態・防災機能などを備えた多機能的な川にしていく必要があり、整備後の川の環境維持には住民自らが環境維持のための活動、住民が川に親しみを持ち、川に触れる活動を行い、継続していくことが重要であることがわかった。

Abstract Climate change is expected to modify temperature and precipitation patterns throughout Europe, leading to warmer drier summers; wetter, milder winters; and an extended growing season. Alterations to feedbacks between important eco‐physical structuring processes driven by climate change may modulate river morphology, floodplain characteristics, and their biological communities. Current understanding is reviewed and synthesised to explore the potential responses, mechanisms, and ramifications of climatic shifts for the European riverscape. Fundamental drivers of change are expected to be (a) disturbance deviation beyond the historical norm and (b) vegetation morphodynamics, a key river process where ecological and fluvial‐geomorphological attributes interact to shape the physical environment. Increased seasonal temperature, summer drought, and winter flooding may affect the colonisation, growth, and mortality of plant species with consequences for riverscape structure and function as succession patterns adjust with repercussions for hydraulics and sediment dynamics. Such opposing winter and summer climate regimes are likely to impact vegetation patch dynamics, reflected in an increasingly variable patch mosaic as disturbance intensity deviates further from historical background conditions. How changes to climate drivers manifest themselves in individual river systems will also be affected by attributes such as catchment topography, geology, vegetation type, and previous human alterations. Where large scale change occurs, it will have consequences for the type and function of biological communities inhabiting the riverscape. Conventional engineering responses to meteorological disturbance will amplify the effect on river biota by reducing their ecological resilience, highlighting the need for a management response that integrates ecological and societal benefits simultaneously.

This pilot study presents an environmental DNA (eDNA) assay for sea lamprey Petromyzon marinus and brown trout Salmo trutta, two species of economic and conservation importance in the Republic of Ireland. The results demonstrate the effectiveness of eDNA for assessing presence of low-abundance taxa (here, P. marinus) for environmental managers, and they highlight the potential for assessing relative abundance of rare or invasive freshwater species.

This chapter contains sections titled: Introduction Stock and fishery status Fisheries management for sea trout Progress in sea trout science Future research needs Concluding remarks

This chapter contains sections titled: Introduction Sea trout life history Materials and methods Results Discussion Acknowledgements

The first systematic study of the metal ion content of the four main Irish Canal Systems is presented. Samples were collected seasonally over a twelve month period and analysed for 16 trace elements and metals by ICP-MS. The results show that three of the four canals (Royal, Grand, Shannon-Erne) have distinctly different elemental profiles, while the fourth (Barrow) is similar to the Grand Canal, which is to be expected, as they are broadly part of the same system, with a common main feeder. Spatial plots reveal local variations in certain elements, which are related to the nature of feeders in those localities. Simple tests based solely on the 16 elements measured showed that it may be possible to broadly define 'normal' compositions for each canal system, which can be then used to identify 'abnormal' data, and hence provide indicators for environmental change.

In summer 1998 European eels infected with Argulus foliaceus (L.) were detected in the Erne catchment, Ireland. This is the first documented report of A. foliaceus parasitizing eels in Ireland or the U.K.

Year-round problems with dense growths of filamentous algae reduce the amenity and conservation value of Irish canals. Because algal control operations were relatively ineffective, trials using barley straw were undertaken. These commenced in October 1990 on a section of the Royal Canal where filamentous algae continuously interfered with amenity exploitation and water management. Bales of barley straw were anchored along the canal banks at roughly 50 m intervals. Further straw applications were made in 1991 and 1992. Algal growth in the control section broadly followed a cyclical pattern, with peak biomass between July and September and low production in February and March. In the treated section, however, algal biomass decreased from the time the straw was first introduced. Thereafter, as long as rotted straw was present, no filamentous algae were recorded. The absence of algae in this section between August 1991 and spring/summer 1993 permitted the recolonisation of higher plants, which are commonly less troublesome and more ecologically useful than algae.

The large western Irish lakes are natural salmonid lakes and a unique ecological resource. Lough Mask (82 km2) and Lough Conn (50 km2), Co. Mayo, are among the finest, natural, wild brown trout fisheries in Europe. Recently, however, threats have arisen to water quality in Lough Conn as a result of agricultural intensification. A doubling of phosphorus (P) inputs to Lough Conn for the period 1980 to 1990 caused a number of ecological changes such as an apparent increase in littoral algal production; while arctic charr (Salvelinus alpinus L.) have also disappeared from the lake over the same period of time. The changes in Lough Conn appear to represent an early phase in the eutrophication process. The western Irish lakes represent a super-sensitive ecological category requiring particularly strict catchment controls in order to protect the diversity of native flora and fauna including unusual glacial relict species and the unique genetic strains of fish which are present. Catchment management committees were established in order to study and reverse the perceived early-stage eutrophication problem in Lough Conn and in order to prevent the occurrence of similar problems in the case of Lough Mask. These committees have a sectoral basis covering: agriculture, local authority functions (sewage, rural septic tanks, planning and environmental control), forestry, peat harvesting and drainage works, as well as having representation from the fisheries boards and the Environmental Protection Agency (EPA). Management of these relatively pristine lakes is perhaps a more difficult problem than that of cleaning up an obviously degraded resource. This is especially so since they are located in regions which are economically underdeveloped and where a real need exists to improve economic returns from farming, tourism and industry in the catchments. The importance of developing a sustainable, ecologically-based management strategy which will maintain existing high quality lakes into the next century with their irreplaceable genetic and ecological resources intact cannot be over-emphasised. The challenge is to devise refined management strategies which will eliminate nutrient wastage to waters and yet allow an appropriate level of sustainable development in the area. The management of Lough Conn and Lough Mask is described in some detail concentrating in particular on the efforts to reduce phosphorus loss from agriculture in the catchment but also emphasising the importance of a multi-sectoral approach to phosphorus load reduction.