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Title: Flow and Level Criteria for Coarse Fish and Conservation Species
Author: I.G. Cowx
Author: R.A. Noble
Author: A.D. Nunn
Author: J.P. Harvey
Author: R.L. Welcomme
Author: A.S. Halls
Author: Environment Agency
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_1028, Representation ID: 308, Object ID: 2307; Environment Agency Project ID:EAPRJOUT_1271, Representation ID: 429, Object ID: 2479
The project is being carried out to develop a tool to evaluate the potential impact of flow and water level criteria on fish species and populations in English and Welsh rivers to allow more scientifically robust and hence defensible assessments to be made. The overall objective of the project is to provide, for various river reach types, generic seasonal flow and water level regime requirements for key life stages of freshwater fish species to advise and influence the management of flow regimes. - The fish community types in rivers were modelled based on the Agency, fisheries data and complementary environmental data. The models discriminated eight major fish community types that broadly followed the classical zonation theory with river gradient from upland salmonid to lowland cyprinid communities. It is was concluded that the influence of flow and the potential impacts of abstractions and releases should be considered within the context of each of these main fish assemblages, linking key species per community type to their functional ecology and flow requirements. The relationship between the rate of flow, the rate of change of flow, the duration of high/low flow events and their seasonal timing, and their influence over the functioning of fish populations (spawning, recruitment and growth) needs to be considered when evaluating anthropogenic changes to flow patterns. - Some biases in the dataset were identified, and it was considered important to remove these biases by filling the gaps in information, especially with respect to regions and river reaches poorly represented in the current dataset. The preferred habitat characteristics of the predominant fish species found in UK fresh waters was reviewed, but a paucity of data for the lesser species, especially those of conservation value, was found. It was recommended that information about habitat relationships of critical species that drive community structure was required, although, it may be better to develop the guild concept for discriminating the impact of flow regulation on fish and fisheries. Too few studies were found to have examined the wider environmental impacts of adjusting flows, especially the issues associated with maintaining longitudinal connectivity and facilitating passage of fish about obstructions. It was recommended that these issues are examined and mechanisms for overcoming them are addressed. Similarly little information is available on the importance of relationships between residence times and access to side channels and backwaters from the main river channel for coarse fish species and no information on these characteristics is available for species of conservation value. - A review of the approaches to assess the impact of modifying flows on fisheries indicated that there were two possible scenarios for development of a tool to meet the requirements for assessing the impact of water resources schemes on fisheries. 1. A process to arrive at the fish requirements is pursued within the existing framework and objectives of CAMS/RAM: In this case a relatively simple method of assigning the sensitivity index, such as one of the hydraulic rating, habitat simulation or HABSCORE methods should be developed. 2. If the intention is to manage the hydrological regime in the interest of fish and fisheries, three potential approaches were proposed. 1) The integration of the various biotic components of RAM to produce a single integrated statistic. 2) The development of a RIVPACS type model for fish, e.g. River Fish Environmental Flow Assessment Matrix (RIFEFAM). This model can either be based on species presence or absence, relative species abundance or incorporate those parameters of the fish such as biomass, condition, and growth and survival rates that are needed to manage the fishery. 3) The development of population dynamics models that will assist in predicting the effects on the quality and quantity of the fish population of various alternative hydrological regimes. It was recommended that all three models are examined in detail and the most appropriate for meeting the objectives of the Agency selected for assessing the impact of water resources schemes on fisheries.
Publisher: Environment Agency
Subject Keywords: RiversRiver fisheriesCoarse fishesWater levelsPopulationFreshwater ecology
Geographic Keywords: River
Extent: 173
Total file downloads: 122

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