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Title: Habitat preferences of the bullhead (Cottus gobio) in some Norfolk rivers
Author: Environment Agency Anglian Region
Document Type: Monograph
The bullhead {Cottus gobio) is listed under Annex II of the EC Directive on the conservation of natural habitats and flora and fauna. Member countries have the duty to ensure the favourable conservation status of the species through conservation of viable populations within special areas of conservation (SACs). In this study, the physical micro-habitat preferences, which were largely unknown, were determined in stretches of the Glaven and Stiflkey in North Norfolk and the Upper Wensum and it's tributary the Whitewater stream, in summer and autumn. Point-abundance sampling by electrofishing was the technique used. Woody debris and associated leaf litter appeared to the optimal microhabitat for bullheads when they were likely to be least active during the day. Where the quantity of woody debris was apparently limiting, bullheads selected for the interstitial spaces between stones which usually occurred in shallow sites on any available riffles. The selection for this microhabitat by 0+ bullheads was thought to be linked to exclusion by larger individuals. In autumn', as the quantity of woody debris and leaf litter in the system increased, small bullheads had the opportunity to also select for this habitat type. It is suggested that the abundance of woody debris may play a significant role in determining the abundance as well as distribution of bullheads within rivers. This has considerable implications for current routine maintenance regimes which result in the removal of woody debris. The adoption of more sensitive regimes, where there is little risk of flooding, in which debris dams are retained is likely to be of considerable benefit to bullhead populations. Overall, bullheads were considerably more abundant in natural rather than modified rivers, being abundant (0.62 nr2) in the Whitewater and absent in the Stiffkey. A continuation of the current work, with sampling in late winter during peak river flows and early spring during the spawning season, thus completing the seasonal cycle of monitoring, is likely to enable a full habitat description to be determined. This is likely to prove to be a valuable component of river rehabilitation programmes.
Publisher: Environment Agency
Publication Date: 1997
Publication Place: Peterborough
Subject Keywords: Freshwater fishesRiversHabitatsHabitat preferencesEcological abundance
Geographic Keywords: NorfolkWensumNorth Norfolk catchmentStiffkey (Norfolk)Glaven (Norfolk)
Extent: 29
Total file downloads: 230

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