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ECON are one of the leading Ecological Consultancies specialising in fisheries work and are acting consultants to a variety of organisations including English Nature and the Environment Agencyas well as also undertaking work for individuals, such as lake owners.
The senior staff comprising Dr Martin Perrow (Director) and Mark Tomlinson (Senior Fisheries Ecologist), have over 22 years of cumulative experience.
ECON comply to all health and safety requirements as specified in the Environment Agency's Electric Fishing Code of Practice as well as operating a comprehensive risk assessment procedure under the company health and safety policy.
Services offered include:
- Population monitoring - e.g. in relation to amelioration of low flows
- Impact assessment - e.g. assessing impacts of quarries, road schemes etc.
- Habitat enhancement schemes
- River and lake restoration through biomanipulation
The case studies below demonstrate some of the types of work we carry out:
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Case Study 1:
Monitoring the ecological response of the recovery enhancement of the River Misbourne
The River Misbourne, a 28 km long, ecologically valuable chalk stream situated in the River Thames catchment in Berkshire, was believed to be one the rivers most affected by abstraction in the UK. A scheme to restore flow and with the general aim of restoring the native fish community of Brown trout Salmo trutta and bullhead Cottus gobio was implemented by the Environment Agency and Three Valleys Water and comprised abstraction reduction and relocation of abstraction points.
The ecological response of the fish community to flow recovery was monitored over an eight year period at six sites along the course of the river. For three years monitoring was undertaken using two different techniques, namely standard depletion electric fishing within stop-nets and point-abundance sampling by electric fishing (PASE) (Copp & Peñáz 1988, Perrow et al. 1996), enabling a comparison between the two survey methodologies to be carried out.
Comparison of the techniques showed that whilst species richness and estimates of total biomass were similar, PASE produced significantly higher estimates of abundance, on account of its apparent ability to sample the dominant, small (and cryptic) species, such as bullhead Cottus gobio, more effectively. Following this, the longer-term response of the river over the remaining five years was undertaken using PASE.
All sites monitored showed responses to increased flow and depth, even sites furthest downstream and closest to the River Colne. Colonization of the upstream sites was generally rapid, even though in some places parts of the river remained dry. The first colonists were sticklebacks, slow-water depositing habitat specialists, although as flow improved the community shifted rapidly to become dominated by bullheads and brown trout, the desirable target community for the river. This process was complicated slightly by the illegal stocking of brown trout at some sites. Whilst the origin of these fish could not be confirmed, they are apparently recruiting successfully. Although stocking issues have confused the process, accompanying changes in habitat structure and plant colonization patterns - initial domination by emergents followed by a decline and subsequent colonization of submerged plants (e.g. ranunculus) - indicates that the results of scheme have been very successful.
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Case Study 2:
The ecological requirements of the bullhead Cottus gobio
Bullhead Cottus gobio L. has recently been recognized as worthy of significant conservation interest under the species annex of the EC Habitats Directive, Member states having a duty to ensure the maintenance of favourable conservation statis within Special Areas of Conservation (SACs).
In 2001 ECON were commissioned by English Nature and the Environment Agency to review the state of knowledge of the ecological requirements of bullheads in relation to salmonids and to make recommendations on the direction and nature of further necessary studies.
Bullhead is a small freshwater (<15cm) cottid found in the UK, easily identifiable due to its large head (up to 25% of body length) and a dorso-ventrally flattened tapering body. Bullheads have no swimbladders, an adaptation to life on the bottom of flowing waters where reduced buoyancy is an advantage.
Despite the relatively wide distribution and occurrence of bullhead in a range of flowing and still waters, its habitat preferences appear to be quite distinct. Natural gravel-bed streams with appropriate channel structure (e.g. riffle/pools), wooded riparian zones (or perhaps macrophytes in some situations) offering shade and refuges from predators and flow, lacking obstructions and containing native, unmanipulated populations of fish and crayfish represent ideal habitat. In such circumstances, the density of bullheads may be high and may even dominate fish production.
Conversely, where streams have been channelised or the natural flow and sediment regimes modified or other fish/crayfish introduced, bullheads are likely to have been seriously adversely affected.
Consequently, bullheads should be seen as vulnerable and sensitive to disturbance. Moreover, they may prove to a valuable indicator of "naturalness" and high habitat diversity in stream systems. Despite this, bullhead remains poorly studied and even basic aspects of the factors limiting populations remain unknown. This seriously limits the maintenance or attainment of favourable conservation status both within SAC's and within its wider range in the UK.
Research priorities include:
- Factors limiting recruitment
- Habitat associations when foraging at dusk/night
- Impacts of disturbance, especially in relation to siltation and fish stocking
- Genetic variation of UK stock com[ared to those in Continental Europe
- Verification of potential indicators of favourable conservation status
- Determination of a minimum acceptable flow regime & key habitat variables
Published Reports
Perrow, M.R. & Côté, I. (1999). The development of ecological requirements to inform the production of conservation objectives for bullhead and spined loach. English Nature Contract EIT 20-21-05, Peterborough, UK.
Perrow, M.R., Punchard, N. T. & Jowitt, A.J.D. (1997). The habitat requirements of bullhead (Cottus gobio) and brown trout (Salmo trutta) in the headwaters of selected Norfolk rivers: implications for conservation and fisheries. Report to Anglian Region, Environment Agency, Ipswich, UK.
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