Salmon and Trout Association: Intertidal Habitat

Estuarine systems, and their intertidal habitat, are some of the most valuable ecosystems on earth because of their high biodiversity and high levels of productivity. Estuaries are dynamic systems with continual fish immigration and emigration from freshwater and marine habitats. They are also very vulnerable to the quality and quantity of fresh and marine water they receive.

It is estimated that 85% of British estuaries have lost individually up to 80% of their intertidal area through human land claim, for reasons such as agriculture, port developments, harbours, industry, dredging and housing.

Value of Intertidal habitat

Intertidal habitat in the UK typically comprises mudflat and saltmarsh habitats, which have long been recognised as key feeding and roosting grounds for birds. They can also deliver a wide range of key functions, including nutrient and carbon storage, and flood defence.

Intertidal habitats are also important nursery areas for fish, providing rich feeding areas and protective habitat. They provide a suitable environment for Atlantic salmon (Salmo salar) and sea trout (salmo trutta) parr to undergo smoltification. Therefore, removing these nursery habitats could significantly affect juvenile fish recruitment, as well as reducing species diversity as many endemic fish species are associated with estuarine habitats.

Intertidal habitats within estuaries are continuations of our river habitats, and their conservation should be viewed as an important step in re-establishing the river corridor for migrating species.

Protection

Saltmarshes are now designated as UK Biodiversity Action Plan (BAP) habitat and form part of Defra’s High Level Target Habitat Series. This has resulted in initiatives requiring no further net loss of saltmarsh habitat, and a growing appreciation for protecting the UK coastlines with soft-engineering methods such as managed realignments; where coastal protection, such as sea walls, are removed to allow the sea to flood land previously not exposed to flooding.

The Habitats Directive supplies a statutory requirement to obtain compensatory habitat if the proposed development can be shown to have a deleterious impact on the site. However, this protection only occurs in Natura 2000 designated sites e.g. SSSI and SACs.

Protection is also set to change with the introduction of the Water Framework Directive (WFD), which requires that all Member States must achieve ‘good ecological status/potential’ in all freshwater, transitional and coastal water-bodies by the end of 2015 (See: WFD). This is the first time transitional waterbodies (estuaries) have been included within required monitoring programmes. Under these new guidelines, the preservation and restoration of intertidal habitats within estuaries should be required to obtain ‘good ecological status/potential’.

Call for Further Action

The destruction of intertidal habitat is resulting in the loss of importance nursery and feeding grounds for a wide range of fish, bird and invertebrate species. We feel further action and political will is required to prevent further intertidal habitat loss. Compensatory habitat should not be used as an acceptable solution to mitigate the large scale loss of extant intertidal habitat. This is particularly topical in light of the proposed Severn Barrage (See: Hydropower).

The S&TA calls for:

• Further protection for intertidal habitat by making them candidates for Marine Protected Areas (MPA). The MPA network should be working to help safeguard different stages of commercial/recreational fish’s life history. Designating intertidal habitat will help achieve maximum recruitment through nursery protection, which will help boost fisheries in the future.
• Further action is also required to address water quality, water removal and sediment problems affecting intertidal habitat survival.

Conclusion

The protection of intertidal habitats is a vital step in improving local commercial and recreational fisheries, through increased juvenile recruitment and production. Intertidal habitats have the ability to achieve a range of ecosystem functions from increasing biodiversity to improving air quality, carbon storage and flood defence simultaneously. The benefits provided by intertidal habitats are extremely important and topical in light of current proposals to harness tidal energy.

For further information see;

S&TA Scientific Briefing Paper: The Value of Intertidal Habitat
Defra/EA. (2008). Managed Realignment Review.
Gray (2007). EA Placement; Fish Utilisation of Intertidal Habitat in the Thames Estuary.
EA. (2003). Wetland Valuation
EA. (2002). The Benefits to Fisheries of UK Intertidal Salt Marsh Areas