The Zoological Society of London (ZSL) has published guidance on fish conservation for planners, developers, local authority officers and consultants, with the goal of improving fish conservation in the Tidal Thames region, encompassing all Local Authorities adjoining the River Thames between Teddington Lock and Gravesend.
ZSL spoke to developers about this guidance at a Thames Estuary Partnership May 2017 event, "The Evolution of the Estuary: an update on Key Projects", at which four major projects at planning stage were presented in a very efficient half-morning hosted at Farrnells office in London.
The ZSL guidance provides links to additional sources of information, regulations, strategies, policy statements and local plans. One such source is the Tidal Thames Habitat Action Plan developed by the Thames Estuary Partnership Biodiversity Action Group as input to the London Biodiversity Action Plan.
The tidal Thames area is of ecological importance as a route for migratory fish to move between freshwater and salt water and vice versa; as a rich foraging ground for fish including certain species that live exclusively in the Thames; and as a territory for fish to spawn and young fish to grow. 124 fish species have been identified in the Tidal Thames since 1964, 15% of which are protected by regulations.
All development operations and decommissioning along the Thames has the potential to cause impact to the fish in the Thames, including through light and water pollution, sound/vibration, change of water temperature, sediment deposition or suspension, and local changes to water flow.
The primary message is that the nature and duration of such impact is contingent on design of the development and scheduling of works; the impact on fish needs to be considered throughout the planning and development process and impacts mitigated and managed if unavoidable. "Permanent loss of inter-tidal and/or sub-tidal habitats should be avoided".
Specific steps needed are:
A baseline survey, scheduling of works to avoid "ecological events" for fish (e.g. mitigation), create additional or replacement foreshore habitat and modify surfaces in contact with the river (e.g. walls, piers, piles), design sustainable drainage systems, plan ways to reduce impact during works (control of sedimentation change, vibration, run-off, etc).