Productivity • Invertebrates • Birds
Fish • Amphibians • Mammals

Fish

Information regarding the extent to which fish communities use UK saltmarshes is limited due to the difficult sampling methods required to collect the data. However, a detailed study in Mont Saint Michel Bay, France, has shown that sea bass fry colonise the marsh creeks during the flooding spring tides and return to coastal waters on the following ebb tide (Laffaille et al., 2001 in Stevenson, 2002). This duration of 1-2 hours allow the juvenile fish to consume, on average, a minimum of 8% of their body weight, feeding on the numerous invertebrate fauna that colonise the marsh creeks. It should also be noted that a number of fish benefit indirectly from marshes by feeding on invertebrates which inhabit the adjacent mudflats and estuarine waters, which themselves feed on organic matter exported from the saltmarshes. The use of saltmarshes by fish (both as nursery and, potentially, breeding areas) is also supported by monitoring of managed realignment sites in Essex undertaken by the Environment Agency (Colclough et al., 2004).

Shellfisheries are not directly dependent on the saltmarsh although, historically, oyster beds are placed in creek bottoms, and pits and pools in the upper marsh are used for their over-wintering. However, the relationship between saltmarsh productivity and its wider role in providing a source of food and a nursery for fish and shellfish is unclear and, possibly, more important than studies have yet revealed.