Fish utilisation of managed realignments

Abstract

One area of ecological benefit not yet fully evaluated in European waters is the utilisation of restored saltmarsh habitats by fish species. This study examines the utilisation of managed realignments and relic saltmarsh by fish species. Factors affecting habitat heterogeneity and fish populations are discussed, and recommendations are made with respect to scheme design and management that will maximise the biological and socio-economic values. Fish populations in the high intertidal areas were assessed using a suite of techniques, including observations on feeding behaviour. Each microhabitat was discussed as a function of the extent of fish colonisation. A positive relationship between the degree of fish utilisation and habitat heterogeneity was ascertained using species richness, abundance and behavioural observations. This study will aid habitat valuation for economic justification of managed realignments, over and above existing drivers, such as compensatory habitat for encroachment, flood defence and the European Union Habitats Directive. The work now forms part of a wider European Interreg IIIb project, COMCOAST.K E Y W O R D S : fish, habitat, intertidal, managed realignment, saltmarsh.

Variations in the feeding of 0-group bass Dicentrarchus labrax (L.) in managed realignment areas and saltmarshes in SE England

“…No large piscivorous fish were caught in the saltmarshes during this study, but piscivorous bass (30-40 cm long) were observed in the deep creeks of the saltmarshes and at the breaches of the managed realignment sites, becoming most active about 2 h after high water on spring tides, catching prey that leave the realignments on the ebb tide. This observation is consistent with those of previous studies which suggest that creek mouths are preferred habitats for piscivorous fish (Simenstad et al, 1998;Colclough et al, 2005). The relationship between the abundance of piscivorous fish and the 0-group bass mortality rate in saltmarshes is unknown, but is thought to be an important influence on feeding behaviour (Sheaves, 2001).…”

“…However, the majority of this work is not directly applicable to UK saltmarshes which have a larger tidal range and where the creeks drain fully on every tide (see Cattrijsse & Hampel, 2006 for a review). Moreover, there is a requirement to understand the value of created habitats in managed realignment areas for fish (Colclough et al, 2005). Fish using an area for feeding is an important indicator of the value of natural and created intertidal habitats (Weisberg et al, 1981;Rozas & LaSalle, 1990;Cattrijsse et al, 1994;Nemerson & Able, 2003) and knowledge of fish feeding behaviour may be used to improve design and management of future realignment schemes.…”

Influence of intertidal seascape on the functional structure of fish assemblages: Implications for habitat conservation in estuarine ecosystems

“…Over the past decades, several restoration projects have attempted to remove tidal barriers in order to re‐establish the accessibility and functionality of intertidal areas (Wolters, Garbutt, & Bakker, ), primarily for fish species (e.g. Colclough, Fonseca, Astley, Thomas, & Watts, ; Lechêne, Boët, Laffaille, & Lobry, ). In this context, our results provide valuable information to determine the expected benefits of potential restoration actions for fish populations depending on their localizations within estuary.…”

Sediment transport on the Freiston Shore managed realignment site: An investigation using environmental magnetism

“…On natural saltmarshes, sedimentation rates normally decline as the surface elevation increases (Allen and Pye, 1992)-but problems may arise when accretion is retarded due to sediment exhaustion rather than elevation gain. For example, insufficient sediment supplies inhibit colonisation and growth of saltmarsh plants and may discourage use of the site by fish, invertebrates and other wildlife (Colclough et al, 2005). One logical solution to this problem would be the application of dredged material to Freiston Shore, as has been done extensively at realignments in the USA (Zelder and Callaway, 2000).…”

“…In a recent review article, French (2006) noted that coastal managers now argue against hard defences because they interfere with natural processes, yet advocate MR as a preferred option while knowing little about its implications. Most existing studies have focused on the structural attributes of MR sites such as: 1) soil properties and geochemistry (Chang et al, 2001;Watts et al, 2003;Blackwell et al, 2004), 2) sedimentation rates Garbutt et al, 2003), 3) plant cover and composition (Alphin and Posey, 2000), and 4) the abundance and diversity of bird, fish, and invertebrate populations (Colclough et al, 2005). This research is crucial for understanding the development of realigned areas and is also often necessary for evaluating compliance with specific criteria or regulations.…”