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Project: Wadden Sea Fish Monitoring - Structure and trophic functioning of Wadden Sea fish fauna, an integrated pro...

Project details

  
Acronym : Wadden Sea Fish Monitoring
Full project name : Structure and trophic functioning of Wadden Sea fish fauna, an integrated programme: the monitoring part
Initiating organisation : IMARES, Wageningen UR, Institute for Marine Resources and Ecosystem Studies, IJmuiden
Project leader : I.Y.M.T. Tulp
Supporting organisation(s)NIOZ Royal Netherlands Institute for Sea Research, Yerseke
IMARES, Wageningen UR, Institute for Marine Resources and Ecosystem Studies, IJmuiden
Financing : nwo
Project number : 83908240
Start date : Jan 01, 2009
End date :
    

Relations

Programme :ZKO - Carrying Capacity: Line 2 - National Programme Sea and Coastal Research (ZKO) - Carrying Capacity: Line 2 - Monitoring
Main project :-
    

Description

Description :

The Dutch Wadden Sea and coastal waters are important as nature conservation areas as well as fishing grounds for shrimp and coastal fisheries and nursery grounds for commercially important fish species such as plaice, sole and herring. Present monitoring activities concerning the fish fauna (including epifaunal species shrimp and crabs) in the Dutch Wadden Sea, are restricted to two programmes: daily fyke net catches near Texel in spring and autumn by Royal NIOZ (1960-present) and a trawl survey of the demersal fish fauna in the subtidal of the Dutch Wadden Sea in autumn by IMARES (1970 to present). This means that temporal variability in fish fauna is only registered at a single spot and that information on spatial variability is restricted to a single moment in time. Furthermore, information on spatial distribution of pelagic species is lacking altogether at the moment.

A recent meta analysis of the functioning of continental shelf ecosystems along the North Atlantic (Frank 2007) concluded that for systems such as the Wadden Sea bottom-up control might be expected as the main forcing function. A study for the western part of the Dutch Wadden Sea (Philippart, Beukema et al. 2007) seemed to support this view. However, a recent combined analysis of both the long term fyke net catches and the demersal fish fauna (Van der Veer et al., 2007), showed a 90% drop in fish biomass in recent years, which is unexpected from the point of view of both a bottom up or top-down control and suggests that other mechanisms are acting. This presentiment is also corroborated by the occurrence of different time trends in different fish species. At present we lack insight in the underlying mechanisms and our present monitoring programmes are insufficient to guarantee any progress in this respect, even to monitor and describe the variability in space and time. Such basic information is crucial for any impact assessment of anthropogenic activities in the area such as eutrophication, climate change, fisheries and mining. With the introduction of towed camera sleds, remote-operated vehicles and small CTD units, fish densities and habitat features can be recorded continuously and simultaneously even in relatively turbid environments and such records result in spatial and temporal information on distribution, abundance and other population parameters (growth, mortality) and allow a comprehensive analysis of fish-habitat associations and species interactions at different scales. Such a multivariate geostatistical description of the demersal fish fauna in the Wadden Sea is a first step to understand the habitat-related spatial and temporal variability.

The monitoring programme proposed deals with the demersal component and aims to fill in the gaps of the existing monitoring programs and provides an approach to process the collected data into metrics that are suitable for managers responsible for the sustainable management of the Dutch coastal waters. Such programme would also provide parameters that reflect the essential ecosystem processes needed to build integrated models of the ecosystem structure and functioning. Data collected comprise (i) the seasonal and spatial distribution and abundance of demersal fish and epifaunal species (shrimps, crabs); (ii) essential fish habitat; (iii) the structure and trophic functioning of the fish community; (iv) growth and mortality rates. Indicators comprise the biomass of demersal fish and epibenthic invertebrates in spring and autumn, the size and the trophic structure of the demersal fish assemblage, and the size and distribution of essential fish habitats. Monitoring comprises a Wadden Sea wide trawl survey in the subtidal in spring (in addition to the existing DFS autumn survey) and a survey covering three areas during six sampling periods covering both tidal and subtidal habitats in at least three tidal basins (Marsdiep/Vlie basin; Lauwers, Ems-Dollard). Sampling tools comprise the standard DFS survey gear (shrimp trawl) and a standard 2-m beam trawl used by NIOZ in the tidal flat surveys, as well as a towed camera sled. The latter allows to record continuously and simultaneously fish densities and habitat features to analyse fish-habitat associations and species interactions at different scales. These methods are complementary where the DFS gear will be used in the subtidal and the 2-m beam in the intertidal. Organising such a survey in combination with the macrobenthos montinoring survey of the Wadden Sea would allow a direct coupling of the benthic macro in- and epifauna in analyses. Such a multivariate geostatistical description of the demersal fish fauna in the Wadden Sea is a first step to understand the habitat-related spatial and temporal variability. The combination of (partly innovative) monitoring techniques allow us to apply landscape ecology for the fish fauna of the Wadden sea and to arrive at predictive models for the presence, distribution and structure of fish communities, identifying the main ecotopes, ecotones and ecoclines, and assessing the structure and function of the food web. Data allow: [1] the estimation of residence time of different fish species in the Wadden Sea, [2] provide the necessary information to estimate production and consumption, [3] to address question on the role of fish in the structure and functioning of the Wadden Sea ecosystem, and [4] to follow the demersal fish fauna by means of various ecosystem indicators (EcoQO''s, ICES).

Bron: NWO.