Den Helder, Netherlands
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Hinrichsen H.-H.,Leibniz Institute of Marine Science | Dickey-Collas M.,Wageningen IMARES | Peck M.A.,Institute of Hydrobiology and Fisheries Science | Vikebo F.B.,Norwegian Institute of Marine Research
ICES Journal of Marine Science | Year: 2011

The potential role of coupled biophysical models in enhancing the conservation, management, and recovery of fish stocks is assessed, with emphasis on anchovy, cod, herring, and sprat in European waters. The assessment indicates that coupled biophysical models are currently capable of simulating transport patterns, along with temperature and prey fields within marine ecosystems; they therefore provide insight into the variability of early-life-stage dynamics and connectivity within stocks. Moreover, the influence of environmental variability on potential recruitment success may be discerned from model hindcasts. Based on case studies, biophysical modelling results are shown to be capable of shedding light on whether stock management frameworks need re-evaluation. Hence, key modelling products were identified that will contribute to the development of viable stock recovery plans and management strategies. The study also suggests that approaches combining observation, process knowledge, and numerical modelling could be a promising way forward in understanding and simulating the dynamics of marine fish populations. © 2011 International Council for the Exploration of the Sea.

Huijbers C.M.,Radboud University Nijmegen | Huijbers C.M.,Griffith University | Nagelkerken I.,Radboud University Nijmegen | Nagelkerken I.,University of Adelaide | And 2 more authors.
Ecology | Year: 2013

Marine spatial population dynamics are often addressed with a focus on larval dispersal, without taking into account movement behavior of individuals in later life stages. Processes occurring during demersal life stages may also drive spatial population dynamics if habitat quality is perceived differently by animals belonging to different life stages. In this study, we used a dual approach to understand how stage-structured habitat use and dispersal ability of adults shape the population of a marine fish species. Our study area and focal species provided us with the unique opportunity to study a closed island population. A spatial simulation model was used to estimate dispersal distances along a coral reef that surrounds the island, while contributions of different nursery bays were determined based on otolith stable isotope signatures of adult reef fish. The model showed that adult dispersal away from reef areas near nursery bays is limited. The results further show that different bays contributed unequally to the adult population on the coral reef, with productivity of juveniles in bay nursery habitat determining the degree of mixing among local populations on the reef and with one highly productive area contributing most to the island's reef fish population. The contribution of the coral reef as a nursery habitat was minimal, even though it had a much larger surface area. These findings indicate that the geographic distribution of nursery areas and their productivity are important drivers for the spatial distribution patterns of adults on coral reefs. We suggest that limited dispersal of adults on reefs can lead to a source-sink structure in the adult stage, where reefs close to nurseries replenish more isolated reef areas. Understanding these spatial population dynamics of the demersal phase of marine animals is of major importance for the design and placement of marine reserves, as nursery areas contribute differently to maintain adult populations. © 2013 by the Ecological Society of America.

Agency: European Commission | Branch: FP7 | Program: CP-IP-SICA | Phase: ENV.2009. | Award Amount: 8.58M | Year: 2010

The Future of Reefs in a Changing Environment (FORCE) Project partners a multi-disciplinary team of researchers from Europe and the Caribbean to enhance the scientific basis for managing coral reefs in an era of rapid climate change and unprecedented human pressure on coastal resources. The overall aim is to provide coral reef managers with a toolbox of sustainable management practices that minimise the loss of coral reef health and biodiversity. An ecosystem approach is taken that explicitly links the health of the ecosystem with the livelihoods of dependent communities, and identifies the governance structures needed to implement sustainable development. Project outcomes are reached in four steps. First, a series of experimental, observational and modelling studies are carried out to understand both the ultimate and proximate drivers of reef health and therefore identify the chief causes of reef degradation. Second, the project assembles a toolbox of management measures and extends their scope where new research can significantly improve their efficacy. Examples include the first coral-friendly fisheries policies that balance herbivore extraction against the needs of the ecosystem, the incorporation of coral bleaching into marine reserve design, and creation of livelihood enhancement and diversification strategies to reduce fisheries capacity. Third, focus groups and ecological models are used to determine the efficacy of management tools and the governance constraints to their implementation. This step impacts practical reef management by identifying the tools most suited to solving a particular management problem but also benefits high-level policy-makers by highlighting the governance reform needed to implement such tools effectively. Lastly, the exploitation and dissemination of results benefits from continual engagement with practitioners. The project will play an important and measurable role in helping communities adapt to climate change in the Caribbean.

Troost T.A.,Deltares | Wijsman J.W.M.,Wageningen IMARES | Saraiva S.,Netherlands Institute for Sea Research | Saraiva S.,University of Lisbon | Freitas V.,Netherlands Institute for Sea Research
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2010

Dynamic energy budget models for growth of individual cockles (Cerastoderma edule) and mussels (Mytilus edulis) are adjusted and calibrated to the Oosterschelde by formulating and parametrizing their functional responses using an extensive set of field observations. The resulting model predictions fit the observations satisfactorily. Results indicate that food quality and the importance of detritus as a food source are site-specific as well as species-specific. Despite these differences in their calibrated parameter values, both species show a very similar functional response. Compared with other systems, however, the functional responses of mussels in the present study are clearly higher than those of mussels in other systems. This may be explained by the absence of intra-specific competition in the measurement set-up that was used, and therefore supports the idea that the generally small functional response of M. edulis is caused by intra-specific competition. © 2010 The Royal Society.

Agency: European Commission | Branch: FP7 | Program: BSG-SME | Phase: SME-1 | Award Amount: 1.51M | Year: 2009

Today, some 45% of fish consumed by humans, 48 millions tonnes in all, is raised on fish farms. The actual relating European market, of which Norway is the leader, produces 1.3 millions of tonnes of fish farming products every year, which represents an approximate value of 3 billion Euros. Due to the highly competitive market the aquaculture business is confronted with the challenge to increase its productivity. The accurate measurement and control of CO2 can contribute to sustain the health of fish and in consequence guarantee the productivity of fish farms and the quality of human food. There are actually no on-line measurement systems available (titration tests and electro-chemical sensors), which are able to determine the CO2 concentration accurately enough over time for an efficient control of the CO2 concentration in intensive cultures. Furthermore there are still no reliable sensors on the market, which can be used for the measurement of dissolved CO2 in oceanography, but they are strongly requested by researchers for stationary and mobile applications. The objective of the project OptoCO2Fish is to develop a CO2 sensor to meet these demands. We intend to develop a novel solid state opto-chemical CO2 sensor system based on the principle of Resonance Energy Transfer. This principle offers the possibility to generate a compact and cost effective sensor system and furthermore is able to meet the essential requirements of fish farming staff, which is high accuracy and stability combined with low maintenance and low re-calibration effort. Titration tests and electro-chemical sensors together dominates the market. This one is currently led by American companies. This project can enhance the competitiveness of European companies, strengthen the position of aquaculture in Europe against the worldwide competition and can contribute a reliable sensor system for the research on effects of global warming due to CO2 emission.

Greenstreet S.P.R.,Marine Scotland - Marine Laboratory | Rogers S.I.,Center for Environment | Rice J.C.,Northwest Atlantic Fisheries Center | Piet G.J.,Wageningen IMARES | And 3 more authors.
ICES Journal of Marine Science | Year: 2011

Development of the Ecological Quality Objective (EcoQO) for the North Sea demersal fish community is described. Size-based metrics were identified as the most effective indicators of the state of the community, but such metrics are also sensitive to environmental influence. Redefining the large fish indicator (LFI) produced a metric more sensitive to fishing-induced change and therefore more useful to managers. Fish stocks were thought to be exploited at a sustainable rate in the early 1980s, so in a process echoing the precautionary approach to fish stock management, this was considered the reference period for the LFI, suggesting a value of 0.3 as the appropriate EcoQO. The LFI declined from around 0.3 in 1983 to 0.05 in 2001, followed by a recovery to 0.22 in 2008. However, analyses of the longer-term groundfish survey data suggest that, even were fishing pressure to be reduced to early 20th century levels, the LFI would be unlikely to rise much above a value of 0.3. The response of the LFI to variation in fishing pressure suggested a more complex relationship than anticipated, underscoring the need for operational theoretical size-resolved multispecies fish community models to support management towards broader ecosystem objectives. © Crown copyright 2010.

Mas-Munoz J.,Wageningen University | Komen H.,Wageningen University | Schneider O.,Wageningen IMARES | Visch S.W.,Wageningen University | Schrama J.W.,Wageningen University
PLoS ONE | Year: 2011

The major economic constraint for culturing sole (Solea solea) is its slow and variable growth. The objective was to study the relationship between feed intake/efficiency, growth, and (non-) feeding behaviour of sole. Sixteen juveniles with an average (SD) growth of 2.7 (1.9) g/kg0.8/d were selected on their growth during a 4-week period in which they were housed communally with 84 other fish. Selected fish were housed individually during a second 4-week period to measure individual feed intake, growth, and behaviour. Fish were hand-fed three times a day during the dark phase of the day until apparent satiation. During six different days, behaviour was recorded twice daily during 3 minutes by direct observations. Total swimming activity, frequency of burying and of escapes were recorded. At the beginning and end of the growth period, two sequential behavioural tests were performed: "Novel Environment" and "Light Avoidance". Fish housed individually still exhibited pronounced variation in feed intake (CV = 23%), growth (CV = 25%) and behavior (CV = 100%). Differences in feed intake account for 79% of the observed individual differences in growth of sole. Fish with higher variation in feed intake between days and between meals within days had significantly a lower total feed intake (r = -0.65 and r = -0.77) and growth. Active fish showed significantly higher feed intake (r = 0.66) and growth (r = 0.58). Boldness during both challenge tests was related to fast growth: (1) fish which reacted with a lower latency time to swim in a novel environment had significantly higher feed intake (r = -0.55) and growth (r = -0.66); (2) fish escaping during the light avoidance test tended to show higher feed intake (P<0.1) and had higher growth (P<0.05). In conclusion, feeding consistency, swimming activity in the tank, and boldness during behavioral tests are related to feed intake and growth of sole in captivity. © 2011 Mas-Muñoz et al.

Wijsman J.W.M.,Wageningen IMARES | Smaal A.C.,Wageningen IMARES
Journal of Sea Research | Year: 2011

A Dynamic Energy Budget (DEB) model for cockles is presented and calibrated using detailed data on cockle growth and water quality in the Oosterschelde. Cockles in the intertidal areas of the Oosterschelde have an important function as a food source for wading birds and as such for the natural values of the ecosystem. In the presented model, special attention is paid to the formulation and parameter estimation of the functional response. With this functional response, the food quantity and quality variables such as Chlorophyll-a, POM, POC and TPM are translated into food ingestion rate for the cockles. The calibration of the specific parameters included in this functional response is done using a detailed, long term dataset (1992-2007) of cockle growth in the Oosterschelde estuary. This dataset gives a good overview of the development of the cockle population in relation to the environmental conditions (food availability and ambient temperature).The DEB model was able to describe the spatial variation in cockle growth in the Oosterschelde as a function of environmental conditions and the parameters of the functional response. Both the data and the model show that growth performance of cockles is highest in the western and central part of the Oosterschelde due to the higher concentrations of Chlorophyll-a, which is an important food source for cockles. The model failed to describe the large variation in ash-free dry weight during the season. It is tested whether this is caused by aggregating the data by running the model for the full life cycle of year class 2001 at a specific location in the western part of the Oosterschelde. Finally, the model simulations have been compared to growth simulations obtained with an existing ecophysiological model for cockles in the Oosterschelde, the COCO model, with identical forcing. The COCO model showed higher growth in terms of shell length compared to the DEB model and the field observations. © 2011 Elsevier B.V.

Brunel T.,Wageningen IMARES
ICES Journal of Marine Science | Year: 2010

Exploitation alters the age structure of fish stocks. Several stock-specific studies have suggested that changes in the age structure might have consequences for subsequent recruitment, but the evidence is not universal. To investigate how common such effects are among 39 Northeast Atlantic fish stocks, relationships were tested between age structure (spawner mean age, age diversity, and proportion of recruit spawners) and recruitment (number of recruits, sensitivity to environment, and recruitment variability). Significant correlations in the expected direction were observed for a few stocks, but not for the majority; significant correlations in the opposite direction were also found. Meta-analyses combining the stock-level tests revealed that none of the effects were significant overall. However, effects were significant for some species (cod, haddock, and plaice) and indices. The low variability in the age structure might explain the absence of significant effects for individual stocks. Other reasons could be the absence of a biological basis (reproductive characteristics not dependent on age) or the stronger influence of environmental variability than of age structure on recruitment. © 2010 International Council for the Exploration of the Sea. Published by Oxford Journals. All rights reserved.

Piet G.J.,Wageningen IMARES | Van Overzee H.M.J.,Wageningen IMARES | Pastoors M.A.,Wageningen IMARES
ICES Journal of Marine Science | Year: 2010

Results are used from traditional fisheries management to explore two potential response indicators: (i) the extent to which scientific advice is incorporated in decision-making, and (ii) the compliance of industry and the relevant authorities to these decisions. Based on the most comprehensive set of data on the management process of 125 stocks for which ICES provided advice over the period 1987-2006, we explored these response indicators and found that for just 8% of the stocks, the official total allowable catch (TAC) equalled the scientific advice, and that in recent years the official TAC overshot scientific advice by >50%. Compliance levels appear to be reflected in the percentage of stocks for which landings exceeded the official TAC, decreasing from ∼8 to 2%. However, because the TAC appears not to be limiting, compliance may not be the most appropriate indicator. Without transparent decision-making that takes scientific advice into account, or the compliance of industry as reflected by the type of response indicators explored, the effectiveness of new developments in fisheries management, such as the application of an ecosystem approach, will be compromised, as has been the case with conventional fisheries management measures. © 2010 International Council for the Exploration of the Sea.

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