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Den Helder, Netherlands

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

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. Source

Leopold M.F.,Wageningen IMARES | Begeman L.,University Utrecht | van Bleijswijk J.D. L.,Netherlands Institute for Sea Research | IJsseldijk L.L.,University Utrecht | And 2 more authors.
Proceedings of the Royal Society B: Biological Sciences

Harbour porpoises (Phocoena phocoena) stranding in large numbers around the southern North Sea with fatal, sharp-edged mutilations have spurred controversy among scientists, the fishing industry and conservationists, whose views about the likely cause differ. The recent detection of grey seal (Halichoerus grypus) DNA in bite marks on three mutilated harbour porpoises, as well as direct observations of grey seal attacks on porpoises, have identified this seal species as a probable cause. Bite mark characteristics were assessed in a retrospective analysis of photographs of dead harbour porpoises that stranded between 2003 and 2013 (n=1081) on the Dutch coastline. There were 271 animals that were sufficiently fresh to allow macroscopic assessment of grey seal-associated wounds with certainty. In 25% of these, bite and claw marks were identified that were consistent with the marks found on animals that had tested positive for grey seal DNA. Affected animals were mostly healthy juveniles that had a thick blubber layer and had recently fed. We conclude that the majority of the mutilated harbour porpoises were victims of grey seal attacks and that predation by this species is one of the main causes of death in harbour porpoises in The Netherlands. We provide a decision tree that will help in the identification of future cases of grey seal predation on porpoises. © 2014 The Author(s) Published by the Royal Society. All rights reserved. Source

Grol M.G.G.,Radboud University Nijmegen | Nagelkerken I.,Radboud University Nijmegen | Bosch N.,Radboud University Nijmegen | Meesters E.H.,Wageningen IMARES
Marine Ecology Progress Series

Coral reef populations of a variety of fish and invertebrate species are replenished by individuals that use inshore coastal habitats as temporary juvenile habitats. These habitats vary greatly in their architecture, and different characteristics of structure could play a role in their selection and utilization by resident fauna. To solely investigate the role of structural complexity in microhabitat selection, in situ habitat preference of 48 individuals of the early juvenile stage of a common reef fish (Haemulon flavolineatum) was studied for 4 structurally very different lagoonal microhabitats (i.e. mangrove, seagrass, rubble, coral), using a multiple-choice experiment in field enclosures. This fish species was selected as it utilizes these habitats during different parts of its life cycle. The structural complexity of each microhabitat was changed in each replicate experiment and assessed on the basis of 7 commonly used measures of structure using digitized photographs. We tested the hypothesis that in isolation of other factors, fish prefer the structurally most complex microhabitat that is available, independent of habitat type. However, fish always preferred seagrass and coral microhabitats even when offered at low complexity, and this choice was rather consistent over a 24 h time period. Structural characteristics appeared to be marginally important for the seagrass microhabitat only. Therefore, the differential preference for distinct lagoonal microhabitats does not appear to be driven by measures of structural complexity that are known to be important at the level of individual habitat types. In this light, continuing loss of coral and seagrass habitats in lagoonal environments due to anthropogenic effects is alarming as it affects preferential habitat of certain stages of the life cycle of fishes. © Inter-Research 2011. Source

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.

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. Source

Mas-Munoz J.,Wageningen University | Komen H.,Wageningen University | Schneider O.,Wageningen IMARES | Visch S.W.,Wageningen University | Schrama J.W.,Wageningen University

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. Source

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