van den Brink N.W.,Wageningen University |
Riddle M.J.,Australian Antarctic Division |
van den Heuvel-Greve M.,Wageningen University |
van Franeker J.A.,IMARES Wageningen UR
Marine Pollution Bulletin | Year: 2011
We demonstrate that pelagic Antarctic seabirds show significant decreases in concentrations of some persistent organic pollutants. Trends in Adélie penguins and Southern fulmars fit in a general pattern revealed by a broad literature review. Downward trends are also visible in pelagic fish, contrasting sharply with steady or increasing concentrations in Antarctic benthic organisms. Transfer of contaminants between Antarctic pelagic and benthic food webs is associated with seasonal sea-ice dynamics which may influence the balance between the final receptors of contaminants under different climatic conditions. This complicates the predictability of future trends of emerging compounds in the Antarctic ecosystem, such as of the brominated compounds that we detected in Antarctic petrels. The discrepancy in trends between pelagic and benthic organisms shows that Antarctic biota are still final receptors of globally released organic contaminants and it remains questionable whether the total environmental burden of contaminants in the Antarctic ecosystem is declining. © 2010 Elsevier Ltd.
Bravo Rebolledo E.L.,IMARES Wageningen UR. |
Van Franeker J.A.,IMARES Wageningen UR. |
Jansen O.E.,IMARES Wageningen UR. |
Brasseur S.M.J.M.,IMARES Wageningen UR.
Marine Pollution Bulletin | Year: 2013
Abundance of ingested debris by seals has been mentioned as a potential indicator of marine litter in the European Marine Strategy Framework Directive (MSFD). A sample of 107 stomachs, 100 intestines and 125 scats of harbour seals from the Netherlands was analysed for the presence of plastics. Incidence of plastic was 11% for stomachs, 1% for intestines, and 0% for scats. Younger animals, up to 3. years of age, were most affected. This is the first quantitative study of plastic ingestion by phocid seals. The observed level of incidence is of environmental concern, but is low in the sense of suitability of seals for MSFD monitoring purposes. © 2012 Elsevier Ltd.
Baptist M.J.,IMARES Wageningen UR |
Leopold M.F.,IMARES Wageningen UR
Ibis | Year: 2010
Human impacts on water transparency may affect plunge-diving seabirds. We studied prey capture success of Sandwich Terns Sterna sandvicensis as a function of six environmental variables during the breeding season. We observed diving terns in the south eastern North Sea and found a non-linear optimum curve for the relationship between Secchi transparency and prey capture probability. High capture probability was found at 1.5-2.0 m, with an optimum of 63% at 1.74 m. At a minimum transparency of 0.4 m and at a maximum transparency of 3.2 m, capture probabilities were about halved. Conversion of transparency to total suspended matter (TSM) concentration showed that the optimum concentration for foraging terns would be 5-10 mg/L under mean summer conditions for chlorophyll- a. However, the summer-averaged TSM concentrations in the nearshore Dutch coastal waters range between 10 and 30 mg/L, which implies that foraging Terns in the breeding season do not encounter optimal foraging conditions. The Full Plunge Dive, with which the largest diving depth can be achieved, was applied dominantly in clear water, while the Partial Plunge Dive and Contact Dip were applied more frequently in turbid water, thus showing that Sandwich Terns adjust their diving technique in response to water transparency. © 2010 The Authors. Journal compilation © 2010 British Ornithologists' Union.
Kuhn S.,IMARES Wageningen UR |
Kuhn S.,Van Hall Larenstein University of Applied Sciences |
van Franeker J.A.,IMARES Wageningen UR
Marine Pollution Bulletin | Year: 2012
In 2011, northern fulmars (Fulmarus glacialis) from Iceland were used to test the hypothesis that plastic debris decreases at northern latitudes in the Atlantic when moving away from major human centres of coastal and marine activities. Stomach analyses of Icelandic fulmars confirm that plastic pollution levels in the North Atlantic tend to decrease towards higher latitudes. Levels of pollution thus appear to link to regions of intense human coastal and marine activities, suggesting substantial current inputs in those areas. © 2012 Elsevier Ltd.
Fijn R.C.,IMARES Wageningen UR |
van Franeker J.A.,IMARES Wageningen UR |
Trathan P.N.,British Antarctic Survey
Marine Ornithology | Year: 2012
Food web knowledge is a prerequisite for adequate resource management in the Antarctic ecosystem. Accurate dietary specifications for the major consumers within the Antarctic ecosystem are needed. Procellariid species are the most numerous avian species in Antarctica and account for 20% to 40% of the overall consumption by seabirds in the area. Diet composition of two important procellariids, Cape and Snow Petrels, was studied at Signy Island during the breeding season 2005-2006. Food samples were obtained by stomach flushing of both chick-feeding birds and self-provisioning birds. Original prey mass was reconstructed from identifiable remains in the stomach samples. Significantly different diet compositions were found between chick-feeding and self-provisioning Cape Petrels based on reconstructed weight (chick-feeders 39:61:0:0, fish:crustacean:squid:other; self-provisioning birds 28:65:7:1, F:C:S:O). By contrast, no significant differences were found between chick-feeding Snow Petrels (66:34:0:0, F:C:S:O) and self-provisioning birds (68:32:0:0, F:C:S:O). Dominant prey items were Antarctic Krill Euphausia superba and the myctophid fish Electrona antarctica. Compared with findings undertaken at other locations, Cape Petrels at Signy Island had higher dietary fractions of crustaceans. Similarly, this study shows higher fractions of krill and lower fractions of fish in Snow Petrels at Signy Island than at other locations. A reasonable explanation for the high crustacean fraction in both seabird species might be the local high abundance of Antarctic Krill. This emphasises that local differences in diets need to be taken into account in modelling studies. Also, fish is an abundant prey item in both species, showing that, even in a strongly krill-dominated region, fish may remain an important part of the diet of Antarctic petrel species. The differences in diet between chick-feeding and self-provisioning Cape Petrels also show the importance of studying both groups in overall dietary research.
Cervencl A.,IMARES Wageningen UR |
Alvarez Fernandez S.,IMARES Wageningen UR
Journal of Sea Research | Year: 2012
The European wintering population of Greater Scaup has declined significantly over the last 20. years and some of the main threats appear to be at the wintering grounds. This contribution aims at describing the local distribution of Scaup in the Dutch Wadden Sea, one of the most important wintering sites for Scaup in relation to available food resources. Data on the distribution of Scaup was obtained from annual aerial counts in January during 1999-2009. This data was related to benthos data of regular shellfish surveys in the sublittoral part of the western Dutch Wadden Sea. Boosted regression tree models were applied to quantify the relative importance of different potential prey items to explain the presence of Scaup. Scaup preferred sites with high abundances of small sized Mya arenaria. A negative influence on Scaup preference for sites with high abundances M. arenaria was found when there was a high abundance of large Cerastoderma edule at the sites, which increased Scaup searching time for M. arenaria. © 2012 Elsevier B.V.
Aarts G.,IMARES Wageningen UR |
Aarts G.,Wageningen University |
Fieberg J.,Biometrics Unit |
Fieberg J.,University of Minnesota |
And 2 more authors.
Journal of Animal Ecology | Year: 2013
If animals moved randomly in space, the use of different habitats would be proportional to their availability. Hence, deviations from proportionality between use and availability are considered the tell-tale sign of preference. This principle forms the basis for most habitat selection and species distribution models fitted to use-availability or count data (e.g. MaxEnt and Resource Selection Functions). Yet, once an essential habitat type is sufficiently abundant to meet an individual's needs, increased availability of this habitat type may lead to a decrease in the use/availability ratio. Accordingly, habitat selection functions may estimate negative coefficients when habitats are superabundant, incorrectly suggesting an apparent avoidance. Furthermore, not accounting for the effects of availability on habitat use may lead to poor predictions, particularly when applied to habitats that differ considerably from those for which data have been collected. Using simulations, we show that habitat use varies non-linearly with habitat availability, even when individuals follow simple movement rules to acquire food and avoid risk. The results show that the impact of availability strongly depends on the type of habitat (e.g. whether it is essential or substitutable) and how it interacts with the distribution and availability of other habitats. We demonstrate the utility of a variety of existing and new methods that enable the influence of habitat availability to be explicitly estimated. Models that allow for non-linear effects (using b-spline smoothers) and interactions between environmental covariates defining habitats and measures of their availability were best able to capture simulated patterns of habitat use across a range of environments. An appealing aspect of some of the methods we discuss is that the relative influence of availability is not defined a priori, but directly estimated by the model. This feature is likely to improve model prediction, hint at the mechanism of habitat selection, and may signpost habitats that are critical for the organism's fitness. © 2013 British Ecological Society.
Eigaard O.R.,Technical University of Denmark |
Marchal P.,French Research Institute for Exploitation of the Sea |
Gislason H.,Technical University of Denmark |
Rijnsdorp A.D.,IMARES Wageningen UR |
Rijnsdorp A.D.,Wageningen University
Reviews in Fisheries Science and Aquaculture | Year: 2014
Many marine fish stocks are overexploited and considerable overcapacity exists in fishing fleets worldwide. One of the reasons for the imbalance between resource availability and fishing capacity is technological development, which continuously increases the efficiency of the vessels-a mechanism referred to as "technological creep." We review how the introduction of new and more efficient electronic equipment, gear design, engines, deck equipment, and catch-handling procedures influences the capture efficiency (catchability) of commercial fishing vessels. On average, we estimate that catchability increases by 3.2% per year due to technological developments, an increase often ignored in fisheries management. The documentation and quantification of technological creep improves the basis for successfully integrating the effects of technological development (and catchability changes) in fisheries management regulations and policies. Ways of counteracting the undesired effects of technological creep are discussed as are the potential management benefits from improved fishing technology. Specific suggestions are given on the selection, application, and tuning of fisheries management tools that can be used to improve the balance between harvesting capacity and resource availability. © 2014 Copyright © Taylor & Francis Group, LLC.
Jongbloed R.H.,IMARES Wageningen UR |
Van der Wal J.T.,IMARES Wageningen UR |
Lindeboom H.J.,IMARES Wageningen UR
Energy Policy | Year: 2014
The increasing demand for renewable energy drives the development of offshore wind energy (OWE) leading to competing claims with other human and nature related uses of the North Sea. This paper investigates possibilities to identify space for new OWE while minimising effects on other uses. An inventory is made of the major uses in the Central and Southern North Sea, including the expected development towards 2030. The spatial distribution of non-wind uses is determined as well as the possibilities for differentiation based on density, economic value or nature value and co-existence. These possibilities are translated into calculation rules quantifying the relative importance. These calculation rules have been incorporated in a Decision Support System (DSS) to analyse how the priority of OWE development could impact non-wind uses. In a low OWE priority scenario consequences for other use was found to be very limited, with fisheries and wildlife affected most. In a high OWE priority scenario a considerable amount of OWE may be developed with substantial claims on sand extraction and military use areas and a shift towards higher value categories for shipping and fisheries. Relocation and co-existence of uses are important means to reduce the impact of increased OWE development. © 2014.
News Article | November 23, 2015
Harbour porpoises eat approximately ten percent of their body weight in fish per day. Their diet mainly comprises gobies, whiting, sand lances, herring and sprats. These mammals are in constant danger of starvation. Other major causes of death include drowning after becoming entangled in fishing nets on the seabed, and being hunted and eaten by grey seals. These findings are from research carried out by Mardik Leopold from IMARES Wageningen UR. He will be awarded a PhD by Wageningen University on 20 November.