Status of marine mammals in the North sea

1990 ◽  
Vol 26 (2-4) ◽  
pp. 427-435 ◽  
Author(s):  
P.J.H. Reijnders ◽  
K. Lankester
1991 ◽  
Vol 24 (10) ◽  
pp. 77-85 ◽  
Author(s):  
J. Klamer ◽  
R. W. P. M. Laane ◽  
J. M. Marquenie

From literature data it is calculated that on an annual basis, 11 to 17 tonnes of PCBs enter the North Sea. Largest sources are the Atlantic Ocean and the atmosphere: together they account for 60-79% of the total input. Sources with greatest impact are the rivers, sewers and sludge. Highest concentrations are found close to the Dutch shore and in the German Bight. The PCB levels result in adverse effects on the seal population in the Wadden Sea. Of the total world PCB production, at least 57% is still in use and their future dispersal into the oceans cannot easily be controlled. If the increase in ocean PCB concentration continues, it may ultimately result in the extinction of fish-eating marine mammals.


2009 ◽  
Vol 88 (3) ◽  
pp. 169-175
Author(s):  
H.H. van Netten ◽  
J.W.F. Reumer

AbstractA number of Tursiops truncatus mandibles in the collection of fossil marine mammals in the Rotterdam Natural History Museum have marks consisting of several parallel linear grooves. These marks are also found on four atlas complexes, a scapula and on one vertebra. The hypothesis that they are bite marks and were caused by scavenging rays (Rajidae, Chondrichthyes) was tested with a real-life experiment using different shark and ray species, allowing them to scavenge on cow ribs as proxies for the dolphin bones. The bite marks of these animals were compared with the fossil marks and show that the fossil marks are most likely caused by scavenging rays.


2013 ◽  
Vol 71 (1) ◽  
pp. 128-142 ◽  
Author(s):  
M. Dickey-Collas ◽  
G. H. Engelhard ◽  
A. Rindorf ◽  
K. Raab ◽  
S. Smout ◽  
...  

Abstract Dickey-Collas, M., Engelhard, G. H., Rindorf, A., Raab, K., Smout, S., Aarts, G., van Deurs, M., Brunel, T., Hoff, A., Lauerburg R. A. M., Garthe, S., Haste Andersen, K., Scott, F., van Kooten, T., Beare, D., and Peck, M. A. Ecosystem-based management objectives for the North Sea: riding the forage fish rollercoaster. – ICES Journal of Marine Science, 71: . The North Sea provides a useful model for considering forage fish (FF) within ecosystem-based management as it has a complex assemblage of FF species. This paper is designed to encourage further debate and dialogue between stakeholders about management objectives. Changing the management of fisheries on FF will have economic consequences for all fleets in the North Sea. The predators that are vulnerable to the depletion of FF are Sandwich terns, great skua and common guillemots, and to a lesser extent, marine mammals. Comparative evaluations of management strategies are required to consider whether maintaining the reserves of prey biomass or a more integral approach of monitoring mortality rates across the trophic system is more robust under the ecosystem approach. In terms of trophic energy transfer, stability, and resilience of the ecosystem, FF should be considered as both a sized-based pool of biomass and as species components of the system by managers and modellers. Policy developers should not consider the knowledge base robust enough to embark on major projects of ecosystem engineering. Management plans appear able to maintain sustainable exploitation in the short term. Changes in the productivity of FF populations are inevitable so management should remain responsive and adaptive.


2021 ◽  
Author(s):  
Lucas Desclos-Dukes ◽  
Andrew Butterworth ◽  
Tristan Cogan

Abstract Plastic pollution is of increasing concern to marine ecosystems worldwide. Specifically, microplastics (<5mm) may interact with a variety of biota with potential to cause harm to organism health. Studies concerning microplastics are increasing, yet their occurrence within live marine mammals remains largely unexplored. Here, faecal samples collected from a haul-out site in the North Sea, were used to investigate microplastic pollution within grey seals (Halichoerus grypus). 71 microplastic particles, consisting of both fibres and fragments in a variety of colours and sizes, were identified across 66 scat subsamples analysed. This indicates that marine mammals are ingesting microplastics and that faecal material can be used to indirectly and humanely record microplastic uptake data in pinnipeds. Since the current paper is the first to document microplastic exposure amongst wild, living and free-ranging grey seals in the North Sea, further research is needed to begin to understand the biological significance of these findings.


2016 ◽  
Vol 230 ◽  
pp. 25-32 ◽  
Author(s):  
Norbert van de Velde ◽  
Brecht Devleesschauwer ◽  
Mardik Leopold ◽  
Lineke Begeman ◽  
Lonneke IJsseldijk ◽  
...  

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