scholarly journals Status and trends of the major roundfish, flatfish, and pelagic fish stocks in the North Sea: thirty-year overview

1996 ◽  
Vol 53 (6) ◽  
pp. 1130-1145 ◽  
Author(s):  
F Serchuk
Keyword(s):  
North Sea ◽  
Pelagic Fish ◽  
Fish Stocks ◽  
The North ◽  
Status And Trends ◽  
The North Sea

scholarly journals Inferring the location and scale of mixing between habitat areas of lesser sandeel through information from the fishery

2010 ◽  
Vol 68 (1) ◽  
pp. 43-51 ◽  
Author(s):  
Henrik Jensen ◽  
Anna Rindorf ◽  
Peter J. Wright ◽  
Henrik Mosegaard
Keyword(s):  
North Sea ◽  
Large Scale ◽  
Pelagic Fish ◽  
Fishing Ground ◽  
Marine Science ◽  
Foraging Habitat ◽  
Small Pelagic Fish ◽  
The North ◽  
The North Sea

Abstract Jensen, H., Rindorf, A., Wright, P. J., and Mosegaard, H. 2011. Inferring the location and scale of mixing between habitat areas of lesser sandeel through information from the fishery. – ICES Journal of Marine Science, 68: 43–51. Sandeels are small pelagic fish that play an important role in the diet of a range of natural predators. Because of their limited capture by traditional survey gear, little is known about their large-scale distribution or the degree of mixing between habitat areas. Detailed information collected directly from the fishery was used to map fishing grounds, which were then assumed to reflect the foraging habitat of the species. Length distributions from individual hauls were used to assess differences in the distributions as a function of distance between samples. Sandeel foraging habitat covered some 5% of the total area of the North Sea. Mixing between neighbouring fishing grounds was too low to eliminate differences in length distributions at distances between grounds down to 5 km. Within fishing grounds, mixing was sufficient to eliminate differences in length distributions at scales <28 km but insufficient at greater distances. The lack of mixing between grounds may result in large differences in sandeel abundance among adjacent fishing grounds. Further, notable abundance at one end of an extensive fishing ground is not necessarily indicative of similar abundance at its other end.

scholarly journals Selective feeding by pelagic fish in the Belgian part of the North Sea

2013 ◽  
Vol 71 (4) ◽  
pp. 808-820 ◽  
Author(s):  
Karl Van Ginderdeuren ◽  
Sofie Vandendriessche ◽  
Yves Prössler ◽  
Hakimu Matola ◽  
Magda Vincx ◽  
...  
Keyword(s):  
North Sea ◽  
Prey Species ◽  
Pelagic Fish ◽  
Horse Mackerel ◽  
Calanoid Copepods ◽  
Oikopleura Dioica ◽  
The North ◽  
Fullness Index ◽  
The North Sea ◽  
Prey Items

Abstract Pelagic fish and their planktonic prey are susceptible to a changing climate, giving rise to mismatches and planktonic bottlenecks. A detailed examination of the feeding ecology of pelagic fish can provide valuable insights in the causes and consequences of these phenomena. The present study investigated the diets of both juvenile and adult herring, sprat, horse mackerel, and adult mackerel in the Belgian part of the North Sea (BPNS) in relation to the distribution of zooplankton and ambient abiotic conditions. A study sampling pelagic fish and zooplankton simultaneously every month during consecutive years, and spanning nearshore to offshore sampling locations, is unprecedented in the southern North Sea. In all, 71 prey taxa were found in 725 stomachs of fish gathered at ten stations, sampled monthly in 2009 and 2010. The proportion of fish with empty stomachs was low (11%), and the number of prey species ranged from 0 to 21 sp. per stomach. The diet of herring and sprat was dominated by calanoid copepods, but herring stomachs also contained many decapod larvae, amphipods, cumaceans, and mysids. Mackerel added sandeels to an otherwise planktivorous diet. Horse mackerel consumed both benthic and pelagic prey. The highest frequency of occurrence in the stomachs was observed for the calanoid copepods Temora longicornis (33 408 of all 55 004 prey items identified) and Centropages hamatus (5003 times found). The fullness index ranged between 0 and 20.6, and averaged highest for sprat (0.86), followed by herring (0.60), horse mackerel (0.26), and mackerel (0.24). We observed a different composition of zooplankton species and life stages in the plankton samples compared with those in the fish stomachs. More adult and female copepods were eaten than the plankton samples would suggest. Also, the calanoid copepod Acartia clausi, the most common calanoid species in the BPNS, was barely eaten, as was the case for fish eggs and larvae, and for common planktonic species known to be preyed upon elsewhere (e.g. Oikopleura dioica, Evadne nordmanni, Euterpina acutifrons). Additionally, plankton densities averaged highest in spring and at midshore (20–30 km from shore) stations, but fullness index was highest nearshore (<12 km from shore) and (apart from sprat) in summer. A significant correlation between fullness index and total density of planktonic prey species was not observed, indicating that zooplankton densities were not restrictive. Yet the fact that more than 100 plankton species occurred in the plankton samples and just two of these (T. longicornis and C. hamatus) accounted for nearly three-quarters of all ingested prey items leads us to conclude that even minor changes in the ecology or phenology of these dominant zooplankters could have profound effects on pelagic fish stocks.

scholarly journals Why do jellyfish bloom in Norwegian waters and what can be done to recover the ecosystems in the North Sea and on the Norwegian coast?

2017 ◽  
Author(s):  
Johannes Hamre
Keyword(s):  
North Sea ◽  
West Coast ◽  
Trophic Levels ◽  
The West ◽  
Fish Stocks ◽  
Norwegian Coast ◽  
The North ◽  
Key Species ◽  
Wide Range ◽  
The North Sea

The ecosystems with their relationships between fish species and stocks, have been established by evolution for millions of years, but during the last 50 years, the ecosystems in the North Sea and along the Norwegian coast have been changed fundamentally by fisheries. The North Sea mackerel stock has been depleted and its feeding grounds have been invaded by the Western mackerel which spawns west of Ireland. This stock is now very rich in numbers and occupies the North Sea, the Norwegian Sea and the western Barents Sea. If the trend continues, mackerel may outcompete many of the other fish stocks in the area. Traditionally and until the beginning of the 1970s, there was a large stock of sandeel spawning in the North Sea and on the Norwegian coast. Sandeel juveniles was an important food source for a wide range of species, including sea mammals and birds. The fact that this stock has also been overfished, may explain many changes observed in the ecosystem on the west coast of Norway, for example a large reduction in the populations of sea birds. There are several instances where ecosystems shift to sustain jellyfish blooms in response to depletion of forage fish stocks. This was registered in Namibia in the 1990’s, where the pilchard stock was decimated and the biomass of jellyfish soon became overwhelming. On the west-coast of Norway, there are now frequent blooms of jellyfish, yet another indication that a controlling factor is missing in the system, in this case sandeel, which is a key species in the transfer of nutrients from zooplankton to higher trophic levels in the area. In this paper, I give a description of the situation and some suggested measures that should be taken in fisheries management.

scholarly journals An echosounder view on the potential effects of impulsive noise pollution on pelagic fish around windfarms in the North Sea

2021 ◽  
pp. 118063
Author(s):  
Annebelle C.M. Kok ◽  
Lisa Bruil ◽  
Benoit Berges ◽  
Serdar Sakinan ◽  
Elisabeth Debusschere ◽  
...  
Keyword(s):  
North Sea ◽  
Impulsive Noise ◽  
Noise Pollution ◽  
Pelagic Fish ◽  
The North ◽  
The North Sea

scholarly journals Indicator-based status assessment of commercial fish species in the North Sea according to the EU Marine Strategy Framework Directive (MSFD)

2013 ◽  
Vol 70 (3) ◽  
pp. 694-706 ◽  
Author(s):  
Wolfgang Nikolaus Probst ◽  
Matthias Kloppmann ◽  
Gerd Kraus
Keyword(s):  
North Sea ◽  
Fish Species ◽  
Marine Strategy Framework Directive ◽  
Commercial Fish ◽  
Fish Stocks ◽  
The North ◽  
The Status ◽  
Status Assessment ◽  
The North Sea ◽  
The Eu

Abstract Probst, W. N., Kloppmann, M., and Kraus, G. Indicator-based status assessment of commercial fish species in the North Sea according to the EU Marine Strategy Framework Directive (MSFD). – ICES Journal of Marine Science, 70: 694–706. The EU Marine Strategy Framework Directive (MSFD) is structured into eleven descriptors of good environmental status (GES). For each descriptor the current status of the marine environment should be assessed against its GES using ecosystem criteria and indicators. Within Descriptor 3 (D3) the MSFD addresses the status of exploited fish stocks according to three criteria (exploitation rate, stock size and size structure). This study performed an MSFD-compliant assessment of exploited fish stocks in the North Sea by aggregating data from analytical stock assessments and scientific research surveys to calculate indicator metrics for each criterion within each stock time-series. A stock achieved GES, when each indicator for each criterion had a good status. Of 43 assessed fish stock suggested by the EU Data Collection Framework, 63% (27) achieved GES. Though the MSFD explicitly demands that all exploited fish stocks achieve GES, this demand may be challenged by reality, because the status of exploited stocks depends not only on fishing impacts, but also on environmental conditions and ecological interactions. Therefore an alternative approach based on binomial distributions is presented to define limits for GES at the descriptor level. The implications and pitfalls of the applied assessment methods are discussed.

scholarly journals Impacts of the local environment on recruitment: a comparative study of North Sea and Baltic Sea fish stocks

2014 ◽  
Vol 72 (5) ◽  
pp. 1323-1335 ◽  
Author(s):  
Laurène Pécuchet ◽  
J. Rasmus Nielsen ◽  
Asbjørn Christensen
Keyword(s):  
Baltic Sea ◽  
North Sea ◽  
Environmental Variables ◽  
Local Environment ◽  
Water Current ◽  
The Baltic Sea ◽  
Fish Stocks ◽  
The North ◽  
The North Sea ◽  
The Baltic

Abstract While the impact of environmental forcing on recruitment variability in marine populations remains largely elusive, studies spanning large spatial areas and many stocks are able to identify patterns common to different regions and species. In this study, we investigate the effects of the environment on the residuals of a Ricker stock–recruitment (SR) model, used as a proxy of prerecruits' survival, of 18 assessed stocks in the Baltic and North Seas. A probabilistic principal components (PCs) analysis permits the identification of groups of stocks with shared variability in the prerecruits' survival, most notably a group of pelagics in the Baltic Sea and a group composed of gadoids and herring in the North Sea. The first two PCs generally grouped the stocks according to their localizations: the North Sea, the Kattegat–Western Baltic, and the Baltic Sea. This suggests the importance of the local environmental variability on the recruitment strength. Hence, the prerecruits' survival variability is studied according to geographically disaggregated and potentially impacting abiotic or biotic variables. Time series (1990–2009) of nine environmental variables consistent with the spawning locations and season for each stock were extracted from a physical–biogeochemical model to evaluate their ability to explain the survival of prerecruits. Environmental variables explained &gt;70% of the survival variability for eight stocks. The variables water current, salinity, temperature, and biomass of other fish stocks are regularly significant in the models. This study shows the importance of the local environment on the dynamics of SR. The results provide evidence of the necessity of including environmental variables in stock assessment for a realistic and efficient management of fisheries.

scholarly journals Why do jellyfish bloom in Norwegian waters and what can be done to recover the ecosystems in the North Sea and on the Norwegian coast?

2017 ◽  
Author(s):  
Johannes Hamre
Keyword(s):  
North Sea ◽  
West Coast ◽  
Trophic Levels ◽  
The West ◽  
Fish Stocks ◽  
Norwegian Coast ◽  
The North ◽  
Key Species ◽  
Wide Range ◽  
The North Sea

The ecosystems with their relationships between fish species and stocks, have been established by evolution for millions of years, but during the last 50 years, the ecosystems in the North Sea and along the Norwegian coast have been changed fundamentally by fisheries. The North Sea mackerel stock has been depleted and its feeding grounds have been invaded by the Western mackerel which spawns west of Ireland. This stock is now very rich in numbers and occupies the North Sea, the Norwegian Sea and the western Barents Sea. If the trend continues, mackerel may outcompete many of the other fish stocks in the area. Traditionally and until the beginning of the 1970s, there was a large stock of sandeel spawning in the North Sea and on the Norwegian coast. Sandeel juveniles was an important food source for a wide range of species, including sea mammals and birds. The fact that this stock has also been overfished, may explain many changes observed in the ecosystem on the west coast of Norway, for example a large reduction in the populations of sea birds. There are several instances where ecosystems shift to sustain jellyfish blooms in response to depletion of forage fish stocks. This was registered in Namibia in the 1990’s, where the pilchard stock was decimated and the biomass of jellyfish soon became overwhelming. On the west-coast of Norway, there are now frequent blooms of jellyfish, yet another indication that a controlling factor is missing in the system, in this case sandeel, which is a key species in the transfer of nutrients from zooplankton to higher trophic levels in the area. In this paper, I give a description of the situation and some suggested measures that should be taken in fisheries management.

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