scholarly journals Changes in the structure and function of the North Sea fish foodweb, 1973–2000, and the impacts of fishing and climate

2005 ◽  
Vol 62 (5) ◽  
pp. 847-868 ◽  
Author(s):  
Michael R. Heath
Keyword(s):  
North Sea ◽  
Secondary Production ◽  
Demersal Fish ◽  
Biological Data ◽  
Similar Species ◽  
The North ◽  
Production And Consumption ◽  
The North Sea ◽  
Vacant Niches ◽  
And Function

Abstract North Sea environmental and biological data were analysed to examine 30-year changes in production and consumption in the fish foodweb. The analysis revealed that the demand for secondary production placed on the ecosystem by fish declined from approximately 20 g C m−2 y−1 in the 1970s to 16 g C m−2 y−1 in the 1990s. Over the same period, the proportion of demand provided by zooplankton production increased from around 70% to 75%. The overall decrease was mainly due to a reduction in piscivorous demersal fish. Average secondary production by omnivorous zooplankton was estimated to be 35 g C m−2 y−1, and annual fluctuations were positively correlated with the gross production of planktivorous fish. The results suggest a “bottom-up” control of the pelagic foodweb. Individual planktivore species have been impacted by fishing, but the populations of other functionally similar species have expanded to fill the vacant niches, thus maintaining the planktivore role in the system. In contrast, the results indicate that benthos production was more “top-down” controlled. Overall, demersal fish species have been depleted by fishing, with no obvious species expansions to fill the vacant niche, releasing the benthos from predation pressure, and leading to an increase in benthic production and fisheries for invertebrates.

scholarly journals Redundancy in metrics describing the composition, structure, and functioning of the North Sea demersal fish community

2012 ◽  
Vol 69 (1) ◽  
pp. 8-22 ◽  
Author(s):  
Simon P. R. Greenstreet ◽  
Helen M. Fraser ◽  
Stuart I. Rogers ◽  
Verena M. Trenkel ◽  
Stephen D. Simpson ◽  
...  
Keyword(s):  
North Sea ◽  
Fish Community ◽  
Size Structure ◽  
Demersal Fish ◽  
Community Size ◽  
The North ◽  
Management Objectives ◽  
The North Sea ◽  
Composition Structure ◽  
And Function

Abstract Greenstreet, S. P. R., Fraser, H. M., Rogers, S. I., Trenkel, V. M., Simpson, S. D., and Pinnegar, J. K. 2012. Redundancy in metrics describing the composition, structure, and functioning of the North Sea demersal fish community. – ICES Journal of Marine Science, 69: 8–22. Broader ecosystem management objectives for North Sea demersal fish currently focus on restoring community size structure. However, most policy drivers explicitly concentrate on restoring and conserving biodiversity, and it has not yet been established that simply restoring demersal fish size composition will be sufficient to reverse declines in biodiversity and ensure a generally healthy community. If different aspects of community composition, structure, and function vary independently, then to monitor all aspects of community general health will require application of a suite of metrics. This assumes low redundancy among the metrics used in any such suite and implies that addressing biodiversity issues specifically will require explicit management objectives for particular biodiversity metrics. This issue of metric redundancy is addressed, and 15 metrics covering five main attributes of community composition, structure, and function are applied to groundfish survey data. Factor analysis suggested a new interpretation of the metric information and indicated that a minimum suite of seven metrics was necessary to ensure that all changes in the general health of the North Sea demersal fish community were monitored properly. Covariance among size-based and species-diversity metrics was low, implying that restoration of community size structure would not necessarily reverse declines in species diversity.

scholarly journals Different bottom trawl fisheries have a differential impact on the status of the North Sea seafloor habitats

2020 ◽  
Vol 77 (5) ◽  
pp. 1772-1786 ◽  
Author(s):  
A D Rijnsdorp ◽  
J G Hiddink ◽  
P D van Denderen ◽  
N T Hintzen ◽  
O R Eigaard ◽  
...  
Keyword(s):  
North Sea ◽  
Management Strategies ◽  
Demersal Fish ◽  
Time Interval ◽  
The North ◽  
The Status ◽  
Fisheries Conservation ◽  
The North Sea ◽  
The Impact ◽  
Trawl Fisheries

Abstract Fisheries using bottom trawls are the most widespread source of anthropogenic physical disturbance to seafloor habitats. To mitigate such disturbances, the development of fisheries-, conservation-, and ecosystem-based management strategies requires the assessment of the impact of bottom trawling on the state of benthic biota. We explore a quantitative and mechanistic framework to assess trawling impact. Pressure and impact indicators that provide a continuous pressure–response curve are estimated at a spatial resolution of 1 × 1 min latitude and longitude (∼2 km2) using three methods: L1 estimates the proportion of the community with a life span exceeding the time interval between trawling events; L2 estimates the decrease in median longevity in response to trawling; and population dynamic (PD) estimates the decrease in biomass in response to trawling and the recovery time. Although impact scores are correlated, PD has the best performance over a broad range of trawling intensities. Using the framework in a trawling impact assessment of ten métiers in the North Sea shows that muddy habitats are impacted the most and coarse habitats are impacted the least. Otter trawling for crustaceans has the highest impact, followed by otter trawling for demersal fish and beam trawling for flatfish and flyshooting. Beam trawling for brown shrimps, otter trawling for industrial fish, and dredging for molluscs have the lowest impact. Trawling is highly aggregated in core fishing grounds where the status of the seafloor is low but the catch per unit of effort (CPUE) per unit of impact is high, in contrast to peripheral grounds, where CPUE per unit of impact is low.

Plastic ingestion by pelagic and demersal fish from the North Sea and Baltic Sea

2016 ◽  
Vol 102 (1) ◽  
pp. 134-141 ◽  
Author(s):  
Christoph D. Rummel ◽  
Martin G.J. Löder ◽  
Nicolai F. Fricke ◽  
Thomas Lang ◽  
Eva-Maria Griebeler ◽  
...  
Keyword(s):  
Baltic Sea ◽  
North Sea ◽  
Demersal Fish ◽  
The North ◽  
The North Sea

Coincident changes in four components of the North Sea ecosystem

1999 ◽  
Vol 79 (1) ◽  
pp. 183-185 ◽  
Author(s):  
K.F. Pearce ◽  
C.L.J. Frid
Keyword(s):  
Time Series ◽  
Species Composition ◽  
North Sea ◽  
Food Chain ◽  
Demersal Fish ◽  
North West ◽  
The North ◽  
The North Sea ◽  
Chain Links ◽  
Single Set

An analysis of species composition of the zooplankton, macrobenthos (two stations) and demersal fish from Northumberland (north-west North Sea) are reported. The four time-series show synchronous changes in species composition. While some of these changes coincide with changes in climateological variables, others do not. The degree of synchrony implies that either all the time-series are responding to a single set of extraneous forcing factors, or that food chain links, rapidly translate the signal through all ecosystem components.

Redescription of Nephtys Assimilis and N. Kersivalensis (Polychaeta: Phyllodocida) and a Key to Nephtys from Northern Europe

1989 ◽  
Vol 69 (4) ◽  
pp. 875-889 ◽  
Author(s):  
S.F. Rainer
Keyword(s):  
Intraspecific Variation ◽  
North Sea ◽  
Abundant Species ◽  
Northern Europe ◽  
Full Description ◽  
Similar Species ◽  
Museum Collections ◽  
The North ◽  
Wide Range ◽  
The North Sea

Descriptions of the polychaete Nephtys hombergii Savigny, 1818 have encompassed a wide range of apparently intraspecific variation in taxonomic features such as the segment on which interramal cirri first occur, and the form and size of pre- and postsetal lamellae (Fauchald, 1963; Woolf, 1968; Hartmann-Schröder, 1971). During the examination of museum collections and of extensive ecological collections from the North Sea (Rainer, 1990) and from Danish waters, it was found that the name N. hombergii has been applied to three morphologically similar species, viz. N. hombergii (s.s.), N. assimilis Örsted and N. kersivalensis Mclntosh. Both are locally abundant species that may occur with N. hombergii. This paper designates a neotype of N. assimilis, provides a full description of N. assimilis and N. kersivalensis, and removes these species from synonymy with N. hombergii.

scholarly journals Do microplastics affect marine ecosystem productivity?

2018 ◽  
Author(s):  
Tineke Troost ◽  
Térence Desclaux ◽  
Heather a. Leslie ◽  
Myra van der Meulen ◽  
A. Dick Vethaak
Keyword(s):  
North Sea ◽  
Secondary Production ◽  
Marine Ecosystem ◽  
Experimental Studies ◽  
Biogeochemical Model ◽  
Laboratory Findings ◽  
The North ◽  
The North Sea ◽  
Negative Impacts ◽  
Secondary Productivity

Marine and coastal ecosystems are among the largest contributors to the Earth’s productivity. Experimental studies have shown negative impacts of microplastics on individual algae or zooplankton organisms. Consequently, primary and secondary productivity may be negatively affected as well. In this study we attempted to estimate the impacts on productivity at ecosystem level based on reported laboratory findings with a modelling approach, using our biogeochemical model for the North Sea (Delft3D-GEM). Although the model predicted that microplastics do not affect the total primary or secondary production of the North Sea as a whole, the spatial patterns of secondary production were altered, showing local changes of ±10%. However, relevant field data on microplastics are scarce, and strong assumptions were required to include the plastic concentrations and their impacts under field conditions into the model. These assumptions reveal the main knowledge gaps that have to be resolved to improve the first estimate above.

scholarly journals Demersal fish biodiversity: species-level indicators and trends-based targets for the Marine Strategy Framework Directive

2012 ◽  
Vol 69 (10) ◽  
pp. 1789-1801 ◽  
Author(s):  
Simon P. R. Greenstreet ◽  
Axel G. Rossberg ◽  
Clive J. Fox ◽  
William J. F. Le Quesne ◽  
Tom Blasdale ◽  
...  
Keyword(s):  
North Sea ◽  
Demersal Fish ◽  
Species Level ◽  
Marine Strategy Framework Directive ◽  
The North ◽  
Fish Biodiversity ◽  
Environmental Status ◽  
The North Sea ◽  
Good Environmental Status ◽  
Species Specific

Abstract Greenstreet, S. P. R., Rossberg, A. G., Fox, C. J., Le Quesne, W. J. F., Blasdale, T., Boulcott, P., Mitchell, I., Millar, C., and Moffat, C. F. 2012. Demersal fish biodiversity: species-level indicators and trends-based targets for the Marine Strategy Framework Directive. – ICES Journal of Marine Science, 69: 1789–1801. The maintenance of biodiversity is a fundamental theme of the Marine Strategy Framework Directive. Appropriate indicators to monitor change in biodiversity, along with associated targets representing “good environmental status” (GES), are required to be in place by July 2012. A method for selecting species-specific metrics to fulfil various specified indicator roles is proposed for demersal fish communities. Available data frequently do not extend far enough back in time to allow GES to be defined empirically. In such situations, trends-based targets offer a pragmatic solution. A method is proposed for setting indicator-level targets for the number of species-specific metrics required to meet their trends-based metric-level targets. This is based on demonstrating significant departures from the binomial distribution. The procedure is trialled using North Sea demersal fish survey data. Although fisheries management in the North Sea has improved in recent decades, management goals to stop further decline in biodiversity, and to initiate recovery, are yet to be met.

The Epifauna of the Northern North Sea (56°–61°N)

1989 ◽  
Vol 69 (2) ◽  
pp. 387-407 ◽  
Author(s):  
D.J. Basford ◽  
A. Eleftheriou ◽  
D. Raffaelli
Keyword(s):  
North Sea ◽  
Regional Differences ◽  
Demersal Fish ◽  
Benthic Assemblage ◽  
Benthic Assemblages ◽  
The North ◽  
Composition And Structure ◽  
The North Sea ◽  
Northern North Sea ◽  
Fish And Shellfish

More than 65% of the demersal fish and shellfish caught by British vessels are landed at Scottish ports, most of the catch being taken from waters north of 56°, i.e. in the northern North Sea. The major resource supporting these fisheries is the benthos, but the distributions of both infaunal and epifaunal benthic invertebrates in the North Sea are poorly documented. Moreover, the environmental factors determining the composition and structure of North Sea benthic assemblages are not well understood. There have been several limited surveys of the benthos (Stephen, 1934; Ursin, 1960), and recently Dyer et al. (1982, 1983), Cranmer (1985) and Cranmer et al. (1984) attempted a more quantitative and systematic survey. Various schemes have been proposed to explain observed regional differences in types of benthic assemblage, usually based on the biological characteristics of water masses, and / or a limited and fragmentary knowledge of the sediments of the North Sea {e.g. Glemarec, 1973; Dyer et al, 1983).

Sign in / Sign up

Export Citation Format

Share Document