scholarly journals Are spatial closures better than size limits for halting the decline of the North Sea thornback ray, Raja clavata?

2011 ◽  
Vol 62 (6) ◽  
pp. 722 ◽  
Author(s):  
Jessica Wiegand ◽  
Ewan Hunter ◽  
Nicholas K. Dulvy
Keyword(s):  
North Sea ◽  
Relative Effectiveness ◽  
Ecosystem Approach ◽  
Thames Estuary ◽  
Trawl Fishery ◽  
The North ◽  
Thornback Ray ◽  
Raja Clavata ◽  
The North Sea ◽  
Size Limits

A key challenge of the ecosystem approach to fisheries management is to sustain viable populations of large-bodied less-productive vulnerable elasmobranchs that are the by-catch of fisheries that target more productive species. The North Sea population of the thornback ray (Raja clavata) is now mainly confined to the Thames Estuary and surrounding SW North Sea, which is subject to a flatfish trawl fishery. We explored the relative effectiveness of seasonal closures versus size-based landing restrictions using a four-season age-structured model. More than a third of adult thornback rays are currently removed by fishing each year, and without effective management, a further 90% decline within 30 years is likely. A three-season closure of the Thames Estuary was the shortest closure that ensured thornback ray recovery and minimal loss of fishery yield. Minimum and maximum landing size restrictions are nearly as effective at recovering thornback rays but less so at improving yield. While long seasonal closures and full marine protected areas are more effective at ensuring the recovery of thornback rays, length restrictions may be simpler to implement under the current institutional framework and may have less impact on the multispecies trawl fisheries operating in the area.

Selectivity experiments with escape windows in the North Sea Nephrops (Nephrops norvegicus) trawl fishery

1999 ◽  
Vol 42 (1-2) ◽  
pp. 167-181 ◽  
Author(s):  
N Madsen ◽  
T Moth-Poulsen ◽  
R Holst ◽  
D Wileman
Keyword(s):  
North Sea ◽  
Nephrops Norvegicus ◽  
Trawl Fishery ◽  
The North ◽  
The North Sea

scholarly journals Predictive framework for codend size selection of brown shrimp (Crangon crangon) in the North Sea beam-trawl fishery

PLoS ONE ◽  
2018 ◽  
Vol 13 (7) ◽  
pp. e0200464 ◽  
Author(s):  
Juan Santos ◽  
Bent Herrmann ◽  
Daniel Stepputtis ◽  
Claudia Günther ◽  
Bente Limmer ◽  
...  
Keyword(s):  
North Sea ◽  
Brown Shrimp ◽  
Beam Trawl ◽  
Crangon Crangon ◽  
Size Selection ◽  
Trawl Fishery ◽  
The North ◽  
Sea Beam ◽  
The North Sea ◽  
Selection Of

scholarly journals Separating species using a horizontal panel in the Scottish North Sea whitefish trawl fishery

2007 ◽  
Vol 64 (8) ◽  
pp. 1543-1550 ◽  
Author(s):  
R. S. T. Ferro ◽  
E. G. Jones ◽  
R. J. Kynoch ◽  
R. J. Fryer ◽  
B-E. Buckett
Keyword(s):  
North Sea ◽  
Water Clarity ◽  
Light Level ◽  
Separation Performance ◽  
Separate Species ◽  
Trawl Fishery ◽  
The North ◽  
Acoustic Methods ◽  
Commercial Species ◽  
The North Sea

Abstract Ferro, R. S. T., Jones, E. G., Kynoch, R. J., Fryer, R. J., and Buckett, B-E. 2007. Separating species using a horizontal panel in the Scottish North Sea whitefish trawl fishery. – ICES Journal of Marine Science, 64: 1543–1550. In the North Sea, Scottish vessels target haddock, cod, whiting, monkfish, saithe, and flatfish in a mixed whitefish trawl fishery. These species mature at different sizes and hence have a range of minimum landing sizes. Their different shapes and swimming capabilities imply different selection characteristics when escaping from trawl gear. However, they are often caught at the same time on the same grounds. Optimal exploitation can only be achieved by ensuring that the selection of each species varies appropriately with length during the fishing process. This paper describes one part of a large European project to develop species-selective trawl gear to improve the exploitation pattern of North Sea cod, while maintaining the catch of other important commercial species. A gear suitable to the Scottish mixed whitefish fishery was fitted with a horizontal panel in the tapered part of the net to separate species into an upper and lower compartment. Trials were conducted on research vessels to measure separation performance for nine species in different light conditions, at different towing speeds, and with different lengths of panel. Most haddock, whiting, and saithe pass above the panel, whereas most cod, flatfish, and monkfish pass below it. Towing speed and panel length had no significant effect on separation. At lower light levels during the night (April at latitude 58° to 61°N), fewer dab, sole, plaice, and cod pass below the panel. Observations and measurements of fish behaviour using acoustic methods are described. They suggest that the height at which fish enter the net mouth may be influenced by light level and water clarity.

scholarly journals OSPAR Ecological Quality Objectives: the utility of health indicators for the North Sea

2008 ◽  
Vol 65 (8) ◽  
pp. 1392-1397 ◽  
Author(s):  
Peter Heslenfeld ◽  
E. Lisette Enserink
Keyword(s):  
North Sea ◽  
Health Indicators ◽  
Ecosystem Approach ◽  
Current Status ◽  
Test Case ◽  
Ecological Quality ◽  
Marine Research ◽  
The North ◽  
History Of ◽  
The North Sea

Abstract Heslenfeld, P., and Enserink, E. L. 2008. OSPAR Ecological Quality Objectives: the utility of health indicators for the North Sea. – ICES Journal of Marine Science, 65: 1392–1397. Committed to the ecosystem approach to management, OSPAR has accumulated 15 years of experience in developing a conceptual framework for ecological indicators and objectives, and in applying the framework to the North Sea as a test case. These Ecological Quality Objectives (EcoQOs) have become a model for the implementation of the new European Marine Strategy Framework Directive. We describe the history of EcoQO development, its current status, and future needs. We also present our positive and negative experiences in developing the approach, and conclude that regional sea conventions and marine research institutes in Europe should join forces to accelerate the development of ecosystem indicators and objectives, using existing concepts.

Grid selection in the North Sea industrial trawl fishery for Norway pout: Efficient size selection reduces bycatch

2006 ◽  
Vol 77 (2) ◽  
pp. 248-263 ◽  
Author(s):  
Kurt Kvalsvik ◽  
Ingvar Huse ◽  
Ole Arve Misund ◽  
Kjell Gamst
Keyword(s):  
North Sea ◽  
Size Selection ◽  
Trawl Fishery ◽  
The North ◽  
The North Sea ◽  
Grid Selection

Combined analyses reveal environmentally driven changes in the North Sea ecosystem and raise questions regarding what makes an ecosystem model’s performance credible?

2014 ◽  
Vol 71 (1) ◽  
pp. 31-46 ◽  
Author(s):  
Steven Mackinson
Keyword(s):  
Primary Production ◽  
North Sea ◽  
Ecosystem Model ◽  
Ecosystem Approach ◽  
Trophic Levels ◽  
Fish Stock ◽  
Supporting Evidence ◽  
Sea Temperature ◽  
The North ◽  
The North Sea

When an ecosystem model of the North Sea is calibrated to data from multiple trophic levels, the model estimated the primary production required to support the food web correlates temporally with observed changes in sea temperature and nutrient levels, supporting evidence from empirical analyses. However, a different result is given from an alternative calibration using fish stock data only. The inference taken from the emergent primary production – temperature relationship and empirical data are that, on balance, there is stronger overall evidence to support the calibration constrained at multiple trophic levels. Two important implications of the findings are (i) that the relative importance of fishing and environmental effects is likely to be interpreted differently depending on the calibration approach and (ii) the contrasting model calibrations would give different responses to fishing policies. It raises questions regarding how to judge the performance (and credibility) of an ecosystem model and the critical importance of conducting empirical and modelling analyses in parallel. Adopting a combined approach to ecosystem modelling is an important step in the pursuit of operational and defensible tools to support the ecosystem approach to management.

scholarly journals Modelling combined harvest and effort regulations: the case of the Dutch beam trawl fishery for plaice and sole in the North Sea

2008 ◽  
Vol 65 (6) ◽  
pp. 822-831 ◽  
Author(s):  
A. Hoff ◽  
H. Frost
Keyword(s):  
North Sea ◽  
Stock Assessment ◽  
Beam Trawl ◽  
Trawl Fishery ◽  
The North ◽  
Feedback Model ◽  
Economic Operation ◽  
The North Sea ◽  
Fishing Fleets ◽  
Fleet Dynamics

Abstract Hoff, A. and Frost, H. 2008. Modelling combined harvest and effort regulations: the case of the Dutch beam trawl fishery for plaice and sole in the North Sea. – ICES Journal of Marine Science, 65: 822–831. Currently, several European fishing fleets are regulated through a combination of harvest and effort control. The two regulation schemes are interrelated, i.e. a given quota limit will necessarily determine the effort used, and vice versa. It is important to acknowledge this causality when assessing combined effort and harvest regulation systems. A bioeconomic feedback model is presented that takes into account the causality between effort and harvest control by switching back and forth between the two, depending on which is the binding rule. The model consists of a biological and an economic operation module, the former simulating stock assessment and quota establishment, and the latter simulating the economic fleet dynamics. When harvest control is binding, catch is evaluated using the biological projection formula, whereas the economics-based Cobb–Douglas production function is used when effort is binding. The method is applied to the Dutch beam trawl fishery for plaice and sole in the North Sea.

scholarly journals Ecosystem-based management objectives for the North Sea: riding the forage fish rollercoaster

2013 ◽  
Vol 71 (1) ◽  
pp. 128-142 ◽  
Author(s):  
M. Dickey-Collas ◽  
G. H. Engelhard ◽  
A. Rindorf ◽  
K. Raab ◽  
S. Smout ◽  
...  
Keyword(s):  
North Sea ◽  
Marine Mammals ◽  
Management Strategies ◽  
Ecosystem Approach ◽  
Integral Approach ◽  
Forage Fish ◽  
Ecosystem Based Management ◽  
The North ◽  
Management Objectives ◽  
The North Sea

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.

Coast erosion and sediment circulation on the coast of eastern England

1972 ◽  
Vol 272 (1221) ◽  
pp. 171-171
Keyword(s):  
Recent Work ◽  
North Sea ◽  
Dynamic Topography ◽  
East Anglia ◽  
Thames Estuary ◽  
Dutch Coast ◽  
Southern North Sea ◽  
The North ◽  
The North Sea

Sediment is considered to travel southward along the English coast and northward along the Dutch coast and this has been interpreted as being part of a counter clockwise circulation in the North Sea. There is evidence that the transport along the English coast is interrupted at a number of places, e.g. the Wash and the Thames Estuary, placing major traps in its path and there are discontinuities in the bank formations due to reversal of movement off East Anglia. Recent work suggests that there are some well defined sediment streams in the southern North Sea with very restricted means of transfer from one stream to another. It is possible that in some sandwave fields we are observing fossil topography rather than present dynamic topography, e.g. in areas such as the Sandettie.

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