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

Abstract The Norway lobster, Nephrops norvegicus, is an important fisheries species in the North-East Atlantic area. In some circumstances, mature females of Nephrops norvegicus can resorb their ovary rather than completing spawning, but the implications of this phenomenon to reproductive biology and fisheries sustainability are not known. To understand after effects of ovary resorption, we studied long-term demographic data sets (1994–2017) collected from the western Irish Sea and the North Sea. Our considerations focused on potential correlations among the frequency of resorption, female insemination, and body size of resorbing females. Resorption was continuously rare in the western Irish Sea (less than 1%); whereas much higher rates with considerable year-to-year variation were observed in the North Sea (mean 9%). Resorption started in autumn after the spawning season (summer) had passed. The frequency stayed high throughout winter and declined again in spring. As sperm limitation can occur in male-biased fisheries, we expected a lack of insemination could be responsible for resorption, but affected females were indeed inseminated. Resorbing females were significantly larger than other sexually mature females in the North Sea, but the opposite trend was observed in the western Irish Sea. It is therefore possible that other, environmental factors or seasonal shifts, may trigger females to resorb their ovaries instead of spawning. Resorption may as well represent a natural phenomenon allowing flexibility in the periodicity of growth and reproduction. In this sense, observations of annual versus biennial reproductive cycles in different regions may be closely linked to the phenomenon of ovary resorption.

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

ICES Journal of Marine Science ◽

10.1093/icesjms/fsm099 ◽

2007 ◽

Vol 64 (8) ◽

pp. 1543-1550 ◽

Cited By ~ 23

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.

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

Fisheries Research ◽

10.1016/j.fishres.2005.10.002 ◽

2006 ◽

Vol 77 (2) ◽

pp. 248-263 ◽

Cited By ~ 6

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

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Histriobdella homari on nephrops norvegicus from the irish sea and clyde sea area

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315400071861 ◽

1997 ◽

Vol 77 (2) ◽

pp. 557-559 ◽

Cited By ~ 1

Author(s):

R.P. Briggs ◽

R.J.A. Atkinson ◽

M. McAliskey ◽

A. Rogerson

Keyword(s):

North Sea ◽

Irish Sea ◽

English Channel ◽

Southwestern Part ◽

Nephrops Norvegicus ◽

The North ◽

The North Sea ◽

The Irish Sea ◽

Clyde Sea ◽

Sea Area

Histriobdella homari is a polychaete annelid belonging to the Order Eunicida and Family Histriobdellidae. Histriobdella homari is normally found in the gill chambers or among the eggs of the lobster Homarus vulgaris from the English Channel (Roscoff) and in the southwestern part of the North Sea (George & Hartmann-Schroder, 1985). Two independent sightings of H. homari living on the pleopods of Nephrops norvegicus from the Irish Sea and Clyde Sea area are reported.

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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 ◽

10.1093/icesjms/fsn057 ◽

2008 ◽

Vol 65 (6) ◽

pp. 822-831 ◽

Cited By ~ 13

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.

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

Marine and Freshwater Research ◽

10.1071/mf10141 ◽

2011 ◽

Vol 62 (6) ◽

pp. 722 ◽

Cited By ~ 16

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.

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Importance of discards from the English Nephrops norvegicus fishery in the North Sea to marine scavengers

Marine Ecology Progress Series ◽

10.3354/meps313215 ◽

2006 ◽

Vol 313 ◽

pp. 215-226 ◽

Cited By ~ 28

Author(s):

TL Catchpole ◽

CLJ Frid ◽

TS Gray

Keyword(s):

North Sea ◽

Nephrops Norvegicus ◽

The North ◽

The North Sea

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Observations on Nephrops norvegicus (L.) and on an epizoic population of Balanus crenatus Brug

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315400012832 ◽

1951 ◽

Vol 30 (2) ◽

pp. 369-380 ◽

Cited By ~ 25

Author(s):

H. Barnes ◽

T. B. Bagenal

Keyword(s):

North Sea ◽

British Isles ◽

Nephrops Norvegicus ◽

General Biology ◽

Far North ◽

North East ◽

The North ◽

Norway Lobster ◽

The North Sea ◽

The Mediterranean

The Dublin Prawn or Norway Lobster, Nephrops norvegicus (L.), is widely distributed on soft muddy bottoms, usually between 10 and 50 fathoms. It is found as far north as Iceland and the North Cape, is common in the North Sea and off the Atlantic shores of the British Isles, and extends as far south as the coast of Morocco; a variety, v. meridionalis (Zariquiey-Cenarro, 1935) is found in the Mediterranean and Adriatic (see Havinga, 1929, and Heldt & Heldt, 1931, for details of its distribution). Some aspects of the general biology of Nephrops have been dealt with by Höglund (1942) and Poulsen (1946) for Scandinavian waters, and by McIntosh (1904, 1908) and Storrow (1912)for the waters off north-east England. To a large extent all these workers relied on market catches.

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The Early Stages of Nephrops norvegicus, from the Northumberland Plankton, together with a note on the post-larval development of Homarus vulgaris

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315400009309 ◽

1925 ◽

Vol 13 (4) ◽

pp. 870-879 ◽

Cited By ~ 15

Author(s):

Olga M. Jorgensen

Keyword(s):

Larval Development ◽

North Sea ◽

Young Fish ◽

Nephrops Norvegicus ◽

Larval Stages ◽

Early Stages ◽

The North ◽

Third Stage ◽

The North Sea

Although adult Norway lobsters are extremely common on the southern part of the Northumberland coast, there were no records of the taking of larvæ of the species in this part of the North Sea until the Plankton Investigation now being carried out at Cullercoats (1) was commenced.During the period 1921–23 a few specimens were taken from time to time in the ordinary plankton hauls, but the best catches of Nephrops larvæ were obtained from the young fish trawl used at a number of stations in 1922 arid 1923. It is, therefore, chiefly on the material from the last two years' samples that the following observations are based.All three of the larval stages have been obtained, together with a single post-larva, but the majority of our specimens are second and third stage larvæ.

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