FIRMS - Marine Resource fact sheets - Norway lobster

Norway lobster - North Sea (Fladen)

Fact Sheet Title Fact Sheet

ICES Advice 2009

Norway lobster - North Sea (Fladen)

Nephrops in Division IVa, West of 2oE, excluding Management Area F (Management Area G)

Owned by

International Council for the Exploration of the Sea (ICES) – ownership

ident Block

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Species List:

Nephrops norvegicus

Species Ref: en - Norway lobster, fr - Langoustine, es - Cigala

ident Block Norway lobster - North Sea (Fladen)

Map legend

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Aq Res
Biological Stock: Yes Value: Sub-Regional Management unit: Yes Reference year: 2008

Table of Contents

Habitat Bio - Geo Dist - Water Area Overview - Management - Bio Assess - Exploit - Aq Res State Trend - Sources

Aq Res State Trend

Aq Res State Trend
	Aq Res State Trend	Aq Res State Trend
Aq Res State Trend	Undefined	Uncertain/Not assessed
Aq Res State Trend	Undefined	Uncertain/Not assessed

UWTV observations indicate that the stock is fluctuating without obvious trend with estimates for the last 2 years increasing to the highest abundance in the series. Considering the UWTV result alongside the indications of stable or slightly increasing mean sizes in the length compositions of catches (of individuals >35mm carapace length) suggests that the stock is being exploited sustainably. The decline in mean length of smaller individuals in the catch may be indicative of recent good recruitment.

Spawning biomass in relation to precautionary limits

Fishing mortality in relation to precautionary limits

Fishing mortality in relation to high long-term yield

Fishing mortality in relation to

agreed target

Comment

Unknown

N/a

Habitat Bio

Depth Zone: Shelf (50 m - 200 m). Vertical Dist: Demersal/Benthic.

Geo Dist

Geo Dist: National

Water Area Overview

Spatial Scale: Sub-Regional

Water Area Overview

Aq Res Struct

Biological Stock: Yes

Exploit

Factors affecting the fisheries and the stock

In the Fladen area the Nephrops stock is restricted to a generally continuous area of muddy sediments extending from 57^°30’N to 60^°N, and from 1^°W to 1^°30’E, with other smaller patches to the north. The Fladen Ground is the largest known Nephrops ground where fishing activity can shift spatially so that effort can vary on parts of the ground.

Nearly three quarters of the landings are made by single-rig vessels and one-quarter by twin-rig vessels. 80 mm mesh is the commonest mesh size. Nearly 40% of the Nephrops landings at Fladen are reported as bycatch, in fisheries which may be described as mixed.

The effects of regulations

The minimum landing size for Nephrops on the Fladen Ground is 25 mm carapace length. Discarding takes place at sea, and rates averaged over the period 2005 to 2007 for this stock were 18% by number, or 11% by weight.

Changes in fishing technology and fishing patterns

In the early years of the fishery, effort was primarily directed to a region that could be reached within 12 hours steaming from ports along the NE coast of Scotland. In recent years, logbook information and GPS loggers show that vessels are fishing more widely over the ground, including to the far eastern and northern edges of the extensive mud area. High fuel prices may limit steaming to some of these areas in 2008.

Bio Assess

Assess Models

Methodology

Scientific basis

Data and methods

The UWTV survey has been conducted since 1992. Potential bias in survey design has been detected and accounted for in the assessment this year (see “Data and methods” section at the start of section 6.4.14.)

Information from the fishing industry

The NSCFP stock survey shows an increase in Nephrops between 2001 and 2002, a slight decrease to 2003, and a marked increase up to 2007. Stock levels are considered to be similar or slightly less in 2008 (Figure 6.4.14.3). This information is broadly consistent with trends in the UWTV survey results.

Uncertainties in assessment and forecast

General comments are found at the start of section 6.4.14

The UWTV survey is conducted over the main part of the ground, representing an area of around 28 200 km²of suitable mud substrate (the largest ground in Europe). The Fladen Ground Functional Unit contains several patches of mud to the north of the ground which are fished, bringing the overall area of substrate to 30 633 km². This area is not surveyed but would add to the abundance estimate. The absolute abundance estimate for this ground is therefore likely to be underestimated by the current methodology.

Comparison with previous assessment and advice

The perception of stock in 2008 is similar to that in 2007 from the assessment in 2008.

The advice in 2008 was based on recent landings as the UWTV surveys were considered inappropriate to use as absolute indices of abundance. Following the outcome of the benchmark in 2009, the major concerns of the UWTV survey have been addressed and the survey is now considered a reliable estimate of absolute abundance.

The landings forecast for 2010 (equivalent to fishing at F_0.1) is 16,419 tonnes. This is an increase of almost 4,000 tonnes on the reported landings in 2008.

Results

Figure 6.4.14.3.1 Nephrops, Fladen (FU 7). Long-term trends in landings, effort, lpues, and mean sizes of Nephrops.

Figure 6.4.14.3.2 Nephrops, Fladen (FU 7). Time-series of the bias adjusted UWTV survey index estimates, with 95% confidence intervals.

Table 6.4.14.3.2 Nephrops, Fladen (FU 7). Total landings (tonnes).

Year	All *Nephrops* gears combined			Single rig			Multirig
	Landings	Effort	LPUE	Landings	Effort	LPUE	Landings	Effort	LPUE
1981	304	8.6	35.3	304	8.6	35.3	na	na	na
1982	382	12.2	31.3	382	12.2	31.3	na	na	na
1983	548	15.4	35.6	548	15.4	35.6	na	na	na
1984	549	11.4	48.2	549	11.4	48.2	na	na	na
1985	1016	26.6	38.2	1016	26.6	38.2	na	na	na
1986	1398	37.8	37.0	1398	37.8	37.0	na	na	na
1987	1024	41.6	24.6	1024	41.6	24.6	na	na	na
1988	1306	41.7	31.3	1306	41.7	31.3	na	na	na
1989	1719	47.2	36.4	1719	47.2	36.4	na	na	na
1990	1703	43.4	39.2	1703	43.4	39.2	na	na	na
1991	3024	78.5	38.5	410	11.4	36.0	2614	67.1	39.0
1992	1794	38.8	46.2	340	9.4	36.2	1454	29.4	49.5
1993	2033	49.9	40.7	388	9.6	40.4	1645	40.3	40.8
1994	1817	48.8	37.2	301	8.4	35.8	1516	40.4	37.5
1995	3569	75.3	47.4	2457	52.3	47.0	1022	23.0	44.4
1996	2338	57.2	40.9	2089	51.4	40.6	249	5.8	42.9
1997	2713	76.5	35.5	2013	54.7	36.8	700	21.8	32.1
1998	2291	60.0	38.2	1594	39.6	40.3	697	20.5	34.0
1999	2860	76.8	37.2	1980	50.3	39.4	880	26.5	33.2
2000	2915	92.1	31.7	2002	62.9	31.8	913	29.2	31.3
2001	3539	108.2	32.7	2162	65.8	32.9	1377	42.4	32.5
2002	4513	109.6	41.2	2833	58.9	48.1	1680	50.7	33.1
2003	4175	53.7	77.7	3388	42.8	79.2	787	10.9	72.2
2004	7274	56.1	129.7	6177	47.5	130.2	1097	8.6	127.6
2005	8849	61.3	144.4	6834	43.4	157.5	2015	17.9	112.7
2006	9396	65.7	143.0	7149	50.2	142.4	2320	15.5	149.7
2007	11055	69.6	158.8	8232	52.2	157.7	2822	17.4	162.2
2008	11432	80.3	142.4	8247	58.8	140.3	3185	21.5	148.1

Table 6.4.14.3.3 Nephrops, Fladen (FU 7). Survey indices with and without bias adjustment. Values after 2002 have been adjusted for revised camera parameters

Year	Mean density	Abundance	95% confidence interval	Adjusted for bias	95% confidence interval


	burrows/m²	millions	millions	millions	millions
1992	0.17	4942	508	3661	376
1993	0.21	6007	768	4450	569
1994	0.30	8329	1099	6170	814
1995	0.24	6733	1209	4987	896
1996
1997	0.13	3736	689	2767	510
1998	0.18	5181	968	3838	717
1999	0.20	5597	876	4146	649
2000	0.17	4898	663	3628	491
2001	0.23	6725	1310	4981	970
2002	0.29	8217	1022	6087	757
2003	0.27	7488	1452	5547	1076
2004	0.27	7729	1391	5725	1030
2005	0.21	5839	894	4325	662
2006	0.23	6564	836	4862	619
2007	0.34	9473	986	7017	730
2008	0.35	9857	1377	7302	1020

Ref Point

F reference point	Harvest ratio	Technical basis
F_0.1	9.3%	WKNEPH 2009
F_max	15.8%	WKNEPH 2009
(unchanged since 2009)

Sci Advice

Single-stock exploitation boundaries

ICES advises on the basis of exploitation boundaries in relation to high long term yield and low risk of depletion of production potential that the Harvest Rate for Nephrops fisheries should not exceed F_0.1. This corresponds to landings of no more than 16 419t for the Fladen Ground

Basis: Bias corrected survey index (2008) = 7302

Rationale	Harvest rate	Landings 2010 (tonnes)
	5.0%	8827
F ₂₀₀₈	8.0%	14124
F_0.1	9.3%	16419
	10.0%	17655
	15.0%	26482
F_max	15.8%	27895
	20.0%	35310

Table 6.4.14.3.1 Nephrops, Fladen (FU 7). Single-stock exploitation boundaries (advice), management, and landings.

Year	ICES advice	Recommended Landings Fladen grounds (FU7)	ICES Landings FU7¹⁾
1989			2.3
1990			2.5
1991			4.2
1992		~2.7	3.4
1993		2.7	3.5
1994		5.0	4.6
1995		5.0	6.4
1996		5.0	5.2
1997		5.0	6.2
1998		7.0	5.1
1999		7.0	6.5
2000		9.0	5.6
2001		9.0	5.5
2002		9.0	7.2
2003		9.0	6.3
2004		12.8	8.7
2005		<12.8	10.7
2006	No increase of effort	-	10.8
2007	No increase in effort and harvest rate below 7.5%	<10.9	11.9
2008	No new advice, same as for 2007	<10.9	12.24
2009	No increase in effort and recent average landings	<11.3
2010	Harvest Rate no greater than that equivalent to fishing at F_0.1	<16.4
Weights in ‘000 t. ¹⁾ Does not include discards.

Management

Management unit: Yes

Advice

Management considerations

To protect the stock in this Functional Unit, management is required to be implemented at the Functional Unit level.

Nephrops fisheries in this area have a bycatch of cod. In 2005, high abundance of 0 group cod was recorded in Scottish surveys near to this ground. This year class of cod has subsequently contributed to slightly improved cod stock biomass and efforts are being made to avoid the capture of cod so that the stock can build further. In 2008 over 90% of the Scottish industry was operating under a voluntary Conservation Credits scheme and has implemented real time closures with a view to reducing unwanted bycatch of cod.

Sources

ICES.2009.Report of the ICES Advisory Committee, 2009. ICES Advice, 2009.

Fisheries and Resources Monitoring System