FIRMS - Marine Resource fact sheets - Megrim - Bay of Biscay and Iberian Basin

Megrim - Bay of Biscay and Iberian Basin

Fact Sheet Title Fact Sheet

ICES Advice 2009

Megrim - Bay of Biscay and Iberian Basin

Megrim (L. boscii and L. whiffiagonis) in Divisions VIIIc and IXa

Owned by

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

ident Block

ident Block

Species List:

Lepidorhombus boscii

Lepidorhombus whiffiagonis

ident Block Megrim - Bay of Biscay and Iberian Basin

Map legend

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Aq Res
Biological Stock: No 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

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 targets

Comment

Undefined

Overfished (L. boscii),

Overfished (L. whiffiagonis)

In the absence of defined precautionary reference points, the state of the two stocks cannot be evaluated with regard to these. SSB of both species has decreased since the late 1980s. However, SSB for L. boscii shows a slightly upwards trend after reaching a minimum in 2001. For both species fishing mortality has decreased since the late 1990s. Recent recruitment for L. boscii has been below average. For L. whiffiagonis recruitment has been low in the last decade.

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: No

Exploit

Factors affecting the fisheries and the stock

Regulations and their effects

Megrims are caught in a mixed fisheries context. Regulations intended to protect others species, mainly hake and Nephrops, could have an effect on megrim stocks. The minimum mesh size for towed gears catching megrims ranges between 40 and 90 mm. The minimum landing size of megrims is 20 cm.

Changes in fishing technology and fishing patterns

Both species are caught in the mixed bottom trawl fisheries by Portuguese and Spanish fleets. Both species are also taken in small quantities by the Portuguese artisanal fleet. During the last decade, the Spanish trawl fleet has changed the main target species focusing more often on species such as horse mackerel, blue whiting, or mackerel, and do not usually take megrim in the catch.

Bio Assess

Assess Models

Methodology

Scientific basis

Data and methods

Age-based (XSA) assessments were conducted for each species separately. They are based on landings data, two commercial lpue series, and one cpue survey series.

Portuguese and Spanish landings of megrim were split into the two species using their relative abundances in the sampled landings. Discards data are not used in this assessment because of the lack of data in some years.

Uncertainties in assessment and forecast

The assessments are uncertain. There is a consistent retrospective pattern with an overestimation of SSB. This has led to a new perception of the stock development especially for L. whiffiagonis.

The lpue series from the La Coruña trawl fleet has been used only up to 1999 for L. boscii. For the most recent years, only a Spanish survey series is used for tuning in the L. boscii assessment. There are no tuning indices for a large proportion of Division IXa.

Since the proportion of catch discarded is in the range of 0.15 – 0.65 (in numbers) the effect of excluding discards from the assessments could compromise their quality.

Comparison with previous assessment and advice

The current assessments are consistent with last assessments. For L. whiffiagonis, SSB in 2007 was revised 18 % downwards and F in 2006 was revised 24 % upwards. For L. boscii, SSB in 2007 was revised 1 % downwards and F in 2006 was revised 7 % upwards. The advice this year is based on high long-term yield. Last year the advice was based on precautionary considerations.

Results

Figure 7.4.2.1 Megrim (L. whiffiagonis) in Divisions VIIIc and IXa. Summary of stock assessment: landings, fishing mortality, recruitment, and SSB

Figure 7.4.2.2 Megrim (L. whiffiagonis) in Divisions VIIIc and IXa. Stock-recruitment plot, yield per recruit analysis, and PA plot.

Figure 7.4.2.3 Megrim (L. boscii) in Divisions VIIIc and IXa. Summary of stock assessment: landings, fishing mortality, recruitment, and SSB.

Figure 7.4.2.4 Megrim (L. boscii) in Divisions VIIIc and IXa. Stock-recruitment plot, yield per recruit analysis and PA plot.

Figure 7.4.2.6 Megrim (L. boscii) in Divisions VIIIc and IXa. Comparison of current assessment with previous assessments (predicted intermediate years are included). 2007 SSB value from 2007 assessment was corrected.

Table 7.4.2.2 Megrim (L.whiffiagonis) in Divisions VIIIc and IXa. Nominal landings by country and area.

Spain				Portugal	Total
Year	VIIIc	IXa	Total	IXa	VIIIc IXa
1986	508	98	606	53	659
1987	404	46	450	47	497
1988	657	59	716	101	817
1989	533	45	578	136	714
1990	841	25	866	111	977
1991	494	16	510	104	614
1992	474	5	479	37	516
1993	338	7	345	38	383
1994	440	8	448	31	479
1995	173	20	193	25	218
1996	283	21	305	24	329
1997	298	12	310	46	356
1998	372	8	380	66	446
1999	332	4	336	7	343
2000	238	5	243	10	253
2001	167	2	169	5	175
2002	112	3	115	3	117
2003	113	3	116	17	134
2004	142	1	144	5	149
2005	120	1	121	26	147
2006	173	2	175	35	210
2007	139	2	141	14	155
2008	159	2	161	17	178

Table 7.4.2.3 Megrim (L. boscii) in Divisions VIIIc and IXa. Nominal landings by country and area.

Spain				Portugal	Total
Year	VIIIc	IXa	Total	IXa	VIIIc IXa
1986	799	197	996	128	1124
1987	995	586	1581	107	1688
1988	917	1099	2016	207	2223
1989	805	1548	2353	276	2629
1990	927	798	1725	220	1945
1991	841	634	1475	207	1682
1992	654	938	1592	324	1916
1993	744	419	1163	221	1384
1994	665	561	1227	176	1403
1995	685	826	1512	141	1652
1996	480	448	928	170	1098
1997	505	289	794	101	896
1998	725	284	1010	113	1123
1999	713	298	1011	114	1125
2000	674	225	899	142	1041
2001	629	177	807	124	931
2002	343	247	590	130	720
2003	393	314	707	169	876
2004	534	295	829	177	1006
2005	473	321	794	189	983
2006	542	348	891	201	1092
2007	591	295	886	218	1104
2008	500	262	761	172	933

Table 7.4.2.4 Megrim (L. whiffiagonis) in Divisions VIIIc and IXa. Summary of stock assessment

Year	Recruitment Age 1 thousands	SSB tonnes	Landings tonnes	Mean F Ages 2-4
1986	9304	2260	659	0.336
1987	12271	1895	497	0.299
1988	11012	2276	817	0.438
1989	9577	2614	714	0.368
1990	12259	2690	977	0.397
1991	4845	1715	614	0.414
1992	10307	1681	516	0.378
1993	4265	1468	383	0.285
1994	1326	1168	479	0.422
1995	8688	990	218	0.190
1996	8117	1305	329	0.189
1997	6594	1412	356	0.219
1998	4137	1369	446	0.359
1999	2137	1195	343	0.270
2000	3282	1341	253	0.236
2001	3134	1030	175	0.208
2002	2635	1025	117	0.131
2003	2899	1157	134	0.154
2004	3111	892	149	0.168
2005	2920	934	147	0.199
2006	2801	974	210	0.294
2007	3628	905	155	0.209
2008	1666	902	178	0.200
2009	2964	906
Average	5578	1421	385	0.277

Table 7.4.2.5 Megrim (L. boscii) in Divisions VIIIc and IXa. Summary of stock assessment.

Year	Recruitment Age 0 thousands	SSB tonnes	Landings tonnes	Mean F Ages 2-4
1986	54114	5772	1124	0.257
1987	34707	7071	1688	0.326
1988	38734	7898	2223	0.372
1989	34304	7548	2629	0.501
1990	21137	6707	1945	0.323
1991	43639	6067	1682	0.263
1992	40323	5455	1916	0.485
1993	12533	5589	1384	0.380
1994	30461	5331	1403	0.370
1995	36420	4723	1652	0.471
1996	24332	4456	1098	0.339
1997	21304	4311	896	0.223
1998	10421	4680	1123	0.282
1999	21701	4401	1125	0.287
2000	25647	4176	1041	0.275
2001	26755	3798	931	0.288
2002	26964	4395	720	0.253
2003	34848	4528	876	0.261
2004	27648	4438	1006	0.329
2005	34384	4602	983	0.262
2006	21796	5130	1092	0.310
2007	19130	5033	1104	0.235
2008	18914	5228	933	0.230
2009	25491	5001
Average	28571	5264	1329	0.318

Ref Point

Four-spotted megrim (L. boscii) in Divisions VIIIc and IXa

Yield and spawning biomass per Recruit F-reference points (2009):

	Fish Mort	Yield/R	SSB/R
	Ages 2–4
Average last 3 years	0.26	0.04	0.21
F_0.1	0.18	0.04	0.25
F_med	0.31	0.04	0.18

Candidate target reference points which are consistent with taking high long-term yields and achieving a low risk of depleting the productive potential of the stock may be identified around F_0.1.

Megrim (L. whiffiagonis) in Divisions VIIIc and IXa

Yield and spawning biomass per Recruit F-reference points (2009):

	Fish Mort	Yield/R	SSB/R
	Ages 2–4
Average last 3 years	0.23	0.07	0.37
F_0.1	0.17	0.07	0.45
F_med	0.26	0.07	0.34

Candidate target reference points which are consistent with taking high long-term yields and achieving a low risk of depleting the productive potential of the stock may be identified around F_0.1.

Projection

L. whiff.: Basis: F_sq = mean F(06–08) unscaled = 0.23; R09–10 = GM 1998–2006 = 3 million; landings (2009) = 0.18; SSB(2010) = 0.94.
L. boscii: Basis: F_sq = mean F(06–08) unscaled = 0.26; R09–10 = GM 1990–2006 = 25 million; landings (2009) = 1.12; SSB(2010) = 4.83.

Outlook for 2010

Sci Advice

Single-stock exploitation boundaries

Considering the options below, ICES advises on the basis of exploitation boundaries in relation to high-long term yield and low risk of depletion of the production potential that combined catches of L. whiffiagonis and L. boscii should not exceed 900 t.

Exploitation boundaries in relation to high long-term yield, low risk of depletion of production potential and considering ecosystem effects

2008 fishing mortality for L. whiffiagonis estimated at 0.20, is above F_0.1= 0.17.

2008 fishing mortality for L. boscii estimated at 0.23, is above F_0.1 = 0.18.

Fishing at F_0.1 in 2010 is predicted to generate SSBs in 2011 that are 6-10% higher than in 2010 for the two megrim stocks

Table 7.4.2.1 Megrim (Lepidorhombus boscii and L. whiffiagonis) in Divisions VIIIc and IXa. Single stock exploitation boundaries (advice), management and landings

Year	ICES Advice/ Single-stock exploitation boundaries from 2005	Predicted catch corresp. to advice¹	Predicted catch corresp to single-stock exploitation boundaries	Agreed TAC¹	ICES landings¹	Landings L. *boscii*	Landings *L. whiff*.
1987	Not dealt with	-		13.0	2.19	1.69	0.50
1988	Not dealt with	-		13.0	3.04	2.22	0.82
1989	Not dealt with	-		13.0	3.34	2.63	0.71
1990	Not dealt with	-		13.0	2.93	1.95	0.98
1991	No advice	-		14.3	2.29	1.68	0.61
1992	No advice	-		14.3	2.44	1.92	0.52
1993	L. boscii no gain in increasing F, L. whiff. safe biological limits	-		8.0	1.76	1.38	0.38
1994	No l gains in increasing F	-		6.0	1.88	1.40	0.48
1995	Concern about low SSB	-		6.0	1.87	1.65	0.22
1996	Mixed fishing aspects	-		6.0	1.43	1.10	0.33
1997	Reduce F by at least 50%	-		6.0	1.25	0.90	0.36
1998	Reduce F by at least 50%	0.9		6.0	1.57	1.12	0.45
1999	Reduce F by at least 50%	1.0		6.0	1.46	1.12	0.35
2000	Reduce F by at least 20%	< 1.5		5.0	1.29	1.04	0.25
2001	No increase in F	1.61		5.0	1.11	0.93	0.18
2002	No increase in F	1.55		4.0	0.84	0.72	0.12
2003	No increase in F	1.55		2.4	1.01	0.88	0.13
2004	No increase in F	1.38		1.336	1.14	0.99	0.15
2005	No increase in F	1.09²	1.05	1.336	1.13	0.98	0.15
2006	No increase in F		1.2	1.269	1.30	1.09	0.21
2007	No increase in F		1.4	1.440	1.26	1.10	0.16
2008	No increase in F		1.4	1.430	1.11	0.93	0.18
2009	Same advice as last year		1.4	1.430
2010	Reduce F to F_0.1		0.9
Weights in ‘000 t. ¹L. whiffiagonis+ L. boscii. ²Single-stock boundary and the exploitation of this stock should be conducted in the context of mixed fisheries.

Management

Management unit: Yes

Objectives

There are no explicit management objectives for these stocks.

Advice

Management considerations

Both species are caught in mixed fisheries targeting demersal fish including southern hake, anglerfish and Nephrops. Management measures aimed at reducing fishing mortality on these stocks should also ensure lowest possible catches of megrim.

The two species are managed under a common TAC. They are caught and recorded together in the landings statistics. It is impossible to manage each species separately under a common TAC. This problem is highlighted by the different status of the two stocks. L. whiffiagonis (the stock in poor status) constitutes around 20% of the total megrim landings.

The spatial distribution of the two stocks shows some differences that could be utilized for separate management of the two stocks. Megrim (L. whiffiagonis) is distributed in both Divisions (VIIIc and IXa), with its highest abundance in Division VIIIc. Four-spotted megrim (L. boscii) is distributed in both Divisions (VIIIc and IXa). There is a certain bathymetric segregation between the two species. L. boscii has a preferential depth range of 100 to 450 m and L. whiffiagonis of 50 to 300 m.

The perception of the L. whiffiagonis stock has changed compared to the last assessment in 2007. For L. whiffiagonis SSB in recent years is now estimated to be lower than it was in 2007, and recruitment continues to be very low. Therefore strong measures should be taken to improve the stock status.

Discards of megrim are substantial. For L. whiffiagonis between 15 % and 45 % of the total catches in numbers are discarded. In the last two years discards of this stock are very low, providing a further indication of low recruitment. For L. boscii between 40 % and 62 % of the total catches in numbers are discarded.

Landings in 2007 and 2008 have been below the TAC.

TACs for combined megrim stocks have not been restrictive, and the fishing mortality of both stock are above candidates for F_MSY. Following the EU Commission consultation paper on TACs for 2010 (COM(2009) 224, 12 May 2009), this corresponds to a TAC reduction of 36%. ICES has not evaluated the proposed option in relation to the precautionary approach.

Sources

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

Fisheries and Resources Monitoring System