FIRMS - Marine Resource Fact Sheet - Sole - Skagerrak and Kattegat, 2006

Sole - Skagerrak and Kattegat, 2006

Marine Resource Fact Sheet

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Stock status report

Sole - Skagerrak and Kattegat, 2006

Sole in Division IIIa

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International Council for the Exploration of the Sea (ICES) more>>

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Species:

Solea solea

Fao Names : en - Common sole, fr - Sole commune, es - Lenguado común

Distribution of Sole - Skagerrak and Kattegat

Map legend Area Details

Main Descriptors
Considered a single stock: Yes Spatial Scale: Sub-Regional Considered a management unit: Yes

Table of Contents

Habitat and Biology - Water Area Overview - Geographical Distribution - Exploitation - Assessment - Management - Biological State and Trend - Source of information

Habitat and Biology

Depth zone: Shelf Vertical distribution: Demersal/benthic

Geographical Distribution

Jurisdictional distribution: National

Water Area Overview

Spatial Scale: Sub-Regional

Geo References

Resource Structure

Considered a single stock: Yes

Exploitation

Factors affecting the fisheries and the stock

Regulations and their effects

The Danish fishery is regulated by half-monthly rations that depend on vessel length and which vary over the year. The rations have been reduced in the period 2002 to 2004, reflecting the decline in the agreed TAC. The Danish sole fishery was closed late in the years 2002 to 2004. Analyses of private logbooks, survey data, and observer data indicate that during 2002–2004 there was considerable economic incentive to land sole without reporting as the entire two-week ration in many cases could be taken in just a few hauls.

The management area includes Division IIIa plus the Western Baltic (Subdivisions 22–24). Danish vessel rations cover the management area and there is therefore no incentive to misreport sole taken in Division IIIa into the Western Baltic.

Changes in fishing technology and fishing patterns

There are no major changes in the sole-directed fishery in recent years. Changes in the regulations for the Nephrops fishery, with the introduction of a sorting grid system in the trawls, may have resulted in smaller bycatch and improved selectivity on sole.

The environment

The stock is probably influenced by both temperature and salinity because it is located near the species’ physiological limits for both of these factors.

Assessment

Assessment Model

Assessment Model Entry

Data

Scientific basis

Data and methods

The analytical assessment includes cpue data from three commercial tuning series (reference fleets) and one scientific survey series. Different assumptions on misreporting/discarding have been explored.

For the period 1991–1993, the official catch statistics are uncertain as a reflection of the actual landings with a significant amount of misreporting. For 1994–2000 the official statistics for Kattegat are assumed to fairly accurately reflect actual landings. In this period most of the sole catches were taken in Kattegat in the sole fishery under an effort control regime. The assessment includes corrections for considerable misreporting by areas in 2000 and 2001.

The current assessment includes non-reported and discarded catch at 50% of the official landings in 2002 and 100% in both 2003 and 2004. These estimates are based on information from the industry. In 2005, in view of the less restrictive TAC, an estimate of 20% misreporting was included. The available data from discard sampling is insufficient to be used directly in the assessment and are not included in the assessment.

Information from the fishing industry

Collaboration between the Danish Fishers’ Organisation and DIFRES was initiated in 2004 to establish a database with data from private logbooks. Haul-specific data from six trawlers and three gillnetters covering the time period 1987 to 2006 were used in the assessment.

Uncertainties in assessment and forecast

The main uncertainty in the present assessment is caused by imprecise catch data and becomes apparent by divergent signals in the cpue data. There is still a need for fishery-independent data as the current survey does not target sole. A sole-directed research survey was initiated in 2004, but this time-series is currently too short to be included in the assessment.

The sensitivity of the assessment to assumptions regarding non-reporting and discarding was evaluated last year for a range of likely scenarios. The sensitivity analysis was repeated this year for the assumption of 20% misreporting in 2005 and indicated that any assumptions up to 20% misreporting will have virtually no effect on the recent SSB and fishing mortality estimates, and only an insignificant effect on the SSB and F estimates for 2005.

Overall Assessment Results

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

A candidate for a reference point consistent with taking high long-term yields and achieving a low risk of depleting the productive potential of the stock is F_0.1.

Comparison with previous assessment and advice

The present assessment is consistent with the 2006 exploratory assessment and supports the perception of a high SSB in recent years (Figure 6.4.9.3). The assessment is robust to assumptions of misreporting ratios in 2002–2005, and appears to be reliable after the inclusion of the catch year 2006 where the catch data has improved due to the discontinuation of misreporting. The present advice is therefore based on short-term forecasts and not on a status quo catch as last year.

Graphs

Figure 6.4.9.1 Sole in Division IIIa. Landings, fishing mortality, recruitment, and SSB.

Graphs

Figure 6.4.9.2 Sole in Division IIIa. Stock recruitment, yield, and precautionary approach.
Figure 6.4.9.3 Sole in Division IIIa. Historical performance of the assessments. Some previous assessments were indicative of trends only.

Graphs

Landing table

Table 6.4.9.1 Sole in Division IIIa. Catches (tonnes) in the Kattegat and Skagerrak 1952–2005. Official statistics and Working Group corrections. For Sweden there is no information 1962–1974.Landing table¹⁾Considerable non-reporting assumed for the period 1991–1993.
²⁾Catches from Skagerrak were reduced by these amounts because of misreporting from the North Sea. The subtracted amount has been added to the North Sea sole catches. Total landings for these years in IIIA has been reduced by the amount of misreporting.
³⁾Assuming misreporting rates at 50, 100, 100, and 20% in 2002–2005, respectively.

Table 6.4.9.2 Sole in Division IIIa.
Stock summary

Year	Recruitment	SSB	Landings	Mean F
-	Age 2	-	-	Ages 4–8
	thousands	tonnes	tonnes
1984	2760	885	337	0.4616
1985	6263	1132	397	0.2507
1986	5149	2014	643	0.3888
1987	5147	2163	722	0.6063
1988	3597	2361	706	0.3588
1989	5730	2404	824	0.4207
1990	7240	2900	1050	0.3433
1991	7298	3301	1011	0.4164
1992	9266	4742	1294	0.4314
1993	6754	4657	1439	0.4605
1994	3555	4682	1198	0.3595
1995	3407	3815	1297	0.5500
1996	2236	3601	1059	0.3352
1997	1145	2973	814	0.3684
1998	4599	2401	605	0.3014
1999	3289	2476	638	0.3061
2000	2514	2492	633	0.3134
2001	4144	2531	455	0.1935
2002	5991	2969	845	0.3460
2003	6296	3302	600	0.2901
2004	5940	4076	782	0.3060
2005	3334	4289	878	0.2497
2006	3937	3947	729	0.2173
2007	3540	4146
Average	4714	3094	824	0.3598

Reference Point

Reference points(established in 1999)

Yield and spawning biomass per Recruit
F-reference points
Reference points

	Fish Mort	Yield/R	SSB/R
	Ages 4–8
Average last 3 years	0.26	0.20	0.93
F_max	0.52	0.21	0.55
F_0.1	0.16	0.18	1.30
F_med	0.50	0.21	0.56

Projection

Short-term implications
Short-term implications

Scientific Advice

Single-stock exploitation boundaries

Exploitation boundaries in relation to existing management plans

There is no management plan implemented for this stock.

Exploitation boundaries in relation to precautionary considerations

The fishing mortality in 2008 should be kept below F_pa, corresponding to catches of less than 970 t.

Management considerations

During the period 2002–2004 there was considerable misreporting due to limiting TACs and weekly rations. Since the middle of 2005, the increase in TAC and improved control are thought to have resulted in a reduction of misreporting.

Sole is taken in a directed trawl fishery with bycatch of Nephrops and cod. Cod in the Kattegat is considered to be severely depleted. Also, sole is taken as bycatch in the Nephrops trawl fishery. There is a directed gillnet fishery for sole.

Management plan evaluations

No management plan is implemented for this stock.

Management

Considered a management unit: Yes

Management Objectives

There are no management objectives for this stock.

Catch and TACs
Catch and TACsWeights in ‘000 t.
¹⁾Uncertain.

Biological State and Trend

Exploitation rate: Harvested sustainably
Abundance level: Full reproductive capacity

State of the stock
Based on the most recent estimates of SSB and F, ICES classifies the stock as having full reproductive capacity and being harvested sustainably. SSB has increased since 1998 to 3900 t in 2006 and is now well above B_pa. Fishing mortality has decreased since 2002 to 0.2 in 2006, which is well below F_pa.

Source of information

Report of the Baltic Fisheries Assessment Working Group. Copenhagen, 17–26 April 2007 (ICES CM 2007/ACFM:15).

ICES