Fishery Resources Monitoring System

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Norway lobster - Firth of Forth, 2008
Marine Resource  Fact Sheet
ICES Advice 2009
Norway lobster - Firth of Forth, 2008
Fact Sheet Citation  
Nephrops in Firth of Forth (FU 8)
Owned byInternational Council for the Exploration of the Sea (ICES) – More
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Species:
FAO Names: en - Norway lobster, fr - Langoustine, es - Cigala
Geographic extent of Norway lobster - Firth of Forth
Main Descriptors
Considered a single stock: Yes        Spatial Scale: Sub-Regional
Management unit: Yes
 
 
Habitat and Biology
Depth zone: Shelf (50 m - 200 m).   Vertical distribution: Demersal/Benthic.  

Geographical Distribution
Jurisdictional distribution: Shared between nations

Water Area Overview
Spatial Scale: Sub-Regional

Geo References
Resource Structure
Considered a single stock: Yes
Exploitation
 

Factors affecting the fisheries and the stock

Landings from the Firth of Forth fishery are predominantly reported from Scotland, with very small contributions from England. The area is periodically visited by vessels from other parts of the UK. There is a risk that owing to fuel costs vessels which would normally fish further offshore will locate to inshore grounds. The Firth of Forth is close inshore and is of small geographic size so that significant influx of effort will have deleterious effects.

Catches of marketable bycatch fish are small from this area and there are few other species in the area for vessels to target.

Estimated discarding rates are 31% by number in the Firth of Forth in 2008. This arises from the use of mainly small-meshed (80 mm) nets and the population size structure which appears to arise from slower growth. Local markets for small whole Nephrops are seasonally important.

Changes in fishing technology and fishing patterns

The Firth of Forth resident fleet contains numerous small boats which are generally restricted to more sheltered inshore waters. There are, however, observations of shifts of Nephrops fishing by larger vessels from the fleet to grounds such as the Devil’s Hole ( an offshore ground not included as part of a Functional Unit).
Assessment
 
Assessment Model
Methodology

Scientific basis

Data and methods

The UWTV survey has been conducted annually since 1993 (no surveys in 1995 and 1997). Monthly market sampling and quarterly on-board observer sampling provides good coverage of length compositions. 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 survey (Figure 6.4.14.3) does not include specific information for the Firth of Forth.

Uncertainties in assessment and forecast

General comments are found at the start of section 6.4.14

Comparison with previous assessment and advice

The perception of the stock in 2008 is very similar to that of the stock in 2007

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 (<1 567 t) is considerably lower than for 2009 (<2500t). This is due to using Fmax as the target F for this stock in the current advice.
Overall Assessment Results


Figure 6.4.14.4.1 Nephrops, Firth of Forth (FU 8). Long-term trends in landings, effort, lpues, and mean sizes of Nephrops.


Figure 6.4.14.4.2 Nephrops, Firth of Forth (FU 8). Time-series of bias adjusted UWTV survey abundance estimates (in millions), with 95% confidence intervals, 1993–2008


Figure 6.4.14.4.3 Nephrops, Firth of Forth (FU 8). Catch length frequency distribution and mean sizes (red line).


Table 6.4.14.4.2 Nephrops, Firth of Forth (FU 8). Total landings (tonnes).
Year All Nephrops gears combined Single rig Multirig
  Landings Effort LPUE Landings Effort LPUE Landings Effort LPUE
1981 945 42.6 22.2 945 42.6 22.2 na na na
1982 1138 51.7 22.0 1138 51.7 22.0 na na na
1983 1681 60.7 27.7 1681 60.7 27.7 na na na
1984 2078 84.7 24.5 2078 84.7 24.5 na na na
1985 1908 73.9 25.8 1908 73.9 25.8 na na na
1986 2204 74.7 29.5 2204 74.7 29.5 na na na
1987 1582 62.1 25.5 1582 62.1 25.5 na na na
1988 2455 94.8 25.9 2455 94.8 25.9 na na na
1989 1833 78.7 23.3 1833 78.7 23.3 na na na
1990 1901 81.8 23.2 1901 81.8 23.2 na na na
1991 1359 69.4 19.6 1231 63.9 19.3 128 5.5 23.3
1992 1714 73.1 23.4 1480 63.3 23.4 198 8.5 23.3
1993 2349 100.3 23.4 2340 100.1 23.4 9 0.2 45.0
1994 1827 87.6 20.9 1827 87.6 20.9 0 0.0 0.0
1995 1708 78.9 21.6 1708 78.9 21.6 0 0.0 0.0
1996 1621 69.7 23.3 1621 69.7 23.3 0 0.0 0.0
1997 2137 71.6 29.8 2137 71.6 29.8 0 0.0 0.0
1998 2105 70.7 29.8 2105 70.7 29.8 0 0.0 0.0
1999 2192 67.7 32.4 2192 67.7 32.4 0 0.0 0.0
2000 1775 75.3 23.6 1761 75.0 23.5 14 0.3 46.7
2001 1484 68.8 21.6 1464 68.3 21.4 20 0.5 40.0
2002 1302 63.6 20.5 1286 63.3 20.3 16 0.3 53.3
2003 1115 53.0 21.0 1082 52.4 20.6 33 0.6 55.0
2004 1651 63.2 26.1 1633 62.9 26.0 18 0.4 49.7
2005 1973 66.6 29.6 1970 66.5 29.6 3 0.1 58.8
2006 2437 61.4 39.7 2432 61.0 39.9 5 0.4 14.2
2007 2628 57.6 45.6 2607 57.1 45.7 21 0.5 43.2
2008 2435 52.2 46.6 2405 51.7 46.5 30 0.5 60.0


Table 6.4.14.4.3 Nephrops, Firth of Forth (FU 8). 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
1993 0.72 655 167 555 142
1994 0.58 529 92 448 78
1995          
1996 0.48 443 104 375 88
1997          
1998 0.38 345 95 292 81
1999 0.60 546 92 463 78
2000 0.57 523 83 443 70
2001 0.54 494 93 419 78
2002 0.66 600 140 508 119
2003 0.99 905 163 767 138
2004 0.81 743 166 630 140
2005 0.92 838 169 710 143
2006 1.07 976 148 827 126
2007 0.90 816 156 692 132
2008 1.14 1040 350 881 297

Reference Point
 


F

reference point

Harvest

ratio

Technical basis
F0.1 8.0% WKNEPH 2009
Fmax 13.7% WKNEPH 2009
(unchanged since 2009)


Scientific 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 Fmax. This corresponds to landings of no more than 1 567 tonnes for the Firth of Forth stock.


Basis: Bias corrected survey index (2008) = 881
Rationale Harvest rate

Landings

2010

(tonnes)

  5.0% 572
F0.1 8.0% 915
  10.0% 1144
  15.0% 1715
Fmax 13.7% 1567
  20.0% 2287
F2008 24.5% 2802


Table 6.4.14.4.1 Nephrops, Firth of Forth (FU 8). Single-stock exploitation boundaries (advice), management, and landings.
Year ICES advice

Recommended landings

Firth of Forth

(FU8)

Recommended

landings

FU6+FU8

ICES

Landings

FU81)

1992     ~4.6 1.8
1993     4.17 2.4
1994     4.17 1.9
1995     4.17 1.8
1996     4.17 1.7
1997     4.17 2.2
1998     4.17 2.1
1999     4.17 2.2
2000     4.17 1.8
2001     4.17 1.5
2002     4.17 1.3
2003     4.17 1.1
2004     4.17 1.7
2005     4.17 2.0
2006 No increase in effort   - 2.4
2007 No increase in effort, harvest rate <15% 1.5 5.0 2.6
2008 No new advice, same as for 2007 1.5 5.0 2.5
2009 No increase in effort and recent average landings < 2.5 2.4  
2010 Harvest Rate no greater than that equivalent to fishing at Fmax < 1.6 --2)  

Weights in ‘000 t.

1) Does not include discards.

2) It is not advised to manage these stocks as a single unit.



Management
Management unit: Yes

Management Advice

Management considerations

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

The advised landings for 2010 imply a reduction of 37% relative to the 2008 landings (2 500 t). ICES advice is for Fmax instead of F0.1 because increased landings in earlier years have coincided with an increase in stock implying perhaps that the present level of exploitation could be sustainable. Even though in the longer term the differences in total catch are expected to be small, the move to F0.1 as a target would imply significant initial reductions in catch. In this case a stepwise approach could be considered. A reduction of the catch corresponding to Fmax could be an intermediate step toward F0.1 (as a proxy for Fmsy). Alternatively, a constraint on the year to year change in catches as is typical of management plans and the Communication on Fishing Opportunities for 2010 [COM (2009) 224] might be considered.

Nephrops discard rates in this Functional Unit are high and there is a need to reduce these and to improve the exploitation pattern. An additional reason for suggesting improved selectivity in this area relates to bycatch. It is important that efforts are made to ensure that other fish are not taken as unwanted bycatch in this fishery which uses 80mm mesh. Larger square mesh panels implemented as part of the Scottish Conservation Credits scheme should help to improve the exploitation pattern for some species such as haddock and whiting.
Biological State and Trend
Exploitation rate: Undefined
Abundance level: Undefined

The evidence from the UWTV survey suggests that the population has been at a relatively high level since 2003. The UWTV survey information, taken together with information showing stable mean sizes, suggest that the stock is being exploited sustainably.


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 Unknown Unknown N/a  


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