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Portuguese dogfish and Leafscale gulper shark - Northeast Atlantic, 2008
Marine Resource  Fact Sheet
ICES Advice 2009
Portuguese dogfish and Leafscale gulper shark - Northeast Atlantic, 2008
Fact Sheet Citation  
Portuguese dogfish (Centroscymnus coelolepis) and leafscale gulper shark (Centrophorus squamosus) in the Northeast Atlantic
Owned byInternational Council for the Exploration of the Sea (ICES) – More
Related observationsLocate in inventorydisplay tree map
 
Species:
Geographic extent of Portuguese dogfish and Leafscale gulper shark - Northeast Atlantic
Main Descriptors
Considered a single stock: No        Spatial Scale: Sub-Regional
Management unit: No
 
 
Habitat and Biology
Depth zone: Slope - Deepslope (500 m - 1000 m).   Vertical distribution: Demersal/Benthic.  

Geographical Distribution
Jurisdictional distribution: Straddling between High Seas and EEZ

Water Area Overview
Spatial Scale: Sub-Regional

Geo References
Resource Structure
Considered a single stock: No
Exploitation
 

Factors affecting the fisheries and the stock

Regulations and their effects

A series of TACs is set for EC waters and EC vessels in international waters of Areas V–XII. The TAC applies to all deep-water sharks. The quotas were much higher than landings in 2006 and 2007. This is partly due to the restrictions on gillnet fishing.

Changes in fishing technology and fishing patterns

The introduction of bans on gillnetting in EC and international waters at depths greater than 600 m in Subareas VI and VII, etc. has diverted effort to other gears, depths, and areas.

The environment

Deep-sea areas are considered to be comparatively stable. Given the low reproductive capacity of these stocks, recruitment is more dependent on female stock size than on environmental drivers
Assessment
 
Assessment Model
Methodology

Scientific basis

Data and methods

Insufficient data are available to perform an analytical stock assessment. Data analyses are based on trends in landings, commercial cpue data, and biological knowledge.

Information is the same as in 2006 and 2007, with updated landings data and survey data from VIa. Preliminary lpue data are available for IXa in 2008 (Figures 9.4.20.3 and 9.4.20.4).

Data and methods

Data from the French fishing industry has been used in the data analyses (Figure 9.4.20.2).

Uncertainties in assessment and forecast

Landings data on these species remain very problematical. For many countries, data are only available for combined deepwater (“siki”) sharks. Many countries continue to report landings in generic categories such as “various sharks nei”. Retrospective splitting of the data into species categories could result in inconsistencies.

Fishery-independent data covers only a small area and a short time-series.

Comparison with previous assessment and advice

There is no information that changes the perception of the stock since last year.

Experimental assessments using production and depletion models were conducted by ICES in 2000 and 2002. In 2000, the combined stock of these species in Subareas V, VI, and VII was estimated to be depleted, below Upa and possibly below Ulim. In 2002, additional data were incorporated, and the strong decline in stock abundance was still evident. In 2002, upward trends in French trawler cpue were reported. Evidence available in 2006 showed that this trend was due to a movement of the fishery to new grounds within Subareas V and VI and did not reflect changes in stock abundance.
Overall Assessment Results


Figure 9.4.20.1. Portuguese dogfish and leafscale gulper shark in the North East Atlantic: International landings by ICES Subarea or Division.


Figure 9.4.20.2. Deep-water “siki” shark in the northeast Atlantic. French cpue of “sikis” by ICES Subarea (ICES, 2006).


Figure 9.4.20.3. Portuguese dogfish – Portuguese longline mean annual lpue +/- std. deviation for ICES Subarea IX (ICES, 2008).


Figure 9.4.20.4. Leafscale gulper shark – Portuguese longline mean annual lpue +/- std. deviation for ICES Subarea IX (ICES, 2008).

Reference Point
 

No reference points have been defined for this species. In common with other deep-water species, Ulim has previously been proposed at 0.2* virgin biomass and Upa at 0.5* virgin biomass (ICES, 1998) but in the absence of abundance indices that correspond to the start of the fishery, the reference points cannot be estimated.
Scientific Advice

Single-stock exploitation boundaries

Due to its very low productivity, Portuguese dogfish and leafscale gulper shark can only sustain very low rates of exploitation. The rates of exploitation and stock sizes of deep-water sharks cannot be quantified. However, based on the cpue information, Portuguese dogfish and leafscale gulper shark are considered to be depleted. Given their very poor state, ICES recommends a zero catch of Portuguese dogfish and leafscale gulper shark.



Year

ICES

Advice

Single-stock exploitation boundaries Predicted catch corresponding to advice Predicted catch corresponding to single-stock exploitation boundaries

Agreed

TAC1

ACOM Landings

Disc.

slip.

ACOM

Catch

1992

No advice

        4.6    
1993

No advice

        5.2    
1994

No advice

        6.5    
1995

No advice

        6.5    
1996

No advice

        7.2    
1997

No advice

        8.2    
1998

No advice

        7.7    
1999

No advice

        6.5    
2000

No advice

        7.1    
2001

No advice

        10.1    
2002

No advice

        8.1    
2003

No advice

        10.9    
2004

No advice

        9.0    
2005 Zero catch F=0

0

0

7.1 5.1    
2006 Zero catch F=0 0 0 7.1 2.7 NA  
2007 Zero catch F=0 0 0 2.6 1.7 NA  
2008 Zero catch F=0 0 0 1.7 - NA  
2009 Zero catch F=0 0 0        
Weights in ‘000 t.


Management
Management unit: No

Management Objectives

No management objectives have been adopted. An EC Action Plan on elasmobranches is being consulted on in 2008.
Management Advice

Management considerations

On the basis of their life-history parameters, these two species are considered highly vulnerable to exploitation. At present, there is insufficient information to determine stock identity. In the absence of such information, they are considered as single stocks for assessment purposes although smaller units may be appropriate for management.

The ban on gillnetting in EC and international waters has diverted fishing effort to other areas, particularly VIII and IXb and part of IVa. As the gillnet ban in waters below 600 m does not cover all ICES areas, it has led to increased effort and/or displacement of effort to other (possibly unfished) areas. These fisheries should not proceed, nor expand, unless they can be demonstrated to be sustainable for deep-water sharks.

It is clear that the quota is restrictive for some countries, if adequately enforced. Programmes to assess discarding and/or misreporting are required. For other countries, the quotas are not effective to regulate fishing effort.

Species-specific landings data are still not presented for these two species by all ICES member countries. ICES considers that fisheries should not proceed in the absence of adequate data to assess the status of these species.

Lost and discarded gillnets may ghostfish. Recent retrieval studies have indicated that ghost fishing in previous shark fisheries west of the British Isles was less of a problem than other gillnet fisheries (e.g. anglerfish).
Biological State and Trend
Exploitation rate: Undefined
Abundance level: Undefined

There is insufficient information to separate the landings of Portuguese dogfish Centroscymnus coelolepis and leafscale gulper shark Centrophorus squamosus. Total international landings of the combined species have steadily increased to around 11000 t in 2003 and have rapidly declined after 2003 to the lowest levels since the fishery started (Figure 9.4.20.1). Substantial declines in cpue series for the two species in Subareas V, VI, and VII suggest that both species are severely depleted (Figure 9.4.20.2) and that they have been exploited at unsustainable levels. In Division IXa, lpue series are stable for leafscale gulper shark (Figure 9.4.20.4) and declining for Portuguese dogfish (Figure 9.4.20.3).
Source of information
 
ICES.2009.Report of the ICES Advisory Committee, 2009. ICES Advice, 2009.
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