Kyne & Simpfendorfer.. - Shark Specialist Group

CASE STUDY 2. NORTHEAST ATLANTIC DEEPWATER FISHERIES
Status: Stocks of the most commonly caught species, the leafscale gulper shark
Centrophorus squamosus and the Portuguese dogfish Centroscymnus coelolepis, are
depleted. Little data on other species, but some declines are also evident.
The most common commercially-encountered deepwater sharks in the Northeast Atlantic are
the leafscale gulper shark Centrophorus squamosus, birdbeak dogfish Deania calcea, black
dogfish Centroscyllium fabricii, velvet belly Etmopterus spinax, great lanternshark E.
princeps, Portuguese dogfish Centroscymnus coelolepis, longnose velvet dogfish
Centroselachus crepidater, knifetooth dogfish Scymnodon ringens and the kitefin shark
Dalatias licha (Basson et al. 2002, ICES 2005). Some scyliorhinid catsharks (Apristurus and
Galeus spp) are also locally common, particularly the blackmouth catshark G. melastomus
(Basson et al. 2002).
Fisheries research in the Northeast Atlantic is coordinated through ICES (the International
Council for the Exploration of the Sea) using data reported from a system of regional Sub
areas. The majority of deepwater shark fishing activities occur in northern ICES Sub areas
(Sub areas V, VI, VII, XII), particularly around the Rockall Trough and on the Porcupine
Bank slopes, which lay to the west of the British Isles (Clarke et al. 2002). Species are taken
in multi-species trawl and multi-species and directed longline fisheries. France, Iceland,
Ireland, Norway, Portugal, Spain and the UK are the main countries in the region landing
deepwater sharks (Walker et al. 2005). The most commonly landed species are C. squamosus
and C. coelolepis, and it is these two species which are the primary focus of this case study.
ICES (2006) presented limited landings data for other deepwater shark species in the
Northeast Atlantic, however no CPUE data are available. It has only been since 1988 that C.
squamosus and C. coelolepis have begun to be landed, initially by the French, then the
Spanish and later by other nations (Heessen 2003, ICES 2006). The short time-period of the
fisheries has generally limited assessments of trend data, until recently when ICES presented
a series of CPUE trends for these species to advise that the stock had been depleted (ICES
2005).
Prior to the ICES advice, Basson et al. (2002) reported a declining trend for French trawl C.
squamosus and C. coelolepis CPUE over a short time-series of 1990–1998 in ICES Sub areas
VI and VII and Division Vb (the area to the West of the British Isles). They used production
models to undertake biomass estimates, with results indicating that the exploitable biomass of
these two species in those regions was below 50% virgin biomass. However, the short timeseries
and the effects of fishing at different depths constrain their results. They also made the
observation that the French trawl fleet was moving into deeper water to exploit sharks as well
as other fish (Basson et al. 2002).
As part of the European-wide DELASS project (Development of Elasmobranch Assessments)
(Heessen 2003) stock assessments were attempted for these two species for the Northeast
Atlantic as a whole. Although Heessen (2003) reports evidence of a decline in abundance
(from CPUE data) for the two species combined in ICES Sub areas V, VI and VII, the stock
assessment was unsuccessful due to a short time-series, a lack of species-specific data and a
poor understanding of the stock structure of the species in the region.
In 2005, ICES advised a zero catch limit for C. squamosus and C. coelolepis in ICES areas
(i.e. the Northeast Atlantic) (ICES 2005). ICES (2005) noted that exploitation increased
significantly from the commencement of fishing at the end of the 1980s while CPUE declined
considerably for French, Irish, Norwegian, Portuguese and Scottish trawlers and longliners
from 1994 to 2005 in the northern region (ICES Sub areas VI, VII and XII). Longline CPUE
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