respective organizations with responsibility for fisheries management and
protection of the marine environment in the open Atlantic, NEAFC and OSPAR are
keen to pursue joint initiatives where overlap exists between them. “One such area
is the biodiversity of deep-water sharks”, states Maurice Clarke, Marine Institute
and chair of the Workshop on the distribution and bycatchmanagement options of listed deep-sea shark species, “These are vulnerable
to bycatch in the NEAFC Area (including the Regulatory Area), and are an
important component of the marine ecosystem”.
that ICES countries hold perhaps the most comprehensive dataset on deep-water
sharks in the world. These data primarily come from surveys conducted by ICES
member countries, many of which either pioneered deep-water research surveys or
maintain long-time data series. However despite this, he concedes that there
are considerable gaps in the data. “These gaps exist because large parts of the
North Atlantic deep sea are simply not able to be surveyed because the sea bottom
is not suitable. The deep-sea floor holds many vulnerable marine ecosystems
(VME) with extremely fragile features such as corals, sponges, and hydrothermal
vents, which cannot be fished upon with survey gears”.
Teresa Moura, Portuguese Institute
for the Sea and the Atmosphere and member of the Working Group on
Elasmobranch Fishes (WGEF) adds that
in addition to unsuitable sampling areas, there is also a lack of knowledge in
the distribution/abundance of species in waters deeper than 800m. Many
deep-water sharks distribute deeper than 800 m but as most research surveys do
not sample at such depths, such information is only available for a few areas.
WGEF is requested to give recurrent advice on three
deep-water sharks - the Portuguese dogfish, the leafscale gulper shark and the
kitefin shark - for the Northeast Atlantic. “All three sharks are now under a
list of species with zero total allowable catch (TAC)” says Moura, “The status of these stocks are
unknown as abundance and biomass indices are restricted to a few areas and
estimates are highly variable and uncertain. Information about the abundance
and biomass of other deep-water sharks is deficient”.
The main species of deep-water shark that ICES gives advice on have been
depleted by fishing by the mid-2000s, and have not recovered. “The Portuguese
dogfish and the leafscale gulper shark are examples of species that are not
doing very well. These are the larger bodied species which were commercially
exploited in the 1990s. Having been depleted, their conservative life
strategies mean that recovery will be slow, and as they continue to be taken as
bycatch in some deep-water fisheries, fishing mortality on them has not
ceased.” continues Clarke, “The smaller bodied species show mixed signals, with
some showing favourable trends, others showing declines. Unfortunately, the
time series available for the smaller bodied species are shorter and do not
extend back to the beginning of fishing mortality on deep-water sharks in the
sharks are no longer commercially exploited or retained as wanted catch, continued
bycatch in some deep-water fisheries is an issue. Clarke explains that
these sharks cannot be selected out of the fishing gear and as they do not
survive being brought to the surface, fishing mortality continues even
though there are effectively zero quotas for them.
Moura adds that WGEF considers that, although uncertain, the level of bycatch is now relatively low given the EU regulations adopted for deep-water fisheries, such as the ban of gillnets at depths of more than 600 m deep and the ban of fishing operations with bottom trawls at depths deeper than 800 m.
considering the issue in 2001, Clarke notes that ICES has examined various possibilities for
managing deep-water fisheries, including closing areas. In this time, ICES
scientists have gained much experience of closed areas as tools for managing
and restoring fish stocks. "Closed areas are usually only effective if they can regulate
fishing mortality. For example if fish aggregate at spawning time and a small
amount of fishing can lead to high mortality in a particular location, then
closing that area could be a good tool to reduce fishing pressure. We don’t
have enough information on deep-water sharks to identify such areas, though many
of these species may not be aggregating in behavior anyway. As an aside,
however, scientists are beginning to understand the importance of VME habitats as nursery grounds for deep-water sharks. This only serves
to illustrate the diversity of the deep-water ecosystems of the
NEAFC/OSPAR/ICES area, and the great importance of this ecosystem for marine
ICES Advice on the status and distribution of deep-water elasmobranchs in response to a NEAFC/OSPAR request is now available.
OSPAR has also requested ICES to provide scientific knowledge on selected elasmobranch species to update the assessments for the
OSPAR List of Threatened and/or Declining Species and Habitats. ICES has responded by providing information for ten single species and one species complex on whether each of the species continues to
justify inclusion in the OSPAR List as compared to the previous
assessment. The advice also includes human activities and pressures, of which the most relevant are directed fisheries and bycatch mortality, including discarding.
Evidence on white skate and angel shark, basking shark, porbeagle and spurdog, the common skate complex (common blue skate and the flapper skate), and the deep-water species gulper shark, leafscale gulper shark, and Portuguese dogfish, suggest that these species continue to justify inclusion.
Thornback and spotted rays have increased in abundance in the areas where they previously had declined and suggests that both species no longer justify inclusion on the criterion of decline.
This advice release on the OSPAR List of Threatened and/or Declining Species and Habitats is now available.
Kitefin shark, a deep-water shark species in the Northeast Atlantic. Photo © OCEANA.