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Deep-sea Fisheries
With the decline of traditional commercial fish
stocks such as hake and cod in shallow water continental shelf
areas, European fishing fleets have increasingly turned their
attention to fish stocks in deeper waters.
Deep-sea stocks are fish populations exploited
in waters beyond the main fishing grounds of the continental shelves.
They are distributed in waters above the outer shelf and the continental
slopes or are associated with seamounts.
Deep-sea fisheries are generally considered to be fisheries carried
out in waters deeper than about 400m. The target fish are often
long-lived, slow growing, late maturing, slow breeding species,
which are particularly vulnerable to exploitation. Many are deep-living
demersal (benthic or benthopelagic [1]) species
found at or above the seabed. Others are pelagic and live in the
mid-water column or towards the sea bottom.
With improvements in fishing technology and increased
exploration, new deep-sea stocks continue to be discovered.
The deep sea and its environment
The environment inhabited by deep-sea fishes is large (comprising
more than 50% of the earth’s surface) and its ocean dynamics,
fisheries biology and ecosystems are poorly understood. However,
over the last two decades, studies of these regions have begun
to describe their often astonishing physical and biological nature.
While many of these areas are flat with silt and mud-covered bottoms,
others are characterized by chains of seamounts and bottom ridges
and knolls. Across the continental shelves, turbidity currents
have excised submarine canyons, whose importance as links to the
deep seas is only beginning to be understood. Other features,
such as seafloor seeps and hydrothermal vents, have produced bizarre
and complex chemosynthetic communities with highly evolved and
unusual faunas.
Diverse and long-lived benthic fauna, most notably the deep-water
corals, are associated with seamounts
and similar seafloor features. Cold-water corals have longevities
potentially in excess of 10,000 years. Their structure, proud
of the bottom, and brittleness make them vulnerable to destruction
by trawls when inexpert skippers allow their trawls to encounter
the surface of seamounts. Also of concern is the apparent high
level of endemism of the species in those seamounts that have
been researched; thus recruitment of many species from other seamounts
may be less than would be expected.
Seamounts have oceanographic features that are important for fisheries.
First, commercially important species form spawning aggregations
in association with seamounts resulting in profitable catch rates,
while those distant from seamounts may produce far lower rates.
Second, currents flowing over seamounts bring nutrient-rich waters
into the photic zone, enhancing biological production. Then, when
Taylor’s Columns (named after the scientist who discovered
these phenomena) form over the top of the seamount, zones are
created that retain fish larvae in the region of the adult fish
habitat. Further enhancement occurs when plankton migrate into
the surface layers at night and are unable to descend when advected
over seamounts, thus providing biomass that can be “captured”
by the seamount-based ecosystems.
State
of World Fisheries and Aquaculture (SOFIA) 2004. Food and
Agriculture Organization of the UN.
West of Ireland
A new and developing fishery continues to expand into the deep-sea
regions beyond Ireland's sector of the European continental shelf
edge, in waters varying in depth from about 400m to between 2,500-4,000m.
This area west of Ireland includes the relatively shallow waters
of the Porcupine Bank as well as the Rockall Trough and the Porcupine
Sea-bight bathyal regions, where the continental slopes plunge
from the shelf edge down to the deep ocean basin.
See the pop-up map
of Ireland's offshore area (125k).
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| OSPAR Commission management regions |
For management purposes, this huge area of the North-East Atlantic
west of Ireland falls into OSPAR
[2] Region V (Wider Atlantic) and the International
Council for the Exploration of the Sea (ICES) sub-areas VI
and VII, although Irish vessels also operate in other deep-sea
areas. Beyond the 200 nautical mile outer limit of Ireland's extensive
exclusive economic zone (EEZ), which corresponds to Ireland's
sector of the EU Common Fisheries Zone [3], are
the High Seas, or "global commons" of international
waters that lie outside national EEZ jurisdictions. Deep-sea fisheries
in these particular international waters are managed under the
auspices of the North-East
Atlantic Fisheries Commission (NEAFC) according to various
agreements under the UN
Convention on the Law of the Sea [4].
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| OSPAR Region III and ICES sub-areas VI &
VII |
The fisheries
Some deep-sea fisheries in the North-East Atlantic are long established
and tend to be artisanal (i.e. traditional and small-scale), using
mainly static gear such as longlines. Fisheries by factory trawlers
and modern longliner [5] fleets started in the
late 1960s and early 1970s and gradually expanded the deep-sea
fisheries. In the 1980s and 1990s, depletion of fish stocks in
shelf waters provided further stimulus for several fleets —
including Ireland's — to turn to deep-sea species to make
a living.
Deep-sea fleets from Belgium, England & Wales, Faroes, France,
Germany, Ireland, Netherlands, Northern Ireland, Norway, Russia,
Scotland and Spain have been actively exploiting deep-sea stocks
west of Ireland in recent years.
Most deep-sea fisheries have more than one target species, and
may thus be considered mixed fisheries exploiting communities
or suites of species. There are exceptions, such as the target
fishery for Argentine (Argentina silus) by midwater or
semipelagic trawls (ICES 2005a).
In addition to the general lack of knowledge about the biology
of deep-sea species and the exploitation rates of stocks, the
mixed catches, which result in considerable quantities of bycatch
that may be discarded, mean that these fisheries are difficult
to manage sustainably.
Deep-sea fishing vessels are known to trawl at depths down to
1,800m or more on the continental slopes. Such trawling activity
has already extensively damaged deep, coldwater coral reefs at
the edges of the continental shelf off the coasts of Ireland,
Scotland and Norway. Only recently explored, these reefs are formed
by just a few species of extremely slow-growing corals. They provide
a habitat for many hundreds of other species, and are spawning
grounds for commercially valuable fishes. Damage to such fragile
and important ecosystems is of great concern (see Habitat
Destruction).
Irish vessels have participated in deep-sea fisheries off the
west of Ireland since 1988. In general, the fishery peaks between
March and June and again from September to November. In recent
years, funding through the Government's Programme for the Renewal
of the Whitefish Fleet and the subsequent Fleet Development Measure
have enabled Irish vessels to focus on deepwater species such
as orange roughy. As well as strictly commercial voyages, vessels
have also participated in trials under the European Commission's
exploratory fishing voyage scheme.
Since the mid-1990s, an international fleet of up to 50 vessels
have been conducting a gillnet fishery on the continental slopes
to the west of Britain and Ireland, north of Shetland, at Rockall
and the Hatton Bank. Although mostly based in Spain, these vessels
are registered in the UK, Germany and "flag-of-convenience"
countries outside the EU such as Panama (BIM 2004). However, vessels
are known to occasionally land their catches at Killybegs, Fenit,
Castletownbere, and Dingle. The fishery is conducted in depths
between 200-1,200m using monofilament nets (gillnets or tangle
nets) which are set on or just above the seafloor. The main target
species are monkfish and deepwater sharks. Problems include a
high level of discards (rotting fish), bycatch of non-target species,
unretrieved and lost nets ("ghost nets"), and unsustainable
catches of deepwater sharks (see Gillnet
Fishery).
Ecosystem impacts of deep-sea
fisheries
The potential ecosystem impacts of deep-sea fisheries fall into
two categories:
One, the predator-prey, food web and other impacts relating to
the removal of large numbers of target and bycatch species from
the deep-sea and open ocean ecosystems in which these species
play a role. However, due to lack of information, the effect of
the removal of large numbers of top predators in deep-sea ecosystems
is poorly known. Koslow et al. (2000) state that there are major
questions concerning the long-term ecological implications of
depleting mid-to-upper level trophic species in deep-sea ecosystems,
and the impacts on prey and predator populations, but that there
are few answers to these questions at present. Gianni (2004) adds
that this is an area that requires urgent scientific attention
given that deep-sea food webs and ecosystems are not likely to
recover easily or quickly, if at all, from major perturbations
caused by fishing.
Two, the physical impact of fishing gears (trawls, longlines,
gillnets) on the sea bottom, in particular on sensitive, fragile
or rare cold-water coral, sponge and other organisms attached
to the seabed that are keystone species and/or shape the basic
structure and function of biologically diverse deep-sea benthic
ecosystems. (See Habitat Destruction).
Vulnerability and unsustainability
Fisheries on deepwater species have developed rapidly and the
resources which they exploit are generally especially vulnerable
to overexploitation. Within the ICES area species/stocks have
been depleted before appropriate management measures have been
implemented. It is also of concern that the landings statistics
that are available may not reflect the true scale of the recent
fishing activity, especially in waters outside the national EEZs.
Experience shows that some deep-sea species with life history
strategies characterised by long life-spans, high age at maturity,
and slow growth (e.g. orange roughy, blue ling) can be depleted
very quickly and that recovery will be slow. Regeneration and
growth are so slow that abundance does not increase in the depleted
populations in the short or medium term. Other species with higher
productivity have also been severely impacted by fisheries, but
show greater resilience and potential for recovery in the medium
term.
The survival rates of discards and of fish encountering gears
and escaping are unknown, but many species are expected to be
very vulnerable to injury, and therefore would be expected to
die even if they escaped through meshes. The body shape of many
deepwater fish combined with a high age/length at maturity often
means that there can be a high fishing mortality of immature fish.
Some species, such as blue ling, orange roughy, red sea bream,
and alfonsinos aggregate in shoals, often associated with seamounts,
and the fisheries have high catch rates once the shoals are located.
Localized sub-units of the population can be quickly depleted
by fisheries, even within a single season. Sub-units of some species
(e.g. red sea bream, blue ling, and orange roughy) are known to
have collapsed in some ICES areas.
It is evident that high catch rates can be maintained by moving
from one concentration to another and progressively depleting
the stock. Furthermore, many deepwater fisheries are on mixtures
of species, making it difficult to manage the species components
individually.
…Fisheries on deepwater species have often developed and
expanded before sufficient information was available on which
to base management advice.
In 2002 ICES concluded that most exploited deepwater species were
considered to be harvested outside safe biological limits, and
recommended immediate reductions in the fisheries unless they
could be shown to be sustainable. New fisheries should be permitted
only when they expanded very slowly, and were accompanied by programmes
to collect data which would allow evaluation of the stock status.
While there has been increasing research activity in deep water
the fisheries have expanded more rapidly.
…Under a precautionary approach regime, and given that no
new assessments could be made, the conclusion on stock status
in 2004 remains similar to that made in 2002.
ICES 2005a
Irish involvement
With funding from Government and the EU PESCA scheme, about €2.5
million was allocated for sea trials aimed at developing Ireland's
deep-sea fishery over a two-year period beginning in March 2000.
The programme was supervised by the Bord
Iascaigh Mhara/Irish Sea Fisheries Board (BIM) Fisheries Development
Division in association with the Marine Institute, and built upon
the commercial experience of the Killybegs (Co Donegal) vessel
Mary-M and the Greencastle (Co Donegal) trawler Arctic
Sun since 1996.
The seven trawlers and one longliner involved in the first year's
trials, completed in November 2000, came from Greencastle, Rossaveal
(Co Galway), Dingle (Co Kerry), Castletownbere (Co Cork) and Union
Hall (Co Cork). Five of these were new vessels brought into the
Irish fleet under the Programme for the Renewal of the Whitefish
Fleet.
The trials were conducted in water depths of 500-1,200m and covered
a wide area from north-west of the Shetlands to south-west of
the Porcupine Bank and as far west as the Hatton Bank, some 200
nautical miles west of Rockall.
Potentially viable catches were taken of Greenland halibut (Reinhardtius
hippoglossoides), redfish (Sebastes spp.), blue ling
(Molva dypterygia), Roundnose grenadier (Coryphaenoides
rupestris), Portuguese dogfish/siki shark (Centroscymnus
coelolepis), black scabbardfish (Aphanopus carbo) and
deepwater cod (Mora moro). Other species taken included
orange roughy (Hoplostethus atlanticus), tusk (Brosme
brosme), bluemouth (Helicolenus dactylopterus), alfonsino/golden
eye perch (Beryx spp) and forkbeards (Phycis spp.).
The 2001 trials included more new whitefish vessels, and focused
on expanding the grounds opened up during 2000, as well as assessing
the potential of other areas to the south-west and south of Ireland
[6].
Deep-sea fleet additions
The Irish government has given a great deal of public subsidy
to the Irish whitefish [7] fleet to, among other
measures, assist the introduction of new boats and modernisation
of others, including vessels equipped to undertake deep-sea fisheries.
The government's Programme for the Renewal of the Whitefish Fleet,
administered by BIM, included grant aid (at 29% of the total cost)
for 32 new and 11 modern second-hand vessels, and the modernisation
of some 70 existing vessels. This was followed by a €95 million
Fleet Development Measure aimed at continuing the renewal of the
whitefish fleet between 2001 and 2006, bringing the combined investment
under both schemes to €195 million. It was described by former
Minister for Marine and Natural Resources, Frank Fahey, as "an
investment unprecedented in the history of the State".
The Fleet Development Measure included almost €56 million
of public aid for the introduction of 38 new vessels into the
whitefish fleet, including several deep-sea vessels up to 46m
in length, plus over €3.5 million for vessel modernisation.
Ironically, the announcement was made on 28 May 2002 — the
same day the European Commission published its proposals for the
reform of the Common Fisheries Policy, which called for an end
of public aid for building new vessels and modernising others
with a view to increasing efficiency.
Recent additions to the Irish whitefish fleet have included:
Emerald Dawn — a 34m demersal twin-rig stern trawler
built to operate offshore and pursue non-quota deepwater species.
Built at a cost of €2.8 million. Launched at Dingle on 7
April 2000.
An Capall Ban — the first purpose-built longliner
in Ireland, at a cost of €1.9 million. The 25m long vessel
was built to target non-quota deep-sea species. Launched at Galway
on 13 May 2000.
Fiona K II — a €1.65 million new-build trawler.
The fourteenth vessel to be delivered under the Programme for
Renewal. Involved in deepwater fishing for non-quota species.
Launched at Dingle on 16 June 2000
Foyle Warrior and Northern Celt — two new trawlers
built at a cost of €1.9 million each. They are fully capable
of participating in the deep-sea fishery. Launched at Greencastle
on 2 July 2000.
Catherine R and Regina Ponti — two new trawlers,
30m and 34.5m respectively, with a combined value of €5.3
million. They have been fishing for deepwater species since their
launch at Greencastle on 10 August 2001.
Avro Chieftain and Avro Warrior — two 52m
"super longliners" built to join An Capall Ban
in longlining operations for deep-sea species west of Ireland,
and in the wider North Atlantic. Each vessel uses a 65,000-hook
autoline longlining system. The Avro Chieftain participated
in BIM-supervised exploratory fishing trials on several seamounts
to the south of the Azores in 500-700m depths. The target species
was wreckfish (Polyprion americanus), a large oceanic species
of high value. Other commercial species by-caught included deepwater
cod (Mora moro), gulper shark (Centrophorus spp.),
forkbeards (Phycis spp.), bluemouth (Helicolenus dactylopterus),
deepwater ray and conger eel. When working the seamounts, the
vessel sustained repeated gear damage. After 5-6 weeks at sea,
catches were landed at Killybegs.
Since 2001, under EU regulations all newly commissioned vessels
have been required to carry both scientific and technical observers,
as required under the general conservation principles of the UN
Convention on the Law of the Sea, and the complementary 1995
FAO Code of Conduct for Responsible Fisheries. Consequently,
BIM began a comprehensive programme of scientific and technical
data collection on Irish vessels. The data is made available to
the Advisory Committee on Fishery Management (ACFM) of ICES. During
2001, five observers recorded 87% of the fishing days of 10 newly
commissioned boats fishing deep-sea species.
Recent Irish fishery activity
Landings data are given in pop-up Table
1.
During 2001 there was a significant increase in deep-sea fishery
activity by Irish vessels. Up to fourteen vessels currently take
part in the various fisheries, including a number of trawlers
targeting orange roughy on seamounts, but also along the slopes
of ICES subarea VII. Other trawlers have been fishing blue ling,
roundnose grenadier, black scabbard, orange roughy and sharks
along the continental slopes of subareas VI and VII and there
has been continued activity in the Faroe-Shetland Channel, catching
redfish and Greenland halibut. Several Irish longliners have been
fishing in a number of different areas including the continental
slopes, Hatton Bank and the Mid-Atlantic Ridge.
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