The deep-water fish of the North Atlantic live
in a cold and dark world. They are adapted to a life with very
little food and at a very slow pace, as the small amount of energy
available must be conserved as much as possible, with little used
on swimming, searching for food, growth or reproduction. As a
result, the fish grow extremely slowly and reproduce at a very
slow rate some species such as the orange roughy do not
even reproduce every year. Many species become mature only at
the age of 15–30 years and can live to over one hundred years
Because they grow and reproduce so slowly, deepsea stocks cannot
be fished and managed in the same way as the faster reproducing
stocks in the North Sea. If a group of fish or stock in the deep
sea is fished out, it is gone for good, at least on a human time
scale. As a result, a fishery on such stocks sometimes appears
for one or two seasons and then disappears for the next 20 or
even 50 years. The only exceptions appear to be blue ling, alphonsino,
tusk or redfish, which have faster reproduction and growth rates
and so can sustain somewhat higher exploitation rates than other
There are some 340 deep-living species of fish recorded in the
North Atlantic. Those targeted commercially or regularly taken
as by-catch in deep-sea fisheries west of Ireland include:
Teleosts (bony fish)
Alfonsinos/Golden eye perch (Beryx spp.)
Two widespread species (Beryx splendens and B. decadactylus)
which are generally caught at depths of 200-550m.
B. splendens occurs in the Eastern Atlantic off southwestern
Europe, Madeira and the Canary Islands. Inhabits the outer shelf
(180 m) and slope to at least 1,300m depth; often found over seamounts
and underwater ridges. B. decadactylus occurs in the Eastern
Atlantic from Greenland and Norway to Western Sahara and South
Africa. Found at around 500m depth on mud or sandy-mud bottom.
Occurs on the continental slope. Both species are caught in EU
fisheries on the continental slope and the Mid-Atlantic Ridge,
but the relative proportion of the two species in catches is unknown
Due to their spatial distribution associated
their life history and their aggregation behaviour, alfonsinos
are easily overexploited by trawl fishing; they can only sustain
low rates of exploitation. Fisheries on such species should
not be allowed to expand above current levels unless it can
be shown that such expansion is sustainable. To prevent wiping
out entire subpopulations that have not yet been mapped and assessed
the exploitation of new seamounts should not be allowed.
ICES 2006 advice on Alfonsinos/Golden
eye perch (pdf 34k). Emphasis in bold is ours.
There is currently no TAC regulation for Alfonsinos. Irish vessels
took 4 tonnes in 2003 and reported a zero catch in 2005. ICES
states: "Underreporting of catches from international waters
is suspected" (ICES 2006).
Anglerfish/Monkfish (Lophius spp.)
Found in shallow shelf waters and waters on the upper continental
slope between the depths of 200-600m. There has been a tendency
for shelf fisheries for anglerfish to extend into deeper waters.
Lophius spp. are targetted in the upper slope gillnet fishery
west of Ireland (see Gillnet
|Black scabbardfish (Aphanopus carbo)
Black scabbardfish (Aphanopus carbo)
This valuable fish is caught all along the eastern North Atlantic
from Iceland to Madeira. It is a fast moving predator found at
depths of 200-1,600m. Spawning is currently only known to take
place off Madeira between November and December, although it may
also occur elsewhere. There is very little objective information
currently available on the stock structure of this species (ICES
Targeted by French and Irish trawlers to the west of the British
Isles in sub-areas VI andVII, particularly in the Rockall Trough.
Taken in a mixed species trawl fishery along with roundnose grenadiers,
blue ling, cochon, siki sharks and other deepwater sharks.
Given the perceived decrease in stock abundance
in the northern areas, ICES recommends a reduction in exploitation
to the level before the expansion of the fishery started (1990-1996)
in Subareas V, VI, VII, and XII, corresponding to landings of
no more than 3500 t.
The fishery should not be allowed to expand unless it can
be shown that it is sustainable.
ICES 2006 advice on Black
scabbardfish (pdf 54k)
Ireland's catch of black scabbardfish rose from 1 tonne in 1999
to 1,050 tonnes in 2002 before falling to 79 tonnes in 2005 (under
an Irish quota of 87 tonnes).
Blue ling (Molva dypterygia)
This deepwater ling is found at depths of 350-500m in the North-East
Atlantic from Northern Norway and Iceland down as far as the south-west
coast of Ireland. An important species for Irish vessels, being
taken as by-catch on the continental slopes in sub-area VI and
in deepwater longlining operations in sub-areas VI and VII. Blue
ling are taken in directed fisheries on spawning aggregations
by French vessels in subarea VI, but also in mixed species slope
fisheries by French, Scottish and Irish trawlers, but also by
Norwegian, Irish and Spanish longliners.
Blue ling is more vulnerable to over-exploitation
than ling due to a slower growth rate and higher age at first
maturity. It is particularily susceptible to rapid local depletion
due to its highly aggregating behaviour during spawning.
Trends in abundance from all areas indicate declines of
varying gravity. In Iceland the decline appears to have halted,
west of the British Isles it is stable but at a very depleted
level, while it appears seriously depleted in Subdivisions I and
II. In all areas the species is at a low level of abundance relative
to when the fisheries commenced.
Blue ling in Subdivisions Vb, VI, and VII
There should be no directed fisheries and measures
should be implemented to reduce/minimise catches in mixed fisheries
to the lowest possible level. Closed areas to protect spawning
aggregations should be maintained and expanded where appropriate.
Experience in Divisions Va and Vb indicates that once stocks
are fished down they do not recover even when fishing pressure
has been low. The introduction of closed areas to protect spawning
aggregations should be accelerated.
New exploratory assessments have not altered the perception
of a declining stock. The advice remains for closed areas and
reduction in exploitation.
ICES 2006 advice on Blue
ling (pdf 60k). Emphasis in bold is ours.
The 2002 catch by Irish vessels in sub-areas VI and VII was 335
tonnes. Under EU quota restrictions this fell yo 18 tonnes in
2004 and 12 tonnes in 2005 (ICES 2006).
Bluemouth (Helicolenus dactylopterus)
Common on the lower continental shelf of Western Europe and extends
as far as South Africa. It lives on mud and sandy mud at depths
Cardinalfish/Bullseye (Epigonus telescopus)
A deep-sea pelagic fish found in mid-water, not on the seabed.
It lives at depths of 180-900m. Commonly caught in deepwater trawls
off Ireland's west coast.
Deepwater cod/Mora (Mora moro)
This fish belongs to the family of the Morids, which are closely
related to the cod family. It is a semi-pelagic fish found at
depths of 600-1,000m and is mainly caught as bycatch on longlines
and occasionally in trawls, mainly in sub-area VII.
Deepwater redfish (Sebastes mentella)
Found at depths up to 1,000m and is caught in large numbers by
deep-water trawlers in the colder regions of the North Atlantic.
Targeted by Irish trawlers mainly in the Faroe-Shetland Channel.
There are indications that there may be three separate components
of S. mentella viz. deep-sea, oceanic and pelagic races.
(See Redfish Fishery)
Greater silver smelt/Argentine (Argentina silus)
Argentine lives on the edge of the continental shelf and is primarily
fished in the depth range 100-700m. Commonly caught in deepwater
trawls. Targeted mainly by Irish pelagic vessels.
Argentine is vulnerable to over-exploitation
due to its low productivity. It is particularly susceptible to
rapid local depletion due to its highly aggregating behaviour.
Greater silver smelt can be a very significant discard of
the trawl fisheries of the continental slope of Subareas VI and
VII, particularly at depths of 300-700m. The existing knowledge
base is insufficient to determine if the current exploitation
ICES 2006 advice on Greater
silver smelt/Argentine (pdf 39k).
Irish vessel landings declined from 7,593 tonnes in 2002 to 19
tonnes in 2005 from a quota of 383 tonnes (ICES 2006).
Greater forkbeard (Phycis blennoides)
An offshore hake-like fish, which may be caught in coastal waters.
Generally found on sandy or muddy bottoms at depths of 100-350m.
Caught mainly on longline as bycatch off south-west Ireland in
sub-area VII, and by demersal trawlers working in shelf waters
such as the Porcupine prawn grounds. ICES (2006) states: "There
is no information available that allows for evaluation of the
stock trends. The state of the stock is unknown
should not be allowed to expand unless it can be shown that it
Greenland halibut (Reinhardtius hippoglossoides)
A demersal flatfish that can be found in depths of 100-1,200m
with the largest concentrations occurring between 250-800m. It
has widespread distribution in the North-East Atlantic. Targeted
by Irish trawlers in sub-areas IV and VI, particularly the Faroe-Shetland
Hake (Merluccius merluccius)
A bycatch species more commonly associated with fisheries above
the continental shelves.
Ling (Molva molva)
Not generally regarded as a "true" deep-water fish species
although it is found in waters on the upper continental slope
between depths of about 200-600m. Ling are mainly found in waters
less than 200m deep on the outer continental shelf. An important
species for Irish vessels, being taken mainly as bycatch. Several
Irish longliners target ling and tusk jointly along the shelf
edge west of Mayo. In 2005 Irish vessels landed 888 tonnes from
a quota of 1,102 tonnes (ICES 2006).
Megrim (Lepidorhombus spp.)
Found in shallow shelf waters and waters on the upper continental
slope between the depths of 200m-600m.
Orange roughy (Hoplostethus atlanticus)
Little is known about their distribution in the North Atlantic
and, until a French vessel caught 20 tonnes in one tow in 1990,
they were thought not to exist in commercial quantities in the
North Atlantic, though they are widely exploited in New Zealand
and Australian waters. They occur at depths generally greater
than 1,000m. Targeted by Irish trawlers on seamounts and along
slopes of sub-areas VI and VII generally as by-catch in
mixed species trawl fisheries. In subarea VII there is a directed
fishery by Irish and French trawlers. (See Orange
Rabbitfish (Harriotta spp.)
Of increasing commercial importance, with markets mainly existing
in France. Irish vessels have landed rabbitfish in 2000 and 2001.
Red seabream (Pagellus bogaraveo)
Based on historical catches, the stock in VI, VII, and VIII appears
to be depleted.
Red seabream are hermaphroditic and are particularly
susceptible to overexploitation, thus measures to ensure balanced
exploitation between younger fish (males) and older fish (females)
are critical. Fisheries on red seabream should always be accompanied
by programmes to collect data on both target and bycatch fish.
The fishery should not be allowed to expand unless it can be shown
that it is sustainable.
A TAC of 350 t was introduced for red sea bream in 2002
for areas VI, VII, and VIII. In 2005 the TAC was reduced to 298
t. Landings have been below 300 t since 1991, averaging about
140 t over the last decade. From 1960 until the 1980s, landings
were of the order of 10,000 t per year.
In Subareas VI, VII, and VIII red seabream appears mostly
as bycatch in longline and trawl fisheries.
ICES 2006 advice on red
seabream (pdf 54k). Emphasis in bold is ours.
Irish vessels have not reportedly landed red seabream since 2001
(11 tonnes), although the 2004 quota was 10 tonnes and 2005 quota
Redfish/Golden redfish (Sebastes marinus)
S. marinus might be segregated into a "giant"
form and the normal-sized form. Targeted by Irish trawlers in
the Faroe-Shetland Channel since 1994. (See Redfish
Roughhead grenadier (Macrorus berglax)
Lives in colder Atlantic waters and are most abundant at depths
of 400-1,500m. Landed in small quantities by Irish trawlers targeting
Greenland halibut and redfish in sub-areas IV and VI.
Roundnose grenadier (Coryphaenoides rupestris)
Roundnose grenadier has a longevity of 80-100 years and a slow
growth rate. Mainly distributed from about 750-2,000m depth over
slope areas and deep banks of both sides of the North Atlantic
basin, as well as on the Reykjanes and Mid-Atlantic Ridges and
on isolated oceanic features.
The main fisheries are located to the west of the British Isles
(ICES areas Vb, VI, and VII) and further offshore along the western
slope of the Hatton Bank and on the Reykjanes and northern Mid-Atlantic
Ridge (sub-area XII). In the mixed bottom trawl fishery to the
west of the British Isles, roundnose grenadier and black scabbardfish
are caught together (ICES 2005d).
Targeted by Irish trawlers in sub-areas VI and VII. Catches
are rapidly increasing in international waters of the Hatton Bank
area and the Mid-Atlantic Ridge.
For the fishery in Divisions Vb, VI, VII, and
XIIb, the fishing pressure should be reduced considerably to low
levels and should only be allowed to expand again very slowly
if and when reliable indicators show that increased harvests are
sustainable. ICES recommends a 50% reduction of effort compared
to the level before the expansion of the fishery started (1990-1996).
This is interpreted as a reduction in catches of 50% over that
period. This means that the catch level in 2007 should be at most
Roundnose grenadier is taken as one of the target species
in a mixed-species fishery, along with other deepwater species
(black scabbard and deepwater sharks in Division Vb, Subareas
VI and VII) or as a bycatch in fisheries for other species (Pandalus
borealis in the deeper parts of Division III). Any measures
taken to manage the stocks of grenadier should take account of
the advice given for all the species taken in the same deepwater
ICES 2006 advice on Roundnose
grenadier (pdf 93k). Emphasis in bold is ours.
In 2002 Irish vessels took 617 tonnes of roundnose grenadier
in sub-areas VI and VII. With a 346 tonne quota in 2004, Ireland
landed 328 tonnes; in 2005, 72 tonnes of roundnose grenadier was
landed from a reduced quota of 294 tonnes (ICES 2006).
Tusk (Brosme brosme)
This fish is caught along the continental shelf and upper slopes
off Norway, Rockall, the Faroes and Greenland. Not generally regarded
as a "true" deepwater fish species although it is found
in waters on the upper continental slope between depths of about
200-600m. Tusk are mainly found in waters less than 200m deep
on the outer continental shelf. An important species for Irish
vessels, being taken mainly as bycatch. Several Irish longliners
target tusk and ling jointly along the shelf edge west of Mayo.
ICES (2006) states: "Tusk is more vulnerable to overexploitation
than ling due to a slower growth rate and higher age at first
maturity." In 2004 ICES advised a 30% decrease in effort
compared to 1998 across divisions IIIa, IVa, Vb, VI, VII, VIII,
IX, XII, and XIV. ICES 2006 advice is for a further 30% reduction
in landings. (See ICES 2006 advice for tusk
in all areas pdf 121k).
Irish vessels landed 47 tonnes of tusk in 2003, 25 tonnes in
2004, and 19 tonnes in 2005 (ICES 2006).
Wreckfish (Polyprion americanus)
Limited landings data exist. However, this species is of increasing
interest to the Irish industry.
Roughhead grenadier (Macrourus berglax)
Smoothhead (Alepocephalus spp.)
Rabbit fish (Chimaera monstrosa and Hydrolagus spp.)
Common mora (Mora moro) and Moridae
Wreckfish (Polyprion americanus)
Bluemouth (Helicolenus dactylopterus)
Silver scabbard fish (Lepidopus caudatus)
Deepwater cardinal fish (Epigonus telescopus)
Vulnerability to exploitation of these species is largely unknown.
In some cases, landings data do not reflect true catches due to
high levels of discarding.
There are no assessments of these stocks. The knowledge
of the biology of the species is insufficient and it is unclear
how vulnerable they are to exploitation.
Many of these species are caught as bycatch in fisheries
targeting other species or as minor components of mixed fisheries.
Landings of many of the traditional target species of these fisheries
have been reduced in recent years as a result of restrictive quotas.
It is possible that this could result in increased targeting
of some of these species. Knowledge of the biology of these species
is not sufficient to determine their vulnerability to exploitation.
The reported landings on roughhead grenadier and smoothhead have
increased substantially in 2005. This could be an indication of
a targeted fishery on these species.
Rapid increases in the reported catch of non-aggregating species
and/or species of low commercial value (e.g. roughhead grenadier,
smoothhead, rabbitfish, and in the past deepwater cardinal fish)
could also be an indication of species misreporting. Even if the
species are not misreported such rapid expansions of deepwater
fisheries is not precautionary and should not be permitted.
None of these species are currently managed by quotas. It
is likely that restrictive quotas on the main deepwater stocks
will lead to increasing levels targeting on these species.
ICES 2006 advice on Miscellaneous
deepwater fish species (pdf 33k). Emphasis in bold
fish) or deepwater sharks
There are several species of deep-sea shark taken in large quantities
by trawl net, longline and gillnet. Two species the Portuguese
dogfish/Siki shark (Centroscymnus coelolepis) and the Leafscale
gulper shark/Cochon (Centrophorus squamosus) are
commercially important, but others such as the longnose velvet
dogfish (Centroscymnus crepidater), greater lanternshark
(Etmopterus princeps) and the black dogfish (Centroscyllium
fabricii) are becoming commercially important. Portuguese
dogfish are known to live to 70-years old.
Deepwater sharks are found exclusively in waters deeper than
400m. Leafscale gulper shark is most abundant from 700-900m and
Portuguese dogfish in waters of 1,100-1,300 m. Both are important
predators and scavengers in the deep-sea habitat. A greater diversity
of sharks exists in the deepwater areas compared to the continental
shelf. The leafscale gulper shark and Portuguese dogfish were
among the most abundant of the deepwater sharks (ICES 2005c)
The newest development in elasmobranch fishing in the ICES area
is for deepwater sharks. These sharks are not highly valuable.
They are caught in large numbers by fleets that diversified into
deepwater fishing in the 1990s as an alternative to traditional
fisheries. The main fleets catching deepwater sharks are French
and UK trawlers, UK and German gill netters, and Portuguese artisanal
longliners. Other countries that have become involved are Spain,
Ireland, and Norway. The diversity and widespread nature of deepwater
sharks means that fishers in deepwater areas cannot avoid catching
What effect have these fisheries had on shark populations?
The effects of fishing on deepwater sharks are a particular concern
because of their slow reproductive rates. The rapid development
of fisheries for deepwater sharks has also made it difficult for
scientists to collect data and perform stock assessments.
The main species taken in these fisheries are the leafscale gulper
shark (Centrophorus squamosus) and the Portuguese dogfish
(Centrophorus coelolepis). The first assessment, in 2000
by the ICES SGDEEP in 2000, was based on catch per unit effort
in kg per hour fished from French deepwater trawlers. The results
suggested that in 1998, the combined stocks of Portuguese dogfish
and leafscale gulper shark were below 50% of their initial biomass.
Unfortunately, this assessment could not give information on the
status of either of these shark species separately, so WGEF has
recently tried to address this problem. All available CPUE data
from France, UK, Ireland, and Norway were pulled together by WGEF
and a stark trend was confirmed: there has been an extreme
decline, particularly in Portuguese dogfish, a species that
was once an abundant shark in deepwater catches.
The low reproductive output of the Portuguese dogfish, coupled
with the fact that females — including pregnant females dominate
the catches, explains this decline.
Not having species-specific catch data disguised an extreme decline
of a vulnerable species. Landings of these species have peaked
at about 11,000 t in 2003. Although it is difficult to advise
on a sustainable catch with so little information, the current
fishing effort is clearly too high.
Deepwater sharks are caught in a mixed fishery for deep-sea species
and as a targeted fishery using longlines and gillnets.
ICES (2005c) states: "Portuguese dogfish (Centroscymnus
coelolepis) and leafscale gulper shark (Centrophorus squamosus)
The status of other deepwater sharks is unknown
their very poor state, ICES recommends a zero catch of deepwater
Irish vessels catch Portuguese dogfish primarily north-west of
the Porcupine Bank mainly using trawls, but also by longlines.
The value of Irish landings of deepwater sharks in 2000 was €135,000.
Whilst efforts are being made to collect separate landings data
for each of these species, at present data are largely being reported
at an aggregated level for all deep-sea sharks combined.
Assessing stock status
Finding out more about deep-sea fish stocks
Firstly, the stock structure must be investigated. Which stock
is found when and where? Do the different stock units mix; is
there gene flow between them? What are their rates of reproduction
and growth? Only when these basic biological questions have been
answered can management units and plans be endorsed and implemented
and, based on this, careful fishing could be sustained. The reality,
however, is different.
Typically, little if anything is known about the behaviour and
ecology of deepwater fish species, such as orange roughy, and
their populations. All the indications are that most, if not all,
stocks can sustain only very low exploitation rates. Yet the deep-sea
fisheries are expanding very rapidly and exploitation rates are
largely unknown. International experience shows that deep-sea
stocks can be depleted very quickly. ICES has said that many deep-sea
stocks are in decline and can only sustain very limited fishing
pressure. "In light of these concerns, ICES has suggested
that there should be an immediate reduction of fishing pressure
on fully exploited or overexploited deep-sea stocks"
Deep-water fish species tend to be long-lived, slow to grow and
reproduce  in the absence of commercial
exploitation, population structures include many old fish ;
fish reach maturity relatively late in life; they produce small
numbers of young that tend to have a high survival rate; they
are top predators in their environment, which are stable; and
have low rates of natural mortality. Hence they do not have the
resilience to recover rapidly from high or even moderate fishing
rates. Stock numbers do not increase in the depleted areas in
the short or medium term, and fisheries often develop and expand
before sufficient information is available on which to base management
advice (Marine Institute 2001).
The OSPAR Commission (2000) reports that ageing techniques have
been validated for only three of the 340 deep-living species of
bony fishes (teleosts) recorded in the North Atlantic, and for
only one of the 40 deep-sea species of sharks, rays and skates
Furthermore, many deep-water species have fragile skins and suffer
considerable damage in a trawl , so that technical
conservation measures such as increased trawl net mesh sizes or
sorting grids are unlikely to be effective for the protection
of these species.
ICES has developed an index in which deep-sea species are ranked
in order of their vulnerability to exploitation. The species ranking
is given below, the lowest number denoting greatest vulnerability
(Marine Institute 2001).
|Leafscale gulper shark/Cochon
|Portuguese dogfish/Siki shark
|Greater silver smelt/Argentine
|Alfonsinos (2 species)
||4.7 & 5.0
"Although we still have a lot to learn about these species
we know that they are particularly vulnerable to overfishing because
of their slow ability to reproduce. ICES has warned that several
deep-sea stocks are now heavily exploited and in some cases severely
depleted. This raises the question as to whether deep-sea fisheries,
at their present levels, are sustainable" (ICES 2005b).
The ICES Working Group on the Biology and Assessment of Deep-Sea
Fisheries Resources (WGDEEP) has the task of providing assessments
of the state of deep-sea stocks in the North-East Atlantic and
Baltic Sea. Assessments are generally based on estimates of the
size of deep-sea stocks and the level of fishing effort that they
can support. However, as the Marine Institute points out, assessments
have been hampered by the lack of adequate data (Marine Institute
Bergstad, Gordon & Large (ICES 2005b) state that analysis
of several of the most important deep-sea fisheries using catch
per unit effort (CPUE) statistics highlights "a clear declining
trend". CPUE is the fish catch taken for a given amount of
fishing effort, such as tonnes per fishing day or tonnes per 1,000
longline hooks. According to ICES:
- Since the 1970s, the CPUE for ling and tusk has fallen by
70% in ICES Subareas north and west of the British Isles.
- There is evidence of a drop in blue ling stocks. French CPUE
data show a decline to a low level during the period 1985-1998.
- The most valuable but also most vulnerable deep-sea fish considered
by WGDEEP is the orange roughy. In deep-water areas north-west
of the UK (ICES Area VI), the CPUE for this species declined
quite quickly after the fishery commenced in 1991, and by 1994
it was 25% of initial catch rates. In recent years CPUE has
increased slightly and has stabilised. The apparent stabilisation
may simply reflect the discovery and subsequent fishing of previously
unexploited aggregations of fish.
- Roundnose grenadier is fished in many ICES Subareas. Assessments
have only been made for areas near the Faroes and west of the
British Isles (ICES subareas Vb, VI, and VII) combined, and
these suggest a strong decline in the stock size to a level
below the precautionary level set by the ICES Advisory Committee
on Fishery Management (ACFM).
A particular feature of deep-sea fisheries is the mixed catch.
In deep-water habitats there are invariably a number of species
present in a location. Thus there is considerable overlap between
one target species and another, and between target and non-target
Most deep-water trawl fisheries are opportunistic, targeting
a species for a certain period then continuing to take it as bycatch.
The OSPAR Commission (2000) states that species richness of deep-sea
fish assemblages increases with depth to depths of 1,000m: "So
as one species is fished out, the temptation is to target another
species, thus maintaining the fishing pressure on the original
For example, to the west of Ireland and France the fishery for
hake (Merluccius merluccius) and/or red sea bream (Pagellus
bogaraveo) has shifted to the exploitation of some of the
deep-living sharks (Deania calceus, Somniosus rostratus,
Centrophorus granulosus, Centroscymnus coelolepis).
Only the livers of these sharks have significant economic value,
so the liver is removed (20-30% of weight) and the rest discarded.
Because the oil (70-80% of the liver's weight) is extracted, converting
the landings to meaningful fishery statistics is a major problem."
The OSPAR Commission (2000) adds that many of the data on landings
of deep-sea species "are of questionable value, one of the
reasons being the uncertainties of many of the species' identifications."
Moreover, with few monitoring programmes and only sporadic participation
in the fisheries by many fleets, "reported catches are highly
suspect for many target and minor species. Nor do the data on
landings reflect the overall impacts on the non-target stocks
or the extent of damage inflicted on some deep-sea habitats. Fishing
effort in the deeper waters tends to be unpredictable, since it
waxes and wanes according to the fluctuations experienced by fishermen
as their access to other stocks is limited by regulation or overfishing."
In October 2001, the ICES ACFM reported 
that many of the deep-sea fish stocks are too heavily exploited
and are considered to be in a state that is actually or potentially
outside safe biological limits . Depending
on the stock in question, ACFM recommended action "implying
the restriction of fishing opportunities" and for stocks
for which little biological information is available, ACFM recommended
that "the expansion of the fisheries should be restricted
until comprehensive data-collection systems have been put in place".