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Deep impact: The rising toll of fishing in the deep sea


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The deep ocean is one of the last great wildernesses. Waters deeper than 1000 m cover an estimated 62% of the planet. In spite of more than 150 years of exploration, the ocean depths remain virtually unknown. Biological science has so far touched upon only one millionth of the deep-sea floor, but new technology is revealing unknown and exotic habitats as quickly as we look. Those technologies are also bringing the deep within reach of industry, with devastating consequences.
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Deep impact: the rising toll of fishing in the deep sea
Callum M. Roberts
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The deep ocean is one of the last great
wildernesses. Waters deeper than 1000 m
cover an estimated 62% of the planet. In
spite of more than 150 years of exploration,
the ocean depths remain virtually
unknown. Biological science has so far
touched upon only one millionth of the
deep-sea floor, but new technology is
revealing unknown and exotic habitats as
quickly as we look. Those technologies are
also bringing the deep within reach of
industry,with devastating consequences.
Cast a dredge over the side of a ship far out
to sea and the chances are that you will
raise a bucket full of mud and worms.
Sediment blankets much of the deep-ocean
floor [1] and was a source of endless tedium
for those lowering dredges and raising
mud during the three-year voyage of
HMS Challenger in the 1870s. This voyage
marked the first systematic look at the
biology of the deep sea. Perhaps all that
mud contributed to the suicide, two cases
of insanity and 61 desertions that are
among its lesser known achievements [2].
Dredges are still a mainstay of deep-sea
biology, but today they are supplemented
by a burgeoning array of sophisticated
technology. Remotely operated vehicles,
video, bottom landers, submarines and
sonar now provide windows on the deep
that are forcing us to rethink our notions of
life there. In the past few decades, we have
discovered remarkable new habitats –
spectacular hydrothermal vents, cold
seeps, gas hydrates and cold-water coral
reefs [3]. A closer look at seamounts and
canyons reveals them to be hotspots of
production that harbour diverse faunas
that are rich in unique species.
However, scientists are not the only
ones taking an interest in the deep. These
waters offer the prospect of lavish rewards
to mining, oil and gas exploitation, and
fishing concerns. In a new report prepared
for the World Wide Fund for Nature
(WWF) and World Conservation Union
(IUCN), scientists from the Southampton
Oceanography Centre and an expert on
international law present a primer in
deep-sea biology and explore current
and potential threats to deep water and
high-seas life [3]. Although deep-ocean
mining still lies in the future, fishing is
already causing great concern.
Fishing deeper
Deep-water fisheries began in the 1960s
and 1970s, coinciding with declines in
shallow-water stocks that stimulated the
development of new and more robust
fishing gear [4]. Larger vessels, more
powerful winches, stronger cables and
rockhopper trawls expanded greatly the
reach of fishing. The move to deep water is
being encouraged further by governments
offering grants and subsidies [5] in efforts
to alleviate hardship brought about by
the collapse of shallow-water fish stocks
caused by overfishing. Consequently, there
has been a worldwide scramble to exploit
these resources and 40% of the world’s
trawling grounds are now in waters deeper
than the continental shelves [6].
Early rewards from deep-sea fishing
can be great. For example, the orange
roughy Hoplostethus atlanticus fishery
began in the 1970s. It took off in the 1980s
when spawning aggregations were
discovered around deep seamounts off
New Zealand and southern Australia.
Catches from these aggregations could be
incredible, sometimes 60 t from a 20-min
trawl (J.A. Koslow, pers. commun.).
However, in just over a decade, stocks
collapsed to <20% of their pre-exploitation
abundance, largely through sequential
depletion of aggregations [4,7]. In the
North Atlantic, populations have met with
a similar fate. Here, the mainly French
fishery peaked at 4500 t during its first
two years, then dropped to 1000 t three
years later [5].
Other fisheries have also flourished
briefly then diminished. For example,
pelagic armourhead Pseudopentaceros
wheeleri were fished over seamounts in
international waters northwest of Hawaii
from the late-1960s to mid-1970s. In 1976,
30 000 t were landed but, the year after,
catches collapsed to just 3500 t and have
never recovered [8]. In the North Atlantic,
blue ling Molva dipterygia fisheries also
rely on spawning aggregations. As new
areas are rapidly depleted, the survival of
the fishery depends upon the continuing
discovery of unexploited aggregations [9].
We know from shallow waters that
unregulated or poorly controlled fishing of
aggregations is a quick ticket to fishery
collapse [10]. For example, throughout the
Caribbean, Nassau grouper Epinephelus
striatus spawning aggregations numbering
tens of thousands of fish were eliminated
in just a few years, never to reform [11].
Spawning aggregations concentrate fish
from a very large area into a very small
one. For example, orange roughy travel
hundreds of kilometres to spawn over
seamounts in the Southern Hemisphere
[12]. Aggregations can also form in other
ways. Adult pelagic armourhead, for
example, migrate to seamounts from broad
areas of the northern Pacific, and live out
the rest of their lives there [13]. Where
fishing effort is difficult to control, as it
is on the high seas, exploiting dense
aggregations can be closer to mining than
to fishing, because depletion is rapid and
recovery unlikely [10].
Deep-water fisheries fail the
sustainability test on another ground.
The almost glacial pace of life in the deep
makes it a particularly unsuitable place
to fish. Many species grow slowly and live
to extraordinary ages. For example, new
radiometric aging methods reveal that
rockfish Sebastes spp. longevity increases
exponentially with the deepest occurrence
of a species (Fig. 1), and some species can
reach 200 years old [14]. Cailliet et al. [14]
suggest that great longevity could be
facilitated by slow metabolism. In deep-sea
fish, metabolic rates are typically an order
of magnitude lower than in fish living near
the surface [15]. However, this is not the
only factor – some species dwelling on
seamounts have metabolic rates similar to
those of species living at the surface yet
still live to a great age, perhaps because of
low rates of predation [15].
Long lifespan is usually paired with
late reproduction. Icelandic roundnose
grenadier Coryphaenoides rupestris can
live to their 70s and mature at ~14–16
years old [16]. Orange roughy, which reach
150 years old, do not mature until their
mid-20s to mid-30s [17]. For shallow-water
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Science & Society
Deep impact: the rising toll of fishing in the deep sea
Callum M. Roberts
fish, a large body size and advanced age
at maturity are two of the most reliable
predictors of vulnerability to
overexploitation [18]. Long life, late
maturity and high fecundity are also
indicators of sporadic recruitment success
[18]. The life-history characteristics
of deep-sea species place them at the
extreme end of the vulnerability
spectrum. What these characteristics
point to is that deep-water fisheries are
repeating the process of sequential stock
depletion that has been the hallmark
of shallow-water fisheries [19]. The
difference is that depletion is more rapid,
and recovery will be much slower and even
less certain than in shallow water.
The collateral costs of deep-water
Deep-sea fisheries are inflicting terrible
collateral damage. Only a handful of
species is marketable, largely because
most have soft, watery flesh that is
undesirable to consumers and of little use
for fishmeal [5]. Most species are discarded
as bycatch – bykill really, because there is
100% mortality of fish brought up from
great depths [20]. Furthermore, most
deep-sea species are adapted to conditions
of low turbulence. They have large scales,
weak skins and lack the well-developed
mucus coating of shallow water fish [21].
Fish that enter trawls are rapidly stripped
of their scales and skin, so that even small
fish that pass through trawl meshes
probably suffer heavy mortality.
Fisheries are concentrated into areas
with some of the greatest biological
significance in the deep sea. Seamounts,
together with steep slopes, such as those of
canyon walls, are among the few deep-sea
habitats where currents are strong enough
to prevent sediment accumulation. The
same currents also bring food, and a rich
benthic fauna of suspension feeders
develops as a result, including corals,
sponges, seafans and hydroids. This
constant input of food supplies the large
fish aggregations that have attracted
fishers. Koslow et al. [22] found 300 species
of fish and invertebrates inhabiting
Tasmanian seamounts. But many of these
seamounts have literally been stripped
bare by trawling. For example, there was
95% bare rock on fished peaks compared
with just 10% on unfished ones [22], and,
on average, unfished seamounts had
double the benthic biomass and 46% more
species than did fished areas.
The closer we look at the deep sea the
more we challenge our previous ideas.
De Forges et al. [23] reported >850 macro-
and megafaunal species from seamounts
of the southwestern Pacific. This is
striking when you consider that only
597 invertebrate species had been
recorded from seamounts between the
HMS Challenger expedition of the 1870s
and 1987. The new samples reveal
hitherto unsuspected levels of endemism.
Between 29% and 34% of the species
collected were potential seamount
endemics and new to science [23]. Many
species, it seems, have extremely limited
geographical distributions and are
restricted to closely spaced ranges of
underwater peaks. The potential for trawl
damage to cause extinctions is high [24].
Other habitats are being caught in
the fishing crossfire. It is only in the past
five years that the extent of coldwater
coral reefs in the North Sea has been
appreciated, although they were first
described over a century ago [25]. This
habitat occurs at depths of 100–2000 m
and is built largely by a single species of
coral Lophelia pertusa. Growing at rates
of just a few millimetres a year, over
millennia the corals have created reef-like
mounds that can reach up to 200 m high
and 4000 m long [26]. Off the Norwegian
coast, oil companies exploring the seafloor
with remotely operated video cameras
came across a region of reefs that extend
for 13 km [27]. Lophelia beds support a
rich assemblage of species (Fig. 2),
totalling >800 at the last count [28].
Evidence from video suggests that they
also form important nursery grounds for
many fish species.
Video and photographic surveys reveal
troubling evidence of the vulnerability of
this fragile habitat to fishing, including
deep parallel grooves of pulverized coral
ploughed by trawl doors [29]. These doors
keep the net open and the trawl on the
bottom, and deeper trawling and rougher
seabeds require heavier doors, which can
weigh 2–5 t each. Norwegian fishers have
long known of the presence of Lophelia
reefs and developed fishing techniques to
reduce net damage and increase catches
(although only over the short term), such
as dragging chains across the bottom
ahead of trawls to mow down obstructions.
At a recent symposium on deep-water
corals, Norwegian scientists estimated
that up to half of these reefs have already
been damaged or destroyed by fishing
(Fossa et al. 2000;
Across the Atlantic, there are similar
problems. To people fishing off Nova Scotia,
glass sponges are a nuisance. In newly
fished areas, they clog nets with literally
tonnes of material akin to fibreglass. Over
time, the problem diminishes as nets clear
the bottom of its biota. This process of
seabed habitat transformation has been
underway since the early days of trawling.
In the 19th and early 20th centuries,
fishers used to regularly trawl up giant
gorgonians [30]. Radioisotope aging of
smaller colonies put them at hundreds of
years old, suggesting ages of 2000 or more
for the largest specimens [30].
There are fishing methods that are
less destructive to deep-water habitats,
including long-lines, traps and gill nets.
However, the use of gill nets is still
problematic, because lost nets can
continue fishing for very long periods. In
shallow water, the fishing power of lost
nets is rapidly reduced by storms, tidal
currents and fouling algae, but in the calm
TRENDS in Ecology & Evolution
TRENDS in Ecology & Evolution
Maximum depth of
occurrence (m)
Longevity (y)
Fig. 1. Deep-sea fish generally live longer than do those
in shallow water. The longevity of rockfish species from
the genus
(Pisces: Scorpaenidae) increases
exponentially with their deepest depth of occurrence.
2=0.51.) Redrawn, with permission, from [14].
Fig. 2.
reef habitat at 273 m on the Sula Ridge,
Norway, showing a cusk fish
Brosme brosme
Photograph reproduced, with permission, from Andre
Freiwald, University of Tübingen.
and dark of the deep, nets remain lethal
for much longer. Fishing with long-lines
does less damage to habitats and there is
less wasted bycatch [21], but there is still
no way out of the problem of extremely
low rates of production. For example, the
sustainable annual take of orange roughy
in the southern ocean has been estimated
at only 1.5% of the unfished biomass [31].
Given the high costs of deep-sea fishing
(specialist gear, larger boats and long
voyages) it seems likely that it can be
profitable only if pursued in the present
mode of serial depletion. There is probably
no such thing as an economically viable
deep-water fishery that is also
sustainable. It is clear that the biology
of deep-sea organisms compels us to
rethink attitudes to exploitation that we
have developed from experience with
organisms living in the ‘fast-lane’ of
shallow seas. Merrett and Haedrich [32]
argue that we must consider deep-sea fish
stocks as nonrenewable resources.
Deep-sea ecosystems need urgent protection
The clear cutting of old-growth redwood
forests in the western USA during the
19th century spurred the creation of the
first national parks. The analogy is
obvious. Ancient groves of invertebrates
are being clearcut by trawling just as
quickly and surely as loggers felled groves
of giant redwoods [33]. The unique
megafauna of these hidden aquatic glades
is being hooked and netted faster than
they can possibly be replaced. As with
rainforests, we are probably losing species
far more quickly than we can describe
them. We urgently need to extend
protection to large areas of the deep sea.
Most deep-sea fishing is unregulated
[3], but no licensing, quota scheme or
effort control will save deep-ocean life,
because it can be depleted or destroyed
much too rapidly for these mechanisms
to work. The answer is to create marine
reserves that are entirely off limits to
fishing. Norway moved fast to protect
its coldwater coral reefs from trawling
in 1999, soon after their extent and
vulnerability became known. To date, no
other country has done so. In Australia,
twelve seamounts have been protected
from bottom fishing within the 370 km2
Tasmanian Seamounts Marine Reserve
(Dahl-Tacconi, 2000;
~eac_hfx/symposium/), New Zealand has
protected 19 seamounts and the USA has
created a small marine-protected area
encompassing two seamounts off Alaska
[34]. However, none is protected from
fishing all the way to the surface. It is still
unclear how closely linked benthic and
pelagic foodwebs are around seamounts.
For example, vertical migrations of
organisms transfer nutrients from shallow
water to bottom habitats. This, together
with the nutrient ‘snowfall’ from animals
aggregated higher in the water column
helps explain why seamount assemblages
are so rich [15]. Consequently, partial
protection measures might not assure
the long-term wellbeing of bottom-living
communities [20,35]. Surface to bottom
protection from fishing offers more security
but could be more difficult to implement due
to greater fishing industry opposition [36].
National initiatives represent a crucial
first step for deep-sea conservation, but
much of the deep lies beyond national
jurisdiction. Fifty percent of the planet
comprises high seas [3], which are outside
the 200-mile national limits. High-seas
regulation poses great challenges [37], but
as the new WWF–IUCN report shows,
present international laws provide a
framework for creating high-seas marine
reserves [3]. Unfortunately, the present
rate of expansion of deep-sea fisheries
gives us little time to act. Unless we
work quickly to establish reserves, we
might realize the Victorian vision of a
deep sea that is devoid of larger life – the
kingdom-of-the-worms once more.
This article is dedicated to the memory
of Don McAllister, who saw the need to
protect deep-sea habitats from fishing,
and worked hard to raise awareness
of what we are losing. Julie Hawkins
suggested many improvements to the
article. This work was supported by a Pew
Fellowship in Marine Conservation from
The Pew Charitable Trusts and The Hrdy
Fellowship in Conservation Biology at
Harvard University in the Dept of
Organismic and Evolutionary Biology.
I am very grateful to Sarah and Daniel
Hrdy for endowing the fellowship and to
Steve Palumbi for his hospitality.
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Environment Dept, University of York, York,
UK YO10 5DD.
TRENDS in Ecology & Evolution
... These deepwater species often have distinctive and complex life histories, exhibiting slow growth and extreme longevity, sometimes in excess of 100 years, and live in dark, cold, low-productivity habitats [1][2][3] . This combination of factors makes sustainable management of deepwater fisheries challenging, as they can be particularly susceptible to overfishing and slow to recover once overfished [4][5][6] . Catches can often be high as a fishery develops and a stock is fished down, but long-term sustainability often necessitates low catches else stocks are rapidly depleted below sustainable levels 7 . ...
... The effect of this random-walk prior is that across a wide range knot numbers the resulting reference series fit is very similar. To assess the accuracy of age estimates, we fit the penalized B-spline to the reference series assuming the expected Δ 14 C reference series value came from a normal distribution (5). the reference series process error. ...
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Many members of the scorpaenid subfamily: Sebastinae (rockfishes and their relatives) exhibit slow growth and extreme longevity (> 100 y), thus are estimated to be vulnerable to overfishing. Blackbelly rosefish (Helicolenus dactylopterus) is a deepwater sebastine whose longevity estimates range widely, possibly owing to different regional levels of fisheries exploitation across its Atlantic Ocean range. However, age estimation has not been validated for this species and ageing for sebastines in general is uncertain. We performed age validation of northern Gulf of Mexico blackbelly rosefish via an application of the bomb radiocarbon chronometer which utilized eye lens cores instead of more traditional otolith cores as the source of birth year Δ¹⁴C signatures. The correspondence of eye lens core Δ¹⁴C with a regional reference series was tested with a novel Bayesian spline analysis, which revealed otolith opaque zone counts provide accurate age estimates. Maximum observed longevity was 90 y, with 17.5% of individuals aged to be > 50 y. Bayesian growth analysis, with estimated length-at-birth included as a prior, revealed blackbelly rosefish exhibit extremely slow growth (k = 0.08 y⁻¹). Study results have important implications for the management of blackbelly rosefish stocks, as extreme longevity and slow growth imply low resilience to fishing pressure.
... Endangered deep-sea species include coral communities, some of which of great environmental importance and can live for centuries if undisturbed (Bo et al., 2015), and elasmobranch communities that may suffer from bycatch and prey reduction (Barría et al., 2018). In addition to the direct effects of removal and damage of these iconic individuals, deep-sea fishing affects the three-dimensional structure of the sea bottom, modifies the turbidity and attracts scavengers, thus resulting in modifications of the overall community composition Roberts, 2002). For these reasons, research aimed to protect deep-sea areas needs detailed estimations of the exploited fishing grounds, and these have become available only in the last decade (de Juan and Lleonart, 2010;Armelloni et al., 2021). ...
... In particular, AIS unencrypted radio signals, compulsorily transmitted by European fishing vessels over 15 m to avoid collisions, result in consistent data to observe large deep-sea trawlers targeting shrimps and this has permitted the observation of the supranational capillary expansion in the eastern regions of the central Mediterranean fleets . Understanding spatiotemporal dynamics of fishing is crucial to prevent stock collapses, especially in deep fishing grounds where several episodes of initial high-reward periods followed by the phenomenon of local depletion are documented (Roberts, 2002). ...
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Deep-sea fishery in the Mediterranean Sea was historically driven by the commercial profitability of deepwater red shrimp (DWRS), and understanding spatiotemporal dynamics of fishing is key to comprehensively evaluate the status of these profitable resources and prevent stock collapse. A 4-year time series of observed monthly patterns and related frequency of trawling disturbance based on an automatic identification system (AIS) is provided with a resolution of 0.01∘×0.01∘, accounting for the spatial extent and temporal variability in deepwater (DW) bottom-contact fisheries during the period 2015–2018. The dataset was estimated from 370 fishing vessels that were found to perform trawling in deep water (400–800 m) during the study period, and they represent a significant part of the real fleet exploiting these fishing grounds in the study area. The reconstructed deepwater trawling-effort dataset is available at: (Pulcinella et al., 2022). This large-scale and high-resolution dataset may help researchers of many scientific fields, as well as those involved in fishery management and in the update of existing management plans for deepwater red shrimp fisheries as foreseen in relevant recommendations of the General Fisheries Commission for the Mediterranean (GFCM).
... The fishing industry is expanding into new, previously untargeted areas such as the deep sea and mesopelagic. While expansion of the deep-sea fishing industry is unlikely to directly affect seabirds, there may be wider ecosystem consequences such as by altering nutrient transfer from the benthos to the sea surface (Roberts, 2002 ). Mesopelagic fish are an important food for many seabirds (Watanuki and Thiebot, 2018 ), and therefore the global expansion of mesopelagic fisheries requires careful management to ensure deleterious ecological impacts are minimized (Hidalgo and Browman, 2019 ). ...
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Knowledge of fisheries impacts, past and present, is essential for understanding the ecology and conservation of seabirds, but in a rapidly changing world, knowledge and research directions require updating. In this Introduction and in the articles in this Themed Set "Impacts of fishing on seabirds" , we update our understanding of how fishing impacts seabird communities and identify areas for future research. Despite awareness of the problems and mitigation ef for ts for > 20 years, fisheries still negatively impact seabirds via the effects of bycatch, competition, and discards. Bycatch continues to kill hundreds of thousands of seabirds annually, with negative population-level consequences. Fisheries for forage fish (e.g. anchovy, sandeel, and krill) negatively impact seabirds by competing for the same stocks. Historically, discards supplemented seabird diets, benefitting some species but also increasing bycatch rates and altering seabird community composition. However, declining discard production has led to potentially deleterious diet switches, but reduced bycatch rates. To improve research into these problems, we make the following recommendations: (1) improve data collection on seabird-vessel interaction and bycatch rates, on fishing ef for t and vessel movements (especially small-scale fleets), and on mitigation compliance, (2) counter the current bias towards temperate and high-latitude ecosystems, larger-bodied species and particular life stages or times of year (e.g. adults during breeding), and (3) advance our currently poor understanding of combined effects of fisheries and other threats (e.g. climate change, offshore renewables). In addition, research is required on under-studied aspects of fishing impacts: consequences for depleted sub-surface predators, impacts of illegal, unreported and unregulated fishing, artisanal and emerging fisheries, such as those targeting mesopelagic fish, have received insufficient research attention. Some of these shortfalls can be overcome with new tools (e.g. electronic monitoring, remote sensing, artificial intelligence, and big data) but quantifying and addressing fishing impacts on seabirds requires greater research investment at appropriate spatio-temporal scales, and more inclusive dialogue from grassroots to national and international levels to improve governance as fishing industries continue to evolve. Background and motivation for a themed article set
... In the present study, signs of overfishing are argued to exist whenever the DC of a certain species is consistently and significantly reduced over time, especially if it drops to zero and remains at zero through the end of the timeline (Constantine 2002). Signs of sequential depletion, on the other hand, are explored based on two different but related criteria: (1) whenever the species shows a geographically progressive disappearance from the habitual catch, usually with a clear directionality identified (Clark 1999;Roberts 2002;Berkes et al. 2006;Morsan 2007); or (2) whenever, in a certain fishing ground, the species' relative participation is consistently and significantly reduced while being replaced with other species in the average catch (Link 2007). Both criteria imply an adaptation of the fisheries to the depletion of a species in a fishing ground, either by changing the target species or by progressively changing the fishing ground. ...
Objective Fish populations targeted by recreational and artisanal fisheries remain largely unassessed in low‐ and middle‐income countries. This generally results in a lack of regulatory action from government agencies, thus aggravating the risk of overfishing. In this context, sources of historical information, such as local ecological knowledge (LEK), are key to providing insight on the status of fish populations and informing management. Systematized elicitation processes have increasingly shown an ability to produce quantitative indicators while reducing biases and caveats inherent to expert knowledge. In this study, we assessed changes in composition of the catch, species abundance, and geographical distribution of the catch for 10 data‐poor coastal groundfish species of Peru using LEK. Methods We designed and conducted a structured elicitation process to gather LEK on these species from 40 recreational and commercial spearfishers in Peru. We then used the obtained data to develop a set of indices and analyzed them statistically to identify trends and the magnitude of changes over time, if any, between the years 1960 and 2019. Result Our results show a significant decline in the relative participation (a species' catch proportion relative to the total catch) and abundance of seven assessed species in the catch as well as a major reduction in their geographical distribution. For some species, decreases in relative participation within the catch and decreases in average daily catch, a measure that may indicate changes in abundance, were statistically significant across the time span of the study. Average daily catch was between 1% and 15% of their historical high values. Some species have experienced a reduction of 60–100% in the geographical distribution of their catch. Conclusion Results suggests a scenario of overfishing and sequential depletion of the Galapagos Sheephead Wrasse Semicossyphus darwini , Pacific Goliath Grouper Epinephelus quinquefasciatus , Harlequin Wrasse Bodianus eclancheri , Grape‐eye Seabass Hemilutjanus macrophthalmos , Chino Medialuna ancietae , Pacific Beakfish Oplegnathus insignis , and Broomtail Grouper Mycteroperca xenarcha . We highlight how the application of expert elicitation methods can help to build LEK‐based fishery indicators that are useful for assessing data‐poor fisheries and providing critical information to prompt management discussions.
... Marine fisheries worldwide have operated at increasing depths since the 1970s, coinciding with declines in shallow-water stocks (Roberts, 2002;Norse et al., 2012;Mejjad and Rovere, 2021). Deepsea fisheries, in fact, catch species generally characterized by long lifespans, slow growth rates and late maturity (Watson and Morato, 2013). ...
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Due to their late maturation, extreme longevity, low fecundity and slow growth rates, deep-sea Chondrichthyes are extremely vulnerable to human impacts. Moreover, assessing the impact of deep-sea fisheries is difficult, as many species (including sharks) are part of the bycatch and are often discarded at sea, and/or landed under generic commercial-species codes. The lack of this information on fishery data sets and the limited availability of species-specific life history data make challenging the management of deep-sea Chondrichthyes. The kitefin shark Dalatias licha is a cosmopolitan elasmobranch, mainly found on continental and insular shelf-breaks and slopes in warm-temperate and tropical waters. This species is a common by-catch of the deep-sea trawling, considered as "Endangered" by the IUCN Red List for all European waters, Mediterranean Sea included. Here we present the results of a study based on a total of 78 specimens of kitefin shark collected over 3 years in the Ligurian Sea (NW Mediterranean) as by-catch from deep-water fisheries. Total length ranged from 380 to 1164 mm, and individual weight ranged from 198 to 8000 g. Immature and mature individuals showed a sex ratio dominated by males. Adult males were observed throughout the year, while mature females were observed only in spring-summer. These data lead to hypothesise a spatial segregation between genders. The kitefin shark diet was dominated by bony Frontiers in Marine Science fish (mainly Macrouridae) and other small sharks (e.g., Galeus melastomus and Etmopterus spinax), but their gut included plastic items and parasites. Data reported here underline the rarity, complex ecology and the threat for this shark species and support the urgency of promoting initiatives for their monitoring and conservation.
... Similar to other marine ecosystems, nowadays deep-sea sponge ground VMEs face a number of threats that challenge their current status. Many areas of the deep sea are targeted by the fishing industry, which have resulted in the depletion of several commercial fish stocks (Morato et al., 2006), and consequently, the largest threat that sponge grounds face is physical damage from bottom-contact fishing (Roberts, 2002;Pham et al., 2019). But impacts from oil prospecting and deep-sea mining are also on the rise, in the search of the discovery of rare elements essential to the low-carbon energy industry (Wedding et al., 2015), resulting in significant decreases in both diversity and abundance of megafauna including sponges (e.g. ...
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Little is known about dispersal in deep-sea ecosystems, especially for sponges, which are abundant ecosystem engineers. Understanding patterns of gene flow in deep-sea sponges is essential, especially in areas where rising pressure from anthropogenic activities makes difficult to combine management and conservation. Here, we combined population genomics and oceanographic modelling to understand how Northeast Atlantic populations (Cantabrian Sea to Norway) of the deep-sea sponge Phakellia ventilabrum are connected. The analysis comprised ddRADseq derived SNP datasets of 166 individuals collected from 57 sampling stations from 17 different areas, including two Marine Protected Areas, one Special Area of Conservation and other areas with different levels of protection. The 4,017 neutral SNPs used indicated high connectivity and panmixis amongst the majority of areas (Ireland to Norway), spanning ca. 2,500-km at depths of 99–900 m. This was likely due to the presence of strong ocean currents allowing long-distance larval transport, as supported by our migration analysis and by 3D particle tracking modelling. On the contrary, the Cantabrian Sea and Roscoff (France) samples, the southernmost areas in our study, appeared disconnected from the remaining areas, probably due to prevailing current circulation patterns and topographic features, which might be acting as barriers for gene flow. Despite this major genetic break, our results suggest that all protected areas studied are well-connected with each other. Interestingly, analysis of SNPs under selection replicated results obtained for neutral SNPs. The relatively low genetic diversity observed along the study area, though, highlights the potential fragility of this species to changing climates, which might compromise resilience to future threats.
... To provide a more detailed description of its growth characteristics, an analysis of otoliths from individuals younger than 22 years and older than 40 years is necessary. The capture of large L. schmidti individuals from an already rare species through longline fishing can have a negative impact on the condition of the population, as long-lived deep-water fish species are highly vulnerable to fishing pressure due to their biological characteristics such as long lifespan, slow growth rates, and low reproductive capacity [1,[51][52][53][54]. ...
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This study presents the first data of growth and age of Schmidt’s cod Lepidion schmidti, a rare and poorly studied member of the Moridae family (Gadiformes, Teleostei). The research was focused on the Emperor Seamounts area with the aim of investigating the age, growth rates, and longevity of this species. The analysis involved examining annual growth increments on sagittal otoliths. Data were taken from longline catches in 2014 and 2016, resulting in the collection of 140 individuals and the use of 70 otoliths for age determination. The results revealed that Schmidt’s cod can live for up to 49 years, with a mean age of 31.5 years in the catches. The relationship between body weight and total length was described by a power function, indicating positive allometric growth. The most suitable growth model for this species was determined to be the Von Bertalanffy growth equation. These results provide valuable insights to add to the limited knowledge of growth and age in the Moridae family and emphasize the long lifespan and slow growth of Schmidt’s cod.
... A wide range of fishing gears and technologies has evolved, allowing fishers to trawl habitats ranging from muddy or sandy sediments, via coarse and mixed sediments to gravel and other hard substrata (Rijnsdorp et al. 2008). Declines of target species in shallow coastal waters have led to expanding fisheries at increasing depths offshore (Roberts 2002;Thurstan et al. 2010). Different fishing gears are designed to have different levels of seafloor contact or penetration depending on the target species and substrate type, and these factors influence the ecological consequences (Hiddink et al. 2017). ...
Great divergences arise when comparing the ecology of meiofauna in freshwater and marine ecosystems. Emphasizing the main differences between freshwater meiofauna and their marine counterparts, we will go on a stepwise journey through three major frontiers in freshwater research, which in turn are hierarchically interrelated: biodiversity, community organization (e.g. food webs structure), and ecosystem processes (e.g. metabolism and organic carbon breakdown). The starting point of this chapter is one of the utmost frontiers, both in marine and freshwater research: meiofaunal diversity. Especially in freshwater ecosystems diversity becomes evident since, here, habitats extend as highly disconnected biotopes, each characterized by an often fundamentally different biocenosis. From the biodiversity level, we move up the theoretical hierarchy to assess the role of meiofauna as an integral part of benthic food webs. Recent research underlines the role of freshwater meiofauna as highly connected nodes and shows their pivotal role in the transfer of energy and carbon along food chains. Distributed over all trophic levels, this structure contrasts with the prevailing conception of meiofauna in food webs, where meiofauna often are considered rather marginal units. Finally, we apply allometric principles from the metabolic theory of ecology in order to assess the role of freshwater meiofauna in the functioning of the benthic systems. With a novel modelling framework we develop an analytical perspective, showing that secondary production of micro- and meiobenthic communities can predict microbial decomposition rates within the benthic interface. Our results demonstrate that productive micro- and meiobenthos act as catalysers in the system of organic carbon breakdown and recycling. These findings underline the relevance of freshwater meiofauna within the biogeochemical carbon cycle. The mechanistic forces behind the processes involved require future experimental research.
Humans have used, and had effects on, marine ecosystems throughout history. As the human population and its economic activities increase, these effects intensify. Yet, our awareness and understanding of the long‐term, pervasive effects of anthropogenic disturbances on the seafloor, and the resident meiofauna, is far from complete. This chapter summarises research on the responses of marine meiofauna to the most widespread anthropogenic disturbances, including bottom-fishing, pollution, introduction of invasive species, and climate change. Anthropogenic disturbance and natural environmental dynamics interact to cause changes in the response of meiofauna species, either in the short-term, through effects on growth and development, or in the long-term, through genetic selection. Species-specific sensitivity to disturbance can propagate to community-level responses, mediated by shifts in interspecific interactions. Meiofauna responses to anthropogenic disturbance are commonly nonlinear and depend on the environmental context in which the disturbance occurs, on the scales at which meiofauna responses are observed, and on the extent to which the disturbance creates novel environments that differ from those to which the resident meiofauna are adapted. Although responses of meiofauna assemblages to anthropogenic disturbance are complex, in general severe disturbance leads to dominance by opportunistic species. The widespread replacement of habitat-specific ecological specialists by broadly-adapted ecological generalists and opportunists often results in biotic and functional homogenisation of once disparate biotas. Their small size, their life history characteristics, and their phylogenetically and functionally diverse species pool, all suggest that meiofauna are resilient, and there is little evidence for the local extinction of meiofauna from anthropogenically disturbed seafloor habitats. It therefore seems likely that meiofauna have the ability to adapt, and thrive, in response to most environmental changes. New horizons for future meiofauna research pertain to the extent to which the resistance or resilience of meiofauna to anthropogenic disturbance buffers ecosystem functioning against further change.
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Over the last twenty years, human exploitation has begun to have an impact in the deep sea, especially in the upper bathyal zone. This has mainly taken the form of deep-sea fishing but more recently oil exploration has extended beyond the continental shelf. Deep-water coral reefs occur in the upper bathyal zone throughout the world. These structures, however, are poorly studied with respect to their occurrence, biology and the diversity of the communities associated with them. In the North-East Atlantic the coral Lophelia pertusa has frequently been recorded. The present review examines the current knowledge on L. pertusa and discusses similarities between its biology and that of other deep-water, reef-forming, corals. It is concluded that L. pertusa is a reef-forming coral that has a highly diverse associated fauna. Associated diversity is compared with that of tropical shallow-water reefs. Such a highly diverse fauna may be shared with other deep-water, reef-forming, corals though as yet many of these are poorly studied. The main potential threats to L. pertusa in the North-East Atlantic are considered to be natural phenomena, such as slope failures and changes in ocean circulation and anthropogenic impacts such as deep-sea fishing and oil exploration. The existing and potential impacts of these activities on L. pertusa are discussed. Deep-sea fishing is also known to have had a significant impact on deep-water reefs in other parts of the world.
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The widespread view that scleractinian corals in cold and deep waters of high latitudes are slow growing organisms that do not form reefs is challenged by the discovery of a huge coral reef over 13 km in length, 10 to 35 m in height and up to 300 m in width formed by the coral Lophelia pertusa in water depths of 270 to 310 m at 64°N on the Sula Ridge, Mid-Norwegian Shelf. Cruises in 1994, 1995 and manned submersible operations in May 1997 provide data and observations from which the structure and development of the Sula Ridge coral reef have been determined. The Fennoscandian icesheet retreated from the Mid-Norwegian shelf prior to 12,000 years before present and modern oceanographic conditions were established at 8000 years before present. Coral growth since that time has resulted in a large deep-water shelf reef for which recent stable isotopic studies have demonstrated high growth rates for these azooxanthellate cold-water corals. Information on the geometry of deep-water coral reefs and their environmental controls is still fragmentary, controversial and raises issues of conservation in this area of active fishing and oil exploration. This paper reports on the discovery of what is probably one of the largest deep-water coral reefs existing in the northeast Atlantic and indicates that its siting is due to post-glacial structures (iceberg plough marks), events (the second Storegga Slide) and local conditions on the seafloor. Surprisingly, reef accumulation rates on the Sula Ridge are comparable with those measured on tropical coral reefs.
Setting the stage. Diversity and distribution of deep demersal fish. Morphological and life history adaptations. Aspects of fish production: general considerations and feeding. Aspects of fish production: growth and reproduction. Adding a trophic link: exploitation beyond the shelf. The ecology of fisheries. Pandora's box: reflections on the future.
Major commercial fisheries for orange roughy (Hoplostethus atlanticus) occur on seamount features, which are widely distributed throughout the New Zealand region. When the fishery developed in the late 1970s to early 1980s, it occurred mainly on flat bottom, but over time has become more focused on seamounts. In the 1995–1996 fishing year, it is estimated that about 70 % of the catch of orange roughy within the New Zealand EEZ was taken from seamounts. Seamounts on the Chatham Rise have been fished for over ten years. Examination of commercial catch and effort data show strong declines in catch rates over time, and a pattern of serial depletion of seamount populations, with the fishery moving progressively eastwards to unfished seamounts along the southern margins of the Rise. Catch rates on seamounts in other regions of New Zealand have also generally shown a similar pattern of rapid decline. There is growing concern over the impact of trawling on seamounts, and the effects this can have on the benthic habitat and fauna, and the long-term sustainability of associated commercial fisheries.