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A report to gauge the health ofthe UK’s sea-life The UK’s marine environment is in crisis. Our seas have been treated as a rubbish and chemicaldump. Our coastal habitats have been ripped up and reclaimed for development and many of ourfish stocks are over-exploited and heading towards commercial extinction. Yet despite the highlevel of threat facing our marine life, little information is publicly available about the health ofour seas.
By examining 16 species and habitat indicators, WWF’s Marine Health Check report is the
first ever attempt to gauge the health of the UK’s sea-life. The 10 species were selected because
they represent a range of wildlife from different levels of the marine food chain. The six habitats
represent the wide variety of marine habitats in UK waters. The species and habitats were also
chosen on the basis that there was sufficient scientific information available for assessment of
their condition to be possible.
The results of the Marine Health Check are deeply worrying. Despite improvements such as
banning the dumping of rubbish and certain other pollutants at sea, and improvements in some
wildlife populations, the big picture remains one of damage and decay. Two-thirds of our fish
stocks are in decline, with many cod stocks heading towards commercial collapse, and the
unsustainable nature of deep-water fisheries, such as the orange roughy, is a further cause for
concern. All the key habitats examined, from saltmarsh to reefs, are damaged, and populations
of bottlenose dolphins and harbour porpoises appear to be in significant decline. It is also of
serious concern that plankton populations, upon which the entire marine ecosystem depends, are
fluctuating in a way not previously recorded.
The research was carried out between June - August 2000. A summary of the key damage andthreats to all 16 species and habitats is given below: The Harbour PorpoiseThere has been a dramatic decline in harbour porpoise populations throughout Europe,including those in UK waters. A study into the numbers of harbour porpoises killed as a resultof certain fisheries in the Celtic Sea suggested that the annual by-catch of harbour porpoisescould be as much as 6 per cent of the total population. If such levels of by-catch persist, they arelikely to result in the eventual extinction of this population. In general the proportion ofporpoises dying after becoming entangled in fishing nets is reported to be increasing. Otherresearch shows that pollution may damage the harbour porpoises’ immune system, increasingtheir vulnerability to disease, which may have fatal consequences. New research reports thatharbour porpoises in the Irish Sea have been found with elevated levels of certain radioactiveelements in their bodies.
The Bottlenose DolphinThere are three resident populations of bottlenose dolphin recorded around the UK. The beststudied population, in the Moray Firth, may be in decline and could be extinct within 50 years.
There is anecdotal information that other populations may also be in decline. Dolphins are alsoseriously threatened by pollution. A bottlenose dolphin calf found washed up in Cardigan Bay,Wales, had among the highest levels of certain pollutants recorded anywhere in the world for amarine mammal. Other threats include entanglement in fishing nets and loss of prey as a resultof over-fishing.
The CodCod stocks are in serious decline, with many populations identified as being “outside safebiological limits” and some in danger of collapse. Due to fishing pressure, cod in the north-eastArctic are now reproducing two and half years earlier than normal. Additionally experimentalresearch into the effects of polyaromatic hydrocarbons (PAHs, chemicals released from theburning of fossil fuels) has revealed that their toxicity to marine life, especially certain planktonspecies such as cod larvae, may be significantly increased through exposure to Ultraviolet light,a component of sunlight. In laboratory tests PAHs had lethal effects on cod larvae in thepresence of ultra violet light at concentrations of PAHs and levels of UV light which are similarto those found within the marine environment. Climate change could be contributing to thedecline in cod stocks. Due to fisheries mismanagement, 40 out of 60 of the commercial fishspecies in the north-east Atlantic are being fished unsustainably.
The Common SkateThe common skate is now believed to be extinct in the Irish Sea and rare in the central andsouthern North Sea. The common skate has a low reproductive rate and is very vulnerable tofishing activity. Although it is now seldom targeted directly by major fisheries due to its rarity,they continue to pose a major threat because the skate is still caught as by-catch. Other speciesof ray are under similar threat.
The Little TernThe population has declined by approximately 40 per cent since the mid-1970s and now standsat only 1,700 breeding pairs. Development on beaches can destroy nesting sites. Sea level riseand storm surges, exacerbated by climate change, also pose a serious threat to nesting pairs.
Flooding is likely to be particularly problematic in the little tern stronghold of East Anglia.
Industrial fisheries may also pose a threat by reducing its food source.
The Orange RoughyThe orange roughy is a deepwater fish that does not become mature until it is at least 30 yearsold. It may live for up to 100 years and is believed not to breed every year. As a result ofoverfishing due to fisheries mismanagement, stocks are classified as “outside safe biologicallimits” and may be in danger of collapse. The catch has declined by 73 per cent to the west ofScotland and 76 per cent to the west of Ireland and south-west England since fisheries startedonly some 10 years ago. A recent scientific publication has cast serious doubt on whether theorange roughy should be fished at all due to its low reproductive rate.
The Native OysterIn the last 100 years, oyster populations have been seriously depleted and commercialproduction has declined a hundred-fold. The oyster is threatened by several species ofintroduced sea snail. One, known as the oyster drill, can kill 20 oysters a day. Oysters in the UKmay also be threatened by a microscopic parasite, Bonamia ostrea, which has killed oystersacross Europe. Pollution has harmed the recovery of stocks. Organotin chemicals used in ship anti-fouling paint have caused deformed oyster shells and affected the oysters’ ability toreproduce.
The SalmonThe Atlantic salmon is in serious decline. UK river catches have declined by 82 per cent in thelast 25 years. Climate change is threatening stocks by altering water temperature, currents andaffecting plankton levels. During summer 2000 there have been reports of increases in thenumber of young salmon returning to UK rivers. Scientists, however, caution that there remainsevidence of long-term decline and these recent reports do not represent a change in the long-term pattern. The highly destructive virus that causes Infectious Salmon Anaemia (ISA) wasrecently introduced to farmed salmon in the UK from Norway. Recent research has revealedthat the virus has also been found in wild stocks in Scotland. Trials involving the growing ofGM salmon in tanks have already been undertaken in Scotland. The chemicals used to combatsea lice in farmed salmon pose a risk to the wider marine environment, and an agriculturalherbicide, Atrazine, has been shown to impair salmon migrational breeding capability.
PlanktonPlankton acts as a sink for significant amounts of the world’s atmospheric carbon. It is also animportant source of oxygen in the air that we breathe. Recent research has discovered thatplankton levels are fluctuating around the UK and there is evidence of a major ecological shiftin the North Sea, both potentially as a result of climate change. Changes in levels of planktonmay in turn exacerbate climate change if their ability to act as a carbon sink is compromised.
Wire WeedWire weed, a species of seaweed, is one of 53 alien species which have invaded UK waters.
Many pose a threat to native species. In UK waters wire weed can grow up to 12 times biggerthan normal and is known to compete with native species. It can now be widely found along thesouthern coast of England. It is has also spread to Strangford Lough in Northern Ireland, one ofonly three Marine Nature Reserves in the UK. Repeated attempts to remove it have failed.
Eelgrass MeadowsEelgrass is a marine flowering plant that provides a vital habitat for many marine species,including seahorses. The outbreak of a wasting disease may have led to the loss of eelgrassmeadows in 85 per cent of the UK’s estuaries. Eelgrass meadows are seriously threatened by sealevel rise due to climate change and are also vulnerable to high levels of pollution.
Maerl BedsMaerl beds are an important marine habitat created by several species of red algae that form acoral-like structure. They are known to be present in less than 1 per cent of the UK’s inshorewaters and some maerl beds may be more than 8,000 years old. Many maerl beds around theUK have been impacted for many years and continue to be damaged by extraction and fishingactivities. They are known to be at particular risk in the Fal Estuary and Firth of Clyde.
MudflatsMudflats are one of the most productive ecosystems on earth and hundreds of animal speciesdepend on them for survival. Mudflats are in decline around the UK and at least 25 per centhave already been lost to land claim, which poses a continuing threat. The Tyne has lost 100 per cent of its mudflats. Sea level rise due to climate change and shellfish dredging are the mostserious threats. Pollution by hormone disrupting chemicals in the UK’s estuaries is leading toserious impacts on wildlife that depend upon mudflat habitat. A recent study has found thatmale flounder in many UK estuaries are displaying female sexual characteristics and evenproducing eggs.
ReefsRocky and biogenic reefs (the latter produced by living organisms) are one of the mostimportant marine wildlife habitats. In some areas the marine wildlife of the reefs has beendegraded and destroyed and is under particular threat from fishing activity and oil and gasexploration. Lophelia coral reefs are under serious threat as oil and gas exploration and fisheriesmove into deeper waters. Dredge fisheries for scallops have caused widespread and long-termdamage to horse mussel reefs. One of the world’s most important sites of Serpula tube wormreefs at Loch Creren in Scotland may be under threat from trawling.
SaltmarshSaltmarsh comprises a range of salt-dependent plants that provide essential habitat for hundredsof species. There are only 45,000 hectares of saltmarsh left around the UK, when once therewere more than 200,000 hectares in England and Wales alone. This represents an estimateddecline of more than 75 per cent. It is estimated that 6 per cent of remaining saltmarsh will belost over the next 20 years due to rising sea levels as a result of climate change. Pollution and oilspills are also serious threats. More than 10 highly toxic chemicals were found in one saltmarshbed in Essex.
Sub-tidal Sand and GravelSub-tidal sand and gravel is an essential habitat for many marine species but is being damagedby aggregate extraction and fishing activity. Extraction of sand and gravel from the seaseriously damages animal communities but the Westminster government plans to allow anincrease in the level of extraction. High levels of lead and cadmium have been found in seaurchins, hermit crabs, worms, starfish and shrimps that live on sand and gravel habitat in theDogger Bank.
The harbour porpoise is the smallest cetacean to be found in British waters, measuring between1.5m and 2m. With a lifespan of up to 12 or 13 years, it lives in small groups, though largergroups have been observed in areas of high prey concentration.
The harbour porpoise reaches sexual maturity at five or six years and mates between June andAugust, with a gestation period which lasts 10 to 11 months. Females give birth to a single calfand the interval between births may be up to three years. Harbour porpoises mainly feed onsmall schooling fish species such as herring and sandeels.
There have been dramatic declines in harbour porpoise populations throughout Europe,including those in UK waters. They have now disappeared from the Mediterranean and arerarely seen in the Bay of Biscay, the Channel and southern North Sea1. Elsewhere around theUK they are also becoming rare. For example, there has been a reported 90 per cent reduction insightings off Cornwall during the last 50 years2.
The most recent survey of harbour porpoises in the North and Celtic Seas estimates that thereare some 340,000 animals present. Evidence indicates that these exist in distinct populationsthat show little intermixing, with the result that individual populations are highly vulnerable toextinction if significantly threatened by human activities. By-catch is one of the most seriousthreats, with one study observing a potential annual mortality of 6 per cent of the localpopulation in the Celtic Sea.
Fishing activityLarge numbers of harbour porpoises in the UK become entangled in fishing nets, threateningsome populations with localised extinction. For example, a study into the numbers of harbourporpoises killed as a result of entanglement in bottom set nets in the Celtic Sea observed a by-catch level equivalent to 6 per cent per annum of the total population. If such levels persist, theyare likely to result in the eventual extinction of the population3. It should be noted that thisfigure is based on the take from a single fishery, and the total rate, when other fisheries withinthe area are taken into account, could be even higher4. In the North Sea, survey work hasestimated an annual by-catch of 2 per cent of the population each year – a level which poses asignificant risk to this population5. It is important to recognise that by-catch problems arespecific to certain fishing gear and should be looked at case by case.
A recent study has revealed that by-catch in nets is the most frequent cause of death amongharbour porpoises found washed ashore in England and Wales. Disturbingly, the study also found that the proportion of porpoises killed in this way increased year on year during the studyperiod6.
Prey depletionIn much of the UK’s waters, poor fisheries management has led to the severe depletion of manyfish stocks. Intensive levels of fishing are also believed to produce potentially far-rangingimpacts upon the broader ecosystems of which fish form a part. This can result in a significantdirect or indirect reduction in prey available to high-level predators such as the harbourporpoise. Concerns over the possible ecological consequences of extensive industrial fisheries inthe North Sea, for example, have recently led the UK government to restrict such fisheries –which account for approximately 50 per cent of all fish landed from the region – in certainareas7.
PollutionAs a top level predator, the harbour porpoise is seriously threatened by pollutants that magnifyor accumulate up the food chain. Harbour porpoises tend to favour coastal waters, whereconcentrations of pollutants such as heavy metals and organic compounds are often at theirgreatest, putting the species at serious risk.
Research has identified the Irish Sea as being a “pollution hot spot” for the harbour porpoise.
Significantly high levels of heavy metals such as lead and mercury have been found inporpoises in the Liverpool Bay area8. High levels of DDT, Dieldrin and polychlorinatedbiphenyls (PCBs) have also been detected in porpoises in the Cardigan Bay area9.
There is evidence that pollution can indirectly result in the death of porpoises, so it potentiallyposes a significant threat to their survival. Recent research into harbour porpoises in UK watershas revealed that chronic pollution by PCBs was responsible for suppressing the animals’immune systems, leaving them highly vulnerable to infection and frequently resulting in theirdeaths10. Recent research has also revealed that harbour porpoises living in the Irish Sea havehigh levels of some man-made radioactive elements in their bodies11.
Similar species under threat: bottlenose dolphin, common dolphin, long-finned pilot whale.
The bottlenose dolphin is one of the UK’s best known dolphin species and can live for up to 50years. The species exists in two forms: a larger type that lives offshore and a smaller one thatfavours inshore waters. Irrespective of its type, the bottlenose dolphin is highly social and isusually found in groups.
Bottlenose dolphins become sexually mature at around 12 years for females and 11 years formales. Mating in European waters takes place in the late spring or summer, with a gestationperiod of 12 months. The period between successive births may be between three and six years.
Research into the diet of North Sea bottlenose dolphins shows that they feed mainly on herring,dogfish, haddock, john dory and sole. Invertebrates such as cuttlefish and squid are also knownto form an important part of their diet.
Evidence suggests that the bottlenose dolphin may be in decline in UK waters.
There are three main groups of “resident” bottlenose dolphins: in the Moray Firth, Scotland; inCardigan Bay, Wales; and off the coasts of Devon and Cornwall. The first two groups comprisearound 130 animals, while the latter group is smaller at around 45. As well as these “resident”populations, areas including the Western Isles, the central North Sea and the Celtic Sea are alsoimportant for the species.
The most widely studied bottlenose dolphin population in UK waters is located in the MorayFirth, Scotland. At present the population is estimated to stand at 129 animals12. A recentpopulation analysis found that the bottlenose dolphin population in the Moray Firth may bedeclining by 5.7 per cent per year. If this trend continues, the population could be extinct within50 years13. The model used was intentionally not over-pessimistic, so the rate of decline may beeven greater and the time to extinction even shorter.
There is anecdotal evidence to suggest dolphins elsewhere may be in decline. Whereasbottlenose dolphins were known to inhabit a range of inshore waters and estuaries around theUK, they have either disappeared from these locations or are now rarely seen. For example, theyhave not been observed in the Bristol Channel since the 1940s.
The bottlenose dolphin faces a number of threats common to other small cetaceans in UKwaters. These include: PollutionThe bottlenose dolphin is a top-level predator and is therefore highly vulnerable to pollutantsthat are magnified or accumulate up the food chain. Studies of bottlenose dolphins in UK watershave revealed high levels of pollutants including heavy metals and organic compounds such asPCBs in body tissues. A study in Cardigan Bay, Wales, revealed that a bottlenose dolphinwashed ashore possessed a loading of organo-chlorine compounds that was among the highestrecorded for any marine mammal anywhere in the world14.
Studies of the Moray Firth group have revealed that they have the highest level of skin lesionsfound among any such grouping of the species in the world. Although these lesions are believedto most likely result from natural conditions such as water temperature and salinity, scientistshave not excluded the possibility that pollutants may be acting in combination with naturalconditions to produce epidermal disease in these animals15.
The species is also threatened by marine litter, which can be accidentally swallowed, as well asby noise pollution, which can cause stress as well as interference with echo-location, used bythe species for hunting and navigation.
Incidental captureBottlenose dolphins are known to have become entangled in fishing nets. They are particularlyvulnerable to “set” or “static” gill nets and are also caught in some towed gear, such as certaintrawls. There is insufficient published information to allow the scale of this problem to be fullyassessed.
Depletion of prey speciesCommercial fisheries for species which form an important part of the bottlenose dolphin dietcan result in a significant reduction in the amount of food available to them in specific areas.
This could lead to food shortage for certain populations, leading to possible population declineor movements of populations in search of food.
Similar species under threat: harbour porpoise, common dolphin, long-finned pilot whale.
The cod is one of the most commercially important fish species to be found in UK waters and isat the heart of the UK’s national dish – fish and chips. A cod can live for more than 10 years,grow as long as 1.8 metres and weigh up to 40kg, though such specimens are now rare due tointense fishing pressure.
The cod favours cool temperate water and is found all around the British Isles. In the north-eastern Atlantic its southern limit of distribution is the Bay of Biscay, extending north to thesub-arctic Norwegian waters. Around the British Isles, cod reproduce from the end of January toMarch. Key breeding areas include the mid and southern North Sea, the Bristol Channel, theIrish Channel, and west of Skye. A female cod will produce anything between half a million andnine million eggs during a single season. Cod feed on a wide range of creatures includingshrimp, squid, sandeels, haddock and whiting.
Cod populations in the waters surrounding the UK have undergone a significant and dramaticdecline during the last few decades.
The figures below show that the spawning stock biomass – the amount of fish within apopulation capable of reproducing – has undergone a significant decline since the 1960s in allthe UK’s seas.
Recruitment – the number of newly-hatched fish joining a stock – also appears to besignificantly below what would be expected in many areas. Looking at the UK’s seas on aregional basis: North Sea and Eastern ChannelIn the North Sea and Eastern Channel, despite an increase in the number of mature cod from therecord low observed in the mid 1990s, recruitment of new fish to the stock has been belowaverage since 1987. The number of fish joining the stock in 1997 and 1998 is the lowest onrecord. The International Council for the Exploration of the Sea (ICES), the internationalorganisation responsible for investigating fish stocks in the north-east Atlantic, considers codstocks in these areas to be “outside safe biological limits”. If the situation does not improve,these stocks are in danger of collapse. Fishing has been severely restricted in this area due to thecrisis affecting this fish stock.
West of ScotlandThe number of cod capable of reproducing to the west of Scotland has been declining since theearly 1980s, reaching a record low level in 1999. ICES considers the stock here to be “outsidesafe biological limits”.
Irish SeaThe cod stock in the Irish Sea is also considered by ICES to be “outside safe biological limits”.
Eighty per cent of cod capable of reproducing comprise fish recruited in a single year, leadingICES to predict a continuing serious decline in the stock in the future. Fishing has beenrestricted in this area due to the crisis affecting this stock.
Western Channel and Celtic SeaIn the area of the western Channel and the Celtic Sea, while recruitment of new fish to the stockhas recently been above average, levels of fishing mortality are still high and this stock isconsidered by ICES to be “outside safe biological limits”.
FisheriesThe primary threat to cod in UK waters is undoubtedly over-fishing. A fundamental problemappears to be that ineffective management has failed to control fishing effort, including thenumber and capacity of fishing boats catching cod, in order to ensure that only sustainablelevels of the species are caught. In the North Sea it is estimated that more than 70 per cent ofcod reaching maturity each year are removed16.
As a result of over-fishing, all cod stocks in UK waters are severely depressed and many areclose to collapse.
High fishing mortality is also affecting the genetic make-up of cod stocks by artificiallyselecting smaller fish that mature younger. Fast-growing fish tend to be selectively removedfrom the population, as do those that reach sexual maturity at a later stage in life – large fish donot readily slip through the net and high fishing mortality among young fish means that latematuring individuals fail to reproduce17. This is a trend observed in other cod stocks exposed tointense commercial fishing pressure, such as the north-east Arctic cod which has been shown tohave exhibited a reduction in the mean age of the spawning stock of 2.5 years during the 20thcentury18.
PollutionAt various stages of their life, cod may be vulnerable to the effects of pollution. As highlightedin the section of this report addressing plankton, recent concerns have been expressed about thecombined toxic impacts of PAHs (chemicals released from the burning of fossil fuels) and UV-light upon planktonic cod larvae.
Climate changeIt is believed that both the abundance and composition of plankton in the seas surrounding theUK may have been affected by climate change during the last 50 years. This in turn may have asignificant influence upon the state of fish stocks, including cod19. Climate change maytherefore impact the future distribution and status of cod stocks in the North Atlantic.
Similar species under threat: A recent report by the OSPAR Commission found that 40 out of 60
commercial fish stocks in the North-east Atlantic, including those for haddock, whiting, saithe
and mackerel, are being fished at unsustainable levels.
The common skate is the largest European member of the skate and ray family – a group of fishclosely related to sharks. It can grow to more than two metres in length, weigh up to 100kg andcan live for up to 50 years.
The common skate inhabits areas of soft-sediment seabed at water depths ranging from 5m to600m and mainly feeds on bottom-living animals such as crabs and scallops. It can also move tomid-water to feed on mackerel, herring, whiting, hake and dogfish.
Males mature at approximately 10 years of age, but the age of maturity for females is unknown.
However, it is known that the number of eggs produced by the female is relatively low,amounting to a maximum of around 40 in any one year. These are deposited during the springand summer and it is believed that females may lay eggs as infrequently as once every threeyears.
As the name suggests, the common skate was once found in all UK waters. However, mainly asa result of intense fishing pressure, the species is now so rare that too few are caught by researchvessels to make analysis of population levels possible. The common skate is now believed to becommercially extinct in the Irish Sea and extremely rare in the central and southern North Sea20.
FisheriesThe common skate’s low rate of reproduction and late age of maturity makes it highlyvulnerable to fishing activity. It is now so rare in the UK’s seas that it is scarcely directlytargeted. Even so, it still impacted by fishing activity because it is caught as by-catch byfisheries targeting other species. The fact that the fish is relatively large when mature alsoresults in juveniles having very little chance of reaching maturity in areas that are heavilyfished: even young fish are susceptible to being caught as by-catch.
Because of the threat posed by fishing, it has been suggested that the species may becomebiologically as well as commercially extinct in many areas around the UK21.
Similar species under threat: thornback ray, spotted ray.
The little tern is the smallest member of the tern family to be found in the British Isles,measuring just 23-26cm in length. Visiting the UK during spring and summer to breed, the littletern inhabits coasts and estuaries where it nests by forming a scrape in gravel or shingle shores.
The female lays two or three eggs that are incubated by both sexes for up to 22 days. The chicksfledge 15-17 days after hatching.
The little tern feeds on a range of small fish and crustaceans. Hunting is done alone or in flocksof up to 50 birds. The little tern is generally widely distributed throughout the UK and Ireland,but populations are concentrated in areas where suitable breeding sites are situated. Theseinclude the Dee Estuary, the Thames Estuary, the Tees Estuary, the Wash, Langstone Harbourin Hampshire, and Pagham Harbour in Sussex.
The little tern population in the UK has been in long-term decline since the late 1970s. From apeak population of 2,800 breeding pairs recorded in 1975, it has been falling by an average 1.23per cent each year. The UK population recorded in 1998 comprised just 1,700 breeding pairs,which represents a 40 per cent decline in numbers since 197522.
Although it has been suggested that this decline may partly result from predation by foxes,crows and rats23, human activities are also responsible. These include: DisturbanceLittle terns nest primarily on mainland beaches. The increased use of such sites since the 1960sfor human recreation and development has disturbed little terns while nesting, or has causeddamage to their eggs. This has almost certainly contributed to increased rates of breeding failurein the UK24.
Climate changeAs little terns often nest very close to the high water mark, their eggs and chicks are prone toflooding during extreme tidal and weather conditions. Such flooding is predicted to worsen as aresult of climate change, which will lead to rising sea levels and increasingly severe stormconditions and associated storm surges. It is predicted that there will be at least a 10 per centincrease in the occurrence of summer gales this century due to climate change25. This is highlylikely to increase inundation of little tern nests, as they nest during the spring and summermonths in the UK.
Flooding is likely to be particularly problematic in the little tern stronghold of East Anglia.
Here, rates of sea level rise are predicted to be particularly high, and strong sea defences preventcoastal habitats from re-forming further inshore26. Overall, this threat is likely to result in areduction in breeding sites for the species and increase the vulnerability of those sites thatremain.
FisheriesMany bird species are reliant on fish such as sandeels, which are targeted by industrial fisheriesfor fishmeal and fish oil. Industrial fisheries are now removing significant quantities of suchsmall fish species, which account for about half the tonnage of fish landed from the North Seaeach year27. Concerns that such fisheries are affecting the viability of seabirds and other marineanimals has recently led the UK to close certain areas to industrial fisheries during seabirdbreeding seasons28.
Recent scientific analysis has indicated that as a result of its ecology and behaviour29, the littletern may be highly vulnerable to localised depletion in its food sources, whether these bethrough fishing or other causes.
Similar species under threat: Other seabird species vulnerable to localised depletion of sandeels
in the vicinity of their breeding grounds include arctic terns, common terns, arctic skuas and
black-legged kittiwakes30.
The orange roughy is a deepwater fish usually found at water depths of 1,000m or more. Thespecies is a deep orange-red in colour and has been recorded to grow more than half a metre inlength and 5kg in weight. The orange roughy is extremely slow-growing and long-lived. It maynot become mature until it is 30 years old and may live for up to 100 years. It is believed toproduce a low number of eggs compared with other, shallow sea fish species and it is thoughtthat even when a fish is sexually mature, it does not breed every year.
In the eastern Atlantic the orange roughy is widely distributed from Europe to southern Africa.
The species is found on the continental slope to the west of the British Isles, including theRockall Trough and the Porcupine Sea Bight.
As a result of poor fishing management, stocks of orange roughy are considered by ICES to beover-exploited and “outside safe biological limits”31.
FisheriesThe main threat to this species is from fishing. The orange roughy is late maturing and has a lowrate of reproduction, making it vulnerable to over-exploitation in a short period of time.
In Australia and New Zealand there are well documented cases of stocks of orange roughybeing initially high, only to dramatically decline after a few years. The same pattern is nowoccurring in UK and Irish waters. In the deep-sea area to the west of Scotland, the population oforange roughy was estimated in 1998 to be 73 per cent lower than the virgin unexploited stock.
Catch levels have mirrored this considerable decline in stocks. A French fishery started in 1991peaked at 4,462 tonnes in 1992 but has since declined to around 1,300 tonnes. The orangeroughy stock to the west of Ireland and south-west England declined by up to 76 per cent by199832. These significant declines in stock levels are caused by fisheries that are less than 10years old.
A recent scientific publication has cast serious doubts on the sustainability of fisheries for deep-sea species such the orange roughy. The report identifies these species as being particularlyvulnerable because reproduction levels are so low. There are also few top level predators atthese depths to which fish have had to adapt, making deep-sea fish populations much morevulnerable than other fish stocks to over-exploitation by fisheries. The report concludes thatexploitation of deep water fish should be considered as a mining operation rather than a fishery,and that recovery may not be possible33.
Similar species under threat: blue ling, deepwater monk fish, black scabbard fish, grenadier.
The native or flat oyster is the only oyster species that is native to the UK and Europe. It is atwo-shelled mollusc which favours estuarine and inshore marine habitats. Adult oysters remainattached to the seabed that they settle upon as juveniles and feed by filtering plankton.
Oysters generally become sexually mature in their third year. They are hermaphrodite, andwhile they do not possess both sexes at the same time, they regularly alternate between maleand female. Breeding usually takes place during the summer and larvae develop in the shell ofthe female before being released. They spend around two weeks in the plankton before settlingon the seabed, often in the vicinity of other oysters, and this results in the establishment ofoyster beds.
Since the late 1800s there has been a dramatic decline in the native oyster population in UKwaters. In the last 100 years, commercial production has declined a hundred-fold to the currentlevel of 100-200 tonnes per annum34. The main UK stocks are found in estuarine and coastalareas including the River Thames, the Solent, the River Fal, Pembrokeshire, the west coast ofScotland, the Orkney Islands and Loch Foyle in Northern Ireland.
A number of human activities have contributed to the decline and continuing depressed levels ofnative oysters in UK waters.
Over-exploitationDemand for oysters increased markedly during the 19th century as transport links improvedrapidly with the advent of the railways35. This led to over-exploitation of established oystergrounds, resulting in a catastrophic decline in stocks. It is likely that stocks fell so low thatspawning activity was not high enough to rebuild them. Commercial harvesters also introduceda bigger foreign oyster to replace the native oyster in commercial fisheries.
Introduced speciesA number of other non-native species have been introduced into UK waters, and havesubsequently had a destructive impact upon the native oyster.
The American oyster drill is a sea snail introduced into the UK along with an American speciesof oyster, which was imported to bolster the declining UK native species. It kills oysters bydrilling through their shells and injecting them with poison before consuming them. A singleanimal can consume up to 20 young oysters a day, so the presence of even a small number ofoyster drills can have a serious impact. However, the fact that the species does not produce planktonic larvae has limited its spread in the UK, and it has also been impacted by the toxicTBT chemical used in anti-fouling paint.
The slipper limpet is another alien snail species introduced into the UK. Although it does notfeed on oysters, it is also a filter feeder competing with the oyster for food. In addition, thespecies grows extensively on oyster beds, producing a smothering effect. The presence of theslipper limpet can also result in oyster beds becoming loaded with fine sediment, whichprevents juvenile oysters from settling.
Native oysters have also suffered from the introduction of a parasitic protozoan (a microscopicsingle-celled animal) called Bonamia ostrea. It has killed a large number of oysters acrossEurope and is now found off the coasts of England and Wales. Infection by the parasite causeslesions in the gills and digestive glands of the oyster, leading to its death. Stringent controlconditions have so far limited the spread of this parasite in the UK.
PollutionAs filter-feeding animals, oysters require good-quality water. High levels of pollution in theUK’s coastal waters may have significantly contributed to the decline in oyster stocks during the20th century. Organotin compounds, used in anti-fouling paints on ship’s hulls, have had aserious impact upon oysters, resulting in deformed shells and impairing their ability toreproduce.
Similar species under threat: mussels, cockles, dog whelks.
The Atlantic salmon, often described as “the king of fish”, is distributed in the northern Atlanticarea. It favours temperate waters and is an unusual fish species in that it hatches in freshwater,migrates to the sea, and returns to freshwater to spawn. Spawning occurs during late autumn andearly winter in the UK, after which 90-95 per cent of adults will die without returning to the sea.
The salmon fry hatch from the gravel of the river bed after three or four weeks and will remainin freshwater, feeding and growing, for up to three years. In the spring of their second, third orfourth year the young salmon migrate to the sea. Adult salmon feed on fish and crustaceansduring their time at sea, and are believed to congregate in sub-arctic areas around Norway,Greenland and the Faeroes during the marine phase of their life cycle. The fish can grow to aconsiderable size: the largest so far captured in UK waters, netted in the River Tay, weighednearly 32kg.
The Atlantic salmon is in serious decline. UK river catch figures show that catches havedeclined by 82 per cent in the last 25 years, falling from 12,700 tonnes in 1973 to 2,300 tonnesin 199736. Regional declines have been recorded as follows: • a fall in catches in Scotland, from a peak of more than 2,000 tonnes in 1967, to around 300 tonnes in 1997 – a decline of 85 per cent; • a fall in catches in England and Wales from a peak of approximately 550 tonnes in 1970 to around 150 tonnes in 1997 – a decline of 72 per cent; • a fall in catches in Northern Ireland from a peak of more than 450 tonnes in 1967 to approximately 100 tonnes in 1997 – a decline of 78 per cent37.
During summer 2000 there have been reports of increases in the number of young salmonreturning to UK rivers. Scientists, however, caution that there remains evidence of long-termdecline and these recent reports do not represent a change in the long-term pattern.
While the complex life history of the salmon means that it is vulnerable to threats at variousstages of its life, there is great concern that threats facing the salmon at sea are playing a majorrole in the decline in salmon stocks. ICES estimates there has been a 65 per cent reduction in theabundance of salmon stocks that spend only one winter at sea38.
Climate changeScientists believe that climate change may be a significant cause behind the decline of salmonstocks39. Salmon prefer water at a temperature of between 4° and 10°C and changes in watertemperature as a result of climate change may be reducing the salmon population40. Scientistsbelieve it is also possible that climate change is affecting the wider ecology of the North Atlantic, such as the levels of plankton, which may also be lowering salmon populations41.
Significantly, it is believed that the rate of climate change responsible for these changes isaccelerating42.
Fishing activityInvestigations are being carried out into the by-catch of young salmon in mackerel and herringfisheries in the Norwegian Sea. The levels of catches for these fisheries are so large that even ifa small proportion of the total fish captured consisted of a by-catch of salmon, it could have asignificant impact upon salmon stocks43. There are also some cases of over-exploitation ofsalmon as they return to rivers to breed.
Salmon farmingLarge numbers of Atlantic salmon are intensively farmed in UK waters, particularly in the sealochs of Scotland. The scale and intensity of commercial salmon farming in the UK has resultedin a number of impacts, including: Disease: The intensive, high concentration conditions associated with salmon farming result in a
higher incidence of disease and parasites among farmed fish. This increases the risk of
transmission of diseases to wild salmon. Migrating salmon are extremely vulnerable to attack by
salmon lice, which are often found in high concentrations among farmed fish, and transmission
of these parasites has been linked to the virtual collapse of wild stocks in some rivers44. The
international nature of salmon farming has also meant that diseases previously unknown in the
UK have been introduced into its waters. For example, the highly destructive virus that causes
Infectious Salmon Anaemia (ISA) was recently introduced to farmed salmon in the UK from
Norway. Recent research has revealed that the virus has now been found in wild stocks in
Scotland45.
Interbreeding: There is scientific evidence that escaped farmed fish have interbred with native
stocks in the UK. Given that stocks in individual rivers are genetically distinct, and therefore
adapted for a particular river environment, such interbreeding may harm their chances of
survival.
GM salmon: Genetically modified fish produced in the US have grown almost three times as fast
as non-GM fish46. Trials involving the growing of GM salmon have already been undertaken in
Scotland, although the fish were reared in tanks on land. However, concerns have been raised
regarding the impact GM salmon would have upon wild stocks, were they to be farmed and
subsequently escape. While GM fish are supposed to be sterile, doubts remain over the
effectiveness of this process. There are also concerns that they are genetically manipulated to
grow faster and larger than wild fish, making any escaped GM salmon more attractive as
potential mates to wild fish. If non-sterile GM salmon were to escape to the wild and reproduce,
this could have significant impacts upon the genetic make-up of wild stocks. And if sterile GM
fish make their way into the wild in sufficient numbers, this, too, could damage wild stocks. As
the GM fish are sterile, breeding would not be successful, and the decline in wild stocks would
be compounded.
Pollution: A number of chemicals are used to treat a range of diseases affecting farmed salmon.
Considerable concern has been expressed over the impact of a number of these, including
ivermectin, upon the wider marine environment47. Originally used for treating worms in cattle,ivermectin is now used to treat sea lice, which are a considerable pest to farmed salmon. Thechemical is incorporated into the food fed to fish, so it can enter the marine environment eitherthrough fish faeces or uneaten food pellets. Ivermectin is not only extremely toxic to marinelife, but is also relatively persistent. Tests on the common mussel show that concentrations ofivermectin in the shellfish were 750 times higher than those found in water48. An agriculturalherbicide, Atrazine, has also been shown to impair salmon migrational breeding capability.
Similar species under threat: sea trout.
The term plankton refers to plants and animals (often microscopic) that live in the sea andpossess such limited powers of locomotion they are they are carried along in prevailing currentsand water movements. Plankton is divided into two groups: • Phytoplankton – comprising (usually single-celled) free-floating plants.
• Zooplankton – which are free-floating animals. Zooplankton are further subdivided into two groupings: holoplankton, which are animals spending their entire lives as plankton; andmeroplankton, which are animals spending only part of their life cycle in the plankton, suchas crabs and many fish species.
Plankton is a particularly important group of organisms, as the entire functioning of the world’soceans is almost exclusively dependent upon it. This is because phytoplankton are the mainprimary producers in the oceans: by using photosynthesis they produce energy-rich organiccompounds such as carbohydrates from inorganic chemicals found in seawater. Manyzooplankton derive their energy by feeding upon phytoplankton and are themselves consumedby other animals. Between them, phytoplankton and zooplankton form the basis for complicatedfood webs, stretching all the way up to top carnivores such as the Orca (killer whale).
Phytoplankton act as one of the world’s most important carbon sinks, absorbing approximatelytwo billion tonnes of CO2 each year. It is estimated that the North Atlantic populations absorb10 per cent of this total annual oceanic uptake of CO 49 dioxide into much of the oxygen we breathe via the process of photosynthesis. Planktontherefore plays a pivotal role in maintaining the balance in the global environment andregulating the global climate. Changes in the nature and amount of plankton in the world’soceans could potentially have serious repercussions on their ability to act as carbon sinks, whichin turn may produce significant impacts upon the global climate.
The nature and quantity of plankton in UK waters and the wider north-east Atlantic is subject toa degree of natural variability. However, a number of unusual changes in the abundance anddistribution of plankton have been detected in recent years, with plankton levels declining insome areas and increasing in others. Scientists believe these changes may be linked to human-induced climate change.
Climate changeFor some 50 years, levels and composition of phytoplankton in the north-east Atlantic havebeen monitored by the Continuous Plankton Recorder (CPR) survey. This survey provides a considerable time series by which changes in phytoplankton can be assessed. Analysis revealsthat there have recently been significant changes in the nature and levels of plankton in thenorth-east Atlantic, including the waters of the UK. Results indicate that between 1948 and1995 there has been a growing trend in the average amount of phytoplankton in the North Seaand central north-east Atlantic, and that this increase has been very rapid since the mid-1980s.
At the same time a decrease in the average amount of phytoplankton has been witnessed in thenorthern reaches of the Atlantic between Iceland, Norway and northern Scotland50. It is believedthat these changes are related to changes in weather and oceanic patterns that are being affectedby human induced climate change51.
As well as these changes in phytoplankton abundance, related and rapid changes inzooplankton, fish and benthos (seabed-dwelling creatures) have been observed in the North Seasince 1988 and these have been interpreted as a major shift in the ecology of the area52. It isbelieved that these related changes may also be brought about by climatic change53. Changesassociated with the ecological shift in the North Sea include: • increased levels of phytoplankton colour – an indication of the amount of phytoplankton present – and a greatly extended season of production compared with any period since1946; • changes in the relative abundance of certain copepod species – small crustaceans that form a • changes in other taxonomic components – ie the species present – in the zooplankton, including the nature of decapod crustacean (eg crab and shrimp), echinoderm (eg sea urchinand starfish) and fish larvae; • a significant increase in the levels and distribution of the stock of western horse mackerel in the North Sea. These changes led to catches of the species in the area general area of thenorth-east Atlantic increasing from 40,000 tonnes in 1982 to more than 300,000 tonnes from1990 to 199454.
The observed changes in the North Sea ecosystem appear unique in living or recorded memory,and if the changes observed in the plankton between 1988 and 1994 become established as thenorm, they will have implications for the future management of living resources in the NorthSea55.
The ecological shift in the North Sea has coincided, and may be associated, with the highest andmost positive index of the North Atlantic Oscillation (NAO) for more than a century. The NAOis the dominant mode of atmospheric behaviour in the north Atlantic and western Europe, and ischaracterised by differences in atmospheric pressure as measured in north Atlantic northernlatitudes (in Iceland) and southern latitudes (in Portugal)56. The status of the NAO has apronounced effect upon wind strength, temperature, circulation, wave height and precipitation insurface and deeper waters of the north Atlantic, and all these factors influence the status ofmarine ecosystems. As a result of increased CO2 levels in the atmosphere, it is expected that theNAO will remain in a positive state until at least 204057. This will have pronounced implicationson the status of the following in the north Atlantic: • the nature, abundance and distribution of plankton, which will itself have consequences for all marine species and ecosystems for which plankton form the basis of the food chain,including most commercial fish species such as cod and salmon; • the formation and path of both surface and deep ocean currents. Significant changes are already being observed in current patterns in the north Atlantic as a result of the NAOstatus, and these could ultimately result in the diversion of the Gulf Stream away fromnorthern Europe. Paradoxically, this would mean that global warming would actually resultin a cooler climate regime for the UK, as the warming effect of the Gulf Stream elevates ouraverage temperature in comparison with other regions at the same latitude58. As currentsystems in the Atlantic are intrinsically interlinked with those in the rest of the world’soceans, such changes could have global consequences; • changes in ocean currents and the abundance and distribution of plankton could also potentially influence the ability of the north-east Atlantic to act as a sink for CO2. Forexample, scientists have already predicted that warmer temperatures and increased rainfall,resulting from climate change, will inhibit mixing in the Southern Ocean which surroundsAntarctica, slowing the circulation that carries large amounts of carbon from surface layersto the ocean floor59. The early signals of continuing climate change are likely to becomeapparent first in plankton60.
PollutionThe release of large amounts of nitrogen and phosphorus, through sewage discharge andagricultural runoff, have been shown to have a demonstrable impact upon phytoplankton,increasing production and bloom duration and potentially altering ecosystems. Such an effecthas been observed in a number of estuaries throughout the UK where such discharges areconcentrated, as well as along the coast of south-east England61.
Recent research has indicated that a number of pollutants may potentially have an impact uponplankton at concentrations much lower than was previously believed. Experimental researchinto the effect of polyaromatic hydrocarbons (PAHs) – a chemical released from the burning offossil fuels – has revealed that their toxicity to marine life, especially certain plankton species,may be significantly increased through the exposure of the organism to UV light, for example.
Further research is now being undertaken to establish the degree to which these phototoxicreactions are occurring in marine ecosystems and their subsequent long-term effects uponplankton species.
To illustrate the threat posed to the UK’s marine environment by the introduction of non-nativespecies, the status and impacts of one of these species – wire weed – is assessed.
Wire weed is the common name given to a species of brown seaweed (Sargassum muticum) thatis native to the western Pacific and was introduced to the UK in the 1970s. In its native range,which extends from south-east Asia to the southern Pacific seaboard of Russia, wire weed is notproblematic. However, in many locations, including the UK, where wire weed has beenintroduced, it overgrows and displaces native species. In its native range it does not usuallygrow to more than one metre in length but in the UK it typically grows to four metres and cangrow up to 12 metres. Wire weed is found just below the low water mark but can also grow inareas of standing water such as channels, pools and lagoons62.
Wire weed was first introduced to Europe together with Pacific oysters, which were broughtfrom the US to be cultured. The first recorded population of wire weed in the UK was in 1973off the Isle of Wight63. It continued to spread and populations are now found along the entiresouth coast from Kent to Cornwall. It is also found at Constantine Bay in north Cornwall,around the Channel Islands and the Isles of Scilly, and in Strangford Lough, Northern Ireland64.
Unlike the other species and habitats featured in this report, wire weed presents a threat tonative species and habitats. Once it becomes established at a site, it spreads out over the seasurface, creating a dense canopy. This canopy can impact other native plant and animal speciesby reducing the level of light penetrating through the water and lowering the water temperaturebelow the canopy65. It is believed that this can result in a decline in the number of nativeseaweed species, which can in turn exclude the animal communities that they support66. Fearshave been expressed that wire weed may displace algal species including Laminaria sp.,Cystoseira sp., Halidrys siliquosa and Scytosiphon sp. as well as eelgrass, an important marinehabitat (see Eelgrass Meadows section, page 27).
Research has revealed that wire weed is a “space filler”: it will rapidly move into areas wherepopulations of native species have declined, filling the space before the native species have achance to return67. For example, at Bembridge on the Isle of Wight, wire weed colonised spaceformerly occupied by eelgrass after it died back as a result of frost damage. This prevented theeelgrass from re-establishing itself68. Wire weed can also be a recreational nuisance, formingextensive mats on the sea surface.
Further research is needed into the impacts of wire weed, given the fact that water temperatureappears to be one of the main factors that limits its distribution, and that climate change mayresult in sea temperatures becoming favourable for its establishment further north along Britishcoasts.
Case Study – Wire weed invades Strangford LoughThe most northerly location at which wire weed is recorded in the British Isles is at StrangfordLough, Northern Ireland. This is one of only three National Marine Reserves in UK waters andis also a candidate Special Area of Conservation (cSAC) under the EC Habitats Directive. Thepotential impacts of the seaweed in the lough are therefore serious.
Of particular concern was the discovery of the plant in the Dorn National Nature Reserve,within Strangford Lough, a nature conservation area of prime importance. In common withevery other incident of wire weed introduction in the UK, all attempts to remove it from thelough have failed. Plants have also been discovered at the mouth of the lough, raising concernsthat wire weed could now spread to other coastal areas of Northern Ireland69.
Other alien marine species found in UK watersA report produced by the Joint Nature Conservation Committee, the government adviser onconservation, has catalogued 53 alien marine species introduced into the UK. These range fromplanktonic algae through to worms, crustaceans, molluscs, seaweed and a sea squirt. There areconcerns that a number of these species pose a threat to native marine animals and plants andthat other non-native species will continue to be introduced.
Eelgrass is the term given to a number of marine flowering plants that occupy intertidal and sub-tidal areas of estuaries and coastlines. There are three types of native eelgrass in the UK: dwarfeelgrass, narrow-leaved eelgrass and common eelgrass.
Growing on sand or mud, eelgrass forms dense meadows. More than 78 species (excludingbirds) are associated with eelgrass beds in the UK, but the total number utilising the habitats aresignificantly greater than this70. They include cockles, starfish, sea urchins and seahorses, fishsuch as the bass, two-spot gobie and 15-spined stickleback. Bird species include the whooperswan, widgeon and brent goose.
Eelgrass favours areas sheltered from wave action, so it is typically found in estuaries, inlets,bays, lagoons and sheltered channels. All three species of eelgrass are found throughout the UK,although their distribution is now patchy71.
It has been suggested that until the outbreak of a wasting disease in the 1920s, the vast majorityof mudflats in Britain were “clothed” in eelgrass72. Since then it has declined significantly73.
Only 20 of Britain’s 155 estuaries now possess eelgrass beds of more than 1 hectare in size – apossible decline in 85 per cent of estuaries74. Eelgrass is in serious danger and recoverycontinues to be impeded by a number of threats including pollution, disturbance and climatechange.
DiseaseA wasting disease has had the most significant impact upon eelgrass populations in the UKduring the last 100 years. The disease was most virulent during the 1920s and ’30s, causingeelgrass to decline severely or to disappear completely in many locations. The cause waspositively identified as a fungus only during the 1980s, and it is believed that this may becontinually present in Zostera beds. It is believed that only when other factors, such as pollution,stress the eelgrass that the fungus causes disease75.
Nutrient pollutionNutrient pollution, caused by sewage and fertiliser runoff, can damage eelgrass meadows byaltering the metabolic balance of the plant and encouraging the growth of algae that blankets thebeds.
Other pollutionEelgrass is impacted by other pollutants including heavy metals and organic compounds – anumber of which have been demonstrated to reduce the nitrogen-fixing ability and therefore the growth and viability of eelgrass. Certain herbicides used in anti-fouling paints and agriculturaltreatments have also been found to be harmful76.
DisturbanceVarious human activities including trampling, dredging, coastal defence work, land reclaim,anchoring of boats and certain fisheries methods also threaten eelgrass meadows.
Climate changeFactors associated with climate change, such as increasing sea temperatures, sea level rise andgreater frequency of storm events, threaten to have a significant impact upon the survival ofeelgrass in the future.
The term maerl refers to several species of red algae that produce a branched skeleton ofcalcium carbonate. Although relatively slow-growing, over considerable time periods thesealgae form extensive fields or beds composed of their skeletal structures on the seabed. Theunderlying structure comprises the skeletal remains of the dead algae, with a pink crust of livingalgae occupying the uppermost layer. The species are so slow-growing that some maerl beds areestimated to be more than 8,000 years old77. Live maerl can be found in water as deep as 40m,but is more commonly encountered from 20m depth to the low tide mark.
Maerl favours sites that produce rapid water flow such as tidal narrows, straits or sounds, orwhere there is sufficient wave action to prevent it from being smothered with sediment. Maerlbeds are patchily distributed throughout the UK, being found almost entirely on the exposedwest coasts. In Scotland they are found in the Orkney and Shetland islands and along the westcoast of the mainland. In England, maerl is found in the Fal Estuary and there are reports ofsmaller deposits around the coasts of Dorset, the Isles of Scilly and Lundy Island. In NorthernIreland the most extensive maerl beds are found on the north-east coast.
Maerl beds are a rare but important home to a wide range of other marine species including thecorrugated crab and the imperial anemone. Recent studies on the west coast of Scotland havediscovered a number of species new to science found living in maerl beds. They are alsovaluable nursery areas for a number of commercially exploited marine species78.
Maerl is considered to be of significant conservation importance due its rarity and valuable roleas a habitat for many other species. In the UK maerl is still being damaged and exploited. It isknown to be present in less than 1 per cent of the UK’s inshore waters79.
ExtractionDespite its rarity and conservation value, maerl is still used commercially as a soil conditioner,an additive in animal feed, in water filtration, and in pharmaceutical and cosmetic products80.
Licences have been granted by the Crown Estate Commissioners for the removal of dead maerlin a number of UK locations. The Commissioners are among the authorities that administer theuse of the land that forms the UK’s seabed. Major historic, actual and potential extractionsinclude: • a licence, granted in 1978, to remove 30,000 tonnes a year of maerl from the Fal Estuary, • an exploratory licence to remove 20 tonnes of maerl from the island of Barra, Scotland (this • the experimental removal of 4,000 cubic metres of maerl a year from Wyre Sound, Orkney (this extraction is monitored by Scottish Natural Heritage)81.
Given the sensitivity of the species to extraction, there is now a predisposition by regulatoryauthorities not to issue further or renew existing extraction licences, and any further applicationswill be subject to environmental assessment82. Even so, evidence suggests that illegal maerlextraction has recently taken place in some parts of the UK.
Removal of live maerl is extremely damaging, as this makes it harder for the bed to regenerate.
Dredging of dead maerl can also be harmful as sediment plumes generated by extraction cansmother and damage adjacent live maerl beds.
Case Study – Fal EstuaryDead maerl has been extracted from the Fal Estuary since 1975. It is believed that plumes ofsediment generated by dredging could cause smothering of live maerl at the nearby St MawesBank. In an attempt to counter this problem, dredging is done on the ebb tide, so that the plumeis taken out to sea. However, survey work shows that between 1982 and 1992 the proportion ofdead maerl on St Mawes Bank increased significantly from 12 per cent to 23 per cent, althoughit is not known if this reduction is related specifically to dredging83.
Dredge fisheriesDredging for mollusc species such as scallops or razor shells can remove live maerl from thesurface of beds, together with other algal species that help to stabilise these beds.
Case Study – Firth of ClydeScallop dredging takes place in the upper Firth of Clyde where maerl beds are comparativelyrare. Research has revealed that the passage of dredges has not only destroyed large animals andalgae associated with the beds, but has also released sediment into the water, which laterresettled, causing stress to filter-feeding animals and reducing the ability of algae tophotosynthesise. Furthermore, dredge teeth were seen to have penetrated up to 10cm into themaerl bed, crushing and burying the maerl fragments which resulted in the death of living maerlalgae. Some months after dredging took place, it was observed that there was less than half asmuch live maerl as was present in an un-dredged control area. The study concluded that theimpact of scallop dredging on maerl beds was extremely serious, compromising the integrityand future recovery of the habitat84.
Fish farmingThe positioning of fish farms above maerl beds can result in the deposition of waste materialsonto the beds, producing anoxic conditions and significantly reducing the amount of lightreaching living maerl algae. Monitoring of a salmon farm anchored over a maerl bed in Shetlandrevealed that anoxic conditions developed during the course of a 10-year period85.
Construction, agricultural and sewage dischargesCoastal construction activity, including sea defences, results in increased amounts of sedimentin the water, which can smother living maerl. Sewage discharge and certain agriculturalpractices result in increased levels of sediment in rivers and coastal waters, which also smothermaerl and reduce the level of light available to it. Nutrient pollution, resulting from the discharge of agricultural and sewage waste, can have a similar impact by promoting the growthof other algal species on the living maerl.
Mudflats are intertidal areas comprising fine silts and clays and are located in sheltered coastalareas such as estuaries. They are among the most productive ecosystems on Earth.
Species that live on mudflats include cockles, mussels, snails, worms, crabs, shrimps and sandhoppers. These animals provide food for a large number of wildfowl such the brent goose,shelduck, pintail, oystercatcher, ringed plover, godwit, curlew, redshank, knot, dunlin andsanderling86. They also provide an important food source for a range of fish species, includingplaice, sole, flounder and dab. Mudflats are also vital nursery areas for a number of these fishspecies. UK mudflats are internationally important due to the habitat they provide for wildfowland wading birds.
Mudflats are widespread in UK estuaries, with important sites located in areas such as theWash, the Solway Firth and Strangford Lough. It has been estimated that intertidal mudflatscover 270,000 hectares87, but they are under threat and in decline. At least 25 per cent of theUK’s mudflats have already been lost to land claim, many are subject to damaging levels ofpollution and a further decline is expected as a result of climate change.
Climate change and sea level riseOne of the greatest threats to mudflats is sea level rise as a result of climate change. This threatis magnified by sea defences around many of the UK’s estuaries, which stop important coastalhabitats such as mudflats from moving back as sea levels rise. Mudflats are therefore beingsqueezed out. At least 8,000 hectares of mudflats are expected to be lost as a result of sea levelrise during the next 10 years88. Impacts are likely to be greatest in south-east England, althoughother areas such as Scotland’s firths will also be affected89.
Land claimMany areas where mudflats are located, such as estuaries, have also been developed as centresof economic and industrial activity. This has led to mudflats being reclaimed for development.
Although the rate of land claim has now reduced, 25 per cent of the UK’s estuarine mudflatshave already been destroyed as a result. In some estuaries, land claim has had a severe impact.
For example, there are no longer any intertidal mudflats in the Tyne Estuary, and the Tees haslost 80 per cent of its intertidal area90. Such losses reduce the productivity of the estuary91:research shows, for example, that land claim in the Forth Estuary has removed 24 per cent offish habitat and 40 per cent of their food supply92. The removal of mudflats in the late 1980s forthe development of the port of Felixstowe also resulted in the loss of important feeding groundsfor fish and waterfowl93.
FisheriesCertain types of fishing activity can significantly damage mudflat animal communities. Mostprominent among these is suction dredging, used to obtain various shellfish species such ascockles. This activity kills a significant number of non-target species and also destabilises thestructure of the mudflats. Tractor dredging for cockles is considered so damaging that it hasbeen banned in Scotland – but it still continues in England and Wales.
DredgingIn a number of coastal and estuarine areas, dredging is done to maintain navigational routes forshipping. This can cause damage to both mudflats and their animal communities.
PollutionMudflats in estuaries are often contaminated by a range of pollutants, including persistentorganic compounds, heavy metals, sewage and agricultural runoff. Of particular concernrecently are the impacts on mudflat-dwelling species of pollutants that can disrupt hormonesystems.
Case Study – Sex-change flounderA recent study of the common flounder, a common species of flatfish in UK estuaries, foundthat many are suffering from “intersex” – that is, male fish have developed female sexualcharacteristics94. The research found that in 11 major estuaries, including the Tyne, Tees,Mersey and Wear, male founder were producing high levels of a protein called vitellogenin(VTG) which is a precursor to egg production. In many cases they were producing more of thisprotein than female flounder. Male fish in the Mersey and Tyne had even begun to develop eggsin their testes. In the most contaminated estuaries, these changes in the sexual characteristics ofthe male flounder are thought to seriously impair their reproductive ability. Further research isrequired to identify which chemicals are causing these impacts, but it is thought that there is arelationship between the occurrence of “intersex” in flounder and the levels of industrialeffluent in the estuaries95.
In the UK, the term “reef” refers to areas of hard substrate, usually rising from an area ofsurrounding soft sediment, that is either continually covered by seawater, or may be partlyexposed at low tide. Reefs are composed either of rock, varying in composition and thereforehardness depending upon the local geological conditions, or they may be biogenic in origin –that is, produced by living organisms. As soft sediments dominate the UK seabed, reefs providean important habitat for a range of marine organisms.
Where rocky reefs receive sufficient exposure to light, the dominant habitat is the kelp forest.
Kelp is large brown algae which grows on hard substrate, and when occurring in stands –termed forests – it is highly important, as these represent possibly the most ecologicallydynamic and diverse habitats on the planet96. Kelp forests are highly productive, providing asource of food not only for the animals that live among them, but also for most animals in thesurrounding areas97. More than 860 species are associated with the five different kelp groupingsidentified in UK waters by the Joint Nature Conservation Committee98.
In addition to those formed geologically from rock, several examples of biogenic reefs arefound in UK waters. These solid, large areas of hard substrate produced by animals include: • colonies of tube-forming worms, including Sabellaria alveolata and Serpula vermicularis;• dense beds of the common mussel (Mytilus edulis) or the horse mussel (Modiolus • the deep-water, colonial, bank-forming coral Lophelia pertusa.
Many of these biogenic reefs support a huge range of species. For example, a study of the deep-water coral Lophelia pertusa, around the Faeroe Islands, revealed a diversity of associatedspecies similar to that found in some shallow water tropical coral species99.
A number of serious threats are facing reefs around the UK, especially biogenic reefs. Manycontinue to be degraded and destroyed, and are particularly at risk from fishing activity and oiland gas exploration.
Fishing activityThere is evidence that heavy towed fishing gear and shellfish dredges have caused seriousdamage to reef communities. Biogenic reefs are particularly at risk. For example, the Sabellariatube worm reefs in Morecambe Bay are believed to have been destroyed by a pink shrimpfishery and there is no sign of recovery100. There is also evidence that deepwater Lophelia coralreefs have been and continue to be damaged by fishing activity101.
Dredge fisheries for scallops and queen scallops have also been identified as causingwidespread and long-term damage to horse mussel reefs in Strangford Lough and to the south-east of the Isle of Man. It is highly likely that similar damage is occurring to horse mussel reefselsewhere in UK waters.
There is great concern over the potential damage that fishing for queen scallops in Loch Creren,Scotland, may have upon the extremely rare and highly fragile Serpulid reefs located there.
These reefs, produced by tube-forming worms, are a major world site for biogenic structuresproduced by this species102. Trawling for queen scallops is known to have taken place in theloch,103 and an area of reef has already suffered damage as a result of discharge from an adjacentalginate factory.
Oil and gas exploitationOil and gas exploitation can cause significant damage to reef communities through the releaseof toxic chemicals and the discharge of drill cuttings. As oil and gas operations move intodeeper water, particular concern has been expressed over the threat to Lophelia coral reefs.
AquacultureThe UK has an extensive aquaculture industry, predominantly based upon the west coast ofScotland. Concerns have been raised about reef communities being damaged by the release ofwaste products and chemicals from cages located above reefs.
Aggregate extractionCertain biogenic reefs, such as those created by the tubeworm Sabellaria, occur in the vicinityof marine aggregate deposits. Aggregate dredging threatens to damage these reefs.104 Saltmarsh refers to the habitat formed by vegetation covering intertidal sand and mudflats.
Important plant species comprising saltmarsh include sea grass, cord grass, common reed andsea-club rush.105 Saltmarsh favours areas that are relatively sheltered from wave action andstrong water movement, so it is typically found in estuaries, saline lagoons and at the heads ofsea lochs.
Saltmarsh provides an extremely important habitat for a range of animal species, especiallywading birds and wildfowl including the brent goose, shelduck, redshank and snipe. They arealso important feeding sites for many migrating bird species and nursery areas for a range offish species such as mullet, bass and plaice.
More than 200,000 hectares of saltmarsh used to exist along the coasts of England and Walesbut there are now only 45,000 hectares left in the whole of the UK – a decline of more than 75per cent.106 Saltmarsh faces a number of serious threats including land claim, climate changeand pollution.
Land claimLand claim – where a marine area is reclaimed for agricultural or industrial use – has led to theloss of a large area of saltmarsh. Large-scale land claim stopped only relatively recently afternearly 1,000 hectares of saltmarsh were destroyed in the Wash in the 1970s107. Small-scalereclaim for projects such as port development, transport, waste disposal and marina constructionis still a threat to saltmarsh and continues to contribute towards its decline.
Climate change and sea defencesSea levels in the UK have risen and will continue to rise as a result of climate change, posing aserious threat to the survival of saltmarsh habitat. The presence of sea defences aroundsignificant areas of the UK coast compounds the problem by preventing saltmarsh from movinginland as sea levels rise. The habitat is therefore squeezed out. Climate change is also expectedto increase the intensity and frequency of erosive storm events, further threatening saltmarshand the many species that depend on it. Loss of saltmarsh is accelerating, particularly in thesouth-east of England, and it is estimated that at least another 6 per cent of saltmarsh habitat willbe lost over the next 20 years, due to climate change and coastal squeeze alone108.
PollutionVarious forms of pollution are damaging saltmarsh habitats. For example, nutrient pollutionresulting from sewage effluent and agricultural runoff has resulted in problematic algal growthat some sites.109 A study of pollutants threatening saltmarsh along the Essex coast provides an example of the chemicals to which such a habitat may be exposed. They include PCBs, DDT,Lindane, Dieldrin, Atrazine, Simazine, mercury, cadmium, lead, zinc and arsenic. All thesepollutants are known to be highly toxic, with some also having bio-accumulating tendencies.
Their presence could therefore potentially have a harmful impact upon the fauna and flora of thesaltmarsh and they may eventually be released into the wider marine environment througherosion.110 Subtidal sand and gravel, found below the low tide mark, form the most common habitatsencountered in UK marine waters. Present all around the UK, the geological nature of thehabitats assumes a rough east-west divide, with sand and gravel to the south and west of the UKbeing mostly derived from shells, and those from the east formed from rock material.
There are at least 13 types of sand and gravel biotopes found in the UK. These support a widerange of marine species including worms, crabs, sea anemones, molluscs, razor shells, whelks,sea urchins, sea cucumbers and starfish. They are also crucial nursery areas for a number ofcommercial fish species such as flatfish and bass.111 Due to the high number of species theysupport, they are considered to be of international conservation importance.
Sand and gravel habitats and their communities are known to be seriously damaged by a numberof activities, including fishing and aggregate (sand and gravel) extraction. Damage fromaggregate extraction is predicted to increase.
Aggregate extractionThe demand for aggregate in the UK is high, as it is used in most construction projects. Some20 per cent of the UK’s total demand for aggregate is met through material extracted from themarine environment, and the UK government is looking to increase this total to 32 per cent by2006112 – an increase in aggregate extracted from the sea of 60 per cent. Around 1,652km2 ofthe UK seabed is presently licensed for aggregate extraction.
It is predicted that the overall requirement for marine aggregate will rise, with a projectedaverage annual demand between 1996 and 2015 forecast as being 38.3 million tonnes per year.
This represents a 63 per cent increase on the average annual amount extracted between 1989and 1996113. In addition to supplying aggregate for construction, substantial quantities of sandare also removed to replenish beaches that have been eroded, and demand is likely to increase asrates of erosion increase due to climate change-related matters.
Marine sand and gravel is not just an aggregate; it is also an important wildlife habitat.
Removing the sand and gravel also removes this habitat and can cause substantial damage to theanimal communities it supports.114 An experimental study into the impacts of sand and gravelextraction off the Norfolk coast shows that some 50,000 tonnes were removed to a depth of30cm from an area of seabed covering some 150,000m2. Surveys immediately after dredgingrevealed that animal populations were substantially reduced in numbers, variety and totalweight. Even some three years after dredging, further survey work revealed that the abundance of animals was still significantly lower than had been recorded at an adjacent, un-dredged,reference site.115 Fishing activitySome fishing methods involve the towing of heavy gear over the seabed – a practice thatdisturbs sand and gravel habitat and causes serious damage to the number of species it supports.
Fragile or large-bodied, slow-growing animals are most at risk of damage, and when thishappens, populations may be slow to recover.116 In certain areas of UK waters, shellfish speciesassociated with sand and gravel habitats, such as the scallop, may be exposed to significantfisheries pressure, which may have potential implications on stock viability on a local orregional level.
PollutionSpecies and communities associated with sand and gravel habitats are exposed to a range ofpollutants including heavy metals, sewage, agricultural runoff and hormone disruptingchemicals.
Because contamination is frequently caused by land-based sources, it is generally assumed thatpollution decreases away from the shore. But several studies show that in the case of certainheavy metal pollutants, this may not be the case. In the Dogger Bank area of the North Sea,concentrations of some pollutants may be comparable with those found in industrialisedestuaries and coastal waters.117 High levels of lead and cadmium have been found in sea urchins,hermit crabs, worms, starfish and shrimps in this area.118 The damage and threats to these species and habitats indicate that the health of the UK’s marine
environment is deteriorating. Rapid action is needed to help our marine life recover. Because the
number of threats facing these species and habitats is so vast, it is not possible in this report to
discuss all the solutions that are needed to address them. However, as part of WWF’s Oceans
Recovery Campaign (ORCA), WWF is pointing to a number of solutions that will help to
kick-start this recovery.
Hundreds of different laws and policies govern our seas – but they frequently conflict with each
other. WWF wants the Westminster government, the Scottish parliament, and the National
assemblies of Wales and Northern Ireland, to introduce an ‘eco-system’ approach to the
management of the oceans. This will require co-ordinated legislation – an Oceans Act – in
order to provide the best legislative support for protecting and managing our precious marine
environment, for the benefit of wildlife and coastal communities.
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Cons. Ciem. vol 46 no 3 Kirkwood, J K, Bennett, P M, Jepson, P D, Kuiken, T, Simpson, V R, Baker, J K, 1997,“Entanglement in fishing gear and other causes of death in cetaceans stranded on the coasts ofEngland and Wales”, The Veterinary Record, 141 Langston, W J, Burt, G R, and Pope, N D, 1999, “Bioavailability of Metals in Sediments of theDogger Bank (Central North Sea): A Mesocosm Study”, Estuarine, Coastal and Shelf Science,1999, 48, 519-540 Law, R J, Jones, B R, Baker, J R, Kennedy, R, Milne, R, Morris, R J, 1992, “Trace Metals in theLivers of Marine Mammals from the Welsh Coast and the Irish Sea”, Marine Pollution Bulletinvolume 24 no 6 pp. 297-304 Leggett, D, Bubb, J M, & Lester, J N, 1995, “The Role of Pollutants and Sedimentary Processesin Flood Defence. A case Study: Salt Marshes of the Essex Coast, UK”, EnvironmentalTechnology, vol 16, pp 457-466 MAFF, 1999, Saving Seabirds and Conserving Fish Stocks: Restriction on Industrial Fishing,MAFF press release 446/99 – (14/12/1999) MAFF/The National Assembly of Wales, 2000, Salmon and Freshwater Fisheries Review,MAFF. Lowestoft Matthiessen, P, Allen, Y T, Allchin, C R, Feist, S W, Kirby, M F, Law, R J, Scott, A P, Law, RJ, Scott, A P, Thain, J E, Thomas, K V, 1998, Oestrogenic Endocrine Disruption in Flounder(Plaitichthys flesus L.) from United Kingdom Estuarine and Marine Waters, CEFAS TechnicalReport No 107 McLay, M. Gorden-Rogers, K. (1997) Report of the Scottish Salmon Strategy Task Force.
Scottish Office Agriculture, Environment and Fisheries Department. Edinburgh Merret, N R, & Haedrich, R C, 1997, Deep-sea Demersal Fish and Fisheries, Published by TheNatural History Museum/Chapman & Hall, London Mills, D H, Hadoke, G D F, Read, J B D, 1999, Atlantic Salmon Facts, Atlantic Salmon Trust.
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Tubbs, C R, 1995, “The Meadows in the Sea”, British Wildlife, 6. 351-355 UK Biodiversity Group, 1999, Tranche 2 Action Plans – Volume V – Maritime Species andHabitats, English Nature, Peterborough The Wildlife Trusts and WWF-UK, 1998, Joint Marine Programme Background Paper onMarine Aggregate Extraction, WWF-UK/Wildlife Trusts Wilson, B, Arnold, H, Bearzi, G, Fortuna, C M, Gaspar, R, Ingram, S, Liret, C, Pribanic, S,Read, A J, Ridoux, V, Schneider, K, Urian, K W, Wells, R S, Wood, C, Thompson, P M,Hammond, P S, 1998, “Epidermal Diseases in Bottlenose Dolphins: Impacts of Natural andAnthropogenic Factors”, Proceedings of the Royal Society of London – B – 266 1 Cornwall Wildlife Trust, 19992 Simmonds, M, Irish R, and Moscrop, A, 19973 Ibid4 Cornwall Wildlife Trust, 19995 OSPAR (In Press)6 Kirkwood, J K, Bennett, P M, Jepson, P D, Kuiken, T, Simpson, V R, Baker, J K, 19977 RSPB (undated)8 Law, R J, Jones, B R, Baker, J R, Kennedy, R, Milne, R, Morris, R J, 19929 Morris, R J, Law, R J, Allchin, C R, Kelly, C A, Fileman, C F, 198910 Jepson, P D et al, 199911 Berrow, S D, Long, S C, McGarry, A T, Pollard D, Rogan, E, and Lockyer, C, 199812 Sanders-Reed, C A, Hammond, P S, Grellier, K, Thompson, P M, 199913 Ibid14 Morris, R J, Law, R J, Allchin, C R, Kelly, C A, Fileman, C F, 198915 Wilson, B, et al, 199816 Gislason, H, 199517 OSPAR (In Press)18 Ibid19 Reid, P C (In Press)20 UK Biodiversity Group, 199921 Information for this section of the report was obtained from UK Biodiversity Group, 199922 Ratcliffe, N, Pickerell, G, Brindley, E (In Press)23 European Commission Environment Directorate (undated)24 Ratcliffe, N, Pickerell, G, Brindley, E (In Press)25 Environment Agency, 199926 Norris, K J, and Bussion, R, 199427 RSPB (undated)28 MAFF, 199929 Furness, R W, & Tasker, M L, (In Press)30 Ibid31 UK Biodiversity Group, 199932 ICES, 200033 Merret, N R, & Haedrich, R C, 199734 UK Biodiversity Group, 199935 Ibid36 Mills, D (ed), 200037 Mills, D H, Hadoke, G D F, Read, J B D, 199938 Mills, D (ed), 200039 Ibid40 McLay, M. Gorden-Rogers, K. (1997)41 Mills, D (ed), 200042 Ibid 43 MAFF/The National Assembly of Wales, 200044 Mills, D H, Hadoke, G D F, Read, J B D, 199945 Scottish Executive, 199946 Cook, J T, Sutterlin, A M, MacNiven, M, (undated)47 Grant, A, & Briggs, A D, 199848 Ibid49 Hengeveld, H, (undated)50 Reid, C R, Edwards, M, Hunt, H G, & Warner, A J, 199851 Ibid52 Reid, C R, Planque, B, & Edwards, M, 199853 Ibid54 Reid P C, de Fatima Borges, M, and Svendsen, E, (In Press)55 Ibid56 Reid, P C (In Press)57 Ibid58 Ibid59 Hurley, B, 199860 Reid, P C (In Press)61 OSPAR, 199962 Davison, D M, 199663 Ibid64 Ibid65 Ibid66 JNCC, (undated)67 Davison, D M, 199668 Ibid69 Northern Ireland Information Service, 199870 Davison, D M, Hughes, D J, 199871 Ibid72 Tubbs, C R, 199573 Davison, D M, Hughes, D J, 199874 Tubbs, C R, 199575 Davison, D M, Hughes, D J, 199876 Ibid77 Birkett, D A, Maggs, M J, Dring, M J & Boaden, P J S, 199878 Ibid79 UK Biodiversity Group, 199980 Ibid81 Ibid82 Crown Estate Commissioners (personal communication). E-mail received from Georgia Markwell, 12 May 200083 Colin Speedie (personal communication)84 Birkett, D A, Maggs, M J, Dring, M J & Boaden, P J S, 199885 Ibid86 Ibid87 Elliot, M, Nedwell, S, Jones, N V, Read, S J, Cutts, N D, Hemingway, K L, 1998 88 UK Biodiversity Group, 199989 Ibid90 Ibid91 Environment Agency, 199992 UK Biodiversity Group, 199993 Elliot, M, Nedwell, S, Jones, N V, Read, S J, Cutts, N D, Hemingway, K L, 199894 Ibid95 Matthiessen, P, et al, 199896 Ibid97 UK Biodiversity Group, 199998 Birkett, D A, Maggs, M J, Dring, M J & Boaden, P J S, 199899 Ibid100 Jensen, A & Frederiksen, R, 1992101 UK Biodiversity Group, 1999102 Dr A Rogers, Southampton Oceanographic Institute, (personal communication), e-mail 21 June 2000103 Moore, C G, Saunders, G R, Harries, D B, 1998104 Alistair Davison, WWF Scotland (personal communication)105 Holt, T J, Rees, E I, Hawkins, S J, and Seed, R, 1998106 Environment Agency, 1999107 UK Biodiversity Group, 1999108 Ibid109 RSPB, 1998110 UK Biodiversity Group, 1999111 Leggett, D, Bubb, J M, & Lester, J N, 1995112 UK Biodiversity Group, 1999113 Environment Agency, 1999114 Ibid115 The Wildlife Trusts and WWF-UK, 1998116 Crown Estate, 2000117 UK Biodiversity Group, 1999118 Langston, W J, Burt, G R, and Pope, N D, 1999119 Ibid

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