ARCHIVE FACTSHEET No. 1
DESCRIPTIONS OF SHELLFISH TYPES
Lobsters: the lobster belongs within a large class of invertebrate animals called Crustacea. Crustacea which are destined for human consumption are usually called ‘shellfish’, because of their hard external shell (exoskeleton). A characteristic of crustacean is that they shed their hard external skeleton at intervals in order to grow, (known as moulting). The claws of the lobster are used for feeding, with one claw shaped for crushing, the other for cutting.
Lobsters have a ‘head’ (carapace) containing most of the animal’s viscera (heart, digestive organs, sex organs), and a ‘tail’ (abdomen) containing the intestine and anus. The eye, mouth parts and brain (cerebral ganglion) are found beneath the carapace. However, lobsters do not have a centralized brain area as mammals do. Instead they have large ganglia (a large cluster of nerve cells, approximating to a brain), above and below the mouth, and smaller ganglia at each segment in the body. It is possible that the lobster feels pain at any one of these points. The central nervous system is a nerve cord that lies along the ventral midline, quite close to the shell. The five pairs of legs attached to the body below the margin of the carapace are a feature of the group of crustacean known as the Decapoda (ten-legged). This group includes most of the commercially exploited species of crustacean such as crabs and prawns.
Lobsters have been know to live for up to 100 years in the wild and can cover more than 100 miles each year, using complicated systems to explore and establish social relationships. They tend to feed on the ocean bottom, and their bodies often have high concentrations of heavy metals such as lead and mercury.
The two most important species of clawed lobster are Homarus Gammarus, the European lobster, which can be found in the Eastern Atlantic waters from the Arctic Circle to the Mediterranean, the British Isles being the centre of distribution, and Homarus Americanus, the American lobster, found on the eastern seaboard of North America from Newfoundland down to Delaware. Although similar in appearance, there are differences, both in colour and in habits.
European lobster: has no spine (sharp points, not to be confused with vertebrae) on the lower rostrum margin (area beyond the eye); the claws (Chelipeds, which are a modified fist) have spines (sharp points) white or white-tipped, with the underside of the claw creamy white or very pale red.
American lobster: has a well-developed spine on the lower rostrum margin, the claw spines are red or red-tipped and the underside of the claw is orange/red.
Rock lobsters (or spiny crayfish, Panulirus, Palinurus and Jasus) differ from the other Decapod crustacea in having spiny antennae, possibly compensating for the lack of the strong claws seen in crabs and more familiar crayfish.
Crayfish: Up until the 1980s the native British crayfish were once widespread in most river catchments in the North and south Wessex and were also found in Devon, but there has been a drastic decline in recent years, largely due to a crayfish plague, carried by the American signal crayfish. They are now known only to occur in the Bristol Avon catchment (North Wessex) and the rivers Ebble, Stour and Piddle (South Wessex). Native crayfish grow to approximately 10cm in length. Signal crayfish are now farmed extensively for the haute cuisine market.
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Crabs: Crabs, like lobsters, are complicated and their sensory organs are highly developed. They have two main nerve centres, at the middle front and at the rear, and their responses to certain stimuli are immediate and vigorous. Some feed on molluscs, some live in discarded mollusc shells and some, such as the spider crab, who feed off dead fish, grow to have a body the size of a man’s hand and have a 3 metre leg span. Crabs can shed their claws in response to a stressful or dangerous situation.
Like lobsters, crabs shed their shells each time they grow, leaving their bodies soft and extremely vulnerable to predators. Most crabs crawl into a crevice, pump themselves up with water, and then wait until the new shell is hardened. However, the spider crabs huddle together in large gangs. According to Dr. Ken Collins of Southampton University’s oceanography centre, the large males moult first and lie on top of the pile, allowing the smaller ones to shed their shells in safety underneath. Unlike other varieties, spider crabs are rarely eaten in Britain, but are considered a delicacy in France and China.
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THE SMALLER CRUSTACEA
Prawns: these animals hide in individual holes on the sea bed. In the UK, the main breeding grounds are in Scottish waters. Many prawns are now farmed, and in the third World the promotion of intensive prawn aquaculture in mangrove forests has proven to be a most destructive activity in the mangrove ecosystems in many countries, including Thailand, the Philippines, Indonesia, Ecuador and others. Large tracts of mangroves are cut down to make way for the ponds where prawns are raised for export. Many of these creatures end up in the US market. The vast trade in ‘black-tiger’, ‘jumbo’ and ‘white’ prawns is contributing to the downfall of mangrove forests and wildlife.
Shrimp: these are of the genus Crangon and are closely related to the prawn. They are long tailed, long legged, chiefly marine crustacea. The Common Shrimp inhabits the sand on the coasts of Great Britain.
MOLLUSCS
The dictionary definition of shellfish is ‘sea animals covered with shell’, and therefore molluscs are included in this category. Most molluscs are free-living in marine environments but there are some who prefer to burrow, attach themselves to rocks or to crawl. There are also some who live in freshwater.
The body of the mollusc is covered by a shell, attached at various sites. A fluid-filled cavity between the animal and the shell is where mineral deposits gather and calcify, continuing the shell-forming process. Molluscs have a muscular foot, for crawling, a head, a tongue-like structure, eyes, tentacles and sensory organs. They also have a heart, gills and an intestine. Research has shown that even the ‘simplest’ invertebrates exhibit responses to averse stimuli (dangerous or painful situations). Creatures included in this research are sea anemones, earthworms, medicinal leeches, insects, gastropod snails and cephalopod molluscs, such as the octopus. Many scientists suggest that it should be assumed that they are capable of feeling pain, and their well-being should therefore be promoted.
Animals in this category include: mussels, oysters, winkles and limpets ( a gastropod, which has only one shell and can stick its head and foot out at the same time to move and feed. Bivalves have two shells, hinged together). Limpets change from male to female with age, can live for 20 years and eat by scraping algae from the rocks.
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Sources:
- Storage and Care of Live Lobsters, MAFF, (now DEFRA) laboratory leaflet 1991.
- Killing Rock Lobsters for Human Consumption. Report to the RSPCA. Brian Paterson. Dec. 1990. (International Food Institute of Queensland).
- Jaren G. Horsley, Ph.d. Letter to People for the Ethical treatment of Animals (PETA). June 1993.
- Dr. Diane Cowan. Woods Hole USA.
- Catching, Handling and Processing Crabs. MAFF advisory note 1987.
- Animal Welfare Unit, New South Wales Agriculture.
- Humane Killing of Animals. Universities Federation of Animal Welfare (UFAW) 1988.
- The Humane Killing of Lobsters and Crabs. John R. Baker D.Sc. (Oxon) FRCS. 1975.
- International Primate Protection League (IPPL). August 1993.
- Oxford English Dictionary.
- A Question of Pain in Invertebrates. Institute of Laboratory Animal Resources USA. Dr. Jane Smith. Spring 1991.
- ‘Go Green’ C4 Teletext. 1997.
ARCHIVE FACTSHEET No. 2
METHODS OF TRAPPING
Lobsters are caught in traps, and any trap lost is considered to be ‘ghost’ fishing.
There are four types of trap:
1: Parlour pots and 2: the pot lock – these are sophisticated traps from which it is difficult for the shellfish to escape, as they have one or sometimes two inner chambers.
3: Creel and 4: Inkwell pots – these are more traditional types and easier for escape.
So called ghost fishing is a major problem around the UK coastline (see https://www.ghostfishing.co.uk/) This includes lobster and crab traps that continue to catch these animals after these traps are lost.
Crabs:
These are also often caught in pot traps, but may also be caught in nets.
Under current UK laws, fishermen can legally remove both claws and then put the animal back into the sea ( See https://www.sciencedaily.com/releases/2007/10/071007210836.htm#:~:text=of%20one%20claw.-,The%20future%20sustainability%20of%20fishermen%20who%20declaw%20edible%20sea%20crabs,questioned%20by%20a%20Queen's%20academic.&text=Under%20current%20UK%20laws%2C%20fishermen,high%20mortality%20rate%20for%20crabs.)
Shellfish general:
Many other species of shellfish are also caught in the traps or nets.
ARCHIVE FACTSHEET 3 : METHODS OF TRANSPORT AND STORAGE
The Welfare of Animals (Transport) (England) Order 2006 is supposed to protect all “cold-blooded invertebrate animals”. This order requires that the transport of these animals should not cause them injury or unnecessary suffering. However, the stipulations of this order seem to be more often ignored than adhered to.
It would, of course, be better that these animals were not transported at all. However, In order that crustacea are housed and transported in conditions that cause less stress, it is essential that there should be:
(a)proper water temperature control;
(b)adequate aeration;
(c)suitable water quality;
(d)only compatible species kept together.
Methods to help to maintain these conditions are water purification and filtration systems and suitable water-testing procedures.
Live crabs should be handled as little as possible after capture, and the claws will be shed if the crab is removed from the trap or net by them. The crabs must never be left exposed on deck as sun and wind may kill them.
Prawns: One method used for the transportation of prawns is in plastic tubes. It seems that, although the tubes are open-ended, the prawn stays inside of its own accord, as though it were hiding on the sea bed.
.Sources:
- MAFF (DEFRA): Catching, handling and processing crabs. Note 1987.
- MAFF (DEFRA): Storage of Lobsters (Lab. Leaflet 66) 1981.
- Animal Welfare Advisory Council (AWAC), New South Wales Agriculture, March 1994.
- South Devon & Channel Shellfishermen Ltd. Kingsbridge, South Devon 1997.
ARCHIVE: FACTSHEET No. 5 (FACTSHEET 4 NOT INCLUDED HERE)
SHELLFISH FARMING
In the UK crayfish and molluscs are farmed. There are a large number of farms in the sea around our coasts farming molluscs. Crayfish farms, of which there are about 70, are found inland in fresh water. Most slaughtering methods are horrendous, including boiling alive.
Bans on fishing in the waters around the Orkney Islands are frequently imposed because of high levels of naturally occurring paralytic shellfish poisoning toxin. These toxins are caused by algae in the sea and calls have been made for the Government to research into the reasons for the occurrence of these algae blooms.
There have been public rows over the use of chemicals like ivermectin and cypermethrin and the siting of bigger fish farms. The Association of Scottish Shellfish Growers (ASSG) has stated that it respects the environment and works to maintain the purity of that environment. To damage it would mean damage to the product and the market.
Oysters: these animals have been cultivated since Roman times. Production of the Pacific oyster (non-native) rose to 2.8 million in 1996, with eight companies producing 72% of that total, according to Scottish Office figures. There was, however, a 47% drop in native oyster production, with nine companies producing 96,000 of the species.
The Pacific oyster is cultivated from seed stock from warm-water hatcheries, the seed bought in from eg the USA. From start to harvest takes 2-4 years. ‘Natural’ (as opposed to cultivated seed stock) oysters are based on on-growing of juvenile stock taken from the wild. Oysters feed themselves, suspended closely confined in nets and trays from a raft, or in trays set on trestles or stacks on the sea bed. Most of what is eaten of the oyster – live – are the gonads. The ASSG is looking at methods of suspended oyster cultivation from mussel rafts, and it has been stated that the need for greater product yields is encouraging oyster farmers to use mechanical grading for the oysters. It is thought that as long as the animals are graded and returned to the sea bed within 24 hours, mortalities should be low.
Scientists in France are trying to genetically-engineer oysters (in an attempt to make them resistant to disease, which of course is a problem, in close-confinement, in sacks on an oyster farm). Asked about the risks of such genetic engineering, the Director of the research programme replied that no-one knows exactly if there is a danger from the genetically altered oysters and, if there is one, where it is. It is planned to control them in a limited, confined environment and to make them sterile. He added that after four or five generations, they will return to their natural, unaltered state’. The director did not make clear how these sterile oysters would return to their natural state after four or five generations! (Thanks to Compassion In World Farming, CIWF, for that).
Mussels: these are farmed in two different systems;
Long-line, raft and bottom-culture (mud) systems. Seed mussels are bought in at between 10 and 20mm. The raft might grow up to 100t of mussels, with 800 growing ropes and 200 seed-collector ropes suspended to 15m depth. In recent years the animals have been grown in the French ‘cotton tube-sock’, which has proved to be the most efficient method of raising crop productivity. It seems that by using this method the small mussels can be recultivated on pegged ropes rather than being discarded as was previously the case. They reach market size at 18-24 months.
Mussels naturally root to the sea bed by the byssus or beard. At low tide, when they are exposed to the air, they clam up. When they are covered they open up to siphon water through the body at 1 pint every 15 minutes, filtering out food particles but taking in any toxins. When these are harvested at about 2-3 years they are purified in salt water for 36 hours. Mussels are sold live and cooked-killed by steaming.
Scallops and Queens: UK production is about 10t a year. Natural stock of these creatures is in lantern nets at about 100 per metre sq. in the final year, or they can be laid out on the sea bed. This takes place between 2 and 5 years old. The growing process can involve being drilled for ‘ear-hanging’; hooked through a drilled hole to hang on string or nylon lines. One company has developed a drilling machine which can ear hang scallops accurately at a rate of one thousand per hour. A portable version of this machine has been developed, and the company has received orders from many countries. The animals are killed by having the shell prised open with a knife, and then being boiled or steamed, and the viscera removed.
Clams: there are about 4 farms in England which produce approximately 100t a year, from hatchery-produced seed. There are about 2 Manila clam farms in England, producing 0.16t a year, also from hatchery-produced seed.
Winkles: these creatures are not farmed as such, but Scottish Natural Heritage (SNH) say that winkles are Scotland’s sixth-largest shellfish business after the trades in different types of scallop, crab and lobsters, with well-established picking operations around Argyll, Sutherland, eastern coasts and the Hebrides. Officially, pickers land well over 2,000 tonnes across Scotland, and some buyers believe the true figures could be double that, with 90 tonnes a week being picked. Winkles are now being heavily over-exploited because travellers and holiday-makers routinely pick winkles during the summer. This interferes with the winkle breeding patterns by harvesting them when they are too small. Since winkles are so plentiful nationwide, they do not have legal protection and will probably re-establish themselves after a few years, but a spokesperson from the local SNH office said that people should look for long-term sustainability rather than short-term profit.
Prawns: There are prawn fisheries in the deep waters to the west of the Hebrides as well as in the Fladen area. It is, however, prawn farms in the Third World that are causing environmental problems. The promotion of intensive prawn aquaculture in mangrove forests in many tropical and sub-tropical countries in Asia, Latin America, Australia and Africa is partly responsible for the alarming loss of the wide variety of marine life, animals and birds that depend on these forests, which are specially adapted to survive in brackish and saltwater environments. In Thailand, for example, prawn farming was responsible for the destruction of over 64% of land lost until 1986. This encroachment of the land is still continuing, despite laws banning prawn farming from many mangrove areas.
Apart from destroying the mangroves, the waste from prawn farms, which consists of dangerous chemicals and antibiotics, has also polluted coastal water, fresh water canals, productive agricultural lands and ground water supplies. This pollution eventually causes the farms to close down, leaving the farmers to live on the unproductive lands.
Japan is the highest importer of the cultured prawns from southeast Asia, while the high demand for prawns in the US market, which generally come from Ecuador’s farmed prawns, is causing the competitive exporters to increase productivity. This easy money from prawn aquaculture is tempting other countries to fall into the same trap – environmental impoverishment, followed by poverty. Cultured prawns include ‘black-tiger’, ‘jumbo’, and ‘white’ prawns.
Crayfish: Most of these animals are farmed in the south of England, producing mainly the non-native signal crayfish (from the USA and Australia). Production for the table is 4-7t a year. Each fish weighs approximately 70-100g at 1-3 years.
Crayfish mate in Autumn and the female can lay up to 300 eggs, four to five days later. The females are put into mesh cages for when the eggs hatch in late Spring. The juveniles moult after 6-8 days, and cling to the female until the second moult, when they leave the mother, who is then released back into the pond. The juveniles moult again several times, and then only two to three times a year until they are mature. USA research forces moulting rates by hormone feed, injection, water bath and ablation (removal of moult-inhibiting eye-stalks). The animals are stocked in water-flow or static ponds, gravel pits or canal channels, and are fed on natural sources of crustacean and vegetable matter, supplemented with potato, carrot and trout pellets.
The more favoured method of crayfish culture is ranching, which stocks ponds etc. with the creatures, letting them breed and multiply naturally, harvesting the surplus. They find their own food, the age groups are not separated and spawning is not controlled. A far greater degree of control is exercised in semi-intensive or intensive farming. Some British farms are now producing seed for stocking purposes. The newly hatched young are best for this as they adapt most readily to their new environments. Sometimes crayfish and carp are farmed in the same pond to enhance profits.
Harvesting takes place after three summers’ growth. Plastic, lobster-pot type traps are generally used. Crayfish ponds can be sited in areas of poor farmland, and intensive stocking can produce a relatively high income yield. Ranching, however, produces more modest profits, and some farmers use their crayfish ponds for such things at attracting wildfowl for shooting.
The British Crayfish Marketing Association (BCMA) co-operative has established two grades of crayfish, the premium and the standard grades. Prices are fixed at the beginning of each season. The animals are sold live and killed by boiling.
Crayfish plague has been mainly responsible for the depletion of the native, smaller crayfish, and it is still disputed that the larger signal crayfish have been responsible for the spread of the disease, since they can be carriers, but are themselves immune.
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Sources:
- Press & Journal (Aberdeen) 29. 7. 1997
- Animal Facts and figures. Barry Kew (Date unknown)
- ‘Fish Farmer’. Dec. 1991
- ‘Agscene’ (Compassion in World Farming, CIWF) Summer 1997
- Financial Times 18. 2. 1997
- Scotland on Sunday 31. 8.1997
- Fisheries – Shellfish Farming
- International Primate Protection League (IPPL) August 1993
- ‘Crayfish’ February 1989
- Independent 3. 12. 1990
FACTSHEET No. 6
DISEASES IN SHELLFISH
- Algal blooms or phytoplankton can create toxins. These toxic algal blooms are often referred to as ‘red tides’ and are increasing in frequency. Many once harmless dinoflagellates (having runners or runner-like branches) now produce dangerous or deadly toxins. Bivalves (such as molluscs, cockles, mussels, scallops and oysters) feeding on these blooms can accumulate the toxic compounds in their flesh in very high concentrations. The compounds may then pass up the marine food chain to crustacea etc. feeding on the bivalves. There are four recognised groups of illnesses associated with toxins from unicellular algae. These are:
i.Paralytic Shellfish Poisoning (PSP)
ii.Diarrhetic Shellfish Poisoning (DSP)
iii.Neurotoxic Shellfish Poisoning (NSP)
iv.Amnesic Shellfish Poisoning (ASP)
PSP is associated with the algae genera Alexandrium, Gymnodinium and Pyrodinium. When ingested by humans the effects can cause numbness of the mouth and fingertips. This is followed by impaired muscle co-ordination. Respiratory problems and paralysis can also occur and may be fatal.
DSP toxins are produced by the algae of the genera Dinophysis and Prorocentrum. These can cause diarrhoea, nausea, vomiting and abdominal pain. (1). Another DSP producer, Prorocentrum lima has been recorded at nine sites in Scotland. (2).
ASP is caused by domoic acid which is produced by marine diatoms of the genus Pseudonitzschia. This can cause vomiting, diarrhoea, abdominal cramps and loss of short-term memory. The effects on memory loss may persist. (1).
(NSP This is not known in the UK. (1).)
In August 1997 an extensive dinoflagellate bloom identified as Gymnodinium cf. mikimotoi occurred. This bloom can cause mortalities in a number of marine organisms, but was the only recorded bloom of this species in Scottish waters within the last five years. (2).
PSP has been a serious problem in some areas of Scotland for many years and there have been regular closures of those fishing areas of up to 2 months at a time since 1990. (2).
In addition, Escherichia coli (E.Coli) and Salmonella have been found in molluscs examined according to EU shellfish bed classification regulations, and thermophilic Campylobacter spp. Were found in 42% of 380 shellfish. (3). Bivalves can also take up antibacterial chemicals which are used to fight diseases in fish and which can enter the environment. (4).
Pacific oyster larvae are prone to be affected by a herpes-like virus, with high mortalities in France. (5). Two year old flat oysters, Ostrea edulis L., found in Cork Harbour, have been found to be affected by the parasite Bonamia ostreae, which spreads quickly and causes rapid mortality. (6). Pacific oysters, Crassostrea gigas, also suffer from Mikrocytosis caused by the pathogen Mikrocytos mackini, and Oyster Velar Virus Disease (OVVD) which is known to kill oyster larvae in America. Manila clam can be affected by brown ring disease, apparently caused by the bacterium Vibrio tapetis. (7).
In addition to the two serious diseases in bivalve molluscs, bonamiosis and marteiliosis (caused by the pathogen Marteilia refringens) which affect flat oysters, there are a number of other listed diseases. These are hapiosporidiosis, marteiliosis (caused by the pathogen Marteilia sidneyi) perkinosis, iridovirosis and mikrokytosis. They mainly affect pacific oysters, American oysters, Argentine flat oysters, Chilean oysters and abalone. Bonamiosis is the only one present in England. Haplosporidiosis, mikrokytosis, perkinosis, iridovirosis and marteiliosis are notifiable diseases of molluscan shellfish. (8) (9). Fish disease can be imported although there are very strict controls in Britain.
A project has been undertaken to analyse E.coli data in conjunction with the evaluation of information on sewage discharges. A comparison was made of the effect of crude, primary, secondary and tertiary treated discharges on the E.coli concentration at routine monitoring points within 2 kilometres of each type of discharge. Concentrations of E.coli in shellfish taken from the monitoring points in the vicinity of secondary-treated discharges were markedly lower than in those from monitoring points in the vicinity of crude or primary-treated discharges. Sources of other forms of pollution were possibly the reason that there was little apparent beneficial effect of tertiary treatment for shellfisheries. E.coli was found in greater concentration in mussels, followed by oysters and clams. (10). Raw oysters can carry fatal flesh-eating bacteria which cause the disease necrotising faciitis. This develops in humans from a bacterial infection and causes skin to die and melt within hours. The disease can also be transmitted through contaminated seawater and air. Mortality rates can be as high as 50%. (11).
Shellfish also have an increased susceptibility to disease when they are stressed. Flat oysters, Pacific oysters and other molluscan shellfish such as clams, mussels and scallops are all susceptible to Bonamia and Marteilia. (12).
In addition to diseases from natural algae, high levels of bacteria have been found in mussel and oyster beds of the Teign, Dart and Avon rivers. Causes may be due to run off from fields after heavy rainfall, or lack of sunlight, as ultraviolet rays kill bacteria. Sewage is another possible cause, but there is no certain proof that any of these are the cause. (13). However, oil spills are certainly the cause of contamination by polyaromatic hydrocarbons in mussels from Prince William Sound, Alaska. The blue mussel, Mytilus trossulus, from the rocky intertidal zone in temperate USA waters is eaten by many wildlife species. Aromatic hydrocarbons are known to cause sublethal and acute toxicity to a variety of biological organisms. After the Sea Empress spill off Newford Haven large numbers of dead or moribund shellfish, mostly bivalve molluscs, were washed ashore, including cockles, striped Venus (Chamelea gallina)and razor shells (Ensis siliqua) and later the rayed troughshell (Mactra stultorum). Polycyclic aromatic hydrocarbons (PAH) such as benzo(a)pyrene are potent human carcinogens. Crustacea also accumulated the smaller PAH such as naphthalene, phenanthrene and alkylated derivatives in affected areas. These compounds can remain in their tissues for some time. Combustion processes can also contaminate bivalve shellfish from PAH releases. (14).
Shellfish ‘pests’ include American tingle, Grepidula and Mytilicola.
- Crayfish, lobster and crab:
Crayfish: The native British crayfish, Austropotamobius pallipes, has been endangered by a lethal plague brought in with the North American species of crayfish, the signal crayfish, Pacifasticus leniusculus. The plague takes the form of a fungus which can wipe out whole populations of the native species. Signal crayfish, along with all North American species, are carriers of the disease and are not immune to infection. But they are resistant unless unduly stressed. This resistance relies on an ability to stop the growth of the fungus by encapsulating it with melanin. In the European crayfish this process is too slow to be effective and the plague has devastated natural crayfish populations throughout Europe. (15). Other diseases are Porcelain disease and Exoskeletal disease. (16).
Lobster: The two most important species of clawed lobster are Homarus gammarus, the European lobster and Homarus americanus, the American lobster. Specific to both species is the disease Gaffkaemia, which may be carried by lobsters from abroad and infect native species. (17). Without treatment massive mortality can also occur from bacterial growth on lobster eggs. (18).
Crab: Black spot disease.
- More Non-natural causes:
In the US Centre for disease Control, it is estimated that waterflesh, including shellfish, causes 66% or some 325,000 cases annually of all US poisoning. Since only the most visible cases are recognised, the actual figures may be much higher. Cadmium, lead, chromium and arsenic are found in shellfish. These impair mental development and can lead to cancer even at low levels. No Food and Drugs Administration (FDA) action level exists for lead in seafood. (19).
Mercury is a dominant toxic metal in sea-food sold in Hong Kong. This can cause fertility and general health problems, (20) and paints which contain ribulytilin can alter the sex of dog whelks and affect other marine animals and should be phased out. (21). Most of Scotland’s fish farmers use copper-based paints and anti-fouling agents to prevent fish cages from being clogged by mussels, algae and seaweed. Zinc is used to galvanise the cages and is a component of salmon feed. Sediments become severely contaminated causing harm to crustacea by damaging their reproductive abilities or killing them. Dipping sheep in synthetic pyrethroids can cause river pollution, toxic to invertebrates. (22).
Crabs at a nuclear plant in Normandy showed high levels of radiation. Cogema is authorised to dump slightly radioactive waste in the water and the crabs from there could travel several miles a day. (23). Between 1993 and 1995 radioactivity monitoring of the Irish Marine Environment was carried out to assess contamination and estimate the risks to human health. Exposure has arisen from various sources of artificial radioactivity including atmospheric testing of nuclear weapons during the 1950s and ‘60s, the Chernobyl nuclear accident and controlled discharges of radioactive effluent from nuclear installations. The main source of artificial radioactivity in the Irish Sea is the routine discharge of low-level liquid radioactive waste from the Sellafield nuclear fuel reprocessing plant on the Cumbrian coast. A Report stated that, whilst the concentrations of potassium-40 in fish and shellfish are considerably higher than those of many other natural radionuclides (Radionuclide – an unstable nuclide that emits ionising radiation. The emissions may be either alpha, beta or gamma radiation), its presence in seafood does not result in an increased radiological hazard. (24).
Prawn/shrimp aquaculture: apart from destroying the mangroves, the waste from prawn farms in the mangrove forests of the Third World, which consists of dangerous chemicals and antibiotics, has also polluted coastal waters, fresh water canals and ground water supplies. Acid sulphate soil contamination, prawn farm created pollution and related disease outbreaks in the ponds along with other, natural imbalances, eventually cause the farms to close down. High demands for prawns in the industrial world and the large amounts that can be earned through prawn aquaculture, are tempting countries like Malaysia, Vietnam, Cambodia, India, Iran, Yemen, Mexico and others to enter the same trap. (25). And ‘Taura syndrome’ is affecting shrimp mariculture in Ecuador, Honduras, Panama, Japan and China. It has also affected Tedas shrimp farms and is moving up the Gulf coast. Taura, named after a river in Ecuador, is a syndrome, with three viruses and one vibrio implicated. In some areas mangrove networks are removed to create the ponds. They lack vegetation to filter and cleanse incoming water carrying nutrients and organisms, and adequate ingresses and egresses. The shrimp are also fed many types of foodstuffs including hamburger meat. Pesticide levels are high in many areas; Chloramphenicol and other broad-spectrum antibiotics are flooded into the ponds to decrease contamination. The result is immunodeficient shrimp suffering from multiple opportunistic infections (OIs). One suspected viral agent is a baculovirus which is insect-borne. In other areas, such as in scallop farms, rickettsial agents have emerged. There is concern about the dissemination of antibiotic-resistant or insensitive (eg viral and protozoan) organisms in downstream water systems. (26).
References
- Shellfish News No. 3. May 1997 The Centre for Environment, Fisheries & Aquaculture Science (CEFAS). All CEFAS references come from this publication.
The Biotoxin Monitoring Programmes for England & Wales. Dr. R.J. Lee, CEFAS Weymouth Laboratory, Dorset DT4 8UB UK 1996 pp 34-35.
- CEFAS The Biotoxin Monitoring Programmes for Scotland. Algal Monitoring. Marie Kelly and Elspeth Macdonald, SOAEFD Marine Laboratory, Aberdeen. 1996/97 pp 38-39.
- CEFAS Research News: Bacteria in bivalve molluscs. Ref: Wilson, I.G. and Moore, J.E., 1996. Presence of Salmonella spp. And Campylobacter spp. In shellfish. In: Epidemiol. Infect., vol. 116, no. 2, pp 147-153.
- Ibid. Uptake by bivalves of antibacterial chemicals used in fish farms. Ref: Pouliquen, H., Le-Bris, H., Buchet, V. and Pinault, L., 1996. Comparative study on the contamination and decontamination of Japanese oyster Crassostrea gigas and the blue mussel Mytilus edulis by oxytetracycline and oxolinic acid. In: Mar. Ecol. Prog. Ser., vol. 133, no. 1-3, pp 143-148.
- Ibid. Bonamia in flat oysters in Ireland. Ref: Culloty, S.C. and Mulcahy, M.F., 1996. Season, age, and sex-related variation in the prevalence of bonamiasis in flat oysters (Ostrea edulis L) on the south coast of Ireland. In: Aquaculture, vol. 144, no. 1-3, pp 53-63.
- Ibid. Herpes virus infection of Pacific oysters. Ref: Le-Deuff, R.M., Renault, T. and Gerard, A., 1996. Effects of temperature on herpes-like virus detection among hatchery-reared larval Pacific oyster, Crassostrea gigas. In: Dis. Aquat. Org., vol. 24, no. 2, pp 149-157.
- Ibid. Shellfish disease Control – the Work of the Weymouth Inspectorate, by A.E. Howard, CEFAS Weymouth Laboratory.
- CEFAS. EU Fish & Shellfish Health-update on Implementation of EU Measures for the Control of Certain Diseases Affecting Bivalve Molluscs. p 32.
- Ibid. p 33.
- CEFAS Impact of Different Types of Sewage Treatment on the Gygiene Status of Shellfisheries. Work undertaken using a geographical information system (GIS) by Pamela Chung. pp 15-16
- Campaign for the Abolition of Angling (CAA) ‘Pisces’ Winter 1998/99
- A Guide to Shellfish Health Controls. Ministry of Agriculture, Fisheries and Food (MAFF now DEFRA), Welsh Office Agriculture Department, Scottish Office Agriculture, Environment and Fisheries Dept. Feb. 1996.
- Daily Telegraph 17. 9. 98.
- Veterinary Invertebrate Society (VIS) Newletter No. 15. Trends in Contamination by Polyaromatic Hydrocarbons in Mussels from Prince William Sound, Alaska – Implications for Oil Spill Cleanup. Ref: Rebecca Hoff, Hazardous Materials Response and Assessment Division, National Oceanic and Atmospheric Administration, Seattle, USA.
- ‘Tragedy of the Cray Brothers’. The introduction of an exotic crayfish has endangered Europe’s native species. Anthony Thompson. Independent 3. 12. 90.
- MAFF (now DEFRA) leaflet ‘Fisheries & Fishfarming’.
- MAFF (now DEFRA) leaflet 1991, ‘Storage and Care of Live Lobsters’.
- CEFAS Research News. Anti-bacterial treatment of lobster eggs. Ref: Uglem, I., Uksnoy, L.E. and Bergh, O., 1996. Chemical Treatment of lobster eggs against epibiotic bacteria. In: Aquacult. Int., vol. 4, no. 1 pp 1-8.
- From ‘The More Shellfish Reasons to Stop Eating Fish’ by Jonathan Talbot. 1996. Ref: Jacobson, M, et al, Safe Food, Living Planet Press, Venice, CA pp 119 and 122. Williams, p 56. Weilbacher, Mike, ‘Toxic shock: The Environment-Cancer Connection’, E Magazine, June 1995.
- Reuters, Hong Kong. 23. 11. 97.
- C 4 Teletext: ‘Go Green’ 4. 4. 98.
- The Vegan magazine. Spring 1998.
- BBC Ceefax ‘Globe Watch’ 25. 9. 97.
- Radioactivity Monitoring of the Irish Marine Environment 1993-95. Report by the Radiological Protection Institute of Ireland.
- ‘The Prawn Connection’, Ian Baird. International Primate Protection League (IPPL). August 1993.
- Paul R. Epstein, M.D., M.P.H., Associate Director, Center for Health & the Global Environment, Harvard Medical School, Boston, Mass. USA