LIGHT AND BAHAVIOUR
Light, both direct and indirect, is of great importance in the lives of fishes. In the majority of fishes, the visual organs play a substantial role in orientation during swimming, towards prey, predators, other individuals of the same species in a school, or immobile objects.
The behaviour of fish, particularly their diurnal activity and many other aspects of their life, are significantlyrelated to the degree of illumination (Kikolsky 1963). Light exerts a definite influence on a fish's metabolism, maturation, behaviour and colouration.
LIGHT WAVELENGTHS AND FISH COLOURATION
Light conditions in water differ from those on land not only in their intensity but also in the depth of penetration of the various wavelengths. The longer wavelengths (i.e. red, orange) are absorbed first, with over 25% of red light being absorbed in the first metreof water. Violet, on the other hand, becomes indistinguishable below a depth of 100 m or more (Nikolsky 1963).
Since a high percentage of red light is filtered out in the first few metres of water, bright red fishes are common. Fishes that are solid red in colour aregenerally either nocturnal or live at moderate depths (Chech andMoyle 1982).
In both situations, red light is virtually absent and ared fish tends to fade into the background rather easily. However,many shallow water fish also have red spots or lines. It is thought that such colouration is important in recognition and/or breeding; red colours would be highly visible over short distances but is difficult to see over large lateral distances (water absorbs the red)(Chech and Moyle 1982).
The visual spectrum of fish depends on the nature of their habitat; fish which live in predominantly shallow waters are more sensitive to the longer wavelengths of light (red) while, as depth increases, the visual spectrum narrows considerably, starting with the longer wavelengths (Nikolsky 1963). The majority of fish can distinguish colours quite well although the maximum distance they can see is apparently not greater than 15 metres (Nikolsky 1963).
FISH ADAPTATION TO LIGHT
Fish have a number of adaptations to varying light levels. The rodsin the retina of the eye are specially adapted for sensing in weaklight. During periods of bright illumination (i.e. daylight), the rods become buried in between pigment cells lining the retina. In contrast, the cones which are adapted to sensing brighter light, move to the surface in response to higher illumination (Nikolsky 1963). The lower part of the retina, in the majority of fish, possesses more cones, and fewer rods, than the upper surface. This is due to the fact that the upper part of the eye receives more dispersed light than thelower half of the eye (Nikolsky 1963).
A rather obvious adaptation to low light levels in a relative increase in the size of eye. This affords a much greater area for light detection. A fish with large eyes is always a give away that it should be kept in a tank with either low light levels or caves and overhangs (i.e. Squirrel fish[Holocentridae] and Cardinal Fish [Apogonidae]).
LIGHT EFFECTS ON FISH BREEDING
Light also has profound effects upon the internal mechanisms of fish. For example, light exerts a great influence on the maturationof fish as well as their development and metabolism. For a number of fishes an increase in the amount of illumination produces asignificant acceleration in the development of the egg. This often takes the form of an increase in development rate in the light and a decrease in the rate in the dark (Nikolsky 1963).
In many fish species, the maturation of the gonads depends to a large extent on the duration of light (the so called photoperiod) and its intensity. In tropical seas, where the photoperiod is not as variable as in temperate areas, the role of light is not as important and many tropical species breed year round (Nikolsky 1963).
If fish do not receive the correct amount and intensity of light, they can be severely crippled and may not develop properly. In many fish species the normal course of metabolism is disturbed if they are reared in light conditions which are abnormal for them (Nikolsky 1963).
LIGHT EFFECTS ON PREDATION
The activity patterns of most fish are also related to light.Vision-orientated predators are most active during the day, oftenwith peaks of feeding in the early morning and evening when invertebrates become more available. Piscivorous fishes are alsomost active at dawn and dusk; attracted by the feeding activities ofthe smaller fish which form their prey. At night, the day-activefish become quiescent and the nocturnal fish become active (Chech andMoyle 1982).
In this article I have pointed out some of the basic reactions of fish to light; both its duration and intensity. It can be seen that light plays a very important role in the lives of fish and this must be taken into account when keeping them in enclosed systems.
Monday, January 8, 2007
Thursday, January 4, 2007
Ethanol-driven vehicle under test in Malawi
conducting road tests on an ethanol-propelled vehicle.
Supporters of the project argue that a switch to ethanol fuel would not only benefit the environment but also increase employment in the country's sugarcane industry and save on foreign exchange spent on fuel imports.
According to Freeman Kalirani, a lead researcher on the project • based at Lilongwe Technical College and conducted jointly with the department of science and technology • a modified Mitsubishi Pajero will be tested over a 350 kilometre route from Lilongwe to Mzuzu.
The five-year, US$1 million project, backed by the Malawi government, is investigating the practicability of flex-fuel vehicles that use either 100 per cent locally manufactured ethanol, or a combination of ethanol and petrol.
Until February 2006, all cars in Malawi used leaded petrol blended with 20 per cent ethanol. Since then, the country has switched to unleaded petrol blended with 10 per cent ethanol. Proponents of ethanol use argue that continued over-dependence on fossil fuels has economic, social, climate and biodiversity impacts for humans and the entire ecosystem.Kendron Chisale, Malawi's deputy director of science and technology, said a switch to ethanol would allow Malawi to comply with procedures aimed at emission reduction, as agreed by parties at the 2006 United Nations Climate Change Conference in Nairobi in November. "This will eventually mitigate climate change related disasters," he says.
Charles Mtonga, an economic analyst, told SciDev.Net that one advantage of using ethanol as a renewable energy source is that it can increase employment in the sugarcane industry. "It can also save on foreign exchange lost through importation of petroleum products," he said.
But Mtonga cautioned against over-enthusiasm, calling for continued research on how vehicles previously propelled by petrol can best be modified to use ethanol.
He also warned that huge investments in production and installation of additional pumps would be required to make ethanol fuel available throughout the country.Malawi produces ethanol from sugar molasses in bulk amounts at Dwangwa, in the central region lakeshore district of Nkhota-kota.
6 times read
Supporters of the project argue that a switch to ethanol fuel would not only benefit the environment but also increase employment in the country's sugarcane industry and save on foreign exchange spent on fuel imports.
According to Freeman Kalirani, a lead researcher on the project • based at Lilongwe Technical College and conducted jointly with the department of science and technology • a modified Mitsubishi Pajero will be tested over a 350 kilometre route from Lilongwe to Mzuzu.
The five-year, US$1 million project, backed by the Malawi government, is investigating the practicability of flex-fuel vehicles that use either 100 per cent locally manufactured ethanol, or a combination of ethanol and petrol.
Until February 2006, all cars in Malawi used leaded petrol blended with 20 per cent ethanol. Since then, the country has switched to unleaded petrol blended with 10 per cent ethanol. Proponents of ethanol use argue that continued over-dependence on fossil fuels has economic, social, climate and biodiversity impacts for humans and the entire ecosystem.Kendron Chisale, Malawi's deputy director of science and technology, said a switch to ethanol would allow Malawi to comply with procedures aimed at emission reduction, as agreed by parties at the 2006 United Nations Climate Change Conference in Nairobi in November. "This will eventually mitigate climate change related disasters," he says.
Charles Mtonga, an economic analyst, told SciDev.Net that one advantage of using ethanol as a renewable energy source is that it can increase employment in the sugarcane industry. "It can also save on foreign exchange lost through importation of petroleum products," he said.
But Mtonga cautioned against over-enthusiasm, calling for continued research on how vehicles previously propelled by petrol can best be modified to use ethanol.
He also warned that huge investments in production and installation of additional pumps would be required to make ethanol fuel available throughout the country.Malawi produces ethanol from sugar molasses in bulk amounts at Dwangwa, in the central region lakeshore district of Nkhota-kota.
6 times read
2007 set to be world's warmest year - Met Office
LONDON (Reuters) - This year is set to be the hottest on record worldwide due to global warming and the El Nino weather phenomenon, the Meteorological Office said on Thursday.
The Met Office said the combination of factors would likely push average temperatures this year above the record set in 1998. 2006 is set to be the sixth warmest on record globally.
This new information represents another warning that climate change is happening around the world," said Met Office scientist Katie Hopkins. The world's 10 warmest years have all occurred since 1994 in a temperature record dating back a century and a half, according to the United Nations' weather agency.
The Met Office makes a global forecast every January with the University of East Anglia, and said it expected the world's average temperature to be 0.54 degrees Celsius above the 1961-1990 long-term average of 14.0 degrees.
There is a 60 percent probability that 2007 will be as warm or warmer than the current warmest year, 1998, which itself was 0.52 degrees above the long-term average it said in a statement.
Most scientists agree that temperatures will rise by between two and six degrees Celsius this century due mainly to carbon emissions from burning fossil fuels for power and transport.
They say this will cause melting at the polar ice caps, sea levels to rise and weather patterns to change bringing floods, famines and violent storms, putting millions of lives at risk.
Former World Bank chief economist Nicholas Stern said in October that urgent action on global warming was vital and that delay would multiply the cost by up to 20 times.
The Kyoto Protocol is the only global action plan to curb carbon emissions, but it expires in 2012, is rejected by the world's biggest polluter -- the United States -- and does not bind booming economies like China and India.
The Met Office said the established moderate El Nino, a phenomenon in the tropical Pacific blamed for disrupting weather patterns, would continue for the first few months of 2007.
It noted that as there was a time lag between El Nino and its full effect on surface temperatures, its influence would therefore be felt well into the year.
It will coincide with what environmentalists say will be a very busy year for climate diplomacy.
Germany, which has an active climate change agenda, has taken over the six-month rotating presidency of the European Union and the year-long presidency of the Group of Eight industrialised nations.
Backed by Britain, which has pushed climate change high up the world agenda, pressure is building for the G8 summit in Germany in early June to set out a framework for discussions to take global action beyond Kyoto
The Met Office said the combination of factors would likely push average temperatures this year above the record set in 1998. 2006 is set to be the sixth warmest on record globally.
This new information represents another warning that climate change is happening around the world," said Met Office scientist Katie Hopkins. The world's 10 warmest years have all occurred since 1994 in a temperature record dating back a century and a half, according to the United Nations' weather agency.
The Met Office makes a global forecast every January with the University of East Anglia, and said it expected the world's average temperature to be 0.54 degrees Celsius above the 1961-1990 long-term average of 14.0 degrees.
There is a 60 percent probability that 2007 will be as warm or warmer than the current warmest year, 1998, which itself was 0.52 degrees above the long-term average it said in a statement.
Most scientists agree that temperatures will rise by between two and six degrees Celsius this century due mainly to carbon emissions from burning fossil fuels for power and transport.
They say this will cause melting at the polar ice caps, sea levels to rise and weather patterns to change bringing floods, famines and violent storms, putting millions of lives at risk.
Former World Bank chief economist Nicholas Stern said in October that urgent action on global warming was vital and that delay would multiply the cost by up to 20 times.
The Kyoto Protocol is the only global action plan to curb carbon emissions, but it expires in 2012, is rejected by the world's biggest polluter -- the United States -- and does not bind booming economies like China and India.
The Met Office said the established moderate El Nino, a phenomenon in the tropical Pacific blamed for disrupting weather patterns, would continue for the first few months of 2007.
It noted that as there was a time lag between El Nino and its full effect on surface temperatures, its influence would therefore be felt well into the year.
It will coincide with what environmentalists say will be a very busy year for climate diplomacy.
Germany, which has an active climate change agenda, has taken over the six-month rotating presidency of the European Union and the year-long presidency of the Group of Eight industrialised nations.
Backed by Britain, which has pushed climate change high up the world agenda, pressure is building for the G8 summit in Germany in early June to set out a framework for discussions to take global action beyond Kyoto
Tuesday, January 2, 2007
LAKE MALAWI MBUNA
Mbuna is the common name for a large group of African cichlids from Lake Malawi. The name mbuna is translated as rock fish. As the name implies, mbuna are the cichilds that live among piles of rocks, as opposed to living in the open water like many other haplochromines.
These cichilds are some of the most colorful freshwater fish for the home aquarium. Mbuna, pronounced with only one syllable, are very aggressive and territorial fish, although they are suitable for beginner fishkeepers who have researched their needs. A suitable aquarium setting includes many rocks, caves and hiding places; plants may be uprooted so they are best avoided but a small number will work well in the aquarium. These include Java fern, which may become the object of mbuna aggression but will not be eaten due to an undesireable taste.
Sand or gravel is the ideal substrate. The hobbyist will want to mix in some sort of so-called "live rock" as a pH buffer. However, crushed coral and specially mixed bags of substrate will do. Generally, tanks of no less than 55 gallons are required for mature Mbuna; 29 gallon tanks will work beautifully for juvenile fish but will need to be upgraded as they mature, grow and become more aggressive and territorial (this will occur in just a matter of weeks or months).
These cichlids are usually kept in well filtered, heavily stocked mbuna-specific aquariums. Over-crowding helps spread out the aggression and no particular individual gets picked on to death. They are maternal mouthbrooders and breed readily in good conditions. Mbuna are mostly herbivorous and their diet should consist of low fat foods. Many species will require spirulina, but worms, beefheart, and meaty foods are best avoided.
There is a wide array of literature out there concerning African cichlids (including references to mbuna in more general aquarium guides and scientific texts). There are subtle but important differences from book to book (and especially from internet site to site). Differences include whether or not to attempt an under-gravel filter and specific species compatibility. Make sure that you double check any recommendations with a second or third shopkeeper, experienced aquarist or printed text. The time and monetary investment required for a 75 gallon or larger aquarium demands it.
Many mbuna cichlids are regularly stocked and sold by pet shops. Some of the most common ones are bumblebee cichlid, auratus cichlid, electric yellow cichlid, red zebra cichlid, and johanni cichlid. Cichilds belonging to any of the genera listed below is usually considered mbuna.
An electric yellow cichlid, Labidochromis caeruleus.
Labeotropheus fuelleborni
Cyathochromis Trewavas 1935
Cynotilapia Regan 1922
Genyochromis Trewavas 1935
Gephyrochromis Boulenger 1901
Iodotropheus Oliver & Loiselle 1972
Labeotropheus Ahl 1926
Labidochromis Trewavas 1935
Maylandia Meyer & Foerster 1984.
Melanochromis Trewavas, 1935
Petrotilapia Trewavas 1935
Pseudotropheus Regan 1922
An electric yellow cichlid, Labidochromis caeruleus.
Labeotropheus fuelleborni
Cyathochromis Trewavas 1935
Cynotilapia Regan 1922
Genyochromis Trewavas 1935
Gephyrochromis Boulenger 1901
Iodotropheus Oliver & Loiselle 1972
Labeotropheus Ahl 1926
Labidochromis Trewavas 1935
Maylandia Meyer & Foerster 1984.
Melanochromis Trewavas, 1935
Petrotilapia Trewavas 1935
Pseudotropheus Regan 1922
The list below includes groups of non-mbuna mouthbrooding cichilds from Lake Malawi.
Peacock cichilds
Haplochromines
LAKE MALAWI FACT FILE
Coordinates
10°00′S 34°00′E
Lake type
Rift Valley lakes
Primary sources
Ruhuhu
Primary outflows
Shire River
Basin countries
Mozambique Malawi Tanzania
Max-length
560 km
Max-width
75 km
Surface area
29,600 km²
Average depth
292m
Max-depth
706m
Water volume
8,400 km³
Surface elevation
500 m
Islands
LikomaChizumulu
Settlements
Niassa, MozambiqueRuvuma, Tanzania
10°00′S 34°00′E
Lake type
Rift Valley lakes
Primary sources
Ruhuhu
Primary outflows
Shire River
Basin countries
Mozambique Malawi Tanzania
Max-length
560 km
Max-width
75 km
Surface area
29,600 km²
Average depth
292m
Max-depth
706m
Water volume
8,400 km³
Surface elevation
500 m
Islands
LikomaChizumulu
Settlements
Niassa, MozambiqueRuvuma, Tanzania
LAKE MALAWI WILDLIFE
Lake Malawi has traditionally provided a major food source to the residents of Malawi as it is rich in fish, the most famous of which are the chambo, consisting of anyone of 4 species of the cichlid genus Nyasalapia, as well as the kampango, a large catfish (Bagrus meridionalis). Lake Malawi is famous for its cichlids, popular in the aquarium trade. Malawi cichlids are divided into two basic groups. These are loosely referred to as the haplochromines and the tilapiines. Within this first group (Haplochrominae) there are two subgroups. The first consists of the open water and sand dwelling species with males usually sporting bright colors while the females show a silvery coloration with irregular black bars or various other markings. The second subgroup is known locally and popularly as mbuna, which means rockdweller. Mbuna are smaller, generally vegetarian, and both sexes are often quite colorful, though many species are dimorphic. The second group, the tilapiines, consists of the only substrate-spawning species in the lake (Tilapia rendalli), as well as the 4 species of chambo (Nyasalapia). Maylandia and Labidochromis are popular cichlids in the international aquarium scene. Cichlids are an important export for Malawi, but wild populations are increasingly threatened by overfishing and localized pollution. Other wildlife resident in the lake includes crocodiles, and a large population of fish eagles which feed off the fish population.
The lake also supports populations of snails some of which carry bilharzia. For many years this was strenuously denied by the government, which feared it would deter tourism in the area, but since the fall of Hastings Banda, the presence of bilharzia in the lake has been more widely acknowledged. (However, due to the overfishing of snail eating cichlids in the lake, this has caused what little bilharzia did exist to greatly increase to the point of being a hazard to bathers in the south east portion of the lake.)
The lake also supports populations of snails some of which carry bilharzia. For many years this was strenuously denied by the government, which feared it would deter tourism in the area, but since the fall of Hastings Banda, the presence of bilharzia in the lake has been more widely acknowledged. (However, due to the overfishing of snail eating cichlids in the lake, this has caused what little bilharzia did exist to greatly increase to the point of being a hazard to bathers in the south east portion of the lake.)
CICHLID HYBRID
Because of the introduced nile perch and water hyacinth, deforestation causing siltation of water, and overfishing, many species of Lake Victoria cichlids have been wiped out or drastically reduced in the wild. Thankfully, the myriad of satellite lakes surrounding Lake Victoria have not been affected, and harbor a vast array of similar species.
Some cichlids have been found to hybridise with closely related species quite readily, both in the wild and under artificial conditions.[23] This is not particularly unusual, having been observed among other groups of fishes, such as European cyprinids.[24] What is unusual is the extent to which cichlid hybrids have been put to commercial use, in particular as fast-growing food fish and as aquarium fish.[25][26] A notable hybrid, known as blood parrot cichlid, has caused controversy among aquarium enthusiasts. Some has called the fish "the Frankenstein monster of the fish world." [27]
Cichlid keeping aquarists tend to divide cichlids into groups based on regions such as Central America, South America, Madagascar and India, Lake Tanganyika, Lake Malawi and Lake Victoria. Others divide the cichlids using the combination of geographical, taxonomical, and behavioral criteria. Some notable groups resulting from this type of categorizing are the mbunas, haplochromines, dwarf cichlids, and shell dwellers.
Cichlids from Lake Tanganyika were first collected by German hobbyists during the 1930's. However, it was during the 1970s and 80s that the cichlids from lakes Tanganyika and Malawi began to become popular aquarium fishes. This trend continues to the present unabated.
Perhaps the most commonly encountered species in retail aquariums is Pterophyllum scalare from the Amazon River basin in tropical South America, known in the trade as the "angelfish". Other cichlids commonly stocked by retail aquaria include:
Some cichlids have been found to hybridise with closely related species quite readily, both in the wild and under artificial conditions.[23] This is not particularly unusual, having been observed among other groups of fishes, such as European cyprinids.[24] What is unusual is the extent to which cichlid hybrids have been put to commercial use, in particular as fast-growing food fish and as aquarium fish.[25][26] A notable hybrid, known as blood parrot cichlid, has caused controversy among aquarium enthusiasts. Some has called the fish "the Frankenstein monster of the fish world." [27]
Cichlid keeping aquarists tend to divide cichlids into groups based on regions such as Central America, South America, Madagascar and India, Lake Tanganyika, Lake Malawi and Lake Victoria. Others divide the cichlids using the combination of geographical, taxonomical, and behavioral criteria. Some notable groups resulting from this type of categorizing are the mbunas, haplochromines, dwarf cichlids, and shell dwellers.
Cichlids from Lake Tanganyika were first collected by German hobbyists during the 1930's. However, it was during the 1970s and 80s that the cichlids from lakes Tanganyika and Malawi began to become popular aquarium fishes. This trend continues to the present unabated.
Perhaps the most commonly encountered species in retail aquariums is Pterophyllum scalare from the Amazon River basin in tropical South America, known in the trade as the "angelfish". Other cichlids commonly stocked by retail aquaria include:
CICHLID REPRODUCTION
All species show some form of parental care for both eggs and larvae, often extended to free-swimming young until they are several weeks or months old.
The discus fish (Symphysodon species) are noted to feed their young with a secretion on the skin from slime glands. Other South American, some Central American and Madagascan cichlds have also been observed with fry feeding on their parents, but not to the extent of the discus.
Parental care falls into one of three categories: mouthbrooders, substrate brooders, and delayed mouthbrooding where the eggs are laid in the open or in a cave, and subsequently brooded in the mouth(s) of the parents. The mouthbrooding strategy for reproduction is primarily found in cichlids indiginous to the Great Rift Lakes in Africa, with South/Central American/New World cichlids tending to be substrate spawners. Mouthbrooding cichlids will generally have the female of the species immediately taking the newly fertilized eggs into her mouth where they will remain until the fry are free swimming. Some species of mouthbrooders will take food while brooding, while others will go the entire incubation period without taking any food. Most cichlids are maternal mouthbrooders, with some exhibiting bi-parental mouthbrooding, where both parents will take a turn holding the eggs in their mouth. Some mouthbrooders will release their fry once free-swimming and show no further parental care while other mouthbrooders will remain continue to guard the fry allowing them back into the mouth to escape predators. The ability to mouthbrood is thought to have been an evolutionary adaptation to reduce fry predation, likely due to the fishes being located in densely populated waters.
The discus fish (Symphysodon species) are noted to feed their young with a secretion on the skin from slime glands. Other South American, some Central American and Madagascan cichlds have also been observed with fry feeding on their parents, but not to the extent of the discus.
Parental care falls into one of three categories: mouthbrooders, substrate brooders, and delayed mouthbrooding where the eggs are laid in the open or in a cave, and subsequently brooded in the mouth(s) of the parents. The mouthbrooding strategy for reproduction is primarily found in cichlids indiginous to the Great Rift Lakes in Africa, with South/Central American/New World cichlids tending to be substrate spawners. Mouthbrooding cichlids will generally have the female of the species immediately taking the newly fertilized eggs into her mouth where they will remain until the fry are free swimming. Some species of mouthbrooders will take food while brooding, while others will go the entire incubation period without taking any food. Most cichlids are maternal mouthbrooders, with some exhibiting bi-parental mouthbrooding, where both parents will take a turn holding the eggs in their mouth. Some mouthbrooders will release their fry once free-swimming and show no further parental care while other mouthbrooders will remain continue to guard the fry allowing them back into the mouth to escape predators. The ability to mouthbrood is thought to have been an evolutionary adaptation to reduce fry predation, likely due to the fishes being located in densely populated waters.
CICHLID DIET
Cichlids are astonishingly diverse in terms of diet. Many are primarily herbivores feeding on algae (e.g. Petrochromis) and plants (e.g. Etroplus suratensis) and small animals, particularly invertebrates, are only a small part of their diet. Some cichlids are detritvores and eat all types of organic materia; among these species are the tilapias of the genera Oreochromis, Sarotherodon, and Tilapia.
Other cichlids are predatory and eat little if any plant matter. These include generalists that catch a variety of small animals including other fishes and insect larvae (e.g. Pterophyllum), as well as variety of specialists. Trematocranus is a specialised snail-eater, while Pungu maclareni feeds on sponges. A number of cichlids feed on other fish, either whole or in part. Crenicichla are stealth-predators that lunge at small fish that pass by their hiding places, while Cichla are open water pursuit predators that chase down their prey. Paedophagous cichlids such as Caprichromis species eat other species' eggs or young (in some cases ramming the heads of mouthbrooding species to force them to disgorge their young). Among the more unusual predators are Plecodus straeleni feeds on scales and fins ripped from other fishes, and Nimbochromis livingstonii, which lies on its side and plays dead, hoping to lure smaller fish close enough for it to snap them up.
Scientists believe it is this wide adaptability of feeding styles that has helped cichlids to inhabit such a wide range of habitats. It is largely the pharyngeal teeth (teeth in the throat) that allows the cichlid so many 'niche' feeding behaviors, i.e. the jaws may be used to hold or pick food, while the pharyngeal teeth are used to crush what was harvested.
Other cichlids are predatory and eat little if any plant matter. These include generalists that catch a variety of small animals including other fishes and insect larvae (e.g. Pterophyllum), as well as variety of specialists. Trematocranus is a specialised snail-eater, while Pungu maclareni feeds on sponges. A number of cichlids feed on other fish, either whole or in part. Crenicichla are stealth-predators that lunge at small fish that pass by their hiding places, while Cichla are open water pursuit predators that chase down their prey. Paedophagous cichlids such as Caprichromis species eat other species' eggs or young (in some cases ramming the heads of mouthbrooding species to force them to disgorge their young). Among the more unusual predators are Plecodus straeleni feeds on scales and fins ripped from other fishes, and Nimbochromis livingstonii, which lies on its side and plays dead, hoping to lure smaller fish close enough for it to snap them up.
Scientists believe it is this wide adaptability of feeding styles that has helped cichlids to inhabit such a wide range of habitats. It is largely the pharyngeal teeth (teeth in the throat) that allows the cichlid so many 'niche' feeding behaviors, i.e. the jaws may be used to hold or pick food, while the pharyngeal teeth are used to crush what was harvested.
CICHLID RANGE
Cichlids are mainly freshwater fish that are most diverse in Africa and South America, with at least 900 species in the former and 290 in the latter.[14] Substanial numbers are also found in Central America as far north as the Rio Grande in southern Texas, and Madagascar has its own distinctive fauna of cichlids phylogenetically only distantly related to those on the African mainland. [15] [16] Endemic cichlids are largely absent in Asia except for four species in the Middle East, one in Iran, and three in the Indian Subcontinent.[17] Europe, Australia, Antarctica, and most of North America do not have any native cichlids, although where environmental conditions are suitable, for example in Florida and northern Australia, feral populations of cichlids have become established as exotics. [18] [19]
Cichlids are less commonly found in brackish and salt water habitats, though many species will tolerate brackish water for extended periods; Cichlasoma urophthalmus, for example, is equally at home in freshwater marshes and mangrove swamps, and can be found living and breeding in salt water environments such as the mangrove belts around barrier islands. [20] However, only a few cichlids are found primarily in brackish or salt water, most notably Etroplus maculatus, Etroplus suratensis, and Sarotherodon melanotheron
Cichlids are less commonly found in brackish and salt water habitats, though many species will tolerate brackish water for extended periods; Cichlasoma urophthalmus, for example, is equally at home in freshwater marshes and mangrove swamps, and can be found living and breeding in salt water environments such as the mangrove belts around barrier islands. [20] However, only a few cichlids are found primarily in brackish or salt water, most notably Etroplus maculatus, Etroplus suratensis, and Sarotherodon melanotheron
GET TO KNOW THE CICHLID FISH
Cichlids are members of a group of perciform fish known as the Labroidei alongside the wrasses Labridae, damselfish Pomacentridae, and surfperches Embiotocidae. This very large grouping shares a single key trait: the fusion of the lower pharyngeal bones into a single tooth-bearing structure. A complex set of muscles allows the upper and lower pharyngeal bones to be used as a second set of jaws for processing food, allowing a division of labour between the "true jaws" (mandibles) and the "pharyngeal jaws". Cichlids in particular have evolved to be very efficient feeders that are able to capture and process a very wide variety of food items and this is assumed to be one reason why they are so diverse (see section on diet below).[11]
The particular features of cichlids that distinguish them from the other Labroidei include:[12]
A single nostril on each side of the forehead instead of two.
No bony shelf below the orbit of the eye.
The lateral line organ is divided into two sections, one on the upper half of the flank and a second along the midline of the flank from about halfway along the body to the base of the tail (except for genera Teleogramma and Gobiocichla).
A distinctively shaped otolith.
The small intestine leaves the stomach from its left side, not from its right side as in other Labroidei.
Extensive brood care, with eggs and fry being guarded by one or both parents
The particular features of cichlids that distinguish them from the other Labroidei include:[12]
A single nostril on each side of the forehead instead of two.
No bony shelf below the orbit of the eye.
The lateral line organ is divided into two sections, one on the upper half of the flank and a second along the midline of the flank from about halfway along the body to the base of the tail (except for genera Teleogramma and Gobiocichla).
A distinctively shaped otolith.
The small intestine leaves the stomach from its left side, not from its right side as in other Labroidei.
Extensive brood care, with eggs and fry being guarded by one or both parents
The ethical guide to eating fish 2
***** Eat at will. **** Some stocks are endangered, so find out where your fish was caught. Bycatch not a major issue. *** Stock depletion is a problem. Often caught or reared in a way that kills other animals or harms the marine environment. ** Best avoided unless you can establish that it came from a sustainable fishery or was farmed using low-impact methods. * Sorry, this is one fish that you'll have to leave well alone.
SalmonTop facts: Migrate from spawning gravel 'redds' in upper reaches of river out to sea before returning to river of birth to spawn. Can reach a length of 1.5m and weight of 36-45kg. Status and problems: Stocks of wild Atlantic salmon have been halved in the past 20 years and are vulnerable to overfishing by driftnet fisheries and to parasites such as sealice and other impacts from salmon farms. More than 99 per cent of salmon sold in UK shops is farmed, with associated environmental impacts. For a clearer conscience: Buy organic farmed salmon, MSC-accredited fresh Alaska salmon or tinned Pacific salmon. Rating: **
Cod Top facts: Found in North Atlantic. Omnivorous and cannibalistic. Flesh is more than 18 per cent protein with virtually no fat. Status and problems: Affected by overfishing and climate change. Assessed as vulnerable on the IUCN Red List (www.redlist.org). North Sea stocks are on the brink of collapse, with 40-45 per cent of 2-8 year-old fish removed every year by fishing. Recovery plans now in place in Irish and North Seas. For a clearer conscience: Only Icelandic cod are from sustainable sources, but keep an eye on Iceland's proposal to cull whales to protect fish stocks. Pollack, coley and hoki (from MSC-accredited fishery) are alternatives. Rating: ***
Haddock Top facts: An important commercial species with a distribution similar to that of cod. Migratory fish, found in inshore, shallow North Atlantic waters in summer and in offshore deep water in winter. Reported maximum age of 20 years and a maximum size of between 0.8m and 1m (growth rates vary with sea temperature). Status and problems: Species listed as vulnerable by IUCN. Many stocks overexploited, including in the North Sea. Quotas reduced between 2000 and 2001, most notably in Irish Sea. For a clearer conscience: As with cod, Icelandic stocks are sustainably managed. Go for line-caught fish for less bycatch. Rating: ****
Prawns Top facts: Two species are popular in the UK: northern prawns, which are found on muddy sea-bottoms in cold water, and larger tiger prawns, from warm, tropical waters. Status and problems: Cold-water prawn stocks in North Sea considered within safe biological limits. Tiger prawn trawl fisheries associated with large quantities of bycatch, including turtles. Tiger prawns are also farmed, requiring large quantities of feed and causing destruction of coral reefs and mangrove swamps. Sea. For a clearer conscience: Try to find cold-water prawns that have been caught in traps rather than trawled. Avoid warm-water species. Rating: ***
Mackerel Top facts: Fast swimming species related to tuna, found in mid-water in huge schools above the continental shelf. Status and problems: Common in the North Atlantic, but large-scale purse-seine fisheries can result in bycatch of marine mammals, such as dolphins, local stock depletion and bycatch of juvenile fish. North Sea stock long since depleted. For a clearer conscience: Buy MSC-labelled fish from the South West Handline Fishery. Contact David Muirhead Tel 01326 555813 or check out the MSC website (details on main page) for certified retailers and distributors. Rating: **
Trout Top facts: Member of salmon family with similar lifecycle. There are two species, of which rainbow trout is non-indigenous introduction from the US. Native species are either sea trout (females which migrate from rivers and lakes out to sea) or brown trout (non-migratory males which stay in freshwater). Status and problems: Both species widely farmed, and being carnivores (like salmon), they require fishmeal. Non-indigenous rainbow interbreeds and competes with native species, and brown trout are threatened as a result. For a clearer conscience: Buy organic trout where you can. Rating: **For a clearer conscience: Try to find cold-water prawns that have been caught in traps rather than trawled. Avoid warm-water species. Rating: ***
Plaice Top facts: Widely distributed in temperate waters of Atlantic, Indian and Pacific Oceans. Bottom-dwelling fish found on sandy bottoms, buried in the sand during the day and active at night. Long-lived, with a reported maximum age of 30 years. Spawns between January and March after long migration.Status and problems: Beam- and bottom-trawling cause damage to seabeds. Overfishing - especially of immature fish - is threatening stocks, as the fish only matures at the age of seven, and so large fish are now rare.For a clearer conscience: Look for line-caught fish from day boats.Rating: ***
Brown crab Top facts: The largest British crab, found on the lower shore down to a water depth of about 100m, usually among rocks or under boulders. Has characteristic 'pie-crust' edge to its shell.Status and problems: Common around UK and European coasts, but many stocks are now overfished - it is estimated that more than 60 per cent of our crab populations are being harvested each year.For a clearer conscience: If you buy your crab alive, you will have to kill it yourself. The most humane method of killing a crab is to 'spike' it in its two nerve centres - behind the eyes and on the underside of the 'apron'.Rating: ***
Herring Top facts: An oily fish rich in Omega-3 acids, it is often sold smoked (as a kipper).Status and problems: Widespread species - the Guinness Book of Records lists it as the most numerous fish - though it can be overfished locally. UK stocks collapsed in 1970s, resulting in a total fishing ban. Now well managed, though industrial harvesting for fishmeal poses future threat.For a clearer conscience: Look for MSC-accredited Thames herring from spawning beds off West Mersea, in Essex. Contact Alex Midlen from the Essex Estuaries Initiative for further details Tel: 01206 282480.Rating: ****
Skate Top facts: From the same family as rays, skates are bottom-dwelling fish usually found in shallow coastal waters. Like other elasmobranchs (sharks and rays), skates are vulnerable to overfishing because they mature late. They grow to more than 1.25m and can live up to 50 years. Status and problems: Two species are exploited - common skate, which is listed as endangered by the IUCN and has probably been fished to extinction in the Irish Sea and is very rare in the central and southern North Sea, and thornback ray, which is assessed as low risk.For a clearer conscience: Avoid, unless you know it's a thornback ray.Rating: *
Sole Top facts: Dover and lemon are the two most popular sole species. Like others in its family, a sole's left eye migrates over the top of the head during growth and ends up beside the other. Status and problems: Both species are caught by beam trawls that damage the seabed. Though not endangered at present, sole are vulnerable to overfishing, particularly of immature fish. For a clearer conscience: Ask for line-caught fish from day-boats working out of small ports in Cornwall and Devon.Rating: ***
Coley [saithe]Top facts: From the same family as cod and haddock. Gregarious fish that occur in both inshore and offshore waters, living close to the seabed, and widely distributed in North Atlantic. Dark green in colour, it can grow up to 1.3m long and for 25 years. Status and problems: Species not threatened, but catches of North-Sea stock are outside safe biological limits, with many immature fish being landed. Bottom-trawling causes damage to seabeds.For a clearer conscience: Go for Norwegian and Icelandic stocks.Rating: ***
Tuna Top facts: Six commercially important species: albacore, bigeye, northern and southern bluefin, skipjack and yellowfin. Most popular tinned fish in UK.Status and problems: World catches have doubled in the past decade, and now albacore, bigeye, northern and southern bluefin are all listed by the IUCN. Bycatch of marine mammals still a problem. For a clearer conscience: Pole-and-line methods of capture are 'dolphin friendly', but may catch seabirds. Avoid scarcer species, such as bluefin, which are popular in sushi and sashimi restaurants.Rating: **
Mussels Top facts: Bivalve mollusc, normally found in large numbers, that attaches itself to the rocks and other mussels with sticky threads known as byssus. Filter-feeds on plankton. May live more than 15 years. New Zealand green-lipped mussels are imported.Status and problems: Mussels are widely cultivated, and stocks are generally considered to be well above maximum sustainable yield. Dredging causes damage to seabed.For a clearer conscience: Buy farmed rather than dredged. Mussel cultivation, like scallop farming, is extensive and low-impact.Rating: ****
Hake Top facts: Moderately deep-water fish which lives close to the bottom during day but moves into mid-water to feed at night. Very popular in the Mediterranean, particularly Spain.Status and problems: Many stocks at serious risk of collapse, in particular northern hake, which are found from Skagerrak (between Denmark and Norway) to the Bay of Biscay. Recovery plans developed by the EU in 2001 include a 74 per cent quota reduction. Bycatch of marine birds and turtles in longline fisheries also an issue.For a clearer conscience: Best avoided.Rating: *
Whiting Top facts: A slender-bodied fish, common in inshore waters, feeding on shrimps, molluscs and small fish. Grows to between 0.3m and 0.5m long. Migrates to open sea after the first year of life and is an important part of the diet of larger fish and seabirds. A good choice for those on a low-fat diet.Status and problems: Caught by bottom-trawling, which causes damage to the seabed, and is part of a complex mixed fishery (like cod), and so discards are a problem.For a clearer conscience: Ask for line-caught fish.Rating: ***
Langoustine (scampi) Top facts: 10-legged crustacean. Much smaller than the common lobster at up to 15cm in length. Lives in burrows in soft mud or sand and feeds on worms, molluscs, crustaceans and scavenged material. Often deep-fried and served as scampi.Status and problems: Widely distributed in North and Irish Seas and in waters west of Scotland. The most commercially important shellfish species in the UK. Catches are mostly inside safe biological limits, but some stocks are overfished.For a clearer conscience: Choose langoustines caught in pots or creels.Rating: *****
Halibut Top facts: Two species are exploited - Atlantic and Greenland - and both live in deep, cold waters. Atlantic halibut is larger than Greenland halibut and can attain a maximum size of 2.5m and live for up to 50 years.Status and problems: Both species vulnerable to overfishing because of their slow growth rates and late age of sexual maturity. Stocks of Atlantic halibut greatly diminished, and the species is listed as endangered by the IUCN. Bycatch of marine wildlife in both longline and gill-net fisheries.For a clearer conscience: Choose Greenland over Atlantic and hook-and-line caught fish.Rating: ***
Scallops Top facts: Bivalve molluscs which live on the seabed and are hermaphrodites (ie, both male and female). They may live for 20 years or more.Status and problems: Distributed widely throughout Atlantic waters from Norway to the Iberian Peninsula. Most common method of capture is dredging, which damages seabed.For a clearer conscience: Ensure you eat either hand-picked or farmed scallops, which are generally larger and of better quality than dredged ones. For more information, contact Jane Grant: Tel: 01445 731477; e-mail: scallops@isle-ewe.co.ukRating: **
Seabass Top facts: Spiny-finned fish closely related to groupers. Migrates to fresh water during the summer. May exceed 25 years of age.Status and problems: Though common in seas off UK, seabass is vulnerable to overfishing as the winter fishery targets spawning and pre-spawning fish. Bycatch of marine mammals in some trawls.For a clearer conscience: Avoid fish caught in winter and by pair-trawling, which is responsible for cetacean deaths in the English Channel. Farmed fish from the Mediterranean available.Rating: **
Lobster Top facts: Territorial, living in crevices or underneath rocks, coming out to feed mainly at night. Its dark blue shell turns red when boiled.Status and problems: Stocks in traditional lobster areas are now depleted, with removal rates of up to 70 per cent. For a clearer conscience: The Cornwall Sea Fisheries Committee has set up a commercial hatchery. Contact Edwin Derriman Tel: 01736 369817. Lobsters are generally boiled alive. The RSPCA advises freezing them for two hours beforehand so that they go unconscious and suffer a less painful death.Rating: **
Spiny [piked] dogfish Top facts: Member of same family as sharks and rays. Gives birth to live young after a gestation of between 18 and 22 months. Nursehound and spotted catshark also referred to as dogfish. Status and problems: Distributed throughout Atlantic, including the Mediterranean and Black seas. North Atlantic stocks have a well-documented history of overexploitation followed by near-collapse. Vulnerable to overfishing because of low reproductive capacity. Listed as near threatened by the IUCN. For a clearer conscience: Sold as rock salmon, flake or huss. Best avoided.
SalmonTop facts: Migrate from spawning gravel 'redds' in upper reaches of river out to sea before returning to river of birth to spawn. Can reach a length of 1.5m and weight of 36-45kg. Status and problems: Stocks of wild Atlantic salmon have been halved in the past 20 years and are vulnerable to overfishing by driftnet fisheries and to parasites such as sealice and other impacts from salmon farms. More than 99 per cent of salmon sold in UK shops is farmed, with associated environmental impacts. For a clearer conscience: Buy organic farmed salmon, MSC-accredited fresh Alaska salmon or tinned Pacific salmon. Rating: **
Cod Top facts: Found in North Atlantic. Omnivorous and cannibalistic. Flesh is more than 18 per cent protein with virtually no fat. Status and problems: Affected by overfishing and climate change. Assessed as vulnerable on the IUCN Red List (www.redlist.org). North Sea stocks are on the brink of collapse, with 40-45 per cent of 2-8 year-old fish removed every year by fishing. Recovery plans now in place in Irish and North Seas. For a clearer conscience: Only Icelandic cod are from sustainable sources, but keep an eye on Iceland's proposal to cull whales to protect fish stocks. Pollack, coley and hoki (from MSC-accredited fishery) are alternatives. Rating: ***
Haddock Top facts: An important commercial species with a distribution similar to that of cod. Migratory fish, found in inshore, shallow North Atlantic waters in summer and in offshore deep water in winter. Reported maximum age of 20 years and a maximum size of between 0.8m and 1m (growth rates vary with sea temperature). Status and problems: Species listed as vulnerable by IUCN. Many stocks overexploited, including in the North Sea. Quotas reduced between 2000 and 2001, most notably in Irish Sea. For a clearer conscience: As with cod, Icelandic stocks are sustainably managed. Go for line-caught fish for less bycatch. Rating: ****
Prawns Top facts: Two species are popular in the UK: northern prawns, which are found on muddy sea-bottoms in cold water, and larger tiger prawns, from warm, tropical waters. Status and problems: Cold-water prawn stocks in North Sea considered within safe biological limits. Tiger prawn trawl fisheries associated with large quantities of bycatch, including turtles. Tiger prawns are also farmed, requiring large quantities of feed and causing destruction of coral reefs and mangrove swamps. Sea. For a clearer conscience: Try to find cold-water prawns that have been caught in traps rather than trawled. Avoid warm-water species. Rating: ***
Mackerel Top facts: Fast swimming species related to tuna, found in mid-water in huge schools above the continental shelf. Status and problems: Common in the North Atlantic, but large-scale purse-seine fisheries can result in bycatch of marine mammals, such as dolphins, local stock depletion and bycatch of juvenile fish. North Sea stock long since depleted. For a clearer conscience: Buy MSC-labelled fish from the South West Handline Fishery. Contact David Muirhead Tel 01326 555813 or check out the MSC website (details on main page) for certified retailers and distributors. Rating: **
Trout Top facts: Member of salmon family with similar lifecycle. There are two species, of which rainbow trout is non-indigenous introduction from the US. Native species are either sea trout (females which migrate from rivers and lakes out to sea) or brown trout (non-migratory males which stay in freshwater). Status and problems: Both species widely farmed, and being carnivores (like salmon), they require fishmeal. Non-indigenous rainbow interbreeds and competes with native species, and brown trout are threatened as a result. For a clearer conscience: Buy organic trout where you can. Rating: **For a clearer conscience: Try to find cold-water prawns that have been caught in traps rather than trawled. Avoid warm-water species. Rating: ***
Plaice Top facts: Widely distributed in temperate waters of Atlantic, Indian and Pacific Oceans. Bottom-dwelling fish found on sandy bottoms, buried in the sand during the day and active at night. Long-lived, with a reported maximum age of 30 years. Spawns between January and March after long migration.Status and problems: Beam- and bottom-trawling cause damage to seabeds. Overfishing - especially of immature fish - is threatening stocks, as the fish only matures at the age of seven, and so large fish are now rare.For a clearer conscience: Look for line-caught fish from day boats.Rating: ***
Brown crab Top facts: The largest British crab, found on the lower shore down to a water depth of about 100m, usually among rocks or under boulders. Has characteristic 'pie-crust' edge to its shell.Status and problems: Common around UK and European coasts, but many stocks are now overfished - it is estimated that more than 60 per cent of our crab populations are being harvested each year.For a clearer conscience: If you buy your crab alive, you will have to kill it yourself. The most humane method of killing a crab is to 'spike' it in its two nerve centres - behind the eyes and on the underside of the 'apron'.Rating: ***
Herring Top facts: An oily fish rich in Omega-3 acids, it is often sold smoked (as a kipper).Status and problems: Widespread species - the Guinness Book of Records lists it as the most numerous fish - though it can be overfished locally. UK stocks collapsed in 1970s, resulting in a total fishing ban. Now well managed, though industrial harvesting for fishmeal poses future threat.For a clearer conscience: Look for MSC-accredited Thames herring from spawning beds off West Mersea, in Essex. Contact Alex Midlen from the Essex Estuaries Initiative for further details Tel: 01206 282480.Rating: ****
Skate Top facts: From the same family as rays, skates are bottom-dwelling fish usually found in shallow coastal waters. Like other elasmobranchs (sharks and rays), skates are vulnerable to overfishing because they mature late. They grow to more than 1.25m and can live up to 50 years. Status and problems: Two species are exploited - common skate, which is listed as endangered by the IUCN and has probably been fished to extinction in the Irish Sea and is very rare in the central and southern North Sea, and thornback ray, which is assessed as low risk.For a clearer conscience: Avoid, unless you know it's a thornback ray.Rating: *
Sole Top facts: Dover and lemon are the two most popular sole species. Like others in its family, a sole's left eye migrates over the top of the head during growth and ends up beside the other. Status and problems: Both species are caught by beam trawls that damage the seabed. Though not endangered at present, sole are vulnerable to overfishing, particularly of immature fish. For a clearer conscience: Ask for line-caught fish from day-boats working out of small ports in Cornwall and Devon.Rating: ***
Coley [saithe]Top facts: From the same family as cod and haddock. Gregarious fish that occur in both inshore and offshore waters, living close to the seabed, and widely distributed in North Atlantic. Dark green in colour, it can grow up to 1.3m long and for 25 years. Status and problems: Species not threatened, but catches of North-Sea stock are outside safe biological limits, with many immature fish being landed. Bottom-trawling causes damage to seabeds.For a clearer conscience: Go for Norwegian and Icelandic stocks.Rating: ***
Tuna Top facts: Six commercially important species: albacore, bigeye, northern and southern bluefin, skipjack and yellowfin. Most popular tinned fish in UK.Status and problems: World catches have doubled in the past decade, and now albacore, bigeye, northern and southern bluefin are all listed by the IUCN. Bycatch of marine mammals still a problem. For a clearer conscience: Pole-and-line methods of capture are 'dolphin friendly', but may catch seabirds. Avoid scarcer species, such as bluefin, which are popular in sushi and sashimi restaurants.Rating: **
Mussels Top facts: Bivalve mollusc, normally found in large numbers, that attaches itself to the rocks and other mussels with sticky threads known as byssus. Filter-feeds on plankton. May live more than 15 years. New Zealand green-lipped mussels are imported.Status and problems: Mussels are widely cultivated, and stocks are generally considered to be well above maximum sustainable yield. Dredging causes damage to seabed.For a clearer conscience: Buy farmed rather than dredged. Mussel cultivation, like scallop farming, is extensive and low-impact.Rating: ****
Hake Top facts: Moderately deep-water fish which lives close to the bottom during day but moves into mid-water to feed at night. Very popular in the Mediterranean, particularly Spain.Status and problems: Many stocks at serious risk of collapse, in particular northern hake, which are found from Skagerrak (between Denmark and Norway) to the Bay of Biscay. Recovery plans developed by the EU in 2001 include a 74 per cent quota reduction. Bycatch of marine birds and turtles in longline fisheries also an issue.For a clearer conscience: Best avoided.Rating: *
Whiting Top facts: A slender-bodied fish, common in inshore waters, feeding on shrimps, molluscs and small fish. Grows to between 0.3m and 0.5m long. Migrates to open sea after the first year of life and is an important part of the diet of larger fish and seabirds. A good choice for those on a low-fat diet.Status and problems: Caught by bottom-trawling, which causes damage to the seabed, and is part of a complex mixed fishery (like cod), and so discards are a problem.For a clearer conscience: Ask for line-caught fish.Rating: ***
Langoustine (scampi) Top facts: 10-legged crustacean. Much smaller than the common lobster at up to 15cm in length. Lives in burrows in soft mud or sand and feeds on worms, molluscs, crustaceans and scavenged material. Often deep-fried and served as scampi.Status and problems: Widely distributed in North and Irish Seas and in waters west of Scotland. The most commercially important shellfish species in the UK. Catches are mostly inside safe biological limits, but some stocks are overfished.For a clearer conscience: Choose langoustines caught in pots or creels.Rating: *****
Halibut Top facts: Two species are exploited - Atlantic and Greenland - and both live in deep, cold waters. Atlantic halibut is larger than Greenland halibut and can attain a maximum size of 2.5m and live for up to 50 years.Status and problems: Both species vulnerable to overfishing because of their slow growth rates and late age of sexual maturity. Stocks of Atlantic halibut greatly diminished, and the species is listed as endangered by the IUCN. Bycatch of marine wildlife in both longline and gill-net fisheries.For a clearer conscience: Choose Greenland over Atlantic and hook-and-line caught fish.Rating: ***
Scallops Top facts: Bivalve molluscs which live on the seabed and are hermaphrodites (ie, both male and female). They may live for 20 years or more.Status and problems: Distributed widely throughout Atlantic waters from Norway to the Iberian Peninsula. Most common method of capture is dredging, which damages seabed.For a clearer conscience: Ensure you eat either hand-picked or farmed scallops, which are generally larger and of better quality than dredged ones. For more information, contact Jane Grant: Tel: 01445 731477; e-mail: scallops@isle-ewe.co.ukRating: **
Seabass Top facts: Spiny-finned fish closely related to groupers. Migrates to fresh water during the summer. May exceed 25 years of age.Status and problems: Though common in seas off UK, seabass is vulnerable to overfishing as the winter fishery targets spawning and pre-spawning fish. Bycatch of marine mammals in some trawls.For a clearer conscience: Avoid fish caught in winter and by pair-trawling, which is responsible for cetacean deaths in the English Channel. Farmed fish from the Mediterranean available.Rating: **
Lobster Top facts: Territorial, living in crevices or underneath rocks, coming out to feed mainly at night. Its dark blue shell turns red when boiled.Status and problems: Stocks in traditional lobster areas are now depleted, with removal rates of up to 70 per cent. For a clearer conscience: The Cornwall Sea Fisheries Committee has set up a commercial hatchery. Contact Edwin Derriman Tel: 01736 369817. Lobsters are generally boiled alive. The RSPCA advises freezing them for two hours beforehand so that they go unconscious and suffer a less painful death.Rating: **
Spiny [piked] dogfish Top facts: Member of same family as sharks and rays. Gives birth to live young after a gestation of between 18 and 22 months. Nursehound and spotted catshark also referred to as dogfish. Status and problems: Distributed throughout Atlantic, including the Mediterranean and Black seas. North Atlantic stocks have a well-documented history of overexploitation followed by near-collapse. Vulnerable to overfishing because of low reproductive capacity. Listed as near threatened by the IUCN. For a clearer conscience: Sold as rock salmon, flake or huss. Best avoided.
The ethical guide to eating fish
The ethical guide to eating fish
The expression 'plenty more fish in the sea' shows how seafood has long been viewed as inexhaustible, but the reality is that fish stocks around the world are under threat. According to the UN, nearly 70 per cent of marine fisheries are either fully or overexploited and 10 per cent are depleted or recovering from depletion.
So should a conscientious consumer stop buying fish altogether or eat only those species that are not overexploited? Or choose farmed fish over wild ones?
Such questions inspired Bernadette Clarke of the Marine Conservation Society (MCS) to write the Good Fish Guide. Clarke recommends that you ask a few questions about the fish you are about to buy. For starters, find out where the fish has come from. North Sea cod is endangered but other populations off the coast of Iceland are healthy and fished sustainably.
Size does matterThe size of the fish or fillet you're buying is important. Catching small, immature fish denies them the opportunity to reproduce. You should also establish how your fish was caught. For example, dredging for scallops involves scouring the seabed with a plough-like apparatus, and the damage is akin to digging up a meadow for the odd turnip.
Diving for scallops has little impact on the environment, but is labour-intensive and unlikely ever to meet demand. Scallop farming is, however, a truly sustainable method of food production.
The problem with fish-farmingNot all aquaculture is so benign. Sealice proliferate in the densely stocked cages of salmon farms, and can infect wild fish, while escaped fish may interbreed with their wild cousins, diluting the gene pools of fish that have evolved into river-specific populations. Furthermore, salmon are fed on small, bony fish, which are being caught in ever-increasing quantities for fish farms and are the prey of beleaguered, wild fish such as cod, haddock - and salmon.
Organic salmon, certified by the Soil Association, is now widely available. At least 50 per cent of the fish-meat in the pellets fed to organic salmon must come from the by-products of wild fish caught for human consumption. The balance must be sourced from sustainable wild resources.
Sustainable fisheriesThe Marine Stewardship Council (MSC) certifies sustainable fisheries. Fish that carry the MSC logo come from healthy stocks and are caught using non-damaging techniques. Similarly, the EC has introduced a regulation ensuring traceability, and from now on all fish will have to be clearly labelled with basic information about its origins. If you need more details, ask the fishmonger or the chef. If you don't get satisfactory answers, don't buy - there are many more ethical fish you can fry.
The expression 'plenty more fish in the sea' shows how seafood has long been viewed as inexhaustible, but the reality is that fish stocks around the world are under threat. According to the UN, nearly 70 per cent of marine fisheries are either fully or overexploited and 10 per cent are depleted or recovering from depletion.
So should a conscientious consumer stop buying fish altogether or eat only those species that are not overexploited? Or choose farmed fish over wild ones?
Such questions inspired Bernadette Clarke of the Marine Conservation Society (MCS) to write the Good Fish Guide. Clarke recommends that you ask a few questions about the fish you are about to buy. For starters, find out where the fish has come from. North Sea cod is endangered but other populations off the coast of Iceland are healthy and fished sustainably.
Size does matterThe size of the fish or fillet you're buying is important. Catching small, immature fish denies them the opportunity to reproduce. You should also establish how your fish was caught. For example, dredging for scallops involves scouring the seabed with a plough-like apparatus, and the damage is akin to digging up a meadow for the odd turnip.
Diving for scallops has little impact on the environment, but is labour-intensive and unlikely ever to meet demand. Scallop farming is, however, a truly sustainable method of food production.
The problem with fish-farmingNot all aquaculture is so benign. Sealice proliferate in the densely stocked cages of salmon farms, and can infect wild fish, while escaped fish may interbreed with their wild cousins, diluting the gene pools of fish that have evolved into river-specific populations. Furthermore, salmon are fed on small, bony fish, which are being caught in ever-increasing quantities for fish farms and are the prey of beleaguered, wild fish such as cod, haddock - and salmon.
Organic salmon, certified by the Soil Association, is now widely available. At least 50 per cent of the fish-meat in the pellets fed to organic salmon must come from the by-products of wild fish caught for human consumption. The balance must be sourced from sustainable wild resources.
Sustainable fisheriesThe Marine Stewardship Council (MSC) certifies sustainable fisheries. Fish that carry the MSC logo come from healthy stocks and are caught using non-damaging techniques. Similarly, the EC has introduced a regulation ensuring traceability, and from now on all fish will have to be clearly labelled with basic information about its origins. If you need more details, ask the fishmonger or the chef. If you don't get satisfactory answers, don't buy - there are many more ethical fish you can fry.
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