1/6/2007 - Dangerously delicious from pristine waters
WEEKEND FEATURE: Dangerously delicious from pristine waters
WORLDWIDE Friday, June 01, 2007, 23:50 (GMT + 9)
It may taste good, but is it good to eat? Recent chemical analysis of tissue samples from organisms living in environments that were once considered “pristine,” such as the far northern waters, or the deep-seas, are showing worrying levels of accumulated toxins such as heavy metals. Is this an isolated phenomenon in a few isolated species, especially long-lived species, or is this a widespread environmental concern?
Masters student Inger Marie Tyssebotn at the University of Bergen, Department of Chemistry and the National Institute of Nutrition and Seafood Research (NIFES) is undertaking a fascinating research project to analyse the bioaccumulation of heavy metals and other environmental toxins in the flesh of the orange roughy, a popular menu item in North America and New Zealand. The name of her project is Metal content in deep water fish from the Mid Atlantic Ridge: Orange Roughy (Hoplostetus atlanticus). Tyssebotn is just one of a number of students working hand-in-hand with the Mar-Eco project.
Living far from land around seamounts and ocean ridges, the orange roughy was first commercially exploited in the 1970s, when concentrations were discovered and technology made the exploitation of such remote environments more economically feasible.
The fish quickly became a popular menu item because of its firm white flesh (that freezes well), mild flavour, and the fact that it is low in fat.
Today the fishery for orange roughy is conducted in many waters around the world, including along the mid-Atlantic Ridge, but the resource is limited and not very productive, so strict regulations have now been introduced in order to avoid the severe depletion of stocks observed in some regions.
Orange roughy fisheries have been described as a ‘boom and bust’ commercial phenomena. This is related to the orange roughy’s biology. Orange roughies are very slow growing, are long-lived. They are believed to grow as old as 150 years, and are believed to sexually mature only until around they are 30 years old. This characteristics, and the fact that they tend to aggregate to feed and breed, make them vulnerable to over-fishing, particularly to modern commercial trawling.
Tyssebotn’s project, however, will investigate another aspect of this fishery, that of food safety. It may be that such a long-lived species can accumulate toxins to levels that are harmful for human consumption.
She is using orange roughies collected on the Mar-Eco Project’s two-month-long research cruise along the northern mid-Atlantic Ridge back in the summer of 2004. There were not too many roughies in the collection, as this species, while targeted, proved difficult to sample in satisfactory numbers. However, the exploratory and multi-depth collection methods used meant that roughies from different age groups and of many different sizes were collected.
Sæthre explains that although there are relatively few fish being studied, Tyssebotn is undertaking analyses from a broader range of organs than is usual in this type of study including samples from muscle and bone and cartilage tissue, the liver, kidney, and gonads.
NIFES has long experience in food safety research. Tyssebotn will use their specially developed protocols to chemically analyse the roughy material to determine the presence of metals (manganese, cobalt, copper, zinc, molybdenum, cadmium, tin, mercury and lead), and non-metals (arsenic and selenium).
NIFES will run tests for polybrominated diphenyl ethers (PBDE). When completed, the results will reveal valuable information about some food safety aspects of this vulnerable deep-sea fishery.
Some hard orange roughy facts
It is difficult to study the biology of deep-sea fish and their ecosystems, as they are both technically difficult and expensive. Many of the traditional methods used to study inshore fish species are of no avail. Despite this, some things are now known about the biology of the little orange roughy.
As many other deep-sea fish, orange roughy are long lived. Studies show that they may commonly live more than 100 years (data from both otolith zone counts and radio-isotope ratios). The long lifetime implies that they are late to mature (23-40 years of age), that they grow slowly (with an average size at maturity of 24 cm off South Africa and 42 cm in the NE Atlantic). They also have a low fecundity (reproductive rate) and may spawn irregularly.
While deep-sea fish species have these life history tendencies, researchers believe that orange roughy are the extreme low end of the productivity and high end of the longevity scales.
They are widely distributed throughout the deep-seas, between 500-1500-metres deep and near topographic deep-sea features. The range includes the Atlantic (from the NE to off north-west Africa), the western Mediterranean Sea, the south Atlantic (off Nambia) and through the ridges of the southern Indian Ocean from Africa to Australia, as well as the SW Pacific Ocean to east of New Zealand and the eastern Pacific, off Chile.
They tend to congregate, travelling as much as 200km, around topographic features such as seamounts, plateaus and canyons for spawning and feeding. Orange roughy populations may also be endemic, localised or resident, associated with specific topographic features and not tending to migrate over large distances.
All of these characteristics make the orange roughy highly vulnerable to exploitation. Field experience gained over the fishery’s 25 year history suggests that it is very difficult, if not impossible for local populations to recover from over-fishing. It is not only the orange roughy themselves that are being destroyed. The fishery has very high by-catch levels. Mortality is nearly 100 per cent for these deep-water species, many of whom are unknown and poorly studied.
The mechanical effects of the fishery effort are also devastating to the deep-sea environment. Not only are the fragile, slow-to-recover, sea-floor communities of the trawl path destroyed, but the disturbance to the sea-floor sediments may spread the destructive effects over large areas. It is estimated that 40 per cent of today’s trawling effort occurs in the highly vulnerable and unexplored sea-floor zones deeper than the continental shelf.
Finally, researchers do not know enough about the deep-sea ecosystem to be able to even estimate the effects of removing of a mid-range predator, such as the orange roughy. The roughy is an opportunistic feeder and eats small fish, crustaceans and squid.
By Elinor BartleMar-Eco
WORLDWIDE Friday, June 01, 2007, 23:50 (GMT + 9)
It may taste good, but is it good to eat? Recent chemical analysis of tissue samples from organisms living in environments that were once considered “pristine,” such as the far northern waters, or the deep-seas, are showing worrying levels of accumulated toxins such as heavy metals. Is this an isolated phenomenon in a few isolated species, especially long-lived species, or is this a widespread environmental concern?
Masters student Inger Marie Tyssebotn at the University of Bergen, Department of Chemistry and the National Institute of Nutrition and Seafood Research (NIFES) is undertaking a fascinating research project to analyse the bioaccumulation of heavy metals and other environmental toxins in the flesh of the orange roughy, a popular menu item in North America and New Zealand. The name of her project is Metal content in deep water fish from the Mid Atlantic Ridge: Orange Roughy (Hoplostetus atlanticus). Tyssebotn is just one of a number of students working hand-in-hand with the Mar-Eco project.
Living far from land around seamounts and ocean ridges, the orange roughy was first commercially exploited in the 1970s, when concentrations were discovered and technology made the exploitation of such remote environments more economically feasible.
The fish quickly became a popular menu item because of its firm white flesh (that freezes well), mild flavour, and the fact that it is low in fat.
Today the fishery for orange roughy is conducted in many waters around the world, including along the mid-Atlantic Ridge, but the resource is limited and not very productive, so strict regulations have now been introduced in order to avoid the severe depletion of stocks observed in some regions.
Orange roughy fisheries have been described as a ‘boom and bust’ commercial phenomena. This is related to the orange roughy’s biology. Orange roughies are very slow growing, are long-lived. They are believed to grow as old as 150 years, and are believed to sexually mature only until around they are 30 years old. This characteristics, and the fact that they tend to aggregate to feed and breed, make them vulnerable to over-fishing, particularly to modern commercial trawling.
Tyssebotn’s project, however, will investigate another aspect of this fishery, that of food safety. It may be that such a long-lived species can accumulate toxins to levels that are harmful for human consumption.
She is using orange roughies collected on the Mar-Eco Project’s two-month-long research cruise along the northern mid-Atlantic Ridge back in the summer of 2004. There were not too many roughies in the collection, as this species, while targeted, proved difficult to sample in satisfactory numbers. However, the exploratory and multi-depth collection methods used meant that roughies from different age groups and of many different sizes were collected.
Sæthre explains that although there are relatively few fish being studied, Tyssebotn is undertaking analyses from a broader range of organs than is usual in this type of study including samples from muscle and bone and cartilage tissue, the liver, kidney, and gonads.
NIFES has long experience in food safety research. Tyssebotn will use their specially developed protocols to chemically analyse the roughy material to determine the presence of metals (manganese, cobalt, copper, zinc, molybdenum, cadmium, tin, mercury and lead), and non-metals (arsenic and selenium).
NIFES will run tests for polybrominated diphenyl ethers (PBDE). When completed, the results will reveal valuable information about some food safety aspects of this vulnerable deep-sea fishery.
Some hard orange roughy facts
It is difficult to study the biology of deep-sea fish and their ecosystems, as they are both technically difficult and expensive. Many of the traditional methods used to study inshore fish species are of no avail. Despite this, some things are now known about the biology of the little orange roughy.
As many other deep-sea fish, orange roughy are long lived. Studies show that they may commonly live more than 100 years (data from both otolith zone counts and radio-isotope ratios). The long lifetime implies that they are late to mature (23-40 years of age), that they grow slowly (with an average size at maturity of 24 cm off South Africa and 42 cm in the NE Atlantic). They also have a low fecundity (reproductive rate) and may spawn irregularly.
While deep-sea fish species have these life history tendencies, researchers believe that orange roughy are the extreme low end of the productivity and high end of the longevity scales.
They are widely distributed throughout the deep-seas, between 500-1500-metres deep and near topographic deep-sea features. The range includes the Atlantic (from the NE to off north-west Africa), the western Mediterranean Sea, the south Atlantic (off Nambia) and through the ridges of the southern Indian Ocean from Africa to Australia, as well as the SW Pacific Ocean to east of New Zealand and the eastern Pacific, off Chile.
They tend to congregate, travelling as much as 200km, around topographic features such as seamounts, plateaus and canyons for spawning and feeding. Orange roughy populations may also be endemic, localised or resident, associated with specific topographic features and not tending to migrate over large distances.
All of these characteristics make the orange roughy highly vulnerable to exploitation. Field experience gained over the fishery’s 25 year history suggests that it is very difficult, if not impossible for local populations to recover from over-fishing. It is not only the orange roughy themselves that are being destroyed. The fishery has very high by-catch levels. Mortality is nearly 100 per cent for these deep-water species, many of whom are unknown and poorly studied.
The mechanical effects of the fishery effort are also devastating to the deep-sea environment. Not only are the fragile, slow-to-recover, sea-floor communities of the trawl path destroyed, but the disturbance to the sea-floor sediments may spread the destructive effects over large areas. It is estimated that 40 per cent of today’s trawling effort occurs in the highly vulnerable and unexplored sea-floor zones deeper than the continental shelf.
Finally, researchers do not know enough about the deep-sea ecosystem to be able to even estimate the effects of removing of a mid-range predator, such as the orange roughy. The roughy is an opportunistic feeder and eats small fish, crustaceans and squid.
By Elinor BartleMar-Eco
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