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New zebra mussels controls
Volume 32/Number 2/February 1996
scientists doubt that any increase in phytoplankton production resulting from fertilizer application will lead to increased fish stocks. Worst still, some fear that ecosystem disruption caused by organic enrichment and increases in secondary producers such as jellyfish could actually lead to reductions in fish stocks and encourage toxic algal blooms. Such fears concerning nutrient run-off from agriculture and sewage pollution have led most countries to adopt measures to reduce these discharges to coastal seas, with the encouragement of the European Commission. Norsk Hydro's scientists argue that these reductions have been a significant factor in the decline of North Sea fish stocks, and that the application of fertilizers will increase these stocks, as well as promoting algal production, from which energy and various useful chemicals could be derived. Norsk Hydro is the world's biggest producer of artificial fertilizers. Other scientists argue that overfishing is the major factor in stock declines, and that simplistic assumptions based on laboratory tests and small scale field trials cannot be used as a basis for large scale marine fertilization projects, as marine ecosystems are too complex and dynamic for the risk of adverse consequences to be ruled out. Furthermore, they point out that even if increased primary production is translated into increased fish production, the inefficiency of marine trophic systems coupled with competition between fish species means that increases in commercial stocks could be insignificantly small. Norsk Hydro maintains that these concerns will be addressed by their research programme and are seeking further funding from the European Commission. Critics maintain that there is no technological solution to fish stock declines, and that such projects are ignoring the basic problem that there are too many vessels chasing too few fish. P E TE R JONES
Canadian Harp Seal Resource Speaking at the Second Consultative Forum on East Coast seal management in Newfoundland, the Canadian Minister of Fisheries and Oceans, William Rowat, stated that harp seals are an abundant, valuable resource which should be harvested like any other marine resource. Apparently, the harp seal population has risen from 3 million in 1990 to 4.8 million in 1994. At the same time, cod stocks are at a record low, despite a 4-year moratorium on fishing which has now been extended to a fifth year. Scientists say seals are eating some 6.9 million tonnes of fish and other marine life every year. The Consultative Forum had been called to consider management strategies to control the increasing harp seal population. Various options were discussed ranging from an increased land-based harvest to a large vessel harvest as ways of achieving increased landings in 1996. The forum was attended by more than 90 delegates, representing sealers, fishermen, processors, provinces and municipalities, and a number of animal rights and
conservation groups. Most delegates agreed that the Total Allowable Catch (TAC) should be in the range between the current level of 186 000 and the replacement yield of 278 000 animals.
New Zebra Mussels Controls Since they first appeared in Lake St. Clair, Michigan, in 1989, zebra mussels have caused millions of dollars in damage each year by fouling the water intakes of electricity generating stations, industrial plants and municipal water treatment units. Once established the bivalve mollusc spread to the rest of the Great Lakes and today are found in 18 states and as far south as Louisiana. The problem is worst in Lake Erie. Here large water treatment and power plants with water requirements of over 300 million gal day -1 can expect to spend $350400000 yr -~ to control the mussels with smaller installations using less than 1 million gal day -1 spending around $20 000 yr - l . A number of different methods are currently being used to combat the menace, the choice of treatment depending mainly on local environmental restrictions. At present, chlorine is the chemical most commonly used to kill the zebra mussels. Mixtures of chlorine, bromine or ozone can also be used, or the water can be simply heated to 40°C. Although effective, these methods are often difficult to use in large installations, particularly in winter as water intake pipes can be up to 5 miles offshore. In 1990 US Congress set up the Michigan Sea Grant College research programme to learn more about the zebra mussel menace and how to control these pests. Future developments include specialized equipment and coatings based on copper, tin, fluoropolymer or silicone to inhibit the mussels. The US Army Construction Engineering Research Laboratories have been involved in a 3-year programme evaluating various coatings and materials, whilst other research institutes and companies are studying systems that would apply ultraviolet radiation, pulsed current and magnetic fields.
Maine Atlantic Salmon Threatened The decline in Atlantic Salmon in seven Maine rivers is being blamed by US government officials on ocean harvesting, low survival rates and past land-use and hatchery stocking practices. The situation is so serious that the species has been proposed for threatened status under the Endangered Species Act (ESA) by the National Marine Fisheries Service. However, the salmon cannot be protected by the act until Congress lifts the current moratorium on listings. The seven rivers affected are the Sheepscot, Ducktrap, Narraguagus, Pleasant, Machias, East Machias and 185
scientists doubt that any increase in phytoplankton production resulting from fertilizer application will lead to increased fish stocks. Worst still, some fear that ecosystem disruption caused by organic enrichment and increases in secondary producers such as jellyfish could actually lead to reductions in fish stocks and encourage toxic algal blooms. Such fears concerning nutrient run-off from agriculture and sewage pollution have led most countries to adopt measures to reduce these discharges to coastal seas, with the encouragement of the European Commission. Norsk Hydro's scientists argue that these reductions have been a significant factor in the decline of North Sea fish stocks, and that the application of fertilizers will increase these stocks, as well as promoting algal production, from which energy and various useful chemicals could be derived. Norsk Hydro is the world's biggest producer of artificial fertilizers. Other scientists argue that overfishing is the major factor in stock declines, and that simplistic assumptions based on laboratory tests and small scale field trials cannot be used as a basis for large scale marine fertilization projects, as marine ecosystems are too complex and dynamic for the risk of adverse consequences to be ruled out. Furthermore, they point out that even if increased primary production is translated into increased fish production, the inefficiency of marine trophic systems coupled with competition between fish species means that increases in commercial stocks could be insignificantly small. Norsk Hydro maintains that these concerns will be addressed by their research programme and are seeking further funding from the European Commission. Critics maintain that there is no technological solution to fish stock declines, and that such projects are ignoring the basic problem that there are too many vessels chasing too few fish. P E TE R JONES
Canadian Harp Seal Resource Speaking at the Second Consultative Forum on East Coast seal management in Newfoundland, the Canadian Minister of Fisheries and Oceans, William Rowat, stated that harp seals are an abundant, valuable resource which should be harvested like any other marine resource. Apparently, the harp seal population has risen from 3 million in 1990 to 4.8 million in 1994. At the same time, cod stocks are at a record low, despite a 4-year moratorium on fishing which has now been extended to a fifth year. Scientists say seals are eating some 6.9 million tonnes of fish and other marine life every year. The Consultative Forum had been called to consider management strategies to control the increasing harp seal population. Various options were discussed ranging from an increased land-based harvest to a large vessel harvest as ways of achieving increased landings in 1996. The forum was attended by more than 90 delegates, representing sealers, fishermen, processors, provinces and municipalities, and a number of animal rights and
conservation groups. Most delegates agreed that the Total Allowable Catch (TAC) should be in the range between the current level of 186 000 and the replacement yield of 278 000 animals.
New Zebra Mussels Controls Since they first appeared in Lake St. Clair, Michigan, in 1989, zebra mussels have caused millions of dollars in damage each year by fouling the water intakes of electricity generating stations, industrial plants and municipal water treatment units. Once established the bivalve mollusc spread to the rest of the Great Lakes and today are found in 18 states and as far south as Louisiana. The problem is worst in Lake Erie. Here large water treatment and power plants with water requirements of over 300 million gal day -1 can expect to spend $350400000 yr -~ to control the mussels with smaller installations using less than 1 million gal day -1 spending around $20 000 yr - l . A number of different methods are currently being used to combat the menace, the choice of treatment depending mainly on local environmental restrictions. At present, chlorine is the chemical most commonly used to kill the zebra mussels. Mixtures of chlorine, bromine or ozone can also be used, or the water can be simply heated to 40°C. Although effective, these methods are often difficult to use in large installations, particularly in winter as water intake pipes can be up to 5 miles offshore. In 1990 US Congress set up the Michigan Sea Grant College research programme to learn more about the zebra mussel menace and how to control these pests. Future developments include specialized equipment and coatings based on copper, tin, fluoropolymer or silicone to inhibit the mussels. The US Army Construction Engineering Research Laboratories have been involved in a 3-year programme evaluating various coatings and materials, whilst other research institutes and companies are studying systems that would apply ultraviolet radiation, pulsed current and magnetic fields.
Maine Atlantic Salmon Threatened The decline in Atlantic Salmon in seven Maine rivers is being blamed by US government officials on ocean harvesting, low survival rates and past land-use and hatchery stocking practices. The situation is so serious that the species has been proposed for threatened status under the Endangered Species Act (ESA) by the National Marine Fisheries Service. However, the salmon cannot be protected by the act until Congress lifts the current moratorium on listings. The seven rivers affected are the Sheepscot, Ducktrap, Narraguagus, Pleasant, Machias, East Machias and 185