Aquafind.com Aquatic Fish Database est. 1991


Search Supplier Directory
    Add Your Company
    Update Your Listing
Wholesale Supplier Short List
Fish Fact Sheets

Search Companies Directory
    Add Your Company
    Update Your Listing

Wholesale Seafood Traders
Wholesale Aquaculture Traders
Wholesale Ornamental Fish Traders

Capelin + Imports & Exports
Catfish + Imports & Exports
Crab/Shellfish + Imports & Exports
Fish Meal + Imports & Exports
Fish Oil + Imports & Exports
Groundfish + Imports & Exports
Grouper + Imports & Exports
Lobster + Imports & Exports
Octopus + Imports & Exports
Oyster + Imports & Exports
Pelagics
Salmon + Imports & Exports
Scallop + Imports & Exports
Seabass + Imports & Exports
Shrimp + Imports & Exports
Squid + Imports & Exports
Tilapia + Imports & Exports
Tuna + Imports & Exports

Auctions
Calendar
Cod Links
Definitions and Terms
Finance/Credit
Fish Fact Sheets
Market Prices
Market Reports
Seafood Links
Tilapia Links






About Aquafind
Aquatic Posters
Articles
Contact AquaFind
Currency Converter
Featured Product Pages
Scientific Aquacultrue Papers
Weather
World Clock
Shrimp & Seafood Recipes

LANGUAGE
Chinese French German Italian Spanish Russian


Custom Search


Bookmark and Share

THE IMPACT OF OVERFISHING ON FISH POPULATION: THE CONCEPT OF OVERFISHING, TYPES OF OVERFISHING & HOW DO WE KNOW OVERFISHING TAKES PLACE?


Parven. A1, Haque. T. ASM2, Hossain. D3


Corresponding Author: Afshana Parven1, Assistant Professor, Department of Agribusiness, Atish Dipankar University of Science &Technology, Dhaka-1213, Bangladesh. 2Lecturer, Department of Agribusiness, Atish Dipankar University of Science &Technology, Dhaka-1213, Bangladesh. 3Lecturer, Department of Agribusiness, Atish Dipankar University of Science &Technology, Dhaka-1213, Bangladesh.


DEFINITION OF OVERFISHING:

Before going to the definition of overfishing we need to know the Definition of bycatch. After a catch is hauled aboard, the non-commercial marine life, is culled out and thrown back, known as "bycatch". Bycatch is not limited to unwanted fish species. Bycatch can be fish with no commercial value, juveniles of marketable species, all types of marine life including whales, dolphins, porpoises, fur seals, albatrosses and turtles are killed as bycatch. For example, a staggering 100 million sharks are killed each year. Tuna fisheries, which in the past had high dolphin bycatch levels, are still responsible for the deaths of 1 million sharks. And Discards are animal returned to the sea after being caught. Overfishing can be defined as the catching of more fish from a single population than can be naturally replaced on an annual basis. Fishing with a sufficiently high intensity to reduce the breeding stock levels to such an extent that they will no longer suppport a sufficient quantity of fish for sport or commercial harvest. The harvesting of a particular species of fish to the point where it can no longer reproduce itself in large numbers in a given area. In other words, catching too many fish; fishing so much that the fish cannot sustain their population. The fish get fewer and fewer, until finally there are none to catch. This official definition of overfishing can also be explained as "The average female lobster should be allowed to live long enough to produce at least 10% of the eggs that she would produce if she were allowed to live her natural life." While it may seem impossible to judge the egg production from an unfished population, considering that the lobster population has been heavily fished for over 100 years, it should be considerably easier to calculate the egg production from a female that lived a natural life span. If we know how often a female produces eggs, how many eggs she produces each time, and how many years she is likely to live, we can calculate how many eggs she would produce over her life time. According to the Magnuson-Stevens Fishery Conservation and Management Act as a rate or level of fishing mortality that jeopardizes the capacity of a fishery to produce the maximum sustainable yield on a continuing basis.


Fishing rate vs mortality


CAUSES OF OVERFISHING:

Overfishing pushed many commercially important fish populations into steep declines for example Canada's northern cod. Some commercially important stocks are in such a critical state that all fishing has been shut down, or sharply curtailed. There are various causes of overfishing, such as:

1. The rapid increase in demand for fish and fishery products leading to increase fish price faster than prices of meat:

During past few decades, the large increase of demand especially for marine fish and marine fishery products leading to increase fish price faster than prices of meat. Fish prices are increasing that encourages people to do fishing because of high technology, high price and high profit. As a result, fisheries investments have become more attractive to both entrepreneurs and governments, much to the detriment of small-scale fishing and fishing communities all over the world. In the last decade, in the north Atlantic region, commercial fish populations of cod, hake, haddock and flounder have fallen by as much as 95%, prompting calls for urgent measures. Some are even recommending zero catches to allow for regeneration of stocks.

Marine fish are the major source for ∞ - 3 and ∞ -6 fatty acid with other types of nutrients like ca, Vitamin A and D and that helps to improve human health with a human desirable flavour and reduce blood cholesterol level in human body. Hence day by day the demand for fish products is increasing remarkably and it leads to overfishing.

2. Rapid advance of fishing technology:

Most of the problems associated with overfishing have been caused in the last 50 years by the rapid advances in fishing technology. The fishing vessels are replaced by huge factory ships which are able to stay out at sea for weeks at a time. These factory boats have all the equipment necessary either to freeze or tin fish caught by their hunting ships, so that they need to return to base only when their holds are full. With the introduction of the new factory boats, there was a 7% growth in catches every year during the 1950's and 60's, but since then there has been little increase in catch size, and at least 20 of the world's most important fisheries have disappeared in the last 25 years, with many more suffering so badly from overfishing that they are unlikely to recover. As catches have gradually become smaller, so the mesh sizes used in fishing nets have decreased, allowing smaller and smaller fish to be caught. Many of these are too small to be used as food, so they are crushed to be made into either animal food or fertilizer. Each GRT in 1995 can catch 4 times as many fish as the same GRT in 1970.

3. The dramatic increase of use of destructive fishing techniques and gear :

The dramatic increase of use of destructive fishing techniques and gear worldwide destroys fisheries, marine mammals and entire ecosystems. Along with the growing fleet come more fishing nets in the water, some of which are very non selective. It is impossible to catch only the desired fish species, this harvest of non-target species is called bycatch. Bycatch constitute all of the animals that are caught but not wanted or used or are required to be discarded by management regulation(Somma 2003). This includes endangered or protected species, fish that are legally to small to catch, or those that have to commercial value. It is estimated that bycatch makes up a quarter of all the fish caught, but most of the bycatch are dead before being thrown back to the water. Equipment such as purse seine nets, longlines, gillnets and trawls are especially harmful to the environment. They tend to catch juvenile fish, birds and other nontarget animals. Gill nets are also dangerous as many are discarded in the water, yet continue to kill fish in what is known as ghost fishing. Trawls are especially dangerous, they produce significant bycatch while damaging the environment as they are dragged along the seafloor.

4. Using smaller mesh size net :

Fishing using nets is indiscriminate. Any fish which get in the way of the net will be caught in it if they are too big to get through the mesh. For every one tonne of prawns caught, three tonnes of other fish are killed and thrown away. 20,000 porpoises die each year in the nets of salmon fishermen in the Atlantic and Pacific Oceans and tens of thousands of dolphins are killed each year by tuna fishermen. Some sea fish live in the upper parts of the water. They are called 'pelagic' fish, and are caught by drift netting. This is where a net suspended from floats is stretched between two boats so that fish swim into it. Fish are unable to swim backwards, so once they are caught in the net, there is no escape unless they are small enough to fit through the net's mesh.

5. More time, effort and money in fishery sector:

Fig: Relationship between total income, total operating costs

As this is profitable so people invest more money and time in this sector then before.

6. Open access to fishing in most fisheries and Non enforcement of modern management regulations:

In the past 25 years, the worldwide number of fishermen has more than doubled. In most developing countries, the poor have no choice but "to glean the last of the resource". Free and open access encourages overfishing as fishermen tend to catch as much fish as they can without taking care to maintain the fish stock.

7. The common property nature of the fishery resources, resulting in unregulated access to many of the resources

FAO reports that due to the common property nature of the fishery resources, resulting in unregulated access to many of the resources illegal, unreported and unregulated fishing worldwide appears to be increasing as fishermen seek to avoid stricter rules in many places in response to shrinking catches and declining fish stocks.

8. Subsidies from governments to the fishing industry :

Today, there isn't a fishing region in the world that does not suffer from fisheries management decisions designed to satisfy short-term economic or political objectives (or both) rather than protecting the marine environment and conserving fish populations.

Indeed, in many countries, governments have played an important part in fueling the expansion of excessive fishing capacity and overexploitation by providing lucrative subsidies, taxpayer funded handouts. The European Union spends a large amount of money on what many would describe as a dying industry. Indeed there is a valid argument that fishing in the EU should be left to die. However the political fallout from this would be immense. Fishing has a political say out of proportion to the number of people it employs (less than 1% of the workforce).

A World Bank study estimates that subsidies, although declining, are still worth a total of up to $20 billion a year. Fisheries subsidies sometimes provide jobs in poor coastal regions and help countries expand their fishing industry. However, most of the time, the same subsidies encourage companies to develop high-tech fishing and thus overfishing.


TYPES OF OVERFISHING:

1. Growth overfishing:

Growth overfishing occurs when animals are harvested at an average size that is smaller than the size that would produce the maximum yield per recruit. The total yield from the fishery is therefore less than it would be if the fishing mortality rate, or percent of the stock removed each year, was lower. In such a case, less fishing would produce higher landings. Growth overfishing still reduces the potential yield from a fishery, and thus the economic and other benefits that could be obtained from the stock. For example: Heavy fishing removes the larger animals and does not give young lobsters a chance to grow to their potential size. Most of the large lobsters in the inshore fishery were caught during the 1800s and early 1900s. Lower fishing pressure on the offshore lobster stocks allows more lobsters to grow to a larger size, but even there the size range is much reduced from the early days of the fishery. The largest lobster ever recorded was a 51 1/2 pound lobster caught in Marine in 1926.

2. Recruitment overfishing:

The rate of fishing above which the recruitment to the exploitable stock becomes significantly reduced. This is characterized by a greatly reduced spawning stock, a decreasing proportion of older fish in the catch, and generally very low recruitment year after year. Recruitment refers to the time when young fish become big enough to be caught. Recruitment overfishing means so many adults have been caught that there are no longer enough young adults to maintain the population. When fishing pressure is too heavy to allow a fish population to replace itself. Occurs in circumstances where an increase in fishing effort from current levels will cause a decline in recruitment to a fishery. Recruitment overfishing can be brought about by:

1) reduction of the spawning stock (which may become so small as to produce a limited number of eggs and hence of recruits), and

2) coastal environmental degradation, which affects recruitment through its effects on the size and/or suitability of nursery areas. [Note that preventing recruitment overfishing is not, as[some] think, a matter of letting 'each female spawn at least once', since, for example, less than one in a thousand anchovy or shrimp larvae reach a mature age, even in the absence of a fishery. Instead the crucial aspect is that the spawning stock should be large enough to ensure that the subsequent recruitment remains independent of the parental stock.]

Fishing stock recruitment

3. Ecosystem Overfishing:

Occurs when the species composition and dominance of an ecosystem is significantly modified by fishing, e.g. with reductions of large, long-lived, demersal predators and increases of small, short-lived species at lower trophic levels. Competition and predation between taxa. It may be described here as what takes place in a mixed fisheries when the decline (through fishing) of the originally abundant stocks is not fully compensated for by the contemporary or subsequent increase of the biomass of other exploitable animals. Overfishing is the biggest threat to the ocean environment. Concern for biodiversity stems finding that overfishing of higher-trophic-level fish stocks (i.e., piscivores)generally results in refocusing of fishing effort on planktivores and a concomitant decline in the average trophic level of the landings (Pauly et al., 1998). One characteristic of overfished ecosystems is sequential depletion of economic stocks (Orensanz et al., 1998). Switching between target species occurs when resources of economic importance are markedly reduced in abundance by overfishing and when there are other more abundant stocks available. Piscivores and valuable invertebrate stocks are particularly vulnerable to this fishing pattern (Christensen, 1996; Oresanz et al., 1998). Overfishing and depletion of some stocks may become so severe that they may be regarded as economically extinct.

The symptoms of ecosystem overfishing include: reductions in diversity; reductions in aggregate production of exploitable resources; decline in mean trophic level, increased by-catch; greater variability in abundance of species; greater anthropogenic habitat modification (Hall, 1999); and, in extreme cases, change to alternative stable species regimes (Steele, 1998).

4. Economic overfishing:

A level of fish harvesting that is higher than that of economic efficiency; harvesting more fish than necessary to have maximum profits for the fishery occurs when the costs of fishing effort are greater than the revenue generated from fishing: Incomes of fishermen continuously decline


FIG: Fishing Mortality rate-F or effective Fishing effoer(boats, Days etc.) MEY-maximum conomice yield, MSY-Maximum sustainable yield

10%eper-the spawning stock biomass that will produce 10% of the eggs that would be produced if all females were laft to live their natural life span, with no fishing.

Note that this optimum level of effort is always less than that required to extract maximum sustainable yied (MSY) and that, therefore, maximum economic yield is always less than MSY. The stated or implicit goals of many management schemes; and that beyond MSY, subsidies will reduce catches(by reducing total cost).

  1. Biological overfishing:

  2. The combination of growth and recruitment overfishing leading to catch decline on the right, descending side of surplus production models (Schaefer 1954, 1957; Fox 1970; Ricker 1975)

Catching such a high proportion of one or all age classes in a fishery as to reduce yields and drive stock biomass, and spawning potential below safe levels. Biological overfishing occurs when fishing levels are higher that those required for extracting the Maximum Sustainable Yield (MSY) of a resource and when recruitment starts to decrease statistically.

6. Malthusian overfishing:

Desperate attempt to fish to survive where fishers destroy the environment that the fish (and they) depend on for survival using poisons, dynamite, etc. In developing countries, small-scale fishers are usually poor and fishing is an alternative employment opportunities to them. Overtime, the number of these fishers usually increase both because of internal recruitment (i.e.their male children) and through new entrance, i.e. new fishers recruited from other sectors usually to landless farmer to whose fishing becomes an occupation of last resort. Occurs these poor fishers, lacking the usual alternative of traditional fishers are faced with declining catches and induce wholesale resource destruction in their effort to maintain their incomes. This may involve in order of seriousness and generally in temporal sequence such as; Use of fishing techniques, gear and/or mesh sizes not sanctioned by government, use of gears not sanctioned within the fisher communities. Use of gears that destroy the resource base and use of destructive gear such as dynamite and fish poisons that endanger the fishers themselves.


EFFECTS AND EVIDENCE OF OVERFISHING:

1. Elimination of the largest and oldest individuals from a population or stock. Fish are found to be smaller than its known size maturity: FAO reported that over 70 percent of the world's fish species are either fully exploited or depleted. Overfished populations are characterized by less-productive fish that eventually lead to a decline in stocks. In the United States, recent average yields of all U.S. fisheries resources are roughly 60 percent of the best estimate of long-term potential yield from these resources.

2. Overfishing Change in total fish catch and Decrease in catch per unit effort:

Catch per unit effort is the quantity of fish caught for each day of fishing at sea or hours trawling or number of pots shot. Catch per unit is important because it gives the differences between earnings(=catches) and the cost of catchings(=fishing effort). Even if total catches did not collapse, fish biomass and catch per unit effort decreased when fishing effort increased.

3. Heavy fishing pressures can change the genetic characteristics of a population:

Heavy fishing pressure can change the genetic characteristics of a population by selecting for or against certain genetically heritable traits like size at first sexual maturity (Policansky, 1993):

Fishing pressure selecting for smaller-sized fish can be found in the case of Pacific pink salmon. Over time, with about 80 percent of the spawning fish being caught, catch data registered a decrease in the average weight per fish. After evaluating and accounting for other factors, such as environmental causes, researchers concluded that fishing pressure was the cause in miniaturization of the pink salmon (Law, 1991) and another example is that, overfishing having induced early maturation in a population can be found in the Northeast Arctic cod. In this case, the trawling practiced was indiscriminate, intensively exploiting all age-classes of the cod. Fishing of Arcto-Norwegian cod on their feeding grounds since the onset of trawling in the 1930s gradually caused the breeding stock to become younger overall (Sutherland, 1990). A "large change in mortality imposed by fishing generate[d] a big selection pressure for early maturation irrespective of any change in size-at-age" (Law, 1991, p. 36). Between the 1930s and 1950s, the fish were known to mature between the ages of nine and 11, and "immature individuals had roughly a 40 percent chance of surviving from age 3 to 8 years" (Law, 1991). Overall mortality was increased by this fishing pressure to such a level that it significantly reduced the chances of the breeding-age cod reaching their spawning grounds to two percent. As a result, remaining faster-growing cod entered the breeding stock, and as such, "there has been a gradual shift toward earlier maturation" (Sutherland, 1990, p. 814). The cod now mature when they are about seven or eight years old.

4. The depletion of stocks & reduction of income from fishing:

In Peru, a small fish called the anchoveta was caught in huge numbers to be made into fish meal for animals. In 1970, more than 69,000 tonnes were caught, making it the biggest fishery in the world. One thousand five hundred boats were catching 100,000 tonnes of anchoveta every day. By 1972, the daily yield had risen to 180,000 tonnes! The fishermen ignored warnings from the United Nations Food and Agriculture Organisation that their catches were too big, and when a natural upwelling of warm water entered the normally cool, nutrient-rich waters the anchoveta inhabited, this combined with a lack of breeding stock in the population was enough to cause the total collapse of the anchoveta fishing industry. Overfishing can seriously affect not only the fish stocks, but also the livelihoods of many people who depend on fishing as a job. There is a delicate balance to be struck between catching large numbers of fish so as to make more money and ensuring that there are enough fish left alive to be able to replenish stocks for future years. It is human nature to try to make as much money as possible, but this has to be weighed against the economic hardship that whole communities have suffered as a result of overexploiting their own fisheries, not to mention the grave consequences of overfishing for fish populations.

5. Overfishing causes the increase of bycatch and non targeted animals:

Harvest of non-targeted animals, or bycatch, is estimated to constitute about one-quarter of the global fish catch. Bycatch comprises all of the animals that are caught but not wanted or used, or are required to be discarded by management regulation. It may include specially protected species such as marine mammals or endangered species, juvenile individuals too small to be marketed, or other species of fish without commercial or recreational value to the fisher. The unwanted species are usually discarded, often dead, either at sea or on shore. Various types of fishing gear are non-selective and can ensnare unwanted catch. Purse seine nets can catch juvenile fish and marine mammals such as dolphins. Longlines catch seabirds, sea turtles, and non-targeted fish along with the targeted catch. Gillnets can also catch seabirds and, lost or discarded gillnets can continue to catch and kill marine animals through what is known as "ghost fishing." Trawls are a particularly non-selective type of gear and can take considerable bycatch of many different species. In addition, concern is also growing about the changes trawls can make to fish habitat. They are often dragged along the bottom of the seabed and may damage habitat.

6. Competition from industrial and distant water fleets:

Despite the blatant warning signs, new industrial-scale fishing vessels are rolling out of shipyards equipped with more efficient ways to find, catch and process fish, and adding to the colossal armada of big boats that are still fishing. Due to the overfishing amount of trash fish catches increase and which is very important for fish processing industry to produce fish meal for that they are releasing more fishing fleet in sea and which are capable to catch fish from deep sea and the fleets are very much modernized for that they can go to the distant water. Over-capitalization of the industry which has led to the buildup of excessive fishing fleets, particularly of the larger-scale vessels catching too many fish. This has led to widespread overfishing (with many fish stocks at historic lows and fishing effort at unprecedented highs).

7. Fishing down the Food Chain:

Overfishing can cause changes in marine food webs, adversely affecting other species. For example, the decline of Steller sea lions in Alaska has been attributed in part to overfishing of the Stellers' main food sources: pollock, cod, and mackerel. FAO shows a gradual shift in the main fish species caught, from larger predatory fish to smaller, plankton-eating species, over the course of time. These species are usually prey for larger carnivorous fish such as tuna or swordfish which are placed at the top of the food web. Species that occupy a middle trophic level are usually of medium size and chase smaller prey animals. And fish towards the bottom of the food web feed on plankton, single-celled algae or tiny crustaceans. The growing harvest of fish from lower trophic levels robs the higher-level species of the food they need to reproduce and maintain their populations. The extent of global fishery could destabilise the ecological balance of the oceans which has grown up over millions of years. The tendency to fish further down the food web could be indicative of the possible collapse of more fishing grounds. There is great difficulty nowadays in sustaining global fisheries production at around 82 million tons. In response to declines of commercially valuable stocks of bigger, slower growing species, commercial fishing fleets have turned to "fishing down the food chain", targeting increasingly large quantities of smaller species of fish with less commercial value. Such fish, called small-pelagic fish, are highly mobile shoaling fish that dwell near the ocean's surface, and they play a critical role in the marine foodweb.

Overfishing also has the potential to indirectly change ecosystems such as coral reef ecosystems. When plant-eating fish are removed from coral reef ecosystems, grazing is reduced, allowing the algae that coexist with corals to flourish and potentially take over, especially if the water contains high levels of nitrogen. Because they often reduce light that enters the water, these algae contribute to the loss of corals, which depend upon light.

8. Fishing Threatens Survival of Marine Wildlife:

Fishing affects much more than fish because the effects of removing too many fish can dramatically alter the populations of other predator species in the marine food web. Many species of marine wildlife are threatened by the competition with fishing operations -- sharks, seals, dolphins, whales, seabirds, turtles, and many more. In addition, millions of animals become the victims of entanglement, incidental capture and death in fishing gear. Food availability is a critical factor which limits the distribution and numbers of animal populations in the oceans. The relationship between predator and their prey (food) can be disturbed by intensive commercial fishing. This can affect marine biodiversity in ways that may be irreversible. For example, the ecological crisis in the Barents Sea ecosystem, off the coast of northern Norway, which was being acutely felt by Norwegian coastal fishing communities during the 1980s when catches in the coastal cod fishery dramatically declined. In response, Norway's Institute of Marine Research investigated. Marine scientist Johannes Hamre concluded that the problems stemmed from an unbalanced state of the relationships between certain key predators and their prey in the Barents Sea, which developed after the herring stock had been fished out as far back as the late 1960s. In the Barents Sea, and right through the entire north Atlantic ecosystem, fish such as herring, capelin are important food for the likes of seabirds, whales (such as the fin, minke and humpback), seals and other marine animals. Population crashes in some seabird populations, for instance have been associated with changes in the abundance and availability of fish stocks. In the British Isles populations of several seabird species have experienced declines which follow those of fish stocks. Overfishing of herring, sprat and sand eels around Britain pose a survival challenge to seabird species dependent on these stocks, particularly in winter. On the other side of the Atlantic, Canadian scientists have issued warnings about overfishing when whales, seals and seabirds off Canada's east coast appeared to be dying of starvation because of large declines in fish stocks. Thousands of harp seals had been found far south of their usual range, while sea bird reproduction was down 75 per cent. In surveys of humpback whales, scientists found that the young whales appeared to be far smaller than normal off the Newfoundland coast, perhaps because they were unable to find the amount of fish they need. Steller sea lions in the North Pacific provide a another example of how a marine mammal population can be affected by overfishing of forage food supplies. Stellers are listed as a "threatened" species under U.S. law, because their total population declined from as many as 300,000 in 1960 to less than 66,000 today. Three-quarters of the world's population of Stellers live in Alaskan waters where pollack, the Steller's major prey species is heavily fished. Millions of marine animals other than fish are severely injured or killed each year through deadly interactions with fishing operations. Many populations of marine wildlife species are threatened or have become endangered, to such an extent that some, like the albatross, are sliding toward extinction. Yellowfin tuna in the eastern tropical Pacific (ETP) commonly swim beneath herds of dolphins and other species such as whales and whale sharks as they migrate through the open oceans. Using floating nets in excess of 2000 meters long, ETP tuna fishing fleets deliberately encircled dolphins, whales or sharks in order to catch the tuna below them. Many populations of dolphins, sharks, whales, even endangered sea turtles could be threatened by purse seine fishing operations. During the 1980s, more than 50,000 kilometer's (32,000 miles) of driftnets were being set in the Pacific Ocean each night, many types of marine animals were dying. Official data pointed to annual death tolls of tens of thousands of dolphins, whales and seals. Up to 750,000 seabirds, as well as millions of fish and sharks were caught and killed. The various species of albatross in the Southern Ocean part of the world, fleets of hundreds of fishing vessels from Japan, Korea, Taiwan and Indonesia hunt the prized southern bluefin tuna. Albatross and other seabird species are caught and dragged underwater to their deaths on these deadly, baited hooks as they are launched from the ships. As many as 100 million hooks a year have been set by the Japanese fleet in the southern bluefin tuna fishery, for instance, so it is not surprising that tens of thousands of birds are being killed annually. One conservative calculation for albatross killed on Japanese longliners is 44,000 per year. Twelve of the world's 14 albatross species are believed to be dying in their tens of thousands each year in this way. Because of the large number of birds affected, commercial fishing has been identified as the most serious threat to the survival of most albatross species. Species of sea turtles are other hapless victims of incidental capture in fishing gear. Twenty thousand loggerhead turtles are captured every year by the Spanish longline fishery in the Mediterranean Sea, and four thousand of them are believed to die because they are returned to the sea with the hook still embedded in the throat. In shrimp trawl fisheries off the southern United States the issue of marine turtle bycatch came to wide public attention relatively recently, largely because of the estimated 48,000 sea turtles caught annually by shrimp fishermen. The US National Marine Fisheries Service estimates that more than 11,000 of these were dying annually.


References

Hall, S. 1999. The effects of fishing on marine ecosystems and communities. Blackwell Science, London. 274 pp.

Marine environment and sustainable development: The oceans as a global resource. Report from the Courier ACP-EU, july-august 2002. Pp. 45 — 47.

Murawski. A.S,2000. Definitions of overfishing from an ecosystem perspective. ICES Journal of Marine Science, 57: 649 — 658.

NMFS, Our Living Oceans: Report on the Status of U.S. Living Marine Resources, 1999, June 1999, pg. 43.

Orensanz, J. M., Armstrong, J., Armstrong, D., and Hilborn, R. 1998. Crustacean resources are vulnerable to serial depletion — the multifaceted decline of crab and shrimp fisheries in the Greater Gulf of Alaska. Reviews in Fish Biology and Fisheries, 8: 117 — 176.

Pauly, D., and Christensen, V. 1995. Primary production required to sustain global fisheries. Nature, 374: 255 — 257.

Paley, D. 1994. From growth to Malthusian overfishing : Stages of fisheries resources misuse. SPC Traditional Marine Resource Management and Knowledge Information Bulletin 3, January 1994. Pp. 7-12.

Pauly, D., Christensen, V., Dalsgaard, J., Froese, R., and Torres, F. Jr 1998. Fishing down marine food webs. Science, 279: 860 — 863.

R. LAE,1997, Does overfishing lead to a decrease in catches and yields? An example of two West African coastal lagoons. Fisheries Management and Ecology
Volume 4 Page 149 .

Somma.A.2003. THE ENVIRONMENTAL CONSEQUENCES AND ECONOMIC COSTS OF DEPLETING THE WORLD'S OCEANS.

What, food security sans fisheries. Report from FAO committee on Food Security, Samudra march 2003. Pp. 35-37.

www.yptenc.org.uk/docs/factsheets/ env_facts/overfishing.html - 19k

http://bss.sfsu.edu/ehines/geog646/overfishing.pdf


Seafood — Fish — Crustacea

Contact | Terms of Use | Article Submission Terms | Advertising | Fish Supplier Registration | Equipment Supplier Registration
© 2017 Aquafind All Rights Reserved