The Life Cycle, Exploitation, and Use of Native Oyster - Essay Example

1 November 2008 Sub Marine Resources, Native Oyster The life cycle, exploitation and use of Native oyster . The aquaculture has rendered us with apotpourri of species including animals and vegetation. Aquatic cultivation caters to almost half of the yearly global fisheries production which is 120 million metric tones as per 2004 fact sheets. Amazingly, the species that had the highest production bulk was Pacific cupped Oyster having production number as large as 4.4 million tones! Carps followed Oysters in terms of production volume. Finfish comprises half of overall aquatic production; aqua plants comprise one-fourth of production and the rest is shrimps, crabs, mollusc and prawns. Carps, Oysters, cockles, freshwater fishes, prawns, Salmons, Mussels are some of the species with highest levels of production. In recent years, cultivated aqua plants have shown significant increase in production too. The gross production of aqua plants in 2004 was worth 6.8 billion US$. Oysters hold the second position when it comes to aquatic culture. The aquatic species variegation is another factor that demands attention. More than 240 cultivated aquatic flora and animal species were recorded in 2004. The fact that needs exposure here is that heterogeneity of aquatic species has been undermined and collection of annual facts and data suggest that species variegation is shooting up. Species introduction is one of the legitimate means of increasing production. Species Introduction has played a significant role in aquaculture and they provide a noticeable share of total aquaculture production. Consider the fact that nearly 17% of the global finfish production is because of alien/introduced species. However they have negative impacts too. Introduced species can impact aquatic ecosystem in terms of predation, habitat modification etc. Proper assessment of effects of introduced species on aquatic life and their negative and positive consequences should be done and suitable plans should be formulated. Fishery products comprises of water, proteins, lipids, minerals, vitamins and other nitrogen compounds. The vital micro-nutrients and minerals in fatty fish are Vitamins A and D, calcium, magnesium, iron, phosphorus whereas iodine, in marine fish. Fish lipids have up to 40% extremely unsaturated long chain fatty acids. Fish proteins hold all vital amino acids. The carbohydrate content in fish muscle is very less, generally lesser than 0.5 percent. There are numerous uses of marine resources; the most prominent use is as a source of food. Fisheries resources are rendering human species with record amounts of food. Fish has proved to be a diet full of proteins and nutrients. World fish production used for direct human intake shot up during 1990s. Other use of fish include 'extracting oil' and as 'feed'. However, excessive use of fisheries resources is endangering the ecosystem of our planet. Continuously increasing demand and exhausting marine life has led to an increment in the gap between demand and supply. As Taras Grescoe states in Bottomfeeder: How the fish on our Plates is Killing our Planet that Good fish like sardine, pilchard is diminishing and that we in our madness are hoovering up the good fish by converting it into fishmeal for salmon in farms. He concludes that it requires 3.9 Kg of wild fish to yield 1 Kg of flabby, artificially colored farmed salmon. Commercial wild salmon fishery has nearly vanished in North Atlantic. The North Sea store of herring, valuable fatty pelagic fish, tumbled in 1970s because of the requirement of the pig feed industry. It can be concluded that overfishing is a compelling marine issue demanding immediate attention. According to EUCC news, China is a country where live reef fish requirement is quite high and is expected to increase in the coming years. Hong-Kong being the capital of world's live reef fish industry exports a lot of reef fish to China. China's increasing demands for coral fish has already endangered species like hump head wrasse. As marine stock has already depleted in nearby waters, Hong Kong traders are moving far for rare fish such as snappers disseminating overfishing across the globe. Overfishing and usage of cyanide to catch live fish has left reefs in Philippines, Malaysia and Indonesia devoid of marine life. Another report from EUCC news states that overfishing of sharks in North Atlantic has caused the reduction of stocks by almost 99% endangering species like crabs and shrimps. The number of hammerhead sharks has gone down by 99% between the period of 1970 and 2005. Consequently, rays and skates, that sharks feed on are growing in population rapidly. Increase in requirement of shark fins for medical industry and as food has worsened the situation. Rays and skates having fed on bay scallops are probable to search for food in protected areas along the coast where other marine life like shellfish dwells in their early months of life. If rays and skates predate these shellfishes, these species would be endangered. It is probable that overfishing of sharks may be a result of previous overfishing of cod. Another article from New York Times by James Kanter states that EU should toil more to prevent the overfishing of blue fin tuna that breeds in the Mediterranean and the Gulf of Mexico and is found widely in North Atlantic. European Union Governments arrived at the decision of putting expert observers to check illegal fishing activities and to monitor U.S and European catches. According to an extract from Reuters News Service article by Lisa Lambert, more than a third of the coastal waters that join America's rivers and oceans are in piteous state, with Puerto Rico and the Northeast coast doing the worst. More than 10% of fish and organisms in the waters facing North Atlantic bore chemical contamination (thecoastalsociety.org, 2008). Some examples of endangered fish are Airsac catfish, albacore tuna, Angel shark, Anguila ciega, Double sash butterflyfish, Estuarine pipefish, dusky grouper, Cave catfish, Coastal stingaree, Coelacanth, and Devil's Hole pupfish whereas Atyid shrimp, Black abalone, Black corals, Blue corals, Cuban cave shrimp are some of the threatened marine invertebrates. Moving on to another threatened marine invertebrate, native oyster, having scientific name Ostrea edulis. It is also known by names 'edible oyster', 'European flat oyster', 'platte oester' and 'common oyster' etc. Native Oyster is indigenous to Europe and has served as part of human food for many centauries. One of the beliefs for eating it is that it serves as aphrodisiac although no scientific proofs to prove the belief exist as yet. Native Oyster belongs to Ostreidae family and has a shell width of up to 11 cm. It falls under endangered species and is listed as a priority species under the UK Biodiversity Action Plan. Native Oyster is a rough, scaly hermaphroditic bivalve mollusc. It is ovular and yellowish-grey in color. It is widely spread across British Isles and is found less on the east and north-east coasts of Britain and Ireland. It is mainly found in west coast of Scotland, the river Fal, the Solent, north-eastern Atlantic and in the whole Mediterranean Basin. Native Oyster initiates its life as male and tends to form cluster with other native oysters. They grow sexually when eight to ten months old. After this period, Oysters shift or change gender depending on water temperature. They change sex to become females every three or four years when water temperature becomes 16C. If water temperature becomes 20C, they change sex and become females annually. They only return to being males on the cooler intervening periods. Native oysters are called hermaphrodites because when they attain adulthood, they first operate as males and then they begin the alternate cycles of changing sex. The male discharges sperms in to the seawater, which are accepted by the female via its inhalant siphon. The eggs brought forth by the female are fertilized inside the parent's shell and larvae are hatched within the mantle cavity until they have a wholly molded shell. This process consumes up to ten days. Henceforth, parent native oyster discharges larvae into water where they float and feed on phytoplankton. The number of larvae discharged depends on the age and size of parent native oyster. The larvae are maturated usually after three weeks. They are called pediveligers when they reach this stage. From Here on, they drop to seabed and search the sediment surface using their foot till they get hold of an appropriate surface to which they fix and root themselves. Henceforth, they carry out a process called metamorphosis and experience physiological changes. The process usually takes three to four days and after this process larvae become juveniles and are called spat or seed as well. The growth rate of native oyster is very swift in the first one and a half years. Oysters can take up to five years to achieve a remarkable size which usually is directly linked to environmental factors and specifically water temperature (seafish.org, 2008). The average lifetime of native oyster is six years but it may live up to as long as fifteen years. Eggs are fertilized in the gill cavity of the female and stay there for seven days, after which they become larvae and are liberated. The larvae link to the plankton in the water till they get hold of a surface to tie themselves. Adult Oysters screen out the plankton by making use of their gills and feed themselves by filtration. Native Oysters require strong bedrock along coastlines, in plankton-plenteous water (less deep than 20 Meters) to which they fix themselves. The towns of Colchester in Essex and Whitstable in Kent have become famous for their Oyster Festivals. In 1920, a massive fatality hit European native oyster population. The native oyster's population recouped later. In early 1970s and 1980s, two oyster diseases dispersed and massively depleted the population of native oyster in entire Europe's rear areas. In spite of modern management practices, and programs, the population of native oyster has stayed low in volume since then. Due to reduction in supply, native oyster has become deluxe seafood item and is reserved for opulent customers. Native oyster has become a serious victim of spread of oyster diseases and over harvesting. In the late 19th centaury, native oyster served as cheap diet for the poor. By now, they have become a luxury item due to overfishing. Bonamiasis is one of the key diseases that affect native oyster and has a substantial presence in native oyster stocks of UK. It is the key factor in inhibiting the production and management of wild and cultured stocks of native oyster in the UK. Currently, the chief dangers to the wild native oyster occur from disease and two introduced species, the American oyster drill shellfish, and the slipper limpet. The reduction in the population of native oyster amounts to past mistakes like want of preventive methods to curb the diffusion of disease and unlawful transport of Bonamia infested oysters from North America to Europe's water isles. This validates the requirement of 'supervising health of native oyster' and 'limiting the spread of disease'. To protect and conserve native oyster, shell fishing industry in the UK is meticulously regulated. Harvesting season is closed from 14 May to the 4 August which is crucial breeding time. This restriction does not apply to farmed oysters although. The chief aim of UK Action Plan is to preserve and protect the current population of native oyster around the UK coastline and to increment the number of practicable oyster beds. In order to augment the native oyster's opportunities, a number of laws and directives have been introduced in recent years. There is also a European Directive regulating the dispersion of diseases common in bivalves. The native oyster is running through across much of the UK (arkive.org, 2008). The maturation and development of native oysters depends on several physical, chemical, biological, salinity factors as well as muddiness, flow rate and nutrient capacity of water. Trade in marine resources has been a common element of all the societies around the world. The fish feed industry is universal and has seen many structural changes in recent years. Salmon feed is the key commodity of fish feed industry. The production potency of the waters has been employed to yield shellfish, fish which are utilized both as feed and food. However, the industries involved in the exploitation of marine resources are not just feed and food industries. A wide variety of industries exploit marine resources like pharmacy, cosmetics, medicine etc. The gross global catch of fish is approximately near to 100 million tones with many species severely exploited. The production figures of industrial fisheries yielding fish meal and oil are near to 30 million tones and slumping. Approximately 90% of the world production of fish oil and 50% of the fishmeal produced is taken up by the aqua feed industry. It is anticipated that the declined availableness of fish oil will be the key factor in inhibiting the development of the world aquaculture industry. The biomass of lantern fish in the Indian Ocean is approximated to be close to 50 million tones and that of Antarctic krill is estimated to be 500 million tones. The biomass of zooplankton is anticipated to be 35 million tones in the northeastern northern hemisphere. Global leaders in fishmeal and fish oil production are Peru and Chile. European production follows South America's whereas key producers are Iceland, Norway and Denmark. The fisheries are being severely exploited round the globe. The anticipated increase in fish farming of carnivore species would increase the exploitation of already exhausting marine resources. WWF fears that the European aquaculture industry will directly place further pressure on already heavy exploited fish species used to produce this fish oil and fishmeal. Some of the commercially exploited fishes in South East Pacific Ocean are Sardinops sagax, Engraulis ringens, Trachurus murphyi. and Clupea harengus. In 1983, fish resources in North Atlantic were termed as fully fished and over fished in 1994 whereas in 1997, it was reported that fisheries of the North-East Atlantic were severely exploited. "The root cause of this poor situation within European waters has been the inability of the member states within the European Union (EU) to control and reduce fleet capacity within the Common Fisheries Policy" (FAO, 1997). In the European Union, presently all the fishing related processes are subject to Common Fisheries Policy (CFP). The International Council for Exploration of Sea (ICES) carries research on commercially-exploited fish stocks and decides about their management (Taija-Riitta Tuominen and Maren Esmark, 2003). Fish distribution usually complies with the environment, with majority of species having constricted zones of orientation or of procreation capability. Since estimations of global warming suggests that water temperature will rise least at the equator and more at the poles, it is anticipated that pole ward changes in distribution will happen. Growth of food preservation and processing technologies has made globalization of fish trade very easy. It is presently anticipated that over 800 fish species are traded internationally. In Europe, the condition of the blue whiting is critical. A total break down may happen if the present fishing practices go on. It has been proposed that raw stuff for obtaining fish feed might be incurred by harvesting marine resources from a lower tropic level in the marine food web than fish. The meat of the idea is that it is more effective and energy efficient to feed the fish straight from a lower tropic level. This is alike the argument that humans should eat more vegetables and other vegetarian food instead of meat, for it requires ten times more energy to 'produce' the meat than if the food grain is eaten up directly. Consequently, aquaculture is growing, flourishing in mostly all area of the world, except for Sub-Saharan Africa,as the world population requirement ofseafood products is anticipated to rise. Universally, catches from capture fisheries have become even and majority of the principal fishing regions have attained their maximum limit. Thus maintaining fish supplyings from capture fisheries will not be able to meet the increasing world demand forseafood. Worldaquaculture production will need to reach 80 million tones by 2050. Works Cited Food and Agriculture Organization of the United Nations, 2008. Fisheries and Aquaculture Department. [Online] Available at:http://www.fao.org/fishery [Accessed 1 November 2008]. Read More

 

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