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Mariculture. Natural cod stocks going down. There has been much press coverage of the decline in natural cod stocks due to over fishing in the North Sea.

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Introduction

Fish- Beneath the Surface (An article for 'Future of Fish' magazine) Natural cod stocks going down. There has been much press coverage of the decline in natural cod stocks due to over fishing in the North Sea. I like my cod and chips and so was quite concerned about this. It may be too late to get the numbers back up to 1970's levels but less documented by the press, is the rapid growth of mariculture, the cultivation of marine organisms for food, which retailers say could 'revolutionise the fishing industry' (2). I visited the Manx Mariculture fish hatchery to investigate the principles behind fish farming and soon discovered that it was not without its problems. As my guide, Rick Fullerton, explained, a bacterial problem in the live feed meant that the hatchery faced a crisis in the year 2006 when only a few hundred cod were produced instead of the target 1 million. This is a common problem in mariculture and there is the potential for exciting new developments in the production of live feed which could eliminate this problem in the future. Use of live feed as an answer In order to kill bacteria, live feed may be disinfected or treated with UV rays (6). ...read more.

Middle

This is most likely because there is limited availability of carbohydrates in marine environments (9). If the diet does not provide enough energy, protein needed for growth will be broken down instead which increases the costs of fish farming. Protein is needed in the diet as it provides the 10 essential amino acids which the fish cannot synthesis. Fishmeal also contains minerals such as calcium, phosphorus and magnesium and vitamins including the B-complex (8). There are, however, ethical concerns over the use of fishmeal as some argue that for every tonne of farmed fish produced, 5 tonnes of fishmeal are used in the process. On the other hand, fishmeal can be seen to reduce pollution to the environment as there is increased nutrient uptake by the fish (8). Green issues Further environmental concerns which surround fish farming include the pollution caused by waste being discharged into the sea. However, made up of fish waste and undigested food, this is natural and it does not cause major problems or damage to marine environments (3). This likely to be accurate and precise information as Nick Fullerton is a professional with a degree in biology and has had many years experience in mariculture. The energy cost of running the hatchery which includes pumping water 24 hours day and the continuous monitoring probes must also be taken into account when considering the environmental implications of fish farming. ...read more.

Conclusion

http://aquanic.org/publicat/state/il-in/as-503.htm [Accessed 14 March 2007]. (11) Leonard N, Blancheton J. P., Guiraud J. P. (2000) Populations of heterotrophic bacteria in an experimental recirculating aquaculture system. Aquacultural engineering, 22(1-2), 109-120 (12) Wikipedia (2007) Environmental sciences. http://en.wikipedia.org/wiki/Dissolved_oxygen [Accessed 13 March 2007]. (13) Hayward G (1992) Applied Ecology. London: Thomas Nelson & Sons Ltd (14) Convention on Biological Diversity (2007) Jakarta Mandate Marine and Coastal Biodiversity - Mariculture. http://www.biodiv.org/programmes/areas/marine/mariculture.aspx. [Accessed 13 March 2007]. (15) Whipple A B C (1983) Restless oceans. USA: Time-Life Books Commentary 1. Biological methods and processes used. The problem of decrease in cod stocks together with difficulties with contamination of feed for 'mariculture' is outlined well (4). There is then a very good discussion of different types of live feed as answer to the problem of contamination (4). In addition some data is given to show just how effective live feed is but perhaps more of this data and evidence could have been provided as part of the discussion (3) (11 marks) 2. Applications and implications of the biology encountered There is a good discussion of the environmental and ethical implications of mariculture (4). In addition, the economics of live feed is looked at as a limitation (4). This is then followed by a discussion of the advantages of weaning the fish off live feed and converting to a diet of hard fishmeal pellets. Plenty of data and examples are given here (4). (12 marks) 3. ...read more.

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