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Can We Sustainably Harvest Cod Essay

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Introduction In the past fifty years commercial fishing has depleted fish stocks considerably and in some cases, fish stocks have been so exploited that they may never recover. An example of this is the severe over-fishing of cod on The Grand Banks of Canada, which caused the entire stock to collapse in the early 1990's. The exploitation of cod stocks started when technological advances made fishing more efficient. The reasons for such a catastrophic breakdown of the cod stocks in this area are countless; from fishermen cheating on the catch quotas to the scientist setting a 'safe' catch limit that was too high, due to the use of inaccurate models.1 The reason for these inaccuracies was that, the models used to manage the fisheries made several assumptions that were wrong and consequently caused major knock-on effects on the size of the fish stocks. One of these assumptions was that the level of recruitment was completely unrelated to the size of the fish, and that a very low number of fish would still be able to spawn and successfully rebuild the population back up to a stable level.1 However this is not the case as, in cod there is a correlation between the age/length of fish and the number of eggs that they produce. Other reasons for failing to save the Canadian cod was that; the extent of the problem was discovered to late and the initial measures to increase the stock were poorly implemented by fishermen. As well as this was the fact that cod are a demersal fish stock and are therefore harvested using nets which dragged along the sea bed. The main problem with this was that many other commercial fish species are demersal, and a ban on the fishing of cod would make it difficult to harvest these other species so instead of a ban, fishermen were expected to sort the fish on deck and throw back cod. However this was unsuccessful as, sorting through a very large catch was time consuming and often the cod died on deck before they were thrown back.4 A sustainable yield is the amount of fish that can be harvested without risking the future of the population. When over-fishing is carried out the maximum sustainable yield is exceeded and this causes population numbers to decline. The fall in cod stocks in Canada shows us that in order to sustainably harvest cod, new management schemes had to be implemented. A successful management scheme should aim at maintaining ecological stability of the cod stocks in the long term and to do this, a broad knowledge of the biology and life-history of cod should be obtained.2 The biology and ecology of cod Cod have pelagic eggs and...

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