Fish Fishing Effects
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.
How Commercial Fishing …show more content…
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 …show more content…
It can have serious effects further up the food chain. Herring is a vital prey species for the cod. Therefore, when herring are overfished the cod population suffers as well. The sandeel is the main food for seabirds such as the puffin. Sandeels have been fished around the Shetland Islands since the mid-1970s, though catches were declining throughout the 1980s. At the same time, the colonies of seabirds nesting around Shetland declined, with some even falling to breed for several years.
In the Antarctic, fishing for krill is threatening to disrupt the delicate balance of nature in these waters. Krill are small, red shrimps, about 6cm long, found in huge numbers in areas of plant plankton, and they make up a significant part of the animal plankton. Krill occur in huge swarms many kilometres across, and it has estimated that there could be up to 650 million tonnes of them in the Antarctic Ocean.
Since the early 1980s, six countries, including Japan and the former USSR have been harvesting krill, which is the main food for the great whales, and which also supplements the diets of seals, penguins, squid and fish. We have no idea what effects this will have on the populations of animals which feed on krill. The natural balance in the Antarctic has already been upset by the overexploitation of the great whales, and heavy fishing of krill may well worsen the