The impact of Fisheries and Fishing on the environment
This course focuses on the flow of energy within the marine food chain. Learn about the different fishing techniques used, the impact of fisheries and fishing on the environment and practice of sustainable fishing.
Sustainable Fishing in our Oceans Course
Fish as a worldwide resource are considered a “pool” resource, which is one where any use of the resource greatly reduces the amount available to use. Timber from the wood of trees and the fossil fuel coal are other examples of pool resources.
The maximum sustainable yield is growing in importance with fisheries management. It is basically a value that represents the maximum fish harvest that will not impair the population’s ability to survive and replace these losses.
So the maximum sustainable yield for Cod in the north sea, for instance, would be the absolute maximum amount of cod that could be caught without causing the north sea cod to become officially “over fished” and unable to replace its losses by reproduction.
A sustainable fishery is one that can provide a constant output, meeting the needs of humans (which we all know are every increasing as the population does so) but at the same time does not harm the long term future of the target species or others around it. Studies have found that protecting areas of the ocean as ‘Fully Protected Areas’ has seen a return in biodiversity and fish stock.
While fisheries are an important way for people to make a living and to feed the ever-growing human population there are some very significant implications for the environment and, without regulation, humans threaten to wipe out the very resource on which they so
ome of them can cause damage to species they are not even targeting; this is called by-catch. This unwanted catch is not even limited to similar species of fish or even fish as a whole; a great deal of animals can get caught up in the by-catch of non-specific methods such as long lining and trawling, including seabirds, dolphins, sharks, turtles and seals.
Perhaps the most maddening aspect of by-catch, of which it was estimated in 1996 that there was about 27 million metric tons, is the fact that unwanted species are simply thrown back into the sea, dead; these are known as discards (figure 2). In the last few years as much as half of the fish caught in the North sea was actually discarded every year- equating to half a million tonnes of fish every year, wasted.
Ghost fishing is the term given to the ability of lost fishing gear to continue fishing and wasting stocks, needlessly killing sea creatures.
Gear can become abandoned or lost for a variety of reasons; bad weather, other fishing activities and even sometimes deliberately thrown overboard once it has served its purpose.
Lost gear then gets caught in a cycle that bodes ill for the surrounding marine community – the weight of the initial catch collapses the net attracting scavenger species such as species of crab and other crustacea who devour the organisms caught in the net.
Once the net is cleared of its originally catch by these scavengers it is relieved of the weight that collapsed it in the first place and it can rise back up in the water column once more and continue fishing; starting this cycle of capture/decay/attract all over again. The cycle continues until the net naturally breaks down or is broken up by the action of waves or rough waters during storms. In relatively calm seas a net can continue ghost fishing for over a year!
Shark-finning: Shark fin soup is considered a delicacy in the far east fetching the equivalent of nearly £50 per bowl; it is reserved for the wealthy and is thought to be a sign of prosperity and wealth. Shark fin soup’s ugly truth though, is that it supports one of the most prevalent, unmanaged and unmonitored fisheries in the world. Shark finning vessels are only after one thing – shark fins; commanding more than £195 per pound of dried product, the fins carry the commercial value; the shark’s body carries very little value indeed and fishers see the body as a waste of space on their vessel that could be filled up with valuable fins before their return to the shore. This is done at rate that is unsustainable – the unselective nature of the process removes young and old alike, this, as was the case with over fishing and by catch earlier, means that there are no individuals left to reproduce and this makes the level of sustainability even worse.