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Bycatch: the fishing net effect

17 Feb 2014

The world’s oceans are under multiple pressures from climate change, pollution, coastal development and fishing. Over a quarter of the world’s fish stocks are either overfished or depleted. And the loss of species as bycatch adds more to the problem. Annually, hundreds of thousands marine species are caught unintentionally, and as these individuals have no commercial value, they are often thrown back into sea, injured or dead. This can be defined as bycatch.


Over the years, technological development and the introduction of sophisticated fishing gears allowed fisheries to catch large amount of fish. However, these gears cannot separate targeted and non-targeted marine species, and catch everything in their path. Subsequently, unwanted species are also caught in large quantities. Seabirds, reptiles, sharks and cetaceans are the most frequent victims of fisheries bycatch. It is estimated that every year larger number of cetacean species die by fishing gears than by any other cause.


Whales, dolphins and porpoises are especially prone due to their slow reproductive output. As these marine mammals have an important role on the top of the food chain, high mortality coupled with slow birth rate can induce changes in the energy flow and species composition at other trophic levels. Eventually, the prey-predator dominance shift can upset entire ecosystems.


In the past few decades, ecosystem based fisheries management and sustainable fishing methods have significantly reduced the number of unwanted catch. Also, between 2015 and 2019, the European Commission will introduce landing obligation in European waters. This means that everything caught by commercial fisheries will have to be landed and counted for.


But despite all these efforts, the lack of management of small scale fisheries and the lack of fisheries law enforcement on national and international waters mean that the removal of unwanted species will continue to have a top-down cascading effect on the marine ecosystem.


by Whalefish Contributor Wanda Bodnar

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