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Tuesday, 21 May 2013

The unintended consequences of simplifying the sea: making the case for complexity - with thanks to Samantha Andrews


Discuss!

The unintended consequences of simplifying the sea: making the case for complexity

So here's the old news....fish targeted by fisheries have been in decline for some time.  Removal or reduction of populations can alter ecological interactions, meaning that other species may become more abundant (or less) in their place.  This is typically done through something called competitive release (the species you compete with are gone, so there is more of a given resource for you) or trophic cascades (as one predator species is removed, its prey becomes more abundant because nothing is eating it.  Of course that means that there is more of those species to nibble away at whatever they eat, causing a population decline in that prey species).

Here's the new..Prawns are really important to UK fisheries....about £110 million per year important, making them the move valuable of the UK fisheries.

Leigh Howarth and colleagues at the University of York, UK argue that this multi-million pound industry only came about because of overexploitation of other marine species - and that industry is not built on solid grounds.

You can read the press release which gives an overview of the paper herehttp://www.york.ac.uk/news-and-events/news/2013/research/fish-into-fisheries

It seems that the paper has some backing from the industry too, with the Sustainable Inshore Fisheries Trust - a Scottish based charity - supporting the findings.  You can read their thoughts here http://www.fishupdate.com/news/fullstory.php/aid/19545

For those with access to the journal 'Fish and Fisheries'you can see the original paper herehttp://onlinelibrary.wiley.com/doi/10.1111/faf.12041/abstract

Image: The ecological effects of intensive fishing. From left to right, fishing effort increases over time. As a result, large predatory fish become depleted and fishers are forced to target new species.

#fisheries   #oceans   #oceanconservation  #marineconservation   #marinebiodiversity   #science  #scienceeveryday

With thanks to +Samantha Andrews


and more: this time from the Herald Scotland and MP Callum Roberts


Fisheries cannot rely on prawns for survival

A COLLAPSING prawn-fishing "bubble" threatens to devastate UK fisheries that have become dependent on crustaceans and shellfish, experts claim.
As stocks of big fish have dwindled, fishermen have turned to smaller fry for their main income. Removal of big predators from the sea has seen catches of prawns, scallops and lobsters rocket.
In many regions, including the UK, shellfish are now the most valuable marine resource. But replacing fish such as cod and haddock with prawns and scallops is a highly precarious strategy, according to the authors of a new study. Shell-fisheries are unstable and at risk of collapse from disease, species invasion and climate change.
Lead researcher Leigh Howarth from the University of York said: "Prawns are now the most valuable fishery in the UK, with catches currently worth over £110 million a year. But this fishery has come to exist only after we over-exploited populations of cod, haddock and other predators.
"If shellfish now collapsed, the social consequences for fishermen would be devastating. There are simply very few remaining species left to target."
The study, published in the journal Fish and Fisheries, reports a similar situation all over the world.
In the US and Canada, lobster, scallops and crab have replaced catches of cod. In the Black Sea, Baltic Sea and off the west coast of Africa, over-fishing has caused areas to be overrun with jellyfish.
This has led to oxygen depletion and excess levels of hydrogen sulphide wiping out important food chains across 100,000 square kilometres of the sea floor.
Co-author Professor Callum Roberts, also from the University of York, said: "The rise of shellfish has been welcomed by many as a lifeline for the fishing industry. However, such changes are not a result of successful management, but rather a result of management failure – a failure to protect stocks and their habitats in the face of industry innovation and over-fishing.
"This study highlights why the UK needs to urgently act to protect our seas. We need more marine protected areas to stop our seas from becoming a wasteland."