How warming seas are forcing fish to seek new waters

Scottish fishermen have uncovered an intriguing way to supplement their income: they have added squid to the menu of marine creatures they regularly pull from the sea. A species normally associated with the warmth of the Mediterranean, rather than the freezing north, may seem an odd addition to their usual catches of cod and haddock. Nevertheless, squid has become a nice little earner for fishing boats from Aberdeen and the Moray Firth in recent years.

Thirty years ago, squid was a rarity in the North Sea. Today, boats bring back thousands of tonnes a year – though cod and haddock still dominate catches. Nor is this warm-water addition to northern fish menus a unique feature. Red mullet, sardines and sea bass have also appeared with increasing frequency in North Sea fishermen’s nets in recent years. All of them are associated with warmer waters and their appearance is seen by many scientists as a sign that climate change is beginning to have a serious impact on our planet’s oceans.

For Scottish lovers of fresh squid, this is good news. However, in many other parts of the world, rising sea temperatures – triggered by climate change – are providing fishing industries and governments with major headaches. Fish are moving hundreds of miles from their old grounds, sometimes out of zones that had been set up to protect them. In other cases, fish are simply disappearing from nets.

Part of the problem has its roots in past overfishing. But now climate change is exacerbating the issue. Last week, scientists revealed that a vast chunk of ice was set to break away from the Antarctic Larsen C ice shelf, while Arctic sea ice extent is now at its lowest level for this time of year since records began.

And if sea temperatures continue to rise, even greater disruption will be caused to fishing stocks. Fishermen will lose their livelihoods and communities will be deprived of their only source of food.

“There is an unambiguous trend,” said marine biologist Andrew Bakun of Miami University. “If you look at the world’s fish catches as a whole, you find they are made up, more and more, of warm-water species as opposed to catches in previous years which had more species that were from cooler waters.”

Seafood is the critical source of protein for more than 2.5 billion people today. However, over-exploitation in the past has resulted in a crash in fish stocks, with the result that the world’s annual catch is now decreasing by more than 1 million tonnes every year – despite the availability of the latest fishing technology: nets big enough to engulf cathedrals, echo locators, satellite navigation, and powerful engines to drive boats.

Now climate change is making the management of this threatened supply even more difficult. “All the world’s oceans are facing intense problems but the problem is going to be particularly serious for tropical countries, which are often underdeveloped and are far less able to maintain sustainable management regimes for their fisheries,” said marine biologist Callum Roberts, of York University. 

Read more https://www.theguardian.com/environment/2017/jan/08/fish-ocean-warming-migration-sea

Courtesy of Guardian News & Media Ltd