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Warming waters an increasing threat to the planet and fishing

Friday 22 May 2020

The volume of chatter about the global environment has been temporarily turned down while the world deals with a more urgent and imminent virologic threat and so it is little wonder that a recent study on the health of the world’s oceans has sunk with hardly a ripple.

“Rebuilding Marine Life”, research published in Nature a few weeks ago and summarised by Max Mossler at the University of Washington, shows plants and animals in the ocean can recover within a generation but if we want to see that happen by 2050 current work around rebuilding populations must be coupled with serious work around climate change.

The study notes that threats to the marine environment have been falling since the late 20th century—in the past 20 years the proportion of marine animals listed as threatened has fallen from 18 percent to 11 percent. The global Moratorium on commercial whaling in 1982 is a big contributor to that fall. As an example of thriving populations, they cite the humpback whales migrating from Antarctica to Australia increasing by 10-13 percent every year with numbers rising from a few hundred in the late 1960s to more than 40,000 currently.

The research makes it clear the work is not done but points to commercial fishing as another success story in progress. Overfishing peaked globally more than 30 years ago, with dramatic improvements from the early 1990s. Fisheries management systems such as New Zealand’s much-acclaimed Quota Management System are rightfully credited with previously overfished areas recovering.

Harm to coastal ecosystems from pollution are a mixed bag. Some pollutants, like sewage have reduced with improved systems and a switch to unleaded petrol in the eighties means lead levels in the ocean are now negligible. Improved systems have reduced oil spills from 24.7 every year in the seventies to fewer than two per annum now.

However, the Report’s authors say newer threats such as fertiliser and manure runoff from food production need urgent work.

The good news is that recovery, once threats are removed is rapid.  Just as a commercial fishery will return to a sustainable level once managed correctly, so do marine ecosystems affected by pollution.

The biggest threat of all, according to the research, remains ocean acidification and warming. In New Zealand, as in other parts of the world, the effect of rising ocean temperatures is becoming much more noticeable, particularly to those who depend on the ocean for their livelihood.

Research shows that since the middle of last century the oceans have absorbed 90 percent of the excess heat generated by greenhouse gas emissions.

The New York Times reports that Iceland has a sobering story about the effect of warming waters on its commercial fishers. On an island called Isafjordur, somewhat better known as a Game of Thrones location, its fishermen can no longer fish for capelin, a type of smelt that was the economic lifeblood of the island. The waters warmed and the fish left. The $143 million fishery has been closed for the past two seasons.

New Zealand is not immune. As fish avoid warming waters quota holders face immediate dilemmas that a slow-moving fisheries management system cannot readily address; large populations of fish species that fishers do not have quota for and decreasing populations of fish they do have quota for in a particular area.

One such example was highlighted in the Otago Daily Times this week. President of the Port Chalmers Fishermen’s Co-op, Ant Smith says the numbers of kingfish being caught in set nets off the Dunedin coast is due to warmer waters and is costing them hundreds of thousands of dollars. With no quota for the fish, and not being able to return live kingfish to the sea it is costing them $10 a kilo in deemed value when fish shops would only buy them for $2 a kilo. In this instance the Ministry for Primary Industries is looking at two solutions; allowing live kingfish to be returned to the sea or reviewing the kingfish quota.

And while our fishers are doing it hard, warmer waters are not much fun for fish either; there is less oxygen in waters that are warmer, and the fish are literally relocating in order to breathe.

Initiatives such as the collaborative Moana Project, which deploys temperature devices on New Zealand’s fishing fleet to monitor marine temperature extremes are critical to inform the debate.

The threat of climate change globally and locally is very real and very imminent.

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