In recent years, mackerel have appeared in Greenland waters, and in their wake new and economically important fisheries have emerged.The first mackerel were caught in Greenland in 2011. And already three years later, in 2014, mackerel fishing had grown to make up entire 23 per cent of the Greenlandic export earnings (78,000 tonnes of mackerel).
"The mackerel's arrival in Greenland is the most extreme example of how climate change can impact the economy of an entire nation," says Senior Researcher Teunis Jansen, DTU Aqua and the Greenland Institute of Natural Resources.
Together with colleagues from DTU Aqua and the Greenland Institute of Natural Resources, Teunis Jansen is behind the first study of the mackerel's arrival and spread in Greenland waters. The results have just been published in the recognized journal Ecological applications.
"We have mapped the occurrence of mackerel in Greenland's economic zone on the east coast from the Denmark Strait and to the south to Cape Farewell. And we more or less found mackerel everywhere in mid-summer. We found the largest quantities in warmer waters at a temperature of more than 8.5 degrees Celsius," says Senior Researcher Teunis Jansen.
And it is precisely the warm surface water which is an important key to understanding the mackerel's distribution in Greenlandic waters, assesses Teunis Jansen, based on the knowledge gathered. For in the same period, record-high temperatures have been measured in the ocean currents from the mackerel's spawning grounds west of the British Isles and toward the north-east of Iceland and Greenland.
When mackerel have spawned in the spring, they normally follow the Norwegian Current toward the north-east where they feed during the summer. But from around 2007, large quantities of mackerel suddenly appeared around Iceland in the Irminger Current -- the north-western branch of the Gulf Stream. Year by year they extended their migrations in this new direction, and in 2011 they were caught in Greenland for the first time.
"One explanation for this is that where they used to turn right to follow the Norwegian Current, they have also kept left and followed the Irminger Current to the north-west. In recent years, record-high temperatures have been measured in the Irminger Current, and thus the mackerel have been able to use it as a 'motorway' while the population has grown and food availability has decreased in the east, so it has been attractive for them to find new feeding grounds," explains Teunis Jansen, DTU Aqua.
Whether a few mackerel have been in Greenland in periods before 2011 is uncertain because these East Greenland regions are deserted without much summer fishing.
"Our results suggest that the local conditions have been acceptable for short periods of time, but compared to the present situation and the expected future scenarios, it has been insignificant. The areas with temperatures that are suitable for mackerel have doubled in the Greenlandic zone in recent years, and our forecasts indicate that they will expand and stretch for longer periods," assesses Teunis Jansen.
However, he stresses that the catches in the fishing industry in 2015 were, in fact, less than in 2014 when the study was carried out:
"Perhaps because the spring of 2015 was a little colder and because there were plenty of plankton to eat around Iceland many mackerel did not need to seek further to the east to become full -- so there is some variation from year to year. We are currently studying this variation, and in a few years, we may be able to provide fishermen with mackerel forecast a couple of months in advance."
For the Greenlandic economy, the mackerel have been a welcome visitor at a time when the traditionally important shrimp fishing has been declining due to a diminishing population.
Other species have followed in the wake of the mackerel, e.g. the Bluefin Tuna which have been caught as bycatch in the mackerel fishery. The mackerel's arrival could, however, become a problem for some of the current species when the mackerel eat their food, and higher temperatures can make life hard for cold water species.
"Climate change is a huge challenge and even if there will be more of these kinds of local positive stories, it is important that we do not use them as an excuse not to implement structural and technological changes. Globally, the disadvantages of climate change are still totally dominant," emphasizes Teunis Jansen, DTU Aqua.
Internationally, the mackerel's journey north has challenged the old agreements on the management of the species that were made at a time when it was not found in abundance in the waters around Iceland and Greenland. This means that the mackerel stock in the north east Atlantic, according to assessments made by the International Council for the Exploration of the Sea (ICES), in total by all countries is fished 48 per cent more than the recommended level. Economically, mackerel are the most important fish species in the EU. And the species is also very important for Danish fishermen. Mackerel are fished by Denmark's largest fishing vessels in the autumn and winter in the northern North Sea and to the west of Scotland. It constitutes one of the Danish fishery's most important species.
The study of mackerel in Greenland was financed by the Danish and Greenlandic governments.
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