Until now, the only way to count fish stocks was literally to trawl the ocean. Scientists believe that new DNA analysis could make the process a whole lot easier.
Monitoring fish stocks is important for scientists investigating the effects of global warmingImage: picture-alliance/landov/O. Aburto-Oropeza/Ilcp
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Scientists in Denmark are developing a new technique to work out how many fish are in a certain area of the sea, without having to throw down a net.
The new method, described in the "PLOS ONE" science journal, involves testing water samples for the genetic material of different types of fish.
"Currently, monitoring of marine fish is largely based on invasive procedures, such as trawler fishing, and on official reports of global hauls, which can be unreliable," says Philip Francis Thomsen of the University of Copenhagen.
Fishermen aboard the French trawler Grande HermineImage: Getty Images/AFP/M. Mochet
Improving upon these monitoring methods could be important for scientists assessing the impact of climate change, as well as for fishing fleets that need to know where to look for good stocks of fish.
Fish DNA in the water comes from their scales and excrement. Researchers say that the number of these traces found in the water gives a reliable indicator of not only which kinds of fish are present, but also how many.
Putting it to the test
The first round of tests involved taking 21 water samples at depths of around 190 meters (623 feet), just off the west coast of Greenland. The DNA analysis was compared with the haul from fishing trawlers that were active in the same area directly after the samples were taken.
Sea creatures from 26 biological groups, such as ray and halibut, were identified in both the DNA analysis and the fishing nets.
There were, however, some discrepancies in the two sets of results. The researchers say this could be because fish lose more or fewer scales depending on their age and species. Alternatively, the genetic material could have been moved to a different area by ocean currents.
Certain species of fish, such as the Greenland shark, are also able to escape fishing nets.
But the researchers remain confident that such problems can be overcome by improving their current methods.
Marine protected areas in pictures
Conserving our seas is a must. As awareness of the problems facing ocean wildlife and habitat grows, so too do the number of marine protected areas. Albeit slowly. Click or swipe through our gallery to learn more.
Image: imago/blickwinkel
Pacific Remote Islands Marine National Monument
Covering an area of almost 1.3 million square kilometers (800,000 square miles), this is among the world's largest marine protected areas. Located in the western Pacific Ocean, it is home to all manner of marine life including green turtles, pearl oysters, giant clams, reef sharks, coconut crabs, dolphins and whales.
Image: imago/blickwinkel
Pitcairn Islands Marine Reserve
Surrounding this British Overseas Territory lies the largest contiguous marine protected area in the world. The 834,334 square kilometers of pristine ocean habitat are monitored via satellite to track potential illegal fishing activity in this vast and remote corner of the South Pacific.
Image: picture-alliance/dpa
The Great Barrier Reef Marine Park
Situated off the northeastern coast of Australia, the Great Barrier Reef is the largest in the world. A vast area of that reef, which is so big it can be seen from space, forms the Great Barrier Reef Marine Park. The reef saw devastating coral bleaching in 2016 and 2017. In an effort to protect the delicate ecosystem, fishing is strictly regulated and commercial ships can only use certain routes.
Image: imago/blickwinkel
Galapagos Marine Reserve
A UNESCO World Heritage Site and home to many animals found nowhere else in the world, the Galapagos Marine Reserve in the Pacific Ocean is administered by Ecuador and is the largest marine park in a developing country.
Image: imago/Westend61
Bowie Seamount marine protected area
The Bowie Seamount is an underwater volcano located 180 kilometers off the west coast of Canada. Although the volcano rises about 3,000 meters from the ocean bed, its highest point is 24 meters below sea level. While it may be invisible to those of us living above water, the submerged mountain is home to a rich mix of marine fauna and flora.
Image: BR
Chagos archipelago
The United Kingdom declared this vast stretch of Indian Ocean a marine protected area in 2010. The legality of the move has been contested by Mauritius, which lays claim to the group of islands. In the 1970s, the UK evicted the entire native population from the archipelago and granted the United States permission to use it as a military base.
Image: NASA Johnson Space Center/Image Science & Analysis Laboratory
The Schleswig-Holstein Wadden Sea National Park
Extending from the German-Danish maritime border down to the Elbe estuary, and with an area of 4,410 square kilometers, this is doubtless Germany’s largest national park. Due to the intertidal nature of the Wadden Sea, some 30 percent of it is only periodically under water.
Image: picture-alliance/dpa
The Pelagos Sanctuary for Mediterranean Marine Mammals
Covering a large area between the French Riviera, Sardinia and the Italian region of Tuscany, this sanctuary was established specifically to protect marine mammals. It is currently the world's only conservation area in international waters.
Image: picture-alliance/Wildlife
Ross Sea Region Marine Protected Area
In October 2016, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) agreed to create a marine protected area off the coast of Antarctica. However, the 1.6 million square kilometers of pristine wilderness will only be protected for 35 years. What happens after remains to be seen.
Image: REUTERS/P. Askin
Aquatic Reserve of the South of Gabon
The government of Gabon announced in June 2017 creation of a 53,000-square-kilometer network of marine protected areas - the largest in Africa. It would apply to a quarter of Gabon's seas, which are incredibly rich in life, including sea turtles, whales, dolphins, corals, even crocodiles. The region is known for rampant overfishing - the reserves are accompanied by a sustainable fishing plan.
Image: Imago/Nature Picture Library
Cook Islands Marine Park
In July 2017, the Cook Islands - a small island nation about halfway between New Zealand and Hawaii - approved designation of the world's new largest marine sanctuaries off its shores. The 1.9-million-square-kilometer preserve includes a core no-fishing zone, otherwise limits on mineral extraction and commercial fishing. It's hoped to help preserve the archipelago's lagoons and reefs.
