There is an area deep in the ocean known as the twilight zone, where daylight cannot reach. New research has revealed that life in this area constitutes a huge potential source of fishmeal and Omega 3 fatty acids.
Consequently, this untapped source of protein could be used to feed the world's population and offset food shortages linked to climate change and reduced crop productivity. However, researchers at the Technical University of Denmark (DTU) warn that it is critical to develop sustainable management strategies before exploiting the deep sea.
The most common fish living in the twilight zone - 200 to 1,000 meters underwater - are lanternfish, including the Bristlemouth Cyclothone, which is considered to be the most abundant vertebrate species on the planet. These fish are commonly called Myctophiids, of which there are 245 species, measuring between 10 and 15 cm long. Myctophiids, along with squid and crustaceans, migrate to the surface from great depths to feed at night. During the day, however, they can be detected using acoustic surveys 500 meters under the surface.
If estimates from the latest study hold true, the twilight zone far surpasses all current fisheries with 90 percent of the world's total fish biomass. This, the researchers say, is the equivalent of 1.3 billion tons of fish biomass per person on Earth, excluding squid and krill. The only problem is that the twilight zone exists in a kind of "no man's water," where there are no rules for fishing.
"Life in the twilight zone is a huge potential source of fishmeal and Omega 3 to feed the world's population. But we have also to deal with a kind of 'no man's water,'" explained lead author Michael St. John, an oceanographer from DTU.
With little knowledge of the biological processes in the twilight zone, the researchers say that it is impossible to accurately estimate how large a fishing stocks it can sustain. In fact, this zone is thought to be home to more than 1 million species not yet known to science.
"Of all the research I've done in my career, this is the most important, I'm sure. We need fundamental knowledge on fish biology and spawning success in order to define the limits of sustainable exploitation," St. John added. "The investigation would focus on the role they play as food for other species, such as tuna and sharks, and we would like to preserve that function. Life in the twilight zone plays a huge role as a buffer in relation to climate change, because they remove carbon from the atmosphere when the community feeds on carbon-carrying marine snow in the water and then swim back into the depths where the carbon is stored and thus can not contribute to global warming."
There are currently no economically viable ways to fish at such great depths. However, researchers expect that this will soon change, as the high essential fatty acid content of some species will make exploitation more economically viable. Therefore, further research is required if fish resources in the twilight zone are to be exploited in a sustainable manner.
"As coastal stocks are overexploited, alternative marine resources in the twilight zone will be of growing interest. There have already been several attempts to exploit the mesopelagic community and the fear is that it may lead to an unregulated 'gold rush,' as soon as the technology is available and the cost justified," St. John concluded. "Therefore, the world community is faced with a major challenge."
The study was published in the March 17 issue of the journal Frontiers in Marine Science.
