Photograph: Paul Caiger/Woods Hole Oceanographic InstitutionĪ lot of fishmeal gets fed to salmon and prawns for food-rich, developed countries, and a growing volume is increasingly being sold as a supplement in pet food. Lanternfish come in a variety of shapes and sizes, all of which have bioluminescent organs. However, even if harvesting lanternfish were to begin, and setting aside other environmental impacts of many types of fish farming, such as pollution from pharmaceuticals and waste, many question whether it would achieve the virtuous goal of securing food for everyone to eat. After the Malaspina discovery, it has been suggested that if just half of the lower estimated mass of twilight-zone fish were caught – still a massive 5 gigatonnes – it could theoretically be turned into enough fishmeal to yield 1.25 gigatonnes of farmed seafood, which is considerably more than the current annual 0.1 gigatonne catch of wild fish. However, their high oil content means they could be mashed down for animal feed, mostly for fish farms. Lanternfish are unlikely to appear directly on anybody’s plate – they are far too oily and full of bones. The prospect of such a colossal harvest raised an old question: could fish from the twilight zone help to feed a growing human population? Too tempting to ignore One study estimated that deep-dwelling fish capture and store the equivalent of 1m tonnes of carbon dioxide every year The Malaspina acoustic survey did not rely on nets, and in 2014 its research led to new estimates of the abundance of twilight-zone fish, ranging between 10 and 20 gigatonnes. But this was most likely an underestimate, it turns out, because lanternfish avoid being caught by swimming away from the open nets. Every night, along with other animals, such as the squid that prey on them, lanternfish undergo the greatest animal migration on the planet.īefore the 2010 Malaspina expedition, studies based on trawl surveys estimated that the twilight zone contains about a gigatonne (1bn tonnes) of fish. In fact, the pulses of sound were echoing off the swim bladders – the internal gas-filled bubbles – of billions of lanternfish, as they congregated in dense layers hiding in the deep, then at sunset swam up thousands of metres to feed at the surface. Huge numbers were first noticed during the second world war, when naval sonar operators saw echoes from what appeared to be a solid seabed, one that rose to the surface at night and fell back down at daybreak. They are lanternfish: there are about 250 species and they are not only the most common fish in the oceans’ twilight zone but the most abundant vertebrates on the planet. Photograph: Oar/National Undersea Research Program
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