Fish that live in the mesopelagic zones constitute 95 percent of the world's fish biomass, marine biologists have found.
Mesopelagic fish live between 100 and 1000 metres below the surface.
The discovery highlights that mesopelagic fish in the earth's oceans constitute 10 to 30 times more biomass than previously thought.
"This very large stock of fish that we have just discovered that holds 95 percent of all the fish biomass in the world is untouched by fishers," said the researchers.
Scientists have attributed the secret behind their vast population to their capacity to avoid fish nets and prowling eyes of the birds.
They have large eyes to see in the dim light, and also enhanced pressure-sensitivity.
"They are able to detect nets from at least five metres and avoid them," noted professor Carlos Duarte of University of Western Australia.
Duarte led a seven-month circumnavigation of the globe in the Spanish research vessel Hesperides with a team of scientists collecting echo-soundings of mesopelagic fish.
He said most mesopelagic species tend to feed near the surface at night, and move to deeper layers in the daytime to avoid birds.
