Fish biomass in oceans 10 times more than believed

Washington: Researchers have dispelled the previously believed estimate of the fish biomass present in the ocean.

With a stock estimated at 1,000 million tons so far, mesopelagic fish dominate the total biomass of fish in the ocean. However, a team of researchers with the participation of the Spanish National Research Council (CSIC) has found that their abundance could be at least 10 times higher. Mesopelagic fishes, like lantern fishes (Myctophidae) and cyclothonids (Gonostomatidae), live in the twilight zone of the ocean, between 200 and 1,000 meters deep. During the 32,000 nautical miles traveled during the circumnavigation, the researchers of the Malaspina Expedition (a project led by CSIC researcher Carlos Duarte) took measurements between 40 degree N and 40 degree S, from 200 to 1,000 meters deep, during the day. Xabier Irigoien , researcher from AZTI-Tecnalia and KAUST (Saudi Arabia) and head of this research, said that the fact that the biomass of mesopelagic fish (and therefore also the total biomass of fishes) is at least 10 times higher than previously thought, has significant implications in the understanding of carbon fluxes in the ocean and the operation of which, so far, we considered ocean deserts. Mesopelagic fish come up at night to the upper layers of the ocean to feed, whereas they go back down during the day in order to avoid being detected by their predators. This behaviour speeds up the transport of organic matter into the ocean, the engine of the biological pump that removes CO2 from the atmosphere, because instead of slowly sinking from the surface, it is rapidly transported to 500 and 700 meters deep and released in the form of feces. The results have been published in Nature Communications journal.