Posts Tagged Mesopelagic fishes

Mar 17 2014

World’s oceans hold 30 times more fish than believed

World s oceans hold 30 times more fish than believed   University World News
Pew research by an international team of marine scientists suggests that the global biomass of fish is 30 times more than the accepted estimate, contradicting previous beliefs about the biomass of fish in the world’s oceans.

The team investigated mesopelagic fish that tend to dominate the world total fish biomass. Mesopelagic fish are open-sea species that occupy the mid-depth of the oceans from 200 metres to 1,000 metres below the surface.

They are small, often migrate to the surface at night, and have remarkable senses – in vision and in sensing pressure and motion – which enables them to avoid nets and fishing gear.

In a report in Nature Communications, the scientists say they had not been able to accurately estimate the biomass of fish in the past because of the difficulties in sampling and the fact that available estimates were based on false premises.

To overcome these problems, the researchers analysed acoustic observations collected during the Malaspina 2010 Circumnavigation Expedition. Their calculations showed that the previous estimate needed to be revised to a higher biomass of at least one order of magnitude.

This means there could be more than 3,000 million tonnes of mesopelagic fish in the ocean – a stock still untouched by fisheries and possibly increasing because of the decline of their main predators, tuna and swordfish.

Read the full article here.

Feb 18 2014

Global Fish biomass may be 10 times higher than thought says acoustic survey

Seafood News

According to a paper produced by Carlos Duarte for the Spanish National Research Council, fish biomass in the ocean is 10 times higher than estimated.  The 6 million euro project consisted of a series of acoustic transects that detected mesopelagic species like lantern fish.  These fish are generally found in the open ocean between 200 and 1000 meters, and the rise to the shallower depth at night, and retreat deeper during the day.  They also detect nets and can flee from trawls.

Mesopelagic fishes, are fish such as lantern fishes (Myctophidae) and cyclothonids (Gonostomatidae), who live in the twilight zone of the ocean, between 200 and 1,000 meters deep. They are the most numerous vertebrates of the biosphere, but also the great unknowns of the open ocean, since there are gaps in the knowledge of their biology, ecology, adaptation and global biomass.

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. The results, published in Nature Communications journal, are based on the acoustic observations conducted during the circumnavigation of the Malaspina Expedition.

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°N and 40°S, from 200 to 1,000 meters deep, during the day.

Duarte states: “Malaspina has provided us the unique opportunity to assess the stock of mesopelagic fish in the ocean. Until now we only had the data provided by trawling. It has recently been discovered that these fishes are able to detect the nets and run, which turns trawling into a biased tool when it comes to count its biomass”.

Read the full article here.

Fish Biomass