Total fish biomass in worlds oceans estimated to be 2 billion tonnes

January 16th, 2009 - 1:00 pm ICT by ANI  

Washington, Jan 16 (ANI): In a first ever estimate, a study has determined that the total fish biomass in the worlds oceans is about two billion tonnes.

A team of international scientists, which included University of British Columbia fisheries researcher Villy Christensen, conducted the study.

It was also discovered that fish play a previously unrecognized but significant role in mitigating climate change by maintaining the delicate pH balance of the oceans.

By drinking salt water, fish ingest a lot of calcium, which needs to be removed or they will get renal stones, said Christensen, an associate professor in the UBC Fisheries Centre.

The team discovered that fish do this by binding the calcium to bicarbonate, and then excreting it as pellets of calcium carbonate, a chalk-like substance also known as gut rocks, in a process completely separate from food digestion.

As the calcium carbonate from these pellets dissolves, it turns the seawater more alkaline, which has relevance for ocean acidification, and is impacted by the oceans exchange of carbon dioxide (CO2) with the atmosphere.

To gauge the global impact of this process, Christensen and Simon Jennings from the UKs Centre for Environment, Fisheries and Aquaculture Science took two entirely different approaches to estimate the total biomass of fish in the worlds ocean.

Jennings examined global ocean plant production and its efficiency as it moves through the food chain, while Christensen tallied global fish catches since 1950 and calculated how much fish there must have been in the oceans to support fisheries.

The two approaches resulted in a close range of numbers: 0.8 to 2 billion tonnes.

This study really is the first glimpse of the huge impact fish have on our carbon cycle and why we need them in the ocean, said Christensen.

We must buck the current trend of clear-cutting of the oceans and foster these unrecognized allies against climate change, he added. (ANI)

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