Sonar scanning that is part of the so-called Census of Marine Life has been able to “see” schools of fish the size of Manhattan, the largest mass of life ever witnessed.
The Census of Marine Life, due to be published in October 2010, will be the first of its kind. The €500+ million project is a hugely ambitious and informative venture that has been undertaken by 2,000 scientists in 82 countries. It aims to provide an authoritative snapshot of what inhabits our waters and where, as well as contrasting this against what we have known from historical sources.
The picture that is being painted by the Census reveals a far more complex marine system than was previously known, inhabited by thousands of hitherto unrecognised species. However, comparisons between fish stocks of today and those of bygone eras are proving unfavourable for the present. Examples such as those from the Gulf of Maine, in the USA, are startling: records from the 1880s show that 70,000 tonnes of cod were caught each year, compared to around 3,000 today.
Ocean Acoustic Waveguide Remote Sensing has been used extensively by the data gatherers in order to track schools of fish. This is a huge advance on conventional sonar as the scanning rate runs a million times faster than its predecessor and can scan thousands of square kilometres of shallow-shelf seas at one time. Off the coast of Maine, 20 million fish were seen as they headed toward their spawning ground, when they came together their school was the size of Manhattan and represents the largest mass of life ever seen.
This technology will be of service to both scientists and fishers, but the way in which its use is managed will have an impact on fish stocks. However, the data that will now become available as a result of the Census should at least enable better informed decisions to be taken by fishery managers.