A plate of slime head or a tasty rat tail might not sound too appetising, but these two very valuable fish species are being trawled to extinction.
The subsidies being paid to the world's fisheries industry by many governments are helping to bring about loss of species by making uneconomic fishing profitable, experts have claimed.
The international fish catch is in decline, requiring governments to provide annual subsidies worth more than €24 billion, according to Dr Daniel Pauly, of the University of British Columbia. The world's catch peaked in the 1980s at about 90 million tonnes, he said. "Now we know this is reducing by a half million tonnes a year."
The decline is forcing trawlermen to go after different species in very deep water in search of fish such as the orange roughy and the grenadier.
These were formerly known as slime head and rat tail, but were renamed to make them sound more appealing to consumers.
"Now we are moving into deeper waters and scraping the bottom of the sea," Dr Pauly told the AAAS meeting in San Francisco. "Fishing in these deep waters is unsustainable. It is very inefficient and very expensive in terms of fuel."
It can take 5 to 8 kg of fuel to recover 1 kg of lobster from deep water, he said.
A report prepared by Dr Pauly indicates that Japan, South Korea and Russia lead the table in terms of subsidy levels. Two EU states - Spain and France - are also within the top seven. Without these subsidies deep-water trawling would not be economic.
But there are serious problems in exploiting these species, according to Dr Selina Heppell, of Oregon State University, who explained that orange roughy is an extremely slow-growing fish which can live to 150 years. "This is a species that grows so slowly it doesn't reach sexual maturity until 30 to 35. They are very easy to over-exploit."
Bottom-trawling in deep water can also damage ancient corals on the seabed. "They can be removed from the sea with one trawler sweep and then they are gone," said Murry Roberts, of the Scottish Association for Marine Science. Corals such as the gold coral or gerardia at 2,000 years of age could be the oldest living creatures on the planet, he added.
There is also the risk of "by-catch" - unwanted species which get trawled up but discarded because they have no commercial value. Included among these is the "blobfish", which Dr Heppell said was so watery people would not eat it.
