The Netherlands now join Norway in the effort to save the European eel Anguilla anguilla from extinction.

Yesterday, the Dutch government announced a two-month long ban on eel fishing that will commence on October 1 this year, followed from 2010 with a yearly three-month prohibition from September. In 2012, the new regulation will be reviewed and its effectiveness assessed.

“I realise this is a very big sacrifice for eel fishers, but ultimately it is also in the interests of the industry that eel numbers are allowed to recover,” Agriculture and Environment Minister Gerda Verburg said in a statement.

Before the regulation can be put into action it will however require the approval of the European Commission. The commission has already rejected a Dutch proposal to enlist the aid of eel fishermen to help boost the eel population by releasing 157 tons of mature, caught eel close to the species spawning waters in the Sargasso Sea.

“The (initial) plan would have offered guarantees for the recovery of the eel population,” the professional fishers’ federation Combinatie van Beroepsvissers said in a statement, describing the new measure as “incomprehensible, unreasonable and unacceptable”.

Eel is a delicacy in the Netherlands and roughly one thousand tons of eel are caught in Dutch waters every year. The Dutch government have designated 700,000 Euros (989,800 USD) to aid the estimated 240 small fishing businesses affected by the eel ban.

Japanese eel (Anguilla japonica) larvae have amazing buoyancy compared to other oceanic plankton, and the reason may be a type of gelatinous goo contained within the body.

When researchers from the University of Tokyo measured the specific gravity of Japanese eel larvae, they found it to be as low as 1.019, rising to 1.043 – showing the larvae to be potentially lighter than seawater itself. (Sea water has an average specific gravity of 1.024.)

When they checked other marine creatures for comparison, such as juvenile jellyfish and the sea snail Hydromyles, their specific gravity turned out range from 1.020 to 1.425. Of 26 plankton creatures tested, the Japanese eel larva was the lightest.

The food consumed by Japanese eel larvae and many other planktons tend to be found in the greatest abundance really close to the water’s surface where there is plenty of light. The low specific gravity may therefore increase the survival rate of Japanese eels by making it easier for them to find a lot of things to eat.

So, why does the Japanese eel float so well? According the Japanese study, the answer may rest in gelatinous goo – or more specifically in a matrix of transparent gelatinous glycosamino-glycans. Controlled by osmoregulation through the chloride cells that cover the body of a Japanese eel larva, this marvellous adaptation makes it possible for the larva to stay close to the surface. Researchers have also suggested that it might help the larva to stay away from predators.

For more information, see the paper: Tsukamoto K, Yamada Y, Okamura A, Kaneko T, Tanaka H, Miller MJ, Horie N, Mikawa N, Utoh, T and S Tanaka (2009) – Positive buoyancy in eel leptocephali: an adaptation for life in the ocean surface layer. Marine Biology, vol. 156, no. 5. pp. 835-846.