This column has frequently discussed the problems experienced by birds as they struggle to cope with changes in the climate and the environment.
Various sophisticated surveys are producing valuable information to help offset some of the more worrying threats to our birds, but beneath the water of the Basin there is a species at even greater risk.
The European eel is in trouble. The number of juveniles arriving from the Atlantic has been declining for the past 30 years and it is currently thought to be only about five per cent of the average level of the 1970s. They are now a protected species and listed as critically endangered.
It is illegal in Scotland to intentionally catch or trap an eel without a licence and no more than a handful of licences have been issued. In May, the first prosecution for illegally catching an eel was brought under the Scottish fish conservation regulations. Anglers who inadvertently catch an eel are required to return it to the water. There are major problems in trying to help with the recovery in numbers of the European eel, because of the gaps in our knowledge. We are aware of the life cycle which involves maturing in European waters and then migrating to the Sargasso Sea, south of Bermuda, to spawn. The larvae then return eastwards on ocean currents, arriving back 12 months later as almost transparent “glass eels”.
Pigmentation develops as they approach the coast and they enter our rivers as “elvers”. They remain in the freshwater systems for varied periods of time. Males can remain for between seven and 20 years and females between nine and 50 years. During that time some eels can make short overland journeys to favoured lochs and lochans.
Surprisingly, no spawning eels have ever been found in the Sargasso Sea and our knowledge is derived simply from the fact that freshly hatched larvae have been found there. We do not know if spawning takes place at only one time of year or how long the mature eels take to travel there. There is even uncertainty about whether the Sargasso Sea is the only spawning ground.
Recent research has revealed that not all eels enter freshwater systems to mature. Some appear to mature around the coast while others move between fresh and salt water systems.
Eels have never featured prominently in the Scottish diet, but they have been trapped here for markets elsewhere in Britain and Europe, where they have been extremely popular.
It is uncertain how long it will take for numbers to recover but it is likely that their recovery will take in excess of 20 years. It is even possible that they might entirely disappear from the wild and become an exclusively farmed food source. This really is a species which is in serious danger of disappearing from our rivers.
Scottish school holidays are now underway, and children’s activities are on offer every Wednesday morning up to, and including Wednesday August 15. The activities run from 10.30am to 12.30pm and are suitable for children aged eight to 12 years.
On Wednesday July 11 there will be a mini-beast hunt to find out what is lurking in the undergrowth in the grounds of the Visitor Centre and on July 18 there will be art activities using natural materials. There is a charge of £3 per child and places can be booked by phoning 01674 83041 or sending an e-mail to email@example.com.