Here in the Gara Valley we’re lucky enough to have a thriving eel population, as this year’s EA fish survey showed, as well as an equally thriving otter population for whom eels are a fast food. The Slapton Ley Field Centre have told us that most female glass eels drift into the Severn Estuary whilst most male glass eels drift around the south coast.
Our eels enter Slapton Ley through the overflow at Torcross before making their way as elvers upstream to mature, which takes several years. They then transform from yellow eels to silver eels to make their way back to the Sargasso Sea to mate. if they fail to reach the sea then they transform back into yellow eels and wait for the next year.
There was much excitement in summer and early autumn as many eels were visible from the bridge and lawns at Watermill Cottages.
To help raise awareness of eels here’s some information from The Environment Agency website – they are quite extraordinary creatures, long-lived and at ease in salt and fresh water.
Eel facts from The Environment Agency
Eel numbers have dropped since the 1980s to very low levels across Europe. As a result European regulations are now in place requiring action by all European member states to reverse this decline. Legislation comes into force on January 1 2015 to protect eels and their diminishing habitats. This includes having all weirs, turbines and abstraction areas checked by The Environment Agency (EA) for eel-friendliness, and installing expensive screens if required.
Why the eel decline? The EA says it’s not caused by one problem alone, but it’s a complicated picture. Over-fishing in some parts of Europe, parasites, climate change, pollutants such as pesticides and heavy metals probably all have parts to play. One of the most likely causes is the huge decrease in available habitat for eels in our freshwater rivers, canals, lakes and tidal estuaries. Since the Second World War, we have drained lowland rivers, straightened channels and created modern flood defence barriers. This sort of water management reduces suitable habitat and makes it difficult for eel to move freely through our rivers.
The eel is a famous international marine traveller completing only part of its life cycle in freshwaters or coastal areas, where it is fished for by both rod and net. Spawning has not been observed, but it is believed to take place in the spring, deep in the Sargasso Sea, between Bermuda and the Bahamas.
Larvae and glass eel
Maturing females, although their eggs have not been collected, are reported to contain up to 10 million eggs. The eggs develop into a ‘leaf-like’ larva called a ‘leptocephalus’ It was originally thought that these larvae took three years to migrate from the Sargasso Sea to the European coast but, recent studies suggest that the journey may take as little as 12 months.
When the larvae reach the continental shelf they change into what is called the ‘glass eel’ stage before continuing with their migration. In the British Isles, from around May, once temperatures have reached about ten degrees Celsius, the glass eel make their migration from the estuaries into freshwater.
Once the glass eel develop pigmentation they are referred to as ‘elver’ and are very similar in shape to the adult eel. To facilitate their passage through the estuary and into rivers they use the tidal currents, migrating upstream on the flood tide. During the ebb tide they move out of the current towards the bank side to prevent being washed out to sea.
In fresh water the eel lives on or near the bottom, often digging into the gravel, and migrates slowly upstream. During this period they are generally referred to as yellow eel. Moving further upstream eel become fewer and more dispersed. Eel in the upper reaches of river systems are generally fewer and they tend to be much larger than in the lower reaches. In the lower reaches the populations have a higher proportion of males, which contrasts with the upper reaches where females predominate.
Silver eel Male eel stay in freshwater for between 7 and 12 years, maturing at an average length of about 36cm. Females stay between 9 to 20 years and mature at a larger average size of about 50cm, though eel can grow larger reaching up to 1 metre in length and live as long as 40 years.
When the fish mature they change to a blue/silvery colour and migrate seaward during the autumn, usually during dark stormy nights.
Species – Eel, Anguilla anguilla (L.)
Weight – rarely 2.3kg (5lb), very few over 3.2kg (7lb)
Length – rarely exceed 100cm
Age – maximum recorded 40 years
Location – estuaries and freshwater
Behaviour – catadromous
Preferred habitat – slow-flowing, deep water, sand, silt and weed
Feeding – May-October, most active at night, forage in debris
Natural food – crustacea, worms, small fish.
Maturity – 8-15 years
Spawning – Sargasso Sea at depth
Migratory habits – August-December, adults migrate to sea; February-May, glass eel arrive at coastal waters; May-September elvers migrate upstream