Key Species of the Cwm Marteg Project

The River Marteg, from its confluence with the Wye upstream to the Gilfach waterfalls forms part of the ‘River Wye Special Area of Conservation' (SAC), a European designation that recognises and gives protection to the richness of the river ecosystem from source to sea.

Upstream of Gilfach, the River Marteg is not protected but is still important for spawning salmon and otters, which are 'designated features' of the SAC. Two key species of the Cwm Marteg Project (lamprey and bullheads) are also ‘features' of the SAC and can be found on the Marteg.

Eels are not a feature of the SAC but have been undergoing a catastrophic decline and are now on the IUCN Red List as a critically endangered species. They are also subject to a European Directive to manage eel stocks in a more sustainable way.

 Water voles are also a protected species in the UK (but not Europe) because of their catastrophic decline. It is illegal to catch or disturb a water vole, or to destroy its habitat.

Gilfach with its mosaic of habitats and damp climate is pretty good for lower plants with at least 143 different mosses and 413 different lichens!

Watch this filmlet on lichens to find out more about them.

Lampreys

Lampreys are primitive, eel-shaped creatures with sucker-like mouths lined with teeth. There are 3 kinds: brook lamprey, river lamprey and sea lamprey and they occupy slightly different places in the river ecosystem. Spawning takes place in gravelly stretches of river and after hatching, the larvae burrow into silty banks, feeding for a few years on organic particles in the water.

After metamorphosing to adults, brook lampreys just spawn and die, while river and sea lamprey swim downstream to the more abundant estuaries and coastal waters where they feed and grow. They are actually parasitic, sucking onto and rasping away at the flesh of other fish (see a gruesome picture on the Arkive website!). Once mature, they migrate back upstream to spawn and die.

Sea lamprey can be seen spawning in the Wye in Boughrood and Builth Wells in May/June, and have been recorded as far up as Rhayader. River and brook lamprey can be found throughout the River Wye system, although both man-made and natural barriers (eg weirs and waterfalls) can prevent the movement of all three species upstream. Siltation and cementation of spawning gravels, severe pollution and a decline in host fish affect populations.

Photo courtesy of Ceredigion County Council

Lampreys have disappeared from many of the UK's rivers so it's important to protect the habitat of the still-viable populations in the Wye system.

Look at the Arkive website for some great photos and film clips of lampreys.

See also a local website showing sea and river lamprey on the River Teifi in May 2011.

Bullheads

A favourite of kids splashing around in streams, the bullhead (often known as a millers thumb because of its rather large head) hides out amongst the stones of moderately flowing, shaded stretches of the water course. Males excavate a nest under a significant stone to attract a female, where she lays the eggs.

Unusually for fish, the male exhibits parental care, protecting them from predators like caddis fly larvae and also fanning the eggs to keep oxygen-rich water flowing over them. Bullheads are territorial and can frequently be found under the same stone in the river.

Bullheads are a favoured food of otters as well as many other predators such as trout, heron, kingfisher and dippers. The non-native North American signal crayfish is also thought to affect bullhead density through predation and competition for shelter and food.

Like lamprey, bullheads are a ‘feature' of the River Wye SAC. They are relatively common in the Wye catchment, although density is much less in upland streams than lowland streams. Threats include siltation over gravels, modification of the channel that changes the dynamics of water flow, and removal of the shading effect of bank-side trees.

Some good footage can be found on the Arkive website of these endearing little fish.

Eels

The European eel is in serious decline and drastic action needs to be taken to restore populations. It is thought that the number of glass eels reaching the coasts is only 5% of what it was in the 1970s. See this lovely slide show of the Eels Story.

Eels are a very important food resource in aquatic ecosystems and are also considered a delicacy for humans, so are still harvested for commercial fisheries with a lucrative market in the Far East.

We don't yet have the skills to breed eels in captivity, so fish farms harvest wild glass eels and grow them on in tanks. Demand for eels worldwide is increasing while stocks appear to be dwindling. In the UK, the centuries-old hand netting of eels takes place in estuaries like the Severn and the cost of a fishing license is only a few £s while a good market will pay £200-300/kg or more for the catch. In Europe, glass eels are commonly caught by trawling, which has a much more damaging effect on their fragile bodies (and the sea floor) than hand netting. Hand-netting is the only legal method of catching eels in the UK.

The European eel has an intriguing lifecycle that is not yet fully understood. It spawns an amazing 5000km away in the Sargasso Sea - though this has never been seen! The larvae wash back to Europe in ocean currents, metamorphosing into 'glass eels' (without pigmentation) as they reach the continental shelf and then colouring up to become known as 'elvers' as they enter freshwaters. They spend many years growing - usually between 7-12 years for males and 9-20 years for females, depending on water temperature and food availability, before heading back to the Sargasso Sea.

Action is now being taken on a European level to protect eel populations and the Environment Agency has produced 'Eel management plans' to guide sustainable eel stock management. However, eel fisheries support local economies in many countries and there is resistance to their closure or reducing catch sizes. People tend to regard glass eels, like other fish, as a 'common' resource available to everyone, making it difficult to regulate or manage catch sizes without agreement across the whole international industry.

The European Directive requires that 60% of the glass eel catch should be grown on by commercial fisheries for re-stocking wild populations by 2013. Many more eels reach maturity under fish farm conditions than they do in the wild, partly because they are not providing a diet for other species in the ecosystem! What is not known is whether the re-stocking policy will deal with the root cause of the decline in glass eels returning to coastal waters. Is the problem that too few adults are returning to spawn, or with the survival of the juvenile lifestage?

Have a look on the Arkive website for pictures and film clips of eels.

The UK glass eels company website provides lots of current and interesting information about eels and on developing a sustainable eel industry.

Water voles

‘Ratty' from Wind in the Willows used to be a common sight on waterways but is now gone from 90% of the places it used to live. They like slow-moving water, soft penetrable banks and dense, overhanging vegetation to provide food and protection, and the general loss of this habitat to grazing and bank modification has made them vulnerable to predation. Following on from this, the invasion of the American Mink has decimated lowland populations in most parts of Britain.

Luckily, recent survey work in the uplands of the Rhayader area has identified small but widespread colonies of water voles living along streams and associated wetlands, and the Elan Valley has now been designated nationally as a Key Site for the species.

Mink numbers seem to be much lower in the upper Wye area now, perhaps because of regular trapping over recent years. The upland water voles colonies appear quite mobile in seeking out new habitat (rushes by water are their main food) and have started spreading into the valleys. Fragile colonies currently exist in ponds near the Wye and a stream near Pantydwr, and in 2009 there were signs on a small stretch of the Marteg at Gilfach.

For more information on what signs to look out for, see our Water Vole Project webpages. Great footage of water voles and mink can be seen on the Arkive website too.

To recognise the difference between mink and polecats look at the excellent ID sheets on the Non-native Species Secretariat website.