Bad news

Elizabeth A Clements – Deputy Director of Conservation, Head of Natural Environment

American Signal crayfish (Pacifastacus leniusculus), are an incredibly successful crustacean – but unfortunately this very success is bad for our aquatic habitats and native species.

Reports of the Invasive Non Native (INNS) Species American Signal crayfish had been getting closer to the North York Moors for a while. But recently the species have been identified within the National Park. Sadly they have been recorded in the River Rye catchment and also at Scaling Dam Reservoir which is connected to Staithes Beck and is close to the River Esk catchment.

There are currently up to six species of non-native crayfish in England, but the ones here now are the American Signal crayfish species from North America. There are a relatively recent arrival. They were imported into England/Wales in the 1970s to kick start crayfish farming ventures. But no one had quite realized what an entrepreneurial creature they would be in their own right, given new territory. They were soon out of control and have continued to be so ever since, marching menancingly on and spreading throughout the country. They can move up and down stream, between water bodies and watercourses, and over land for short distances crossing physical barriers. They can even survive out of water for a few days.

American Signal crayfish. Copyright Canal and River Trust.

Signal crayfish out compete other species and disrupt the interconnected biodiversity chain. They are particularly fertile producing up to 500 eggs in one go, and can live up to 20 years.

They eat fish and amphibian eggs, tadpoles and juvenile fish as well as aquatic vegetation. It’s not that they don’t have any predators, they do – otters, salmon, trout and eel can eat them – but they can reproduce in such large numbers that predation has little impact on the growing populations. Another adverse impact on the ecosystem is their habit of burrowing into banks to hibernate in the winter – banks are therefore weakened and more prone to erosion, increasing sedimentation and flood risk, and decreasing water quality.

In the National Park we are very lucky to still have a population of Britain’s only native freshwater crayfish the White-clawed crayfish (Austropotamobius pallipes). White-clawed Crayfish are declining throughout its range and are therefore protected by European and UK legislation. These native crayfish are declining due to competition, predation and disease. The American Signal crayfish are not only more aggressive and can tolerate poorer water quality and habitat conditions, but they also carry ‘crayfish plague’ (Aphanomyces astaci), a fungal disease which has devastating impact on our native species. Remaining populations of White-clawed crayfish are at risk of being wiped out once the Signal crayfish turn up.

White-clawed crayfish. Copyright Dan Lombard.

Researchers have been striving for years to find a way of successfully controlling and eradicating non-native crayfish but as of yet nothing has been successful so far. That research continues but out native crayfish are under threat in the meantime.  It’s not possible to safely exterminate a whole population in a connected watercourse or a large waterbody but many alternatives have been tried. Trapping and removing larger adult crayfish only allows the smaller younger population to thrive. Trials of chemical treatments have not yet been a success and in the aquatic environment have been particularly tricky. There have been attempts to remove adult crayfish, castrate them, and return them to the population in the hope they would control the population but that has not worked out yet either. Attempts have been made to erect physical barriers to prevent their free movement but only with very limited success. There is also a persistent rumour that people purposefully release Signal crayfish presumably to resuscitate the failed 1970s vision of crayfish farming.

It’s illegal to introduce Signal crayfish, that includes using crayfish as fishing bait – either dead or alive. A licence is needed in England to purposefully trap any species of freshwater crayfish, in an effort to assert some control over the situation.

The best thing we can all do at the present time is follow very clear biosecurity guidelines when we are in and around water.

Check, Clean, Dry campaign poster

It’s very important to note that people can unintentionally spread crayfish plague as well as the actual Signal crayfish but following the Check, Clean, Dry campaign is good practice and should help people avoid spreading the plague.

If you see any kind of crayfish please report these sightings to the Environment Agency (and the National Park Authority too).

We can all do our bit to help protect, conserve and enhance our native species populations in the North York Moors and beyond.

For further information see these JNCC, Buglife, and Natural England pages.

Another crustacean crisis

Due to the sustained period of dry and hot weather recently an emergency rescue was required last week. We’ve blogged about similar operations in the previous two years, where the River Rye in Duncombe Park, Helmsley tends to dry up during summer months because of numerous natural sink holes. This leaves large numbers of fish and other water-dependent creatures stranded in shrinking pools. This year the crisis was particularly acute with no effective quantities of rain in the short term weather forecast.

The River Rye is one of only a few rivers in the North East of England which supports a population of White-clawed crayfish (Austropotamobius pallipes). The species are “Globally Threatened” according to the IUCN’s Red List of Threatened Species. They are the only native crayfish in the UK, and the majority of populations here are declining due to competition from introduced crayfish species, crayfish plague and water pollution.

So last week, alerted by the local fishing club, staff and apprentices turned up in force under the supervision of Simon our River Esk Officer (because he has a licence to handle the protected crayfish). Using gloves and buckets everyone scooped up what creatures they could and then relayed the buckets upstream to where the collected creatures were released back into the River Rye, safely above the sink holes. Over 500 White-clawed crayfish were rescued along with a variety of fish species – Bullhead (250+), Brown Trout (20+), Stone Loach (20+) and Brook Lamprey (50+).

White-clawed crayfish rescue, River Rye, July 2016. Drought conditions. Copyright NYMNPA.

White-clawed crayfish rescue, River Rye, July 2016. Drought conditions. Copyright NYMNPA.White-clawed crayfish rescue, River Rye, July 2016. Bucket collection. Copyright NYMNPA.White-clawed crayfish rescue, River Rye, July 2016. Cooling buckets to adjust water temperature before releasing. Copyright NYMNPA.White-clawed crayfish rescue, River Rye, July 2016. Releasing White-clawed crayfish (adult). Copyright NYMNPA.White-clawed crayfish rescue, River Rye, July 2016. Releasing White-clawed crayfish (female carrying young). Copyright NYMNPA.The translocated fish and White-clawed crayfish will inevitably recolonise the dried up section once the flows return to normal. The habitat here is ordinarily really good, the only down side being the disastrous disappearing water phenomenon during the summer.

The future for local White-clawed crayfish is somewhat uncertain. Further survey work is needed to establish the location of populations in the Rye, in order to help direct and prioritise effective measures to bolster the populations and make them more resilient to climate change risks like flash flooding and drought crisis. Rescue events may need to become a regularised occurrence.

We have no current evidence that the introduced Signal crayfish, which are such a threat to the White-clawed crayfish, have made it into the River Rye yet. Elsewhere in the country ark sites have been established, away from river networks, where populations of White-clawed crayfish can be introduced and kept in blissful isolation. If feasible here this could be a useful additional safety measure, but the first priority is keeping the Rye White-clawed crayfish populations in the river for as long as possible and conserving this particular element of our local natural heritage.

Beside the sea

John Beech – Land Management Adviser

The spectacular coastline that makes up the eastern edge of the North York Moors National Park consists of a great number of composite habitats which in turn are home to a great number of complex plants and animals. The number of habitats – from grasslands to woodlands, farmland to coastal slope, rocky shore to marine environment – means the biodiversity interest on the coast is particularly abundant.

North York Moors coastal landscape - looking out to sea - NYMNPA

On the clifftop farmland plateau, a network of traditional field boundaries provide corridors for a variety of wildlife. Small mammals such as Field voles, Mice and Shrews take advantage of the cover that old walls and growing hedges offer, whilst high in the hedgerows farmland birds such as Yellowhammer, Linnet, Whitethroat and Goldfinch call out to mark their territories and deter predators from their nest sites. Old stone walls and also buildings offer cover for herptiles along the coast such as Slow worms and Adders. The large open fields on the clifftop are often lookout points for Brown hare and Roe deer at dawn and at dusk.

Yellowhammers - http://northeastwildlife.co.uk/

Slow worm - http://northeastwildlife.co.uk/Hare - http://northeastwildlife.co.uk/Intersecting the plateau there are coastal woodland gills (narrow valley with stream) running down to the sea which contain their own microclimates. Sycamore often dominate the frontage to coastal gill woodlands as they seem to tolerate the cold north easterly winds; further up the gills where the growing conditions are less harsh, indicators of ancient woodlands are prevalent. English Oak and Ash are common along with a healthy understory of Hazel, Holly, Hawthorn and Blackthorn. Below this layer during springtime a plethora of ground flora comes to life with Wild garlic, Lesser celandine, Wood anenome and Dog-violets providing dashes of colour to the woodland floor.

Wild garlic - http://northeastwildlife.co.uk/

Hayburn Wyke near Cloughton retains many native tree species growing alongside more recently planted introductions such as Larch and Rhododendron, a Victorian favourite! Introduced into the United Kingdom from Southern Europe and South East Asia in the late 19th century, Rhododendron flowers may be pretty, but the plant has become a serious problem in many woodlands due to its vigorous ability to colonise via seed and underground suckers. In doing so the evergreen canopy of the bush shades out much of the native ground flora leaving a barren ground layer below. Which is why the National Trust at Hayburn Wyke are actively controlling this non-native invasive species and bringing the native ground flora back to life.

Magic wood of Hayburn Wyke by robiuk - http://www.trekearth.com/gallery/Europe/United_Kingdom/England/North_Yorkshire/Cloughton_Newlands/photo155135.htm

The coastal cliffs and crags are temporary homes to seabirds such as Kittiwakes, FulmarsCommon gulls and Herring gulls before they take to the wing and patrol the waters below. Sand martin colonies also exist in the soft cliffs if you know where to look. Kestrels and the occasional Peregrine falcon will also use the craggy outcrops as they search for prey on the undercliffs and rocky shore.

Kittiwakes - http://northeastwildlife.co.uk/

Coastal slope grasslands on the undercliff (below soft cliffs) offer some of the most unimproved habitats in the whole of the National Park. They have evaded the plough and fertiliser spreader and have therefore remained an almost natural habitat with an abundance of wild plant life. The grasslands are home to a variety of orchid species but these can become choked by ranker vegetation such as bracken and bramble. This is where management is needed to conserve the best features of the habitat through grazing by livestock to keep the invasive domineering species in check. In the sheltered hollows within the cliffs mosses and lichens grow, the lichens being good indicators of unpolluted, clean air in the atmosphere.

Exmoor ponies grazing the coastal slope - NYMNPA

Butterwort, Beast Cliff - NYMNPA

Marine life abounds along the rocky shore between land and sea – intertidal habitats. Covered by seawater twice a day, plants and animals that live in the rock pools are super resilient and have adapted to the constant flooding and desiccation that the harsh coastal environment brings. Barnacles, Blennies, Butterfish, Anemones, Periwinkles, Dog whelks and Limpets have all developed intricate methods of survival as the tides recedes for 6 hours before returning to overtop their pools and hiding places and plunge them underwater again. Common seals and Grey seals also regularly visit our shores during the summer and autumn months, hauling out at the remotest headlands to rest and give birth to pups.Rocky Shore - tide out - near Port Mulgrave - NYMNPA

Periwinkles - http://northeastwildlife.co.uk/Marine mussles - http://northeastwildlife.co.uk/Limpets - http://northeastwildlife.co.uk/

Out into the sea along the North York Moors coast marine cetaceans thrive during the summer months. Along with Bottlenose dolphin and Harbour porpoise, five different species of Whale have been recorded off the coast not that far from the shore – Pilot, Fin, Sei, Minke and even Humpback whales – as they follow the herring shoals around the North Sea.

Dolphin - http://northeastwildlife.co.uk/

What with cliffs, crags, caves, coves, crabs and cobblestones this post on the coast was meant to be part of the next instalment of our North York Moors National Park A to Z – but it just felt like it needed its own space.