Tayside Biodiversity Partnership Local Action Plan

Tayside Biodiversity - Tayside Biodiversity Action Plan - Water - Rivers and Burns

DEFINITION
Rivers and burns are flowing watercourses and in their natural state are dynamic systems continually modifying their form.

The rivers and burns habitat consists not only of the watercourse itself - the “wetted channel”, but also the bank and associated land or riparian zone.

This definition provides for overlap with Habitat Action Plans for other habitats closely associated with rivers such as Wet Woodland. These valuable habitats are covered by other action plans which should be referred to in conjunction
with this one.

Key Features
Rivers and burns support a wide range of plants and animals. A watercourse’s biodiversity is determined by its mosaic of features, geographical area, underlying geology and water quality. The rivers and burns in Tayside tend to be fastflowing and nutrient poor and hold a wealth of habitats and rare wildlife. The Highland boundary fault separates the metamorphic bedrock of the highlands and the old red sandstone underlying the lowlands.

The rivers and burns rush down the Highland mountains and only after breaching the Highland boundary fault with famous waterfalls such as Reekie Linn and Rumbling Bridge do they begin to slow slightly and meander across the lowlands. In the lowland stretches the rivers deposit silt on land underlain by relatively more nutrient rich sandstone. Here they have created fertile agricultural land such as that in the lowlands of Angus which the North and South Esks flow through.

In addition to their intrinsic value rivers and burns also act as important wildlife corridors, enabling dispersion and migration of species. They allow mobile species to utilise patchy areas of habitat and interconnect fragmented populations. They are particularly valuable in Tayside with a total length of over 5,000km not only making them essential to wildlife but also a familiar and important part of everyone’s environment.

The River Tay has the largest mean average annual flow of any river in the UK in terms of volume at nearly 200 cubic metres per second. Many of its tributaries are significant rivers in their own right and include the Lyon, Tummel, Isla, Almond and Earn. In addition the Rivers North and South Esk and the Dighty Water drain the Angus and Dundee areas on their way to the North Sea. All the rivers of the Tayside catchment eventually converge on the Firth of Tay.

CURRENT STATUS AND EXTENT OF HABITAT
Tayside rivers and burns have a rich natural heritage and provide numerous resources. Many parts of the system have been modified in urbanisation and for agriculture, forestry and industries such as hydro-power generation. However, the majority of rivers and burns maintain good water quality and rich, diverse habitats.

Habitat Quality
The River Habitat Survey (RHS) assesses the physical structure of watercourses, including the channel, the banks and the river corridor. A survey of Scottish sites undertaken between 1995 and 1997 revealed that of 34 RHS sites on major rivers and burns in Tayside, 56% were ‘semi-natural’, 8% were ‘predominantly unmodified’, 18% were ‘obviously modified’and 18% were ‘significantly modified’. No sites were ‘severely modified’. Compared to the rest of Scotland, these results confirm the relative good health of Tayside’s rivers and burns.

Water Quality
SEPA currently classifies about half of mainland Scotland’s rivers (over 50,000 km) based on their chemical and biological quality. SEPA’s river classification scheme, as applied to 1996 monitoring data, shows that about 91% of the classified river length was of excellent or good water quality. The remaining 4,000 km of rivers were classified as polluted (defined as fair, poor or seriously polluted). In 2000, of a total monitored Tayside river length of nearly 800km, about 75% were classed as either of excellent or good water quality. Less than 3% were classed as poor or seriously polluted.

KEY SITES
Tayside has an abundance of high quality rivers and burns. Many of these have features which, if not necessarily unique, are uncommon in the United Kingdom. Although this section highlights key sites within the Tay catchment, the whole catchment can itself be viewed as a key site. Reaches of unmodified rivers adjoined by natural or semi-natural habitat are not uncommon in Tayside and all can justifiably be regarded as being of importance. In a similar fashion the whole area could be regarded as a key site in the UK and European context for the Freshwater Pearl Mussel Margaritifera
margaritifera.

There are a number of sites in the Tay catchment which stand out in the national context for their intact or unique habitat, their size or for the diversity or rarity of the species they support:

River Tay pSAC

South Esk cSAC

Craighall Gorge SSSI on the River Ericht

The Den of Airlie SSSI, River Isla

The Lunan Burn system between Dunkeld and Blairgowrie

Meikleour SSSI, River Tay

Shingle Islands cSAC

A large site that includes all key parts of the river and its tributaries accessible to Salmon Salmo salar. The site is also of international importance for its populations of Otter Lutra lutra, Sea lamprey Petromyzon marinus, River lamprey Lampetra fluviatilis, and Brook lamprey Lampetra planeri.

This site was designated for its internationally important populations of Salmon and Freshwater Pearl Mussel.

A river gorge containing a diverse assemblage of species, including the River Jelly Lichen Collema dichotomum. There is an excellent continuity of habitat from a high quality river into broad-leaved, mixed and yew woodland.

Similar in many ways to Craighall Gorge.

The lochs on the system are discussed further in the Mesotrophic Lochs Habitat Action Plan, but the burn itself, especially between Clunie and Marlee lochs (SSSI), is the best example of a lowland burn in Tayside.

A section of the River Tay in the lowlands with large shingle banks adjoining unimproved lowland pastures and fen vegetation. This area is important for the diversity of habitats and species it supports, including over-wintering wildfowl.

An area of shingle banks and islands formed by the River Tummel and Tay showing a variety of transition and mosaic communities from bare shingle, grassland and important fluvial alder woodlands. It has an extremely high biodiversity in terms of flowering plants, lichens, mosses and liverworts.

NATURE CONSERVATION IMPORTANCE

The Freshwater Pearl Mussel (FWPM) Margaritifera margaritifera, is a filter-feeding bivalve mollusc with a compressed kidney-shaped, black-brown shell; it may grow to 15cm in length.
It is one of our longest living invertebrates - perhaps up to 140 years, although normally living between 80 - 100 years.

Fertilised eggs develop into tiny bivalve larvae called glochidia. In late summer the female sheds these into the water column. An estimated 0.01% of perhaps 3 million per female will survive to be inhaled by a host salmonid fish where they lodge on the gills. The following spring the juvenile mussels fall off into clear, calcium-poor, fast flowing rivers where they have to find a fine gravel site amongst large stones in which to partially bury
themselves. There they will grow and mature. Perhaps only 1% of the juvenile mussels will survive, but adults have few natural predators and can tolerate moderate disturbance.

FWPM populations have declined by about 90% across Europe in the last 20 - 30 years and Scotland now accounts for 60% of the remaining vulnerable population. On a European scale causes of the decline include pollution, nutrient enrichment and acidification of the water; siltation of gravel beds; decline of host salmonid populations; habitat destruction through river engineering; and overfishing for pearls. In the Tay Catchment the main problem has been overfishing. The FWPM is protected under the Wildlife and Countryside Act, so it is illegal to purposefully kill or injure them. Although fishing for pearls was banned in 1998, it still goes on and actions are being taken to ensure it is stopped. Any publicity of sites containing pearl mussel can act as a stimulus for illegal fishing, so caution over publicity is required. SNH’s surveys and monitoring are establishing the locations and health of populations. These, together with general awareness raising, will help to improve prospects for the FWPM’s long term survival in Tayside.

Myth has it that the Romans
invaded Scotland in search of
pearls.

Strictly speaking, lampreys are not true fish at all, but form a separate, more primitive group of jawless vertebrates. These ancient fish superficially resemble eels and have a large sucker-like mouth as adults. Fossils - clearly recognisable as lampreys - have recently been found in 500 million year old rocks in China.

There are three species: Brook lamprey Lampetra planeri live entirely in fresh water; River lamprey Lampetra luviatilis and Sea lamprey Petromyzon marinus migrate downstream to the sea, returning to spawn later in their lifecycles. They hatch in gravel riverbeds and migrate as larvae to silty parts of the river. Here they live in burrows and filter feed, helping to keep the water clean. As adults they leave these nursery grounds and ultimately migrate and spawn.

The numbers and distribution of lampreys have declined in some parts of Europe because of increased pressure
on the habitats on which they rely. These include water pollution, siltation clogging gravel beds used for spawning,
and river engineering that may destroy important habitats or impede migration. However, the Tay’s catchment
size and suitable habitat mean that it supports an important population of all three lamprey species.

Actions being taken to ensure long term survival of the lampreys includes avoiding disturbance of spawning and
nursery areas; avoiding migration impedance; carrying out surveys and monitoring to establish locations and
health of populations; awareness raising.

The most unusual and
unfamiliar fish of the Tay.

KEY SPECIES
Key species have been selected for Tayside for a number of different reasons. Tayside contains nationally or internationally important populations of some species, including River jelly lichen and Freshwater Pearl Mussel. Ospreys Pandion haliaetus and Otters Lutra lutra have been selected as species representing a success story, illustrating what can be achieved. The Atlantic salmon is of economic importance and a notable feature of the region’s rivers. Other species, including the stiletto fly Thereva lunulata, are nationally rare and their distributions uncertain, but they have been recorded in our region in the past. A locally important species, the Daubenton’s bat Myotis daubentoni, feeds on insects flying over the rivers and roosts nearby in the hollow limbs of old trees.

P = UK Priority species C = UK species of conservation concern

Mammals	Water vole	Arvicola terrestris	P
	Otter	Lutra lutra	P
	Pipistrelle bat	Pipestrellus pipistrellus	P
	Daubenton’s bat	Myotis daubentoni	C
Birds	Goosander	Mergus merganser	C
	Dipper	Cinclus cinclus	C
	Kingfisher	Alcedo atthis	C
	Osprey	Pandion haliaetus	C
Fish	Salmon	Salmo salar	C
	Sea trout/brown trout	Salmo trutta
	Sparling/smelt	Osmerus eperlanus	C
	Sea lamprey	Petromyzon marinus	C
	River lamprey	Lampetra fluviatilis	C
	Brook lamprey	Lampetra planeri	C
	Allis shad	Alosa alosa	P
Invertebrates	a cranefly	Rhabdomastrix laeta	P
	a stiletto fly	Spiriverpa lunulata	P
	a stonefly	Brachyptera putata
		poss extinct
	Freshwater pearl mussel	Margaritifera margaritifera	P
Plants	River water-crowfoot	Ranunculus fluitans	C
	River jelly lichen	Collema dichotomum	P
	Ear-lobed dog-lichen	Peltigera lepidophora	P
	Spruce’s bristle moss	Orthotrichum spruce	P

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