The status of Arctic charr Salvelinus alpinus in Britain and Ireland

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1 Ecology of Freshwater Fish 2007: 16: 6 19 Printed in Singapore Æ All rights reserved Copyright Ó 2006 Blackwell Munksgaard ECOLOGY OF FRESHWATER FISH The status of Arctic charr Salvelinus alpinus in Britain and Ireland Maitland PS, Winfield IJ, McCarthy ID, Igoe F. The status of Arctic charr Salvelinus alpinus in Britain and Ireland. Ecology of Freshwater Fish 2007: 16: Ó 2006 Blackwell Munksgaard Abstract The Arctic charr occurs in lakes across Britain and Ireland and was previously described here as 15 separate species. Most authorities now agree that all these stocks belong to a single polymorphic species complex Salvelinus alpinus (L.). This fish is given little protection in British and Irish law and there has been a steady loss of natural populations in recent years in all the countries concerned. A few new stocks have been created either intentionally or accidentally. In Scotland, only a small proportion of the 258 recorded natural populations has been studied and at least 12 of these are now extinct. There are at least four introduced populations originating from native Scottish stocks, but the fate of stocks introduced from Canada for aquaculture is uncertain. In England, there are eight extant populations in Cumbria and four others extinct. The status of introduced stocks in England is uncertain but there is probably one population surviving in Yorkshire. In Wales, eight lakes with resident Arctic charr populations have been recorded, three of these populations are natural, one is extinct and four have been introduced. In Ireland, of the 74 known populations, approximately 30% are extinct. There is no evidence to indicate that introduced stocks (some of them from Iceland) in a small number of lakes have survived there. A range of factors is involved in the extinction of populations and these include pollution, eutrophication, acidification, afforestation, engineering, exploitation, aquaculture, introductions and climate change. Much research remains to be done and unique stocks of this valuable species will continue to be lost unless positive action is taken through local conservation management backed by appropriate national legislation. P. S. Maitland 1, I. J. Winfield 2, I. D. McCarthy 3, F. Igoe 4 1 Fish Conservation Centre, Gladshot, Haddington, UK, 2 Centre for Ecology & Hydrology, Lancaster, UK, 3 School of Ocean Sciences, University of Wales, Wales, UK, 4 Irish Char Conservation Group, Dublin, Republic of Ireland Key words: conservation; threats; management; introductions; habitat change P. S. Maitland, Fish Conservation Centre, Gladshot, Haddington EH41 4NR, UK; savingfish@maitland60.freeserve.co.uk Accepted for publication March 6, 2006 Introduction The purpose of this paper is to review the present status of Arctic charr, Salvelinus alpinus (L.) in Britain and Ireland. This species is a cold-loving, salmonid fish which is distributed throughout the temperate and subarctic regions of the northern hemisphere. It is an anadromous species in the northern part of its distribution but in the southern part is nonmigratory and confined to fresh waters. The many natural populations in the south of its distribution are believed to have been derived from anadromous stocks which dispersed at the end of the last ice age but were then isolated in a variety of lakes as the climate warmed up. Stocks have been introduced successfully to a number of lakes in various countries. All stocks in Britain and Ireland are land-locked, even though many are sympatric with Atlantic salmon Salmo salar (L.) and sea trout Salmo trutta (L.) and thus migration to and from the sea is physically possible for many. In Britain and Ireland, most populations of Arctic charr (Morton 1955) in individual lakes have been 6 doi: /j x

2 Status of Arctic charr in Britain and Ireland isolated from each other for thousands of years and have developed a variety of phenotypic characteristics (Günther 1865; Day 1887; Regan 1909, 1914) which are probably genetically based (Nyman 1972; Child 1977, 1984; Ferguson 1981). The differences between some populations are so great that many were originally described as distinct species and the following 15 were recognised by Regan (1911) and others in Britain and Ireland. Salvelinus gracillimus Shetland charr Loch Girlsta Regan (1909) Salvelinus Orkney charr Loch Heldal Regan (1909) inframundus Salvelinus killinensis Haddy Loch Killin Günther (1865) Salvelinus mallochi Malloch s charr Loch Scourie* Regan (1909) Salvelinus maxillaris Largemouthed charr Ben Hope Lochan Regan (1909) Salvelinus struanensis Struan charr Loch Rannoch Maitland (1881) Salvelinus lonsdalii Lonsdale s charr Haweswater Regan (1909) Salvelinus willughbii Willughby s charr Windermere Günther (1862) Salvelinus perisii Torgoch Llyn Peris Günther (1862) Salvelinus collii Cole s charr Lough Eask Günther (1863) Salvelinus fimbriatus Coomasaharn Lough Regan (1908) charr Coomasaharn Salvelinus grayi Gray s charr Lough Melvin Günther (1862) Salvelinus obtusus Blunt-snouted charr Lough Luggala Regan (1908) Salvelinus scharffi Scharff s charr Lough Owel Regan (1909) Salvelinus trevelyani Trevelyan s charr Lough Finn Regan (1908) *Presumed to be Loch a Bhadaidh Daraich. Many other populations of Arctic charr have been discovered since these species were recognised, most of them exhibiting characteristics intermediate to or differing from the above species (e.g., Friend 1956) and most authorities now recognise just one species S. alpinus (Linnaeus 1758). On account of the variation, some workers regard this name as covering a species complex. Scotland Natural populations In Scotland, relatively little was known about Arctic charr distribution and biology a few decades ago (Hardie 1940) and new populations are still being discovered (Lyle & Maitland 1992). Very few of the populations have been studied in detail. However, since the initial work here by Friend (1959) and the review by Maitland et al. (1984), there has been increasing interest in this species and a number of recent studies are available (e.g., Campbell 1979; Gardner et al. 1988; Walker et al. 1988; Greer 1991; Maitland et al. 1991; Hartley et al. 1992a,b; Adams et al. 1998; Maitland 1998, 1999a,b; Alexander & Adams 2000). A recent revision of the database initiated by Maitland (1992a)) includes 258 lochs in Scotland which are believed to have, or have had, populations of Arctic charr. There are undoubtedly additional charr lochs which have yet to be identified. Of the Scottish charr lochs on the database, only 142 have been verified to have charr in recent years. The remainder are known only from old records and their present status is unknown. A number of lochs in Scotland have some conservation status as Sites of Special Scientific Importance (SSSIs) on account of their important charr populations. These include Lochs Builg, Doon, Eck, Girlsta and Insh. Studies by Gardner et al. (1988) and Walker et al. (1988) have demonstrated the presence of sympatric populations in Loch Rannoch and these are being further studied, as is sympatry elsewhere (Fraser et al. 1999; Kettle-White 2001). In a study of the genetic variability across Scottish populations, Wilson et al. (2004) showed significant genetic differences among all 19 populations examined. Similarly, Adams et al. (in press) showed phenotypic variation in around half of the pairwise comparisons of Arctic charr from 21 lochs across Scotland. Extinctions At least 12 populations of Arctic charr are known to have become extinct since they were recorded, for example Lochs Achray, Dungeon and Grannoch. This number may be much larger since, as indicated above, many sites have not been examined in recent years and it is probable that some of their populations have disappeared. Most of the known Scottish losses have been in the south, although some populations in the north (e.g., at Loch Heldal on Orkney, the type and only locality for Regan s (1909) nominal Salvelinus inframundus) have also become extinct. The populations concerned and the reasons for their demise have been reviewed by Maitland (1992b) and are discussed further below. Lochs where Arctic charr may be under particular threat include Loch Doon (Maitland et al. 1991), Loch Lee (Maitland 1999b), Loch Girlsta (Swan 1964) and many of those now supporting floating fish farm cages, as at Loch Awe. At Loch Lee, for example the dam intended to enlarge the loch for water supply purposes was constructed close to a charr spawning area. In many years, during the spawning period (October), large numbers of adult fish are washed out of the loch during periods of strong wind. Most of them survive and are found in the river below but cannot make their way back into the loch. Translocations Several new populations have been created in Scotland in recent years. Some of these have been accidental, 7

3 Maitland et al. due to connections created by hydropower schemes. A good example is at Cruachan Reservoir, where Arctic charr have been pumped up several hundred metres from a power station on Loch Awe to the upper reservoir of this large pumped storage scheme (Maitland 1992b). Other translocations have been intentional, for example stock from Loch Doon, where the population was believed to be threatened by acidification, was successfully transferred to Talla Reservoir, creating a successful new population there (Lyle & Maitland 1998). Notable stocks Very few of the Scottish populations have been studied in any detail. Some appear to be of particular interest and require considerable further research. Populations which are little known but appear to be of particular interest are those in Loch Eck sympatric with Powan, Coregonus lavaretus (Friend 1956), Loch Insh river spawning, many kilometres upstream in the River Spey (Walker, in press), Loch Meallt sympatric with three-spined stickleback, Gasterosteus aculeatus (L.), on which its feeds; no other fish species present (Campbell 1984), Loch Croispol a shallow, clear, limestone loch, an unusual habitat for Arctic charr (Maitland et al. 1984), Loch Ness (Bean et al. 1996) and Loch Morar (Maitland 1981) the largest lochs in Britain by volume and depth respectively, in both of which Arctic charr are known to occur at considerable depths. Many other stocks of Arctic charr may be of significance but nothing is known of them. England Natural populations All the native Arctic charr populations of England occur in the English Lake District of Cumbria, where they are found in the eight lakes of Buttermere, Coniston Water, Crummock Water, Ennerdale Water, Haweswater, Thirlmere, Wastwater and Windermere, with the latter lake also known to contain a number of subpopulations (e.g., Frost 1955; Mills 1989). Of these lakes, Windermere and Ennerdale Water are SSSIs, while Buttermere, Crummock Water and Wastwater are both SSSIs and candidate Special Areas of Conservation (csacs). Extinctions The only recorded extinctions of Arctic charr in England are those of Goat s Water, Loweswater, Ullswater and Rydal Water in Cumbria (see Day 1887; Regan 1911; Watson 1925; Frost 1955). The stock in Ullswater is believed to have become extinct in the 1940s as a result of lead mining pollution in its stream spawning habitats. Along with Haweswater and Loch Eck, Ullswater was one of only three British sites where Arctic charr occurs sympatrically with schelly or powan, C. lavaretus (L.). Charr were recorded as being fairly plentiful in Goat s Water by Day (1887), but two nettings in 1986 failed to catch any (Partington & Mills 1988). In addition to the four populations known to have been lost from England, there are currently concerns over the future of stocks in Coniston Water (Winfield et al. 2004), Ennerdale Water (J. Westgarth, Environment Agency, personal communication) and Windermere (Winfield & Durie 2004) for a number of reasons, including eutrophication, species introductions and possibly land use changes. All three lakes are currently the subject of active study as a support to the management of their Arctic charr populations. There is also some concern about the future of the Haweswater population due to the high level of predation by cormorants, Phalacrocorax carbo (L.), at this site. Translocations There has apparently only been one recent attempt to translocate Arctic charr in England, during which donor material was taken from Windermere to Grimwith Reservoir in Yorkshire (D. Hopkins, Environment Agency, personal communication). Eggs stripped from an autumn-spawning population of the south basin of Windermere were incubated in a hatchery and then introduced to Grimwirth Reservoir as fingerlings in 1989, 1990 and Gill netting soon afterwards suggested reasonable initial survival and growth, but no full survey of the introduced population has been carried out since However, individual Arctic charr have since been detected during electrofishing surveys of the River Dibb downstream of the reservoir in 1995 and Although the reservoir is not formally operated as a fishery, some casual angling occurs and it is reputed that Arctic charr are still present. Notable stocks The biology and ecology of the Arctic charr population of Windermere, with its subpopulations of autumn and spring spawners in the north and south basins, have been studied extensively for many decades (Frost 1955, 1965). An introduction to this considerable literature, too extensive to review in detail here, is provided by Elliott & Baroudy (1995). Since the early 1990s, this population has also been continuously studied using hydroacoustics, contributing to our understanding of its spatial distribution (Baroudy & Elliott 1993), its reaction to the management of 8

4 Status of Arctic charr in Britain and Ireland Windermere s eutrophication problem (Elliott et al. 1996) and the development of hydroacoustic survey techniques (Winfield et al., in press). The study of other Arctic charr populations in England has been largely limited to examinations of genetic diversity (e.g., Partington & Mills 1988), although substantial ecological research is currently in progress or planned for the immediate future at Coniston Water, Ennerdale Water and Haweswater. Wales Natural populations In Wales, only four natural populations of Arctic charr have ever been recorded (Ward 1931). One is now extinct. Llyn Padarn is protected as an SSSI. In the 1980s there was concern that eutrophication (from sewage works discharge) was affecting the charr resulting in faster growth and larger adult size and in the late 1980s a phosphate stripper was installed on the sewage works. Surveys conducted by the Environment Agency Wales have shown that the size frequency distribution of adult spawning Arctic charr has now returned to historical values (R. Brassington, Environment Agency Wales, personal communication). The stock is considered as healthy at the moment but possible future pressures on this population are increased recreational use of the lake by anglers (although fishing pressure is currently low) and boat users. The Environment Agency plans to conduct a sonar survey of the Arctic charr in Llyn Padarn in the near future (R. Brassington, Environment Agency Wales, personal communication). Llyn Cwellyn is protected as a csac. There is no regular monitoring of this population but a daytime hydroacoustic survey in 2003 suggested a density of 51 adult fish per hectare (c adults) (McCarthy I.D. & Adams C.E., unpublished data). This stock is considered healthy as pressures are low (very little fishing pressure or recreational boat use). A dam was constructed on the outflow from the lake in 1976 and the lake is a regulated water supply providing water for the Caernarfon District (Roberts 1995). There is an operating agreement between the Environment Agency and Dwr Cymru/Welsh Water to ensure that water levels in the lake are not reduced to levels that would affect the spawning grounds of Arctic charr during the spawning season (R. Brassington, Environment Agency Wales, personal communication). Llyn Bodlyn is afforded no protection at present. It is the smallest lake containing a natural population of Arctic charr and may be the most at risk. No information is available on population density. There is no fishing pressure or boat use but lake size is such that climate change may reduce the deep water thermal refuge in the lake. A dam was constructed on the outflow from the lake in 1894 and the lake is a regulated water supply providing water for the Barmouth District (Roberts 1995). Extinction Llyn Peris is a sister lake to Llyn Padarn and was the type locality for Gunther s (1862) nominal Salvelinus perisii. The Arctic charr stock was eradicated in the late 1970s by the development of the Dinorwig pump storage scheme when the lake was drained and dug out to deepen it. However, a genetic survey had suggested that the stock was genetically similar to Padarn (Child 1977). Approval for the pump storage scheme was granted on the condition that Arctic charr were transplanted into suitable lakes in North Wales (Ffynnon Llugwy and Llyn Dulyn). Translocations Ffynnon Llugwy Fish were transferred to this lake between 1977 and 1982 from all four native populations but mainly Llyn Padarn (Jones 1983). Surveys conducted in 1982 showed that a spawning population was established (Jones 1983). Recent surveys, conducted in 2004, showed a healthy spawning population is still present in this lake (McCarthy I.D. & Berrill I.K., unpublished data). No information is available on population density. The lake is a regulated water supply providing water for Bangor and Anglesey (Roberts 1995). Llyn Diwaunedd A spawning population was discovered in this lake in the early 1990s. It is thought that the Arctic charr are not native to the lake and have been transplanted into the lake, although the timing of the transplantation and the original source of the fish are uncertain (R. Brassington, Environment Agency Wales, personal communication). Llyn Dulyn and Llyn Cowlyd Llyn Dulyn was originally stocked with Arctic charr as part of the Dinorwig pump storage scheme transplantation programme although no stocking details (i.e., the original source of the fish, the numbers stocked and stocking dates) are available (R. Brassington, EA Wales, personal communication). These two lakes form part of a series of lakes in the Dolgarrog catchment (Conwy Valley) that are interconnected by a series of leats/pipes and are all regulated water supplies for Dolgarrog Power Station (RWE npower). Anglers have caught Arctic charr in both these lakes (Roberts 1995; Closs-Parry 1997; Lyttle 2002; 9

5 Maitland et al. McCarthy in press) and recent survey work has shown that separate healthy spawning populations are established in both lakes (McCarthy & Berrill, unpublished data), although no data exist on population densities. As a result of the movement of water between lakes in the Dolgarrog catchment for hydroelectric power generation, Arctic charr have been occasionally caught in Llyn Eigiau and Coedty Reservoir, but it is thought that these lakes do not contain resident populations (McCarthy 2004). Ireland Natural populations The distribution of Arctic charr in Ireland was first described by Went (1945) and subsequently updated by a number of authors during the latter half of the 20th Century (e.g., Went 1971; Whilde 1993). A detailed review of their distribution and their status was carried out by Igoe et al. (2003). This established that Arctic charr have been recorded from 70 lakes throughout the country with greatest concentrations along the Western seaboard in Counties Kerry, Galway, Mayo and Donegal. An additional four new charr loughs were recorded from County Kerry during surveys carried out by the Irish Char Conservation Group in It is likely that more populations will be discovered in loughs in remote areas, particularly Counties Kerry and Donegal. Recent high-profile extinctions in Lough Owel (the type locality for Salvelinus scharffi), Loughs Corrib and Conn (Igoe et al. 2001) and Lough Dan (Igoe & Kelly-Quinn 2002) have focused attention on the need to assess the status of Arctic charr in Ireland and understand mechanisms affecting their survival. There are few publications on the biology and ecology of Arctic charr in Ireland (e.g., Conneely & McCarthy 1984; Doherty & McCarthy 2001; Igoe & Hammar 2004). To date, no sympatric polymorphic populations have been identified in Ireland. This may reflect the limited survey work carried out so far rather than a true absence. Igoe & Hammar (2004) provides more detail on ecology and biology of Irish charr, including recent survey results by the Irish Char Conservation Group on a number of Irish lakes. Extinctions Of the 74 lakes in Ireland from which Arctic charr have been recorded, it is estimated that 25 (34%) of the populations are now extinct (Igoe & Hammar 2004) and the status of many others (20) is still unknown. All populations in the Shannon catchment, east of it and in County Clare now appear to be extinct. Igoe et al. (2003) examined a list of worldwide threats to Arctic charr identified by Maitland (1995) in the context of Irish populations. The greatest threats are interspecific interactions from introduced native and nonindigenous fish species, eutrophication, acidification and climate change particularly in lakes already affected by fish introductions and eutrophication. Heavy engineering projects and over-abstraction of water for domestic supply is also of some concern in a number of lakes containing Arctic charr. Aquaculture of Arctic charr is limited in Ireland but if the industry does expand the possibility of introgression with nonindigenous strains of Arctic charr and the spread of disease would need to be carefully considered. It is recommended that no farming of Arctic charr should take place where they may have access to waters containing indigenous populations (Igoe & Hammar 2004). Translocations Arctic charr of Icelandic origin were introduced into three lakes in the Burrishoole system, County Mayo, in 1970 and Although juveniles and one sea run finnock were noted subsequently, the success of these introductions is unclear (Quigley & Flannery 1997). One of the lakes, Bunaveela Lough, was surveyed in 2001 by the Irish Char Conservation Group, and although it was found to support a good population of Arctic charr it is unknown whether these were native fish already in the lake or the product of the above introductions. Icelandic Arctic charr were also introduced into the Crumlin system but no specimens have since been recorded (Quigley & Flannery 1997). Almost 5000 Arctic charr fingerlings (hatchery reared 1+) of Lough Kindrum origin were stocked into Lough Owel in 1995, in an attempt to reestablish a stock in the lake. The absence of Arctic charr from subsequent gill netting surveys suggest that this attempt may have been unsuccessful (Igoe et al. 2003). Notable stocks As in Scotland, few Irish populations have been studied in detail. Although Ferguson (1981) concluded from a genetic study of samples of Arctic charr from seven Irish lakes (including specimens from lakes where separate species were once described by taxonomists) that they were derived from a common ancestor, he did recommend that efforts should be made to conserve as many as possible as they provide good models for genetic changes in isolation. Irish Arctic charr certainly exhibit a range of colour and morphometric and meristic characteristics. Arctic charr in one notable population (Lough Coomasaharn) not only have a higher gill raker count than most other western European populations but also have an interesting parasite community Igoe & Hammar 10

6 Status of Arctic charr in Britain and Ireland (2004). The size attained by Arctic charr in most Irish lakes is moderate (c. 25 cm). However, growth potential is greater in the large limestone lakes in the west of Ireland, where sizes up to 37 cm have been recorded. With the exception of Lough Mask, these populations are now extinct and therefore the conservation of the Lough Mask population must become a national priority. Other lakes with interesting features include Lough Melvin, Counties Fermanagh and Leitrim; Muckross Lough, County Kerry, Lough Finn, Lough Eske, and Lough Fad, County Donegal (Igoe & Hammar 2004). Conservation efforts The Irish Char Conservation Group was set up in the year 2000 as an NonGovernment Organisation (NGO) with a particular focus on Arctic charr, although the group does also concern itself with other native Irish fish species. The primary objective of the group is to increase public awareness of the plight of Arctic charr through public talks and seminars, a website and brochures. For example, 15,000 leaflets were mailed to people living in the Lough Conn catchment in an effort to inform people of the facts surrounding the decline in the lake s water quality and the disappearance of Arctic charr from that lake, which had become a local politically divisive issue. The group aims to be proactive by collecting scientific material and is actively collecting biological information on Arctic charr in Ireland and to date has surveyed over 24 loughs. The information gathered is used to promote awareness of Arctic charr through the media and help inform statutory agencies with a role in planning and fishery protection. The group is of the opinion that the state should focus efforts into protecting the remaining populations of Arctic charr. Efforts can then be made to restore stocks to lakes from which they have recently disappeared, e.g., Lough Conn, once the causal agents have been removed (e.g., phosphorus loading addressed). In the interim, it is important that all remaining populations of Arctic charr in Ireland are identified and their status established, so that conservation efforts can be directed more effectively. Threats to arctic charr The Arctic charr is a sensitive northern species which is vulnerable to a range of anthropogenic pressures. Pollution Most point-source pollution is discharged to running waters, usually after treatment of some kind and so there are relatively few Arctic charr lakes in Britain which have been seriously affected by domestic or industrial pollution (though see eutrophication below). However, stocks of Arctic charr have been directly affected by pollution and the loss of this species from Ullswater is attributed to discharges from the mines at Glenridding. In Ireland, Loughs Leane, Keel, Conn, Caragh, Currane, Corrib, Mask, Ennel and Clare have all been affected to a greater or lesser degree by polluting discharges. Eutrophication The process of eutrophication may have both direct and indirect effects on fish populations and the latter may be particularly dramatic when combined with the introduction of alien species. Arctic charr populations are usually directly impacted through the reduction of dissolved oxygen levels in the hypolimnion, which itself results from the decomposition of increased algal populations produced by elevated nutrient availability. A thorough account of such a direct eutrophication threat to Arctic charr in Windermere, England, is provided by Mills et al. (1990), who also note that warm surface temperatures may prevent this species avoiding such low hypolimnetic dissolved oxygen levels. In such situations, Arctic charr can only be effectively conserved by the restoration of their habitat and Windermere again provides an excellent example of how this can be done through the introduction of phosphorus stripping (Elliott et al. 1996). Acidification Arctic charr have disappeared from at least two lochs in Scotland (Lochs Grannoch and Dungeon), apparently as a result of acidification. The extinction of Arctic charr in three Irish loughs (Dan, Tay and Glendalough) has also been attributed to acidification (Igoe & Kelly-Quinn 2002). One of the most characteristic effects of acidification on fish populations is the failure of recruitment of new age classes into the population (Rosseland et al. 1980; Harvey 1982). This is manifest in an altered age-structure and reduction in population size, with decreased intraspecific competition for food and increased growth or condition of survivors. To anglers, the fish stock then appears to improve because larger fish are caught albeit in lower numbers. However, with no recruitment the population contains fewer and fewer fish until eventually there are none. Several workers have tried to define and classify various levels of acidification and the resultant fish communities. Kelso & Minns (1982) have produced such a scheme which, if applied to recent conditions in some Arctic charr lochs in Scotland, fits the disappearance of this species there and indicates that there should be concern for other lochs if acidification continues. 11

7 Maitland et al. Afforestation The impact of coniferous afforestation and forestry practice on freshwater habitats in Britain and Ireland has caused much concern in recent decades. The effects of each stage of the forestry cycle ground preparation, tree planting to canopy closure, the maturing crop and felling may have an impact on local fresh waters (Maitland et al. 1990). It seems highly likely that extensive afforestation in the catchments of Loch Grannoch, and to a lesser extent Loch Dungeon, exacerbated the acidification which had already taken place in their headwaters and caused the extinction of Arctic charr in these two waters (Maitland et al. 1987). Land use changes may also be involved in the apparent decline of Arctic charr in Ennerdale Water (J. Westgarth, Environment Agency, personal communication). Engineering It is well known that hydroelectric schemes can have deleterious effects on local fisheries and this is certainly the case with Atlantic salmon in some waters. However, Arctic charr seem to be less affected than other salmonids and there is evidence that some stocks (which are mainly plankton feeders) may be favoured by the fluctuating water levels, which adversely affect brown trout. It is believed that, because the fluctuating levels often devastate the littoral flora and fauna (Smith et al. 1987), the trout population, which mainly feeds in the littoral area, is also adversely affected. The plankton, on the other hand, is affected much less and so charr may still have their main food source. However, it is important that any drops in water level during the incubation period of Arctic charr eggs are avoided. Work at Haweswater suggests that the charr population there suffered from this problem in the past. However, many hydroelectric reservoirs have large populations of Arctic charr and indeed new populations have developed in some reservoirs (e.g., Cruachan Reservoir above Loch Awe) where water (and Arctic charr) have been pumped up from a loch containing Arctic charr. In contrast, the Arctic charr population in Llyn Peris in Wales is now extinct due to the development of a pumped storage scheme there. Water supply schemes may also have significant effects on fish populations, especially where large volumes of water are transferred from one catchment to another. However, in England, where Arctic charr and schelly (C. lavaretus) are pumped out of Haweswater each year as part of the water supply system supplying much of north-west England, including the City of Manchester (Maitland 1985a), this entrapment kills only a small fraction of the populations and is not regarded as significant (Winfield et al. 1994, 1998, 2002). In Scotland and Wales, several new populations have been accidentally created due to engineered connections between lakes. However, the impact can be serious where no account is taken of local fish ecology when the engineering works are being designed. This can lead to damage to fish stocks as, for example, at Loch Lee, where substantial numbers of adult fish are washed out of the loch each year at spawning time, due to construction of a spillway near charr spawning grounds. Exploitation At present, very few anglers fish specifically for Arctic charr, though they are caught inadvertently on many waters by people fishing for brown trout. However, there are some specialist charr anglers and it is likely that this number will increase as fishing for this species becomes more popular and pressures on other game species increase. There are several conservation concerns in relation to angling. Overfishing is certainly a potential threat, especially in very small lochs where the stocks are likely to be small (e.g., Loch Meallt on Skye or the charr lochan on Ben Hope). It is a characteristic feature of catch records of Arctic charr in Scotland that, on occasion, huge bags may be obtained; hundreds may be taken in a single day and, as these fish are usually removed, small stocks are thus vulnerable. In Ireland, Arctic charr are sometimes caught by anglers fly fishing for resident or anadromous brown trout (e.g., Loughs Fermoyle, Inagh and Fad), and most of the pre-1970 records were based on these incidental captures (Went 1945, 1971). Arctic charr are specifically fished for in Lough Eske, County Donegal, where local fishermen use maggots to catch charr from the shore during the spawning season usually in November. This tradition is at least 150 years old and does not occur anywhere else in Ireland (Igoe 2002). Semicommercial fisheries for Arctic charr using plumb lining, a form of angling, continue to operate in England on Windermere and, to a lesser extent, Coniston Water. However, both fisheries are closely controlled by restrictions on fishing season and minimum takeable size and there is no indication that fishing pressure in either lake has any negative impacts on the populations (Mills 1989; Winfield et al. 2004) Netting for Arctic charr has been on a very limited scale and very little is carried on at present. In the past, there have been some fisheries for this species, notably at Loch Leven (Burns-Begg 1934) and St Mary s Loch (Robson 1986). More recently, De Gernier (1991) promoted the idea of the commercial use of Arctic charr in Scotland following trials to explore the commercial 12

8 Status of Arctic charr in Britain and Ireland viability of limited commercial netting carried out previously by Greer (1984). Aquaculture The success of the farming of Atlantic salmon and rainbow trout Oncorhynchus mykiss (Walbaum) has led at times to an overproduction of these species with consequent reduction of prices in the market place and many farmers have been looking round for possible alternative species which might have a high market value. Already shown to be successful in Canada and other countries, a number of farmers are currently rearing Arctic charr and finding that they have considerable potential. The increasing interest in Arctic charr as a farmed fish poses a distinct threat to the genetic integrity of individual stocks if charr are moved around the country for commercial purposes. The recent suggestion that farmed Arctic charr be moved from England to be farmed in the north of Scotland must be deplored. Even worse was the importation in 1991 of stocks of Arctic charr from two sources in Canada to two different fish farms in Scotland. There is no adequate scientific or economic justification for such practice and the evidence from salmon farming, where numerous rivers on the west coast of Scotland now have significant numbers of farm escapees breeding with native stocks, should be a lesson learned. The recent advent of fish farming in several lochs containing Arctic charr has led to a number of changes. There is clear evidence that charr learn to aggregate around the fish cages and feed on waste food falling through the meshes. These charr also grow much larger than normal and all the recent rodcaught records for Arctic charr have been of fish taken in the vicinity of cages. However, many of the rainbow trout being reared in these cages escape and grow to a large size, becoming potential predators of Arctic charr and of Atlantic salmon smolts. Introduction of alien species The deliberate or accidental introduction of new fish species is considered to pose one of the most insidious threats to fish conservation around the world (Lowe- McConnell 1990) and specifically in Britain and Ireland, where new fish species may act as predators, competitors or environmental degraders (Winfield 1992). The fish communities of water bodies containing Arctic charr in Britain and Ireland are particularly at risk from this threat because they are relatively species-poor and often have pools of potential invader species in close geographical proximity. The roach, Rutilus rutilus (L.), is one such species which has increased in distribution greatly in recent years as a result of live-baiting practices, with resulting concerns over potential competitive effects on native planktivorous fish species including Arctic charr (Winfield & Durie 2004). This problem is considered to be of such magnitude in England that the use of live bait has recently been banned in 14 lakes of high conservation value, including all those which contain native populations of Arctic charr (Winfield & Durie 2004). In Ireland, the extinction of Arctic charr in Lough Corrib was closely associated with the rapidly expanding and recently introduced roach population (Igoe et al. 2001). Although the use of live bait has been illegal in Ireland for almost 30 years, introductions still occur. Climate change There is increasing evidence that human activities of various kinds are altering the atmosphere to such an extent that global warming may create major climatic changes over the next few centuries. The most certain changes seem to be a rising sea level and a general rise in atmospheric temperatures, especially at high latitudes. Changes in precipitation, wind and water circulation patterns are also likely but their nature is uncertain. These changes are highly likely to affect Arctic charr and a number of scenarios are possible (Maitland 1991). Everywhere there is likely to be a shift of southern species to the north and a retreat northwards of northern species, restricting the geographic distribution of species such as Arctic charr. In the open sea, changing temperature and circulation patterns are likely to affect pelagic, demersal and migratory species, including Arctic charr along its northern distribution. Along the coast and in estuaries, increased sea levels will create many changes and could affect low-lying charr lochs. In fresh waters, as well as the latitudinal changes there are also likely to be parallel changes related to altitude, with coldwater species being more restricted to higher cooler waters and their place being taken in the lowlands by warmwater species. In rich lochs in summer there will be an increasing tendency to low oxygen conditions in deep water, with summer kill ; there will be less freezing in winter and so a lesser tendency to winter kill with less ice in these lochs. Apart from political and practical measures to reduce the amounts of greenhouse gases entering the atmosphere, aquatic biologists can help species like Arctic charr by improving understanding and subsequent planning by developing existing monitoring programmes, devising ecological experiments, implementing conservation plans for threatened species, controlling northward movement of undesirable species, analysing existing data and developing better models. 13

9 Maitland et al. Conservation As indicated above, the Arctic charr is under threat in various parts of Britain and Ireland and has disappeared from a number of waters. It is clear that active conservation measures are necessary now if vulnerable stocks are to be saved and the genetic integrity of others preserved. The main future options for fish conservation in the British Isles are habitat management and restoration, stock transfer to new sites, captive breeding and cryopreservation (Maitland & Lyle 1992). The first two of these are the most useful for the long-term conservation of threatened species. Improved legislation would also help, especially in relation to preventing the import and transfer of potentially harmful species including stocks of Arctic charr from other countries and between lakes already containing populations of Arctic charr. Habitat restoration and management Habitat restoration and management is a major goal in the conservation of most species and communities. Obviously enormous damage has been done to many fish habitats and the situation is often not easy to reverse especially in the short term where fish species or communities are severely threatened. In many cases, potentially unique stocks have completely disappeared. Even where habitat restoration is contemplated, stock transfer or captive breeding (discussed below) could be important interim measures. However, there are a number of important examples of habitat restoration in temperate areas and it should be emphasised that habitat restoration, protection and management are the principal long-term means through which successful fish conservation will be achieved. Windermere is an example where habitat restoration (through phosphate stripping) has been carried out to aid charr conservation. become extinct or to provide an additional safeguard for valuable stocks in threatened waters (Maitland 1985b). Any species which is found in only a few waters could be in potential danger and the creation of additional independent stocks is an urgent and worthwhile conservation activity. There have been several successful translocations of stocks of Arctic charr to new waters in Scotland, England and Wales. Specific criteria have been developed in planning such translocations. For example, the translocation activities must pose no threat to the parent stock, nor to the ecology or scientific interest of the introduction site, which clearly must be ecologically suitable. In general, sites from which the species concerned has disappeared should be considered unsuitable unless the causal factors have been identified and removed. Ideally, the introduction site should be in the same catchment or the same geographic region as the parent stock; or in the same geographic region as a former stock, now extinct. Permission must be obtained from riparian owners, relevant statutory authorities or conservation agencies in the case of nature reserves. The legal position regarding fish introductions is complex and statutory requirements vary considerably from country to country irrespective of whether the waters in question are nature reserves or have any other formal nature conservation status. Stock may be transferred as eggs, fry, juveniles or adults, but the removal of adults could pose a threat to the parent stock. Special consideration should be given to the genetic integrity of the stock to be translocated. Once the stock has been defined, maximum genetic diversity should be sought by selecting material widely in space and time. The transfer of undesirable diseases or parasites can be avoided by taking eggs only from the parent stock and checking for disease. Notes of each translocation experiment should be kept and details published where relevant. Finally, it is important that the fate of the translocated stock is monitored. Translocation One of the most positive areas of management for endangered stocks of fish lies in the establishment of new populations either to replace those which have Table 1. A summary of the current status of Arctic charr populations in Britain and Ireland. Extinct Extant Uncertain Introduced Totals Scotland England Wales Ireland Totals Captive breeding Captive breeding is widely used throughout the world for a variety of endangered animals, including fish (Maitland & Evans 1986). However, for most animals it can really be regarded only as a short-term emergency measure, for a variety of genetic and other difficulties are likely to arise if small numbers of animals are kept in captivity over several generations or more. Captive breeding in the long term does not seem appropriate to any of the freshwater fish species under threat in the British Isles. However, short-term captive breeding involving only one generation does have some advantages for a number of species. It is especially relevant where 14

10 Status of Arctic charr in Britain and Ireland translocations are desirable but it is difficult to obtain reasonable number of eggs or young because of ecological or logistic constraints. In such cases, there are considerable advantages to be gained in rearing small numbers of stock in captivity and then stripping them to obtain much larger numbers of young for release in the wild. Because of genetic problems related to inbreeding and loss of genetic diversity it should not be carried out for more than one generation from wild stock. Cryopreservation Modern techniques for rapid freezing of gametes to very low temperatures have proved successful for a variety of animals, including fish. After freezing for many years and then thawing, the material is still viable. However, the technique is successful only for sperm and though much research is at present being carried out on eggs, no successful method of cryopreservation has yet been developed. The technique is therefore at the moment only of limited value in relation to the conservation of fish species. However, where a particular stock seemed in imminent danger of dying out it would be worthwhile giving consideration to saving at least some of its genetic material through the cryopreservation of sperm. At the very least these sperm can be used to help maintain the genetic diversity of captive stocks of Arctic charr which are being kept over more than one generation. Legislation Freshwater fish in Britain and Ireland are protected in a variety of ways which may vary in the five different countries involved. The two main forms of protection are through the creation of protected sites of one kind or another and individual pieces of legislation protecting species. Most of the latter are concerned with fish of sporting or commercial interest but recent European legislation has proved very effective in giving protection to a much wider range of fish species. Native Arctic charr are not presently an important fish economically or recreationally in Britain or Ireland where statutory fish protection measures have traditionally focused on species such as Atlantic salmon, brown trout and European eel, Anguilla anguilla (L.). However, Directives from Europe (e.g., Habitats Directive and Water Framework Directive) are changing how statutory agencies (and governments) view water as a resource and how they carry out their responsibilities. In this context, much can be gained by increasing public awareness of environmental issues which help to improve the public understanding of biodiversity issues relating to water and the requirements of species such as Arctic charr and the need for proper implementation of these important directives. Anglers and environmental NGOs play an important role here by making these directives more relevant to peoples daily lives and increasing public access to relevant information. Research Three species of native salmonid are of major ecological and economic importance in northwest Europe: Atlantic salmon, brown trout and Arctic charr. The recent history of all three species in this area is believed to be relatively similar. However, the Arctic charr is the more widely distributed species, occurring across the whole of the holarctic region and penetrating further north than any other freshwater fish species. It is believed that the data obtained from studying Arctic charr, using it as a keystone species, will be relevant to other members of the family and their ecosystems. This species offers a unique opportunity to carry out comparative studies of populations of a keystone organism which is known to be sensitive to acidification, climate change and other pressures but which is isolated in a wide range of habitats in Britain and Ireland. Conclusions There is little doubt that a number of stocks of Arctic charr have now become extinct in various parts of the world (Maitland 1995), including Britain and Ireland (Table 1). This is a matter of considerable regret, not only for the loss of an attractive and colourful species which was a useful local resource, but also because their individual genetic make-up was likely to be unique and therefore cannot be replaced. Because of this it is important to review the remaining stocks of Arctic charr in Britain and Ireland and elsewhere, and implement conservation management plans for the future. This valuable fish has flesh of very high quality, often pink, which is much sought after in some countries. As a resource, it is useful in three ways: (i) a species sought after by specialist anglers; (ii) a commercial species of high value for the table; and (iii) a farmed fish of high value. In some areas, it is quite feasible to envisage a scenario where the local populations of Arctic charr provide a welcome addition to the resources of the district by providing employment to those helping with fishing (both commercial and angling) and a distinctive and highquality addition to the menus of local hotels and restaurants. This is already happening in Cumbria, for 15

11 Maitland et al. example. It must be stressed that the resource is a finite one and it is not envisaged that there would be sufficient quantities of fish to market elsewhere, except on a very modest scale. So far there has been relatively little interest in the consumption of wild Arctic charr elsewhere in Britain or Ireland. However, over the last few years there has been a distinct increase in interest in this species from anglers and from fish farmers. It is important that the resource is looked at closely now in relation to these new developments so that there is no danger to the stocks of fish and that any utilisation which takes place is carried out in a sustainable fashion. Internationally, relatively little attention has been paid to the conservation of freshwater fish, but fortunately, this attitude has changed in recent years and there is now an increasing interest in this topic in most parts of the world (e.g., McDowall 1983; Pollard et al. 1990; Kirchhofer & Hefti 1996; Collares-Pereira et al. 2002). In North America in particular, there have been several important initiatives (Williams 1981) including the creation of a facility devoted entirely to the captive breeding and rearing of rare species. Though the Arctic charr is rarely mentioned specifically in international legislation, two recent EU Directives (the Habitats Directive and the Water Framework Directive) should help in the conservation of the species through improved habitat protection and management. The general conclusion from the review is that, although there has previously been some legislation and management in relation to both fish and various general aspects of conservation (such as the establishment of nature reserves), little of this has been aimed directly at the protection of threatened fish species. This situation must be improved if further valuable stocks of native species, such as Arctic charr, are not to be lost. Arctic charr deserve conservation in their own right as an important component of lake biodiversity. However, there is every reason to hope that, given adequate support, Arctic charr and other valuable native species can be managed more positively, thereby saving for posterity this valuable and renewable resource, so important for scientific, recreational, commercial and aesthetic purposes. Acknowledgements We acknowledge the pioneering work on Arctic charr in Britain and Ireland in the past by G.F. Friend, W.E. Frost and A.E.J. Went. Thanks for information and advice are due to Richard Brassington, David Hopkins, Jeremy Westgarth and Catherine Duigan. Valuable comments on a draft of the manuscript came from Gavin Alexander and Cameron Durie. References Adams, C.E., Fraser, D., Huntingford, F.A., Greer, R.B., Askew, C.M. & Walker, A.F Trophic polymorphism amongst Arctic charr from Loch Rannoch, Scotland. Journal of Fish Biology 52: Adams, C.E., Wilson, A.J., Fraser, D., Alexander, G. & Ferguson, M.M. in press. Patterns of phenotypic and genetic variability in the Arctic charr show hidden diversity in Scottish Arctic charr. Ecology of Freshwater Fish (in press). Alexander, G.D. & Adams, C.E The phenotypic diversity of Arctic charr, Salvelinus alpinus (Salmonidae) in Scotland and Ireland. Aqua, Journal of Ichthyology and Aquatic Biology 4: Baroudy, E. & Elliott, J.M The effect of large-scale spatial variation of pelagic fish on hydroacoustic estimates of their population density in Windermere (northwest England). Ecology of Freshwater Fish 2: Bean, C.W., Winfield, I.J. & Fletcher, J.M Stock assessment of the Arctic charr (Salvelinus alpinus) population in Loch Ness, U.K. In: Cowx, I.G., ed. Stock assessment in inland fisheries. Oxford, U.K.: Blackwell, pp Burns-Begg, R The Loch Leven angler. Kinross, U.K.: Barnett, 144. pp. Campbell, R.N Ferox trout, Salmo trutta L., and charr, Salvelinus alpinus (L.), in Scottish lochs. Journal of Fish Biology 14: Campbell, R.N.B Predation by the arctic charr on the three-spined stickleback and its nests in Loch Meallt, Skye. Glasgow Naturalist 20: Child, A.R Biochemical polymorphism in charr (Salvelinus alpinus L.) from Llynnau Peris, Padarn, Cwellyn and Bodlyn. Heredity 38: Child, A.R Biochemical polymorphism in charr (Salvelinus alpinus L.) from three Cumbrian lakes. Heredity 53: Closs-Parry, N Arctic charr in the lakes of Snowdonia. Llandybie: Y Naturiaethwyr. Collares-Pereira, M.J., Coelho, M.M. & Cowx, I.G Conservation of freshwater fishes: options for the future. Oxford, U.K: Fishing News Books, Blackwell Science, 462 pp. Conneely, J.J. & McCarthy, T.K The metazoan parasites of freshwater fishes in the Corri catchment area, Ireland. Journal of Fish Biology 24: Day, F British and Irish salmonidae. London: Williams & Norgate. De Gernier, D Commercial eel and charr fisheries in Scotland: their feasibility and interaction with the environment. Proceedings of the Institute of Fisheries Management Annual Study Course 22: Doherty, D. & McCarthy, T.K The metazoan parasites, diets and general biology of arctic char, Salvelinus alpinus L., in two Irish lakes. Proceedings of the International Association of Theoretical and Applied Limnology 27: Elliott, J.M. & Baroudy, E The ecology of Arctic charr, Salvelinus alpinus, and brown trout, Salmo trutta, in Windermere (northwest England). Nordic Journal of Freshwater Research 71: