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Climate change can affect fish species directly (e.g. through physiological stress) or indirectly (e.g. species interactions). Whether individual species will experience net benefits or net losses is important to understand from a fisheries management perspective. Ireland has a unique freshwater fish community that faces considerable uncertainty in relation to the impact of climate change. Vulnerability of fish species and subspecies (n = 32) in Ireland were investigated through an expert‐based questionnaire and a trait‐based assessment. Fish species were assessed based on exposure, sensitivity and adaptive capacity. The expert‐based questionnaire predicted that one species, Arctic char Salvelinus alpinus was assigned the rank of high vulnerability, seven species were assigned moderate to high vulnerability, twenty species were assigned moderate vulnerability, and four species were of low to moderate vulnerability. Life‐history characteristics of the fish species were analysed to identify traits characteristic of vulnerable fish species (e.g. Vulnerability to fishing and Trophic level). Coldwater species are highly vulnerable, with indirect effects through interactions with other species or in combination with non‐climatic stressors (e.g. water quality & barriers to migration) being a significant concern. The results provide a vulnerability ranking for Ireland's freshwater fish, that can be utilised by fisheries managers and allows for prioritising of an often‐limited conservation resource. [ABSTRACT FROM AUTHOR]

Salmonid (Salmonidae) sympatric diversity is the co‐occurrence, in a lake or river, of two or more reproductively isolated populations/subpopulations, or phenotypes resulting from phenotypic plasticity. Sympatric populations can arise through allopatric and/or sympatric evolution. Subsequently, allopatric lineages can occur in sympatry due to independent colonisation and/or through anthropogenic introduction. Sympatric divergence is often driven by feeding opportunities, with populations segregating as planktivorous, benthivorous and piscivorous ecotypes ("trophic polymorphism"), and further segregation occurring by feeding depth and body size. Subpopulations evolve by natal homing where a water has two or more discrete spawning areas, often resulting in phenotypically and ecologically cryptic sympatry. Most known sympatric populations/phenotypes in trout of the genus Salmo (Eurasian trout aka brown trout) involve sympatric piscivorous (ferox) and lifetime invertivorous trout. Segregation on the benthic–limnetic axis has been poorly studied in Eurasian trout compared with other salmonids but is likely commoner than currently described. While three sympatric populations/species of Eurasian trout are recognised from Lake Ohrid (Albania/North Macedonia), limited ecological information is available and there are only two lakes with three or four sympatric populations with described benthic, limnetic and piscivorous trophic segregation: Lough Melvin (Ireland) and Loch Laidon (Scotland), the latter having the only identified case of a sympatric profundal benthic feeding populations, possibly due to the absence of Arctic charr (Salvelinus alpinus) in the lake. Many thousands of waters are yet to be examined. Some sympatric populations are extinct, and others are vulnerable with conservation action being urgently required. This should ideally be based on populations/conservation units, but the lack of recognition of intraspecific units in most legislations in the native Eurasian trout range necessitates a pragmatic approach, with species classification, where appropriate, based on integrative taxonomy. Some sympatric populations clearly merit species status and should be formally classified as such if a valid previous name is not available. [ABSTRACT FROM AUTHOR]

Climate change has been identified as a global threat to Arctic char Salvelinus alpinus L. populations. Bayesian statistical models were used to identify important physical and ecological factors explaining Arctic char presence and persistence in Irish lakes. Maximum lake depth and the presence of mixed fish communities (i.e. including non‐salmonid fish species) were the most important drivers of Arctic char presence. There was a 75% probability that an Irish lake would contain Arctic char when maximum depth exceeded 40 m, if only a salmonid community was present. However, the required depth increased to 57 m when a mixed fish community (e.g. pike, perch or roach) was present. Similar variables explained char persistence, with surviving Arctic char populations being more likely in lakes with greater maximum depth and fewer non‐salmonid fish species. Tested temperature covariates were not important in explaining Arctic char presence or persistence in Irish lakes. A risk analysis was undertaken to identify which Arctic char lakes are vulnerable to colonisation by thermally plastic mixed fish communities due to flooding. Results indicated that 32 out of 45 lakes were not at any risk from the colonisation of thermally plastic mixed fish communities and 13 lakes had some level of risk. [ABSTRACT FROM AUTHOR]

The article focuses on the use of snorkelling as a potential alternative, non-destructive technique for monitoring the recruitment of Arctic char in Ireland. The method reportedly allows to calculate the incubation period which is said to be an important consideration where water abstraction may be affecting water levels in a lake. It is said to be possible to determine the size of the female portion of the spawning population in smaller Irish char loughs based on egg deposition calculations.

The article focuses on the suitability of fyke nets as a non-destructive method to trap mature Arctic char Salvelinus alpinus (L.) close to their spawning beds based on work in southwest of Ireland. The use of fyke nets, along with information from snorkelling surveys can provide information on the location and characteristics of char spawning beds in Ireland. Fyke netting was found to be limited in its effectiveness as a tool for catching Arctic char when used outside of the spawning period.

This article reports on the work of the Irish Char Conservation Group, a voluntary Non-Government Organisation set up in 2000 to promote the conservation of Arctic char Salvelinus alpinus in Ireland. The basic terms of reference of the group, its operations and achievements are outlined. Since 2001, the Irish Char Conservation Group has surveyed 47% of known Arctic char loughs in Ireland, updating records and recording previously undiscovered populations ( n = 8). Research in partnership with other agencies is ongoing, providing information necessary for informed management decisions concerning the species. The group interfaces with the relevant statutory bodies in Ireland on a number of levels and endeavours to be as proactive as possible in facilitating research by collecting material and archiving samples for scientific research. The group interfaces with the public through a range of media in an effort to promote understanding amongst the general public of issues affecting Arctic char and its importance from biodiversity and heritage perspectives. In some instances, specific targeted campaigns have been carried out in an effort to address issues affecting Arctic char in particular loughs. [ABSTRACT FROM AUTHOR]

A reputedly ‘unique’ Irish form of Arctic char, characterised by its long and numerous gill rakers and referred to as Salvelinus fimbriatus [Regan, The Annals and Magazine of Natural History 2 (1908) 225], has long been known to inhabit Coomasaharn Lough in the south-west of Ireland. However, this species description was based on a single specimen and, in the intervening period, little research on the unusual gill attributes of the char population has been published. In 2000, the char population of the lake was surveyed by gill netting. The morphometrics of the head region and the gill raker attributes of this population of Irish char were compared with two other Irish char populations. The results of this analysis highlighted the specialised morphology of the Coomasaharn char in an Irish context and demonstrated the planktivorous nature of the Coomasaharn char. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

There is a very high degree of discrete variation in phenotype between populations of Arctic charr. This takes the form of variation not only in morphometric and meristic characters traditionally used to distinguish species, but also in characteristics of life-history, behaviour, coloration and ecology. This variability has a number of consequences, one of these is that there is a strong case for the conservation of populations with extreme phenotypes. However, if variation is discrete between populations but continuous across many populations, this poses difficulties in separating those populations of high conservation value from those of lower conservation value. In this paper we describe a statistical technique which enables populations on the extreme edges of the range of phenotypic variation to be identified and apply this to the morphometric characters of charr from 25 populations from across Scotland and Ireland. The technique enables the identification of any proportion of the most extreme phenotypes. When applied to our data, one population (Loch More) was in the top 2 percentile of the most extreme phenotypes from across the range of all populations included. Three populations were within the top 10% most extreme phenotypes (Lochs More, Uaine and Earn) and a further five within the top 20% (previously mentioned lochs plus Lochs Eck, Merkland, Uaine, Talla and Lough Nalughraman). This technique can potentially be used on any species and on any suite of characteristics as an objective measure of conservation value of a population within a continuous phenotypic range. [ABSTRACT FROM AUTHOR]

From both a modern and a historical perspective there is little doubt that the Arctic charr, Salvelinus alpinus, in Britain and Ireland (as well as elsewhere) is a ‘difficult’ species. Historically 15 separate species have been recognised from populations in Britain and Ireland and there have been recent attempts to reassert these specific names. Here we review the evidence for the status of these ‘species’. We conclude that the evidence for these 15 being afforded full species status is poor. However, both historical and contemporary data show that Salvelinus alpinus (Linnaeus 1758) in Britain and Ireland exhibits levels of variability in form that is much greater than in other species. We argue that a comprehensive genotypic and phenotypic survey of charr populations in Britain and Ireland is required to determine the full extent of variability and the status of populations with a view of providing suitable protection. [ABSTRACT FROM AUTHOR]

1. This paper highlights the recent extinctions of two native Arctic charr populations in the West of Ireland, one population from the Lough Conn catchment, and a second from the Lough Corrib catchment, respectively. 2. The distribution of charr populations in the two catchments is reviewed. The current distribution information is drawn from recent fish stock surveys (Lough Corrib in 1996, and Lough Conn in 1997 and 1998). Previous records of charr in the literature and unpublished data are described to place the current distribution of charr within these catchments into a historical perspective. 3. The importance of the charr population in Lough Mask (Lough Corrib catchment) is emphasized, as it is one of the last extant examples of charr from a large Irish alkaline lake. 4. Impacts on charr populations in both catchments are discussed and conservation measures proposed. Copyright © 2001 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]