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Ireland's Most Threatened and Rare Freshwater Fish: an International Perspective on Fish Conservation

2004; Royal Irish Academy; Volume: 104; Issue: 3 Linguagem: Inglês

10.3318/bioe.2004.104.3.5

2009-003X

Peter S. Maitland,

Fish biology, ecology, and behavior

Ireland's native fish fauna, like that of much of the rest of Europe, is declining. It is likely that some of the unique elements of Ireland's fish communities will become extinct in the next few decades unless urgent action is taken soon. This paper reviews the relevant international conventions and legislation related to fish conservation as well as Ireland's obligations to meet these. Several management options are available, including further legislation, habitat management, translocation, captive breeding and cryopreservation. The present activity in Great Britain in relation to the preparation of Biodiversity Action Plans and other statements of intent is commendable, but what is really needed is prompt practical action in the field if many of these unique wildlife resources are not to be lost. Peter S. Maitland, Fish Conservation Centre, Haddington EH41 4NR, Scotland. E-mail: SavingFish @maitland6O. freeserve.co. uk INTRODUCTION Due to recent glaciation, temperate fish communities are much less diverse than those of the tropics, and in Europe there is a marked reduction in species from south to north. In particular, islands like Ireland are especially impoverished since, for the most part, only fish with marine affinities were able to reach them. Worldwide, human impact has destroyed fish habitat on a wide scale and many populations of rare species have disappeared over the last two centuries. In addition, numerous distinct stocks of common species and a number of important fish communities have become extinct (Maitland 1986; 1987a). For many years, fish were greatly neglected in terms of conservation, and most attention was given to conserving animals and plants of more appeal to the public, for example, birds, mammals and flowers. Starting in the 1970s, however, it was gradually realised that all over the world fish were facing severe threats, and that many species were declining or becoming extinct (Maitland 1974; 1987b). Gradually, more and more countnres started to assess the status of the members of their fish fauna and appropriate conservation legislation and Red Data Books started to appear. Unfortunately, much of the action taken so far is too little too late, for Red Data Books and Red Lists are only the beginning and not the end of the conservation process. Ireland is fortunate in having had a Red Data Book for fish for many years (Whilde 1993), whereas Great Britain, in spite of criticism (Maitland and Lyle 1990; 1991), has so far failed to produce one. In most countries, freshwater fish are a significant part of the biodiversity, and many of species of freshwater fish also support a wide variety of important fisheries. Altogether, there are over 250 freshwater fish species found in Europe as a whole (Maitland 2000), including several species that are diadromous and a few that are mainly brackish but also come into fresh water for significant periods. A number of international agreements have come into effect over the last 30 years and these are aimed at protecting Europe's most threatened species. Without such agreements it is likely that many countries would have taken no action to protect their native fish faunas. Numerous difficulties arise when many countries are involved in the compilation of lists of threatened species. Firstly, the extent to which a species is threatened can vary from one country to another. Secondly, both commercial and sport fishing have major economic and political implications that need to be taken into account, even though the pnrmary aim is the maintenance (or restoration) of threatened species. In many countries too, no species of fish are legally protected, whereas individual bird and mammal species have legal protection. One of the major obstacles in assessing the threat to many fish species (especially non-commercial ones) concerns the enormous gaps in our knowledge of their biol ogy. Lastly, protection measures may prove to be complex and onerous since any decline in numbers may not be due solely to overfishing. Decline can be due to a variety, often a combination, of other BIOLOGY AND ENVIRONMENT: PROCEEDINGS OF THE ROYAL IRISH ACADEMY. VOL. 1041, No. 3, 5-16 (2004). ,C ROYAL IRISH ACADEMY 5 This content downloaded from 207.46.13.124 on Wed, 22 Jun 2016 05:58:02 UTC All use subject to http://about.jstor.org/terms BIOLOGY AND ENVIR-ONMENT unrelated factors, especially water quality (Maitland 1984; Maitland et al. 1987; 1990). SOME BASIC PRINCIPLES Several major principles are involved in establishing conservation criteria for fish and applying these to populations in the wild. Certain characteristics of freshwater fish are especially relevant to the structure of their communities and to their conservation. Their habitats are discrete and thus fish are contained within particular bounds. This leads to the differentiation of many independent populations with individual stock charactenrstics developed dunrng their isolation. This is true even of migratory species for whom, even though there is substantial mixing of stocks in the sea, the homing instinct has meant that there is a strong tendency for genetic isolation. Because each fish population is usually confined to a single body of water, the entire population is vulnerable to the effects of pollution, disease and other factors. Thus for a fish species, the number of separate populations is usually of far greater importance than the number of individuals. Migration is a feature of the life cycle of many fish species, and at migration times these may be particularly vulnerable. This is most marked in diadromous riverine species, where the whole population has to pass through the lower section of its natal river on its journey to and from the sea. If this section of river is polluted, obstructed or subject to heavy predation, entire populations of several species may disappear leaving the upstream community permanently impoverished. DEFINING CONSERVATION STATUS One of the first tasks in preparing conservation plans for the fish fauna of any geographic area is a proper assessment of the conservation status of each species. This is essential for prioritising those species under greatest threat and for the preparation of conservation management plans. Most countries now accept the IUCN (1994) definitions of threat, which are summanrsed in Table 1. TAXONOMY AND CONSERVATION Conservationists often fail to realise just how important taxonomy is in relation to the conservation of animal (and plant) species. Firsdly, the animal must have a scientific name. A number of years ago, this led to Scott and Rines (1975) giving a scientific nameNessiteras rhombopteryx to an aquatic animal popularly known as the Loch Ness monster, so that legal steps could be taken to protect it. Secondly, the more distinct a species is in relation to other species, the greater the priority given to its conservation. Thus, in the jargon of taxonomy, 'lumpers' and 'splitters' can have an important influence on the conservation status, and indeed the future, of fish populations. Table 1 Summary of IlJCN (1994) definitions of threat. Threat Abbreviation IUCN definition Extinct EX When there is no reasonable doubt that the last individual has died. Extinct in the wild EW When it is known only to survive in cultivation, in captivity or as a naturalised population (or populations) well outside the past range. Critically endangered EC When it is facing an extremely high risk of extinction in the wild in the immediate future. Endangered EN When it is not critically endangered but is facing an extremely high risk of extinction in the wild in the near future. Vulnerable VU When it is not cnrtically endangered or endangered but is facing a high risk of extinction in the wild in the medium-term future. Lower risk LR When it has been evaluated, does not satisfy the criteria for any of the categories cnrtically endangered, endangered or vulnerable. Data deficient DD When there is inadequate information to make a direct, or indirect, assessment of its risk of extinction based on its distribution and/or