The Importance of Identifying Conservation Units: Brown Trout and Pollan Biodiversity in Ireland
2004; Royal Irish Academy; Volume: 104; Issue: 3 Linguagem: Inglês
10.3318/bioe.2004.104.3.33
ISSN2009-003X
Autores Tópico(s)Fish Biology and Ecology Studies
ResumoABSTRACTThe systematics and nomenclature of European freshwater fishes, especially salmonids, are in achaotic state. The implications of this chaos for the conservation of Irish biodiversity are outlinedwith reference to pollan and brown trout. The recognition of Irish pollan as a postglacial relict of theAlaskan / Siberian species Coregonus autumnalis makes it one of the most unique components of theentire Irish fauna, not just the fish fauna. Brown trout (Salmo spp) shows considerable geneticdiversity that is not adequately represented by designation as a single species, and it is moreappropriate to regard it as either a species complex or as separate designated species in particular areas.One example of brown trout diversity is the occurrence in Lough Melvin of three types of browntrout, known locally as gillaroo, sonaghen and ferox. These three types are genetically distinct, dueto independent ancestry and natal homing to separate spawning areas, which means that minimalhybridisation has occurred since sympatry was established. They differ also in their morphology andecology. These three types therefore merit designation as separate species: gillaroo as Salmostomachicus; sonaghen as Salmo nigripinnis and ferox as Salmo ferox. Their conservation importanceneeds to be recognised, and practical conservation measures need to be put in place as a matter ofurgency. Long-lived piscivorous ferox trout, which probably share a common ancestry with Melvinferox, are found in many of the larger Irish lakes. Further work will undoubtedly reveal other uniquepopulations. Many threats to brown trout diversity exist, including the introduction of non-nativefish and invertebrate species, such as the zebra mussel, and stocking with hatchery-reared browntrout. Although the Melvin brown trout types can be designated as distinct species, conservationactivities should ideally be based on local populations and communities rather than formallydescribed taxa. This approach is limited by current European legislation but may be achievablethrough other facets of national fisheries and wildlife legislation.INTRODUCTIONBiodiversity exists at all levels, from geneticvariation among individuals within a population,through species, to communities; and conservationat all levels is integral to the Rio Convention onBiological Diversity. Conservation of biodiversity,whether of freshwater fish or any other group oforganisms, requires correct identification of the unitto be conserved. How do we know whether anorganism is common or rare if its species or otherunit cannot be defined and recognised? If a fish thatis not recognised scientifically as being distinctbecomes extinct, there is no apparent loss.Incorrect taxonomy leads to the lack ofidentification of threats to the survival ofimportant components of biodiversity, i.e. badtaxonomy can kill! Conversely, conservationresources can be wasted by focusing onsupposedly rare species that are merely non-genetic phenotypic variants of a common species(Avise 1994).Traditionally, species is the main category onwhich conservation legislation and management arebased. However, for many organisms, speciesdesignation is still both arbitrary and subjectiveand is often based on the opinions of individualtaxonomists. Although there are at least 22 speciesconcepts that have been proposed by variousauthors (Mayden 1997), there are three main waysin which species are defined:1. Species are groups of individuals that aresimilar in their external or internal struc-ture (morphological or typological speciesconcepts).2. Species can be recognised on the basis ofreproductive discontinuities (biological speciesconcept). That is, species are groups ofindividuals that can interbreed with eachother but not normally with members ofother species.3. Species can be identified as groups ofindividuals sharing a common evolutionary
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