9781934874547-ch10

Trout and Char of the World

10: Trout and Char of the North Atlantic Isles

Andrew Ferguson, Colin E. Adams, Magnús Jóhannsson, Fiona Kelly, R. Andrew King, Peter Maitland, Ian McCarthy, Martin O’Grady, Paulo A. Prodöhl, Skúli Skúlason, Eric Verspoor, and Ian J. Winfield

doi: https://doi.org/10.47886/9781934874547.ch10

This chapter covers Britain (England, Scotland, and Wales), Ireland (Northern Ireland and Republic of Ireland), Iceland, the Faroe Islands, and Greenland. Most of the current land area was covered by the Last Glaciation, which reached a maximum circa 18,000 years ago. Other than for southern and southeastern England, there was no postglacial freshwater connection to mainland Europe, and thus, the only native populations of freshwater fishes outside southern and southeastern England today are the euryhaline salmonids (Salmo spp., Salvelinus spp., and Coregonus spp.), European Smelt Osmerus eperlanus, Threespine Stickleback Gasterosteus aculeatus, Ninespine Stickleback Pungitius pungitius, and European Eel Anguilla anguilla. Brown Trout Salmo trutta, which belongs to the Eurasian and North African species complex, is native to all regions in the North Atlantic Isles (NAI) with the exception of Greenland. Arctic Char Salvelinus alpinus is native to all regions covered. During the Last Glaciation, Brown Trout and Arctic Char, along with other freshwater fishes, survived in a number of ice-free refuges in northwestern Europe and colonized accessible waters as the ice melted. The geographical position of the NAI makes these islands a contact zone for colonizers emanating from multiple refugia. Founder effects, together with genetic drift and natural selection in reproductively isolated or partially isolated populations have led to considerable intra- and interpopulation genetic variation. This, along with substantial environmental heterogeneity, is reflected in considerable phenotypic diversity in terms of coloration, morphology, life history, feeding, reproductive behavior, and so forth. Extensive diversity resulted in the description, in the 19th century, of some 12 species of Brown Trout and 15 species of Arctic Char in Britain and Ireland alone (Günther 1862; Day 1887). Many biologists no longer regard these as valid. However, Kottelat and Freyhof (2007) recognize 4 species of Brown Trout and 19 species of Arctic Char here. While these Brown Trout species are supported by phylogeographical evidence (Ferguson 2004; McKeown et al. 2010), most of the char species are described solely by phenetic characteristics, many of which are known to be phenotypically plastic (e.g., Adams et al. 2003), and thus the validity of such species has been questioned (Adams and Maitland 2007).