Morphological, ecological and behavioural differentiation of sympatric profundal and pelagic Arctic charr (Salvelinus alpinus) in Loch Dughaill Scotland

• Published in: Hydrobiologia Vol. 783; no. 1; pp. 209 - 221
• Main Authors: Hooker, O. E., Barry, J., Van Leeuwen, T. E., Lyle, A., Newton, J., Cunningham, P., Adams, C. E.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.12.2016; Springer; Springer Nature B.V
• Subjects: Animal behavior; Animal populations; Aquatic ecology; Biomedical and Life Sciences; carbon; Carbon isotopes; Charr II; Diphyllobothrium; Ecology; fins; Fish; Fish populations; Fishes; foraging; Freshwater; Freshwater & Marine Ecology; head; isotopes; Lakes; Life Sciences; lipid bodies; lipid content; Morphology; pelagic fish; Pelagic zone; phenotypic variation; Phenotypic variations; Plankton; Salvelinus alpinus; Scotland; stomach; sympatry; Zoobenthos; Zoology; British Isles, Scotland; Scotland; Evolution; Ecology; Sympatric divergence; Arctic charr; Speciation; Evo-devo (evolution and development)
• ISSN: 0018-8158; 1573-5117
• DOI: 10.1007/s10750-015-2599-0

Phenotypic variation in populations of fishes that inhabit postglacial lakes is often associated with trophic specialisations. A common sympatric foraging divergence seen in Arctic charr is into either plankton or littoral-zoobenthos feeding specialisms. In this study, we report a sympatric polymorphic Arctic charr population which is not centred on this divergence but instead manifests as a plankton (pelagic)—profundal zoobenthos foraging specialisms. The head shape of profundal fish was round and robust, the body thick set and pectoral fins long and wide. In contrast, the head of pelagic fish was pointed and slender, the body fusiform in shape and with short, narrow pectoral fins. There was no difference between profundal and pelagic fish in gill raker number. Body lipid content was significantly higher in pelagic fish as were the number or Diphyllobothrium cysts. The carbon isotope ratio was more heavily depleted in profundal fish. There was no dietary overlap in the prey items recovered from stomach contents of profundal and pelagic fish. We suggest the proximate driver behind the sympatric divergence was the successful exploitation of the profundal zone. The consequences of this have led to the development of adaptations in morphology and behaviour to support and maintain this divergence.