Natural Resources Scotland, Berbice, Blair Atholl, Perthshire, PH18 5SZ, Scotland, U.K.
Trophic polymorphism amongst Arctic charr from Loch Rannoch, Scotland
Article first published online: 1 APR 2005
Journal of Fish Biology
Volume 52, Issue 6, pages 1259–1271, June 1998
How to Cite
Adams, C. E., Fraser, D., Huntingford, F. A., Greer, R. B., Askew, C. M. and Walker, A. F. (1998), Trophic polymorphism amongst Arctic charr from Loch Rannoch, Scotland. Journal of Fish Biology, 52: 1259–1271. doi: 10.1111/j.1095-8649.1998.tb00970.x
- Issue published online: 1 APR 2005
- Article first published online: 1 APR 2005
- (Received 24 May 1997, Accepted 22 February 1998)
- sympatric polymorphism;
- head structure;
- trophic morphology
This paper describes the results of a multivariate and univariate morphometric analysis of three groups of Arctic charr Salvelinus alpinus from Loch Rannoch, Perthshire, Scotland, distinguished a priori on the basis of coloration (bright v. cryptic) and site of capture (from two locations 12 km apart). The analysis produced a clear and highly significant distinction, not only between brightly and cryptically coloured charr, but also between the two cryptically coloured groups, one of which was more robust in terms of several size-independent head measurements. Stomach analysis showed that the brightly coloured charr fed entirely on zooplankton, the less robust, cryptically coloured fish, fed on benthic macroinvertebrates, whereas a significant proportion of the diet of the more robust cryptically-coloured form consisted of other fish. Differences in length at age also distinguished the three forms, with the robust, piscivorous charr, which live longer and potentially reach a larger final size, attaining smaller sizes at a given age. These data clearly confirm the previous identification of a distinct planktivorous morph of Arctic charr in Loch Rannoch and extend the morph analysis by distinguishing two additional morphs, a benthivorous morph and a piscivorous morph that are morphologically and ecologically distinct. The results are discussed in the context of other systems in which sympatric morphs of Arctic charr have been described.