Life Science Mass Spectrometry Facility

Polymorphism in Arctic charr

Recent NERC and EC funded studies on Arctic charr in Scotland have identified populations containing two or more sympatric forms or morphs, each differentiated on the basis of its morphology and dietary specialisation: 3 sympatric morphs (benthivore, planktivore and piscivore) in Loch Rannoch, 2 sympatric morphs (planktivore and piscivore) in Loch Ericht and 2 possible sympatric morphs (dietary specialisation unknown) in Loch Tay (Adams et al. unpubl.).

To date, dietary specialisation of sympatric morphs has been assessed using stomach contents analysis, however this only provides a simple snapshot of the trophic status. Stable isotope analysis (SIA) provides a more powerful tool in examining trophic ecology: it provides a measure of long-term feeding habits and integrates the relative importance of different prey items to assimilated intake and growth. The aim of this project was to use SIA to determine the trophic ecology of these sympatric Arctic charr morphs by comparing the d15N and d13C signature in the muscle with the d15N and d13C signatures of their major prey items.

Analysis of d15N and d13C in muscle showed highly significant differences between the two Loch Tay populations, demonstrating a difference in trophic ecology between the two body-size morphs. Overlap in the ranges of d15N and d13C for the two morphs, however, suggested that they occasionally shared a common diet.

For more information please see Division of Environmental and Evolutionary Biology - University Field Station