Morphological and Ecological Differentiation of Sympatric Forms of Arcrtic Charr Salvelinus alpinus (Salmonidae) in Lake Tokko (Northern Transbaikalia)

• Published in: Journal of ichthyology 2021, Vol.61 (1), p.109-129
• Main Authors: Alekseyev, S. S., Samusenok, V. P., Yur’ev, A. L., Matveev, A. N., Pichugin, M. Yu, Khlystov, V. S., Korostelev, N. B., Misharina, E. A.
• Format: Article
• Language: English
• Subjects: Animal morphology; Anthropogenic changes; Anthropogenic factors; Benthos; Biomedical and Life Sciences; Fish; Fish eggs; Growth rate; Hybridization; Insects; Lakes; Life Sciences; Morphology; Ova; Population structure; Pupae; Reproductive isolation; Salvelinus alpinus; Summer; Sympatric populations; Water temperature; Zoology
• ISSN: 0032-9452; 1555-6425
• DOI: 10.1134/S0032945221010021

Based on data from 1997–2019, morphology, growth, feeding, reproduction and early development of Arctic charr from Lake Tokko (Olekma basin, northern Transbaikalia) were studied. Three charr forms, large, small and dwarf differing in growth rate were recorded in the lake. During the last years, the large form disappeared, the small form became rare and the dwarf form became highly abundant; the proportion of old small and dwarf charr sharply decreased. The dwarf form differs in morphology from the small and large forms, which are morphologically similar. In the summer period of 1997–2001, the large form fed on fish, the small form fed mainly on amphibious insects (chironomid pupae), and the dwarf form fed on amphibious insects and benthos. Presently the small form transited to piscivorous and the dwarf form to predominantly planktivorous feeding. The dwarf form spawns from late July to mid-August at stony sites of underwater shore slope when water temperature is 5.0–6.5°С; laid eggs develop till late November–early December at water temperature decreasing to 3.0–3.5°С. According to data needing verification, the small form spawns in late autumn, but some individuals spawn in summer at the same time as the dwarf form. The results suggest substantial, though incomplete reproductive isolation between the dwarf and the small forms. It is supposed that nowadays the degree of their introgressive hybridization has increased following anthropogenic changes in population structure.