Morphological shifts, body length and developmental stages during the ontogeny of the grayling (Thymallus thymallus): a between-river comparison
Hedtke, H.; Gaudin, P.; Sagnes, P.; Bohle, H. W.
The five morphological groups which have previously been described for 0+ grayling from one river (Sagnes et al. 1997) have now been demonstrated for two other rivers differing in abiotic characteristics. These morphological groups were determined by variables which are known to be relevant for the hydrodynamic potential (i. e. drag coefficient) and are therefore related to the habitat use of the fishes (Sagnes et al. 1997). Thus, this study confirms the importance of considering the physical habitat of young stages of fish in management studies. The comparison of the morphological groups from the different rivers revealed that the parameters which are conventionally used for the characterization of 0+ graylings (body length, developmental stages sensu Penáz 1975) do not coincide with the morphological groups. Genetic and environmental aspects should be examined in future studies.