Genetic structure in relation to movements in wild European grayling (Thymallus thymallus) in three Norwegian rivers

Abstract

The relationship among genetic structure, movements, and barriers was studied in European grayling (Thymallus thymallus). Gene flow is closely related to movement patterns, and genetic differentiation may be negatively correlated with movement. Grayling movements in the Glomma River (8149 tagged) and the neighboring Trysilelva River (4070 tagged) were different among sampling sites. Most individuals were stationary (±0.5 km), but some individuals moved long distances (≤153 km). The movement data indicated potential for gene flow between the two upstream sampling sites in the Glomma River and between the two midstream sites in the Trysilelva River. Allele frequencies at seven microsatellite loci indicated pairwise differentiation across sampling sites. Genetic structuring was generally consistent with the observed movement pattern. Isolation-by-linear-distance or number of potential barriers (dams, lakes) was not significant among sites within streams or among sites within the two southern streams. They were significant, however, if two outlying northern populations in the Pasvik River were included. Our results suggest that although grayling may move long distances, they also exhibit genetic structuring within large continuous river systems. Fish movement, often the result of flexible and adaptive behavioral strategies, is the ecological mechanism for gene flow. Movements may be the adaptive link explaining how environmental conditions affect genetic structuring.

Genetic variation of European grayling (Thymallus thymallus) populations in the Western Balkans

“…5). This observation is in accordance with the proposed stationary life of grayling (Ovidio et al, 2004;Heggenes et al, 2006) and confirms a notion that present-day grayling is a poor invader in waters already inhabited by a local population (Gardiner, 2000). High level of overall genetic variation and genetic distinctiveness of local populations are also concordant with an extensive morphological variation of grayling observed in former Yugoslavia as well as with highly distinct morphological characters not only between grayling populations from different river systems but also within neighbouring populations of the same river system (Janković, 1960).…”

Conservation genetics and management implications for European grayling, Thymallus thymallus: synthesis of phylogeography and population genetics

“…2004). This was supported by Heggenes, Qvenild, Stamford & Taylor (2006) who found that most T. thymallus in three Norwegian rivers were stationary (±0.5 km) and only a few individuals migrated more than 100 km. Both population genetic results and the migratory behaviour of T. thymallus confirm the discrete population character of the species (Koskinen et al.…”

Habitat fragmentation has interactive effects on the population genetic diversity and individual behaviour of a freshwater salmonid fish

“…Adults migrate over long distances among spawning, feeding, and overwintering locations (Heggenes et al, 2006). In winter, European grayling inhabit slowflowing parts of rivers or lakes (Nykänen & Huusko, 2002;Van Leeuwen et al, 2016).…”

“…The European grayling is a long-distance migratory fish that spawns repeatedly in fast-flowing rivers or tributaries of lakes. There are populations described that live in rivers year-round, spawning in fast-flowing sections and overwintering in slow-flowing sections (Heggenes, Qvenild, Stamford, & Taylor, 2006). Other populations live in lakes and migrate annually into smaller tributaries to spawn in spring (Barson, Haugen, Vøllestad, & Primmer, 2009).…”

“…Among important impacts are habitat loss and reduced connectivity between the remaining habitats (Heggenes et al, 2006;Junge, Museth, Hindar, Kraabøl, & Vøllestad, 2014;Van Leeuwen, Museth, Sandlund, Qvenild, & Vøllestad, 2016). The strongest impact of habitat loss can be expected on fish that repeatedly rely on specific spawning locations as a result of philopatry.…”