Sympatric Char Research Articles

A comparison of turbine entrainment rates and seasonal entrainment vulnerability of two sympatric char species, bull trout and lake trout, in a hydropower reservoir

AbstractPotadromous salmonids that reside in hydropower reservoirs often have a high recreational and conservation value. However, the potential seasonal turbine entrainment vulnerability patterns of potadromous salmonids are not well understood. Here, we use acoustic telemetry to test the hypothesis that adults of two species of the Salvelinus genus (bull trout and lake trout) differ in their seasonal patterns of entrainment and entrainment vulnerability over a 2‐year period. Our results show that while both species were entrained at similarly low annual rates (~1%), these two salmonids differed in their patterns of forebay residency and proximity, with implications for entrainment risk. Bull trout occupied the forebay at low rates across all seasons, with no clear seasonal pattern of forebay proximity. In contrast, lake trout displayed a strongly seasonal pattern of entrainment vulnerability with a distinct movement away from the forebay during the summer, and a large increase in forebay proximity and use in the winter and spring. These findings provide a novel species‐specific demonstration of the potential entrainment vulnerability of lake trout. The seasonal patterns of entrainment vulnerability seen in previous bull trout studies, where bull trout occupied top pelagic predator niches, were not replicated in our study where bull trout occur in sympatry with another top pelagic predator. These findings, which indicate that species composition plays an important role determining entrainment vulnerability, have important implications for the conservation of indigenous lake trout and bull trout populations, and together highlight the need for a site‐specific approach to entrainment quantification.

Genetic analysis of sympatric char populations in western Alaska: Arctic char (Salvelinus alpinus) and Dolly Varden (Salvelinus malma) are not two sides of the same coin

The North Pacific Ocean has been of great significance to understanding biogeography and speciation in temperate faunas, including for two species of char (Salmonidae: Salvelinus) whose evolutionary relationship has been controversial. We examined the morphology and genetics (microsatellite and mitochondrial DNA) of Arctic char (Salvelinus alpinus) and Dolly Varden char (Salvelinus malma) in lake systems in western Alaska, the eastern and western Arctic, and south of the Alaskan Peninsula. Morphologically, each lake system contained two forms: one (Arctic char) largely confined to lake habitats and characterized by greater numbers of pyloric caeca, gill rakers, and shallower bodies, and another (Dolly Varden) predominated in adjacent stream habitats and was characterized by fewer pyloric caeca, gill rakers, and deeper bodies. MtDNA partial (550 bp) d-loop sequences of both taxa were interspersed with each other within a single 'Bering' clade and demographic inferences suggested historical gene flow from Dolly Varden to Arctic char had occurred. By contrast, the taxa were strongly differentiated in sympatry across nine microsatellite loci in both lakes. Our data show that the two taxa are highly genetically distinct in sympatry, supporting their status as valid biological species, despite occasional hybridization. The interaction between these species highlights the importance of the North Pacific, and Beringia in particular, as an evolutionary wellspring of biodiversity.

Variation of cytochrome b gene in sympatric chars from kronotsky lake (Kamchatka Peninsula)

In previously identified sympatric char forms (species) from Kronotsky Lake (Kamchatka Peninsula) and a number of other chars from the genus Salvelinus, nucleotide sequences of the mtDNA cytochrome b gene were determined and phylogenetic analysis of these forms was performed. The divergence of the cytochrome b gene in the Kronotsky char group (0.48%) coincided with the interpopulation difference estimates in northern Dolly Varden, which indicates a relatively recent divergence of the chars from Kronotsky Lake. Haplotypes of each form of the Kronotsky Lake chars are divided into two groups, which belonged to two different phylogenetic mtDNA lineages of northern Dolly Varden from Chukotka and Kamchatka. The formation of the Kronotsky char forms proved to be unrelated to the observed variability of the mtDNA cytochrome b gene.

Differentiation of the Dolly Varden Char (Salvelinus malma) and the Taranetz Char (Salvelinus taranetzi) Inferred from the PCR–RFLP Analysis of Mitochondrial DNA

Genetic differentiation of two sympatric char species, the Dolly Varden char (Salvelinus malma Walbaum) and the Taranetz char (S. taranetzi Kaganovski), has been studied. Restriction fragment length polymorphism (RFLP) analysis has been used to compare three mitochondrial DNA (mtDNA) fragments (ND1/ND2, ND5/ND6, and Cytb/D-loop) amplified via polymerase chain reaction (PCR). The divergence between S. malma and S. taranetzi inferred from mtDNA nucleotide sequences is 2.8%; between S. leucomaenis and S. taranetzi, 7.1%; and between S. malma and S. leucomaenis, 7.5%. The absence of common haplotypes and the degree of divergence indicate that the Dolly Varden char and the Taranetz char are genetically isolated and confirm that S. taranetzimay be regarded as a separate species.

Retinal Structure of Sympatric and Allopatric Populations of Cutthroat Trout (Salmo clarki clarki) and Dolly Varden Char (Salvelinus malma) in Relation to their Spatial Distribution

Retinal structures of cutthroat trout (Salmo clarki clarki) and Dolly Varden char (Salvelinus malma) were compared to determine if these features were consistent with the different light regimes in which the species live, depending on their sympatry or allopatry in lakes. Cone cell density in sympatric trout was over twice that of sympatric char and rod cell density was slightly less. The cross-sectional size of cone cells in sympatric trout was approximately 30% less than in sympatric char. The ratios of photoreceptor cells to ganglion cells in sympatric trout and char retinas were approximately 40:1 and 80:1, respectively. There were no differences between sympatric and allopatric trout with respect to these structural features. Estimates of cone cell density, cone size, and number of photoreceptor cells per ganglion cell for allopatric char were significantly different and intermediate between those for sympatric trout and char. All four populations had similar cone cell mosaics with four paired cones surrounding each single cone. Results are considered in relation to differences in vertical distribution and feeding of sympatric and allopatric populations in three study lakes.