Systematics and biology of the East Siberian char <Emphasis Type="Italic">Salvelinus leucomaenis</Emphasis>

A review that considers in detail for the first time the taxonomic position, phenetic diversity, and principal features of the endemic species East Siberian char Salvelinus leucomaenis in the range from the northeast of Asia to Japan based on own and published data is provided. In comparison with other species of chars, S. leucomaenis is characterized by a smaller morphological and ecological diversity. A migratory form feeding on fish is dominant in the range. At the same time, parallel to large migratory forms, other life forms—resident riverine and lacustrine-riverine forms represented by males and females and riverine and dwarf males were found in S. leucomaenis. Individuals with various color variations occur everywhere. Resident forms are rare in the north of the range; they are dominant in the south of the range, in Japan.     

Hybridization between native white-spotted charr and nonnative brook trout in the upper Sorachi River,Hokkaido, Japan

Invasion status and impacts of nonnative brook trout (Salvelinus fontinalis) in a Hokkaido stream were investigated with field surveys and genetic analyses. Nonnative brook trout was detected in nine (41 %) of the 22 sampled reaches in three tributaries of the Sorachi River, Hokkaido, Japan. Based on the external pigmentation, twelve putative hybrids between brook trout and native white-spotted charr (Salvelinus leucomaenis) were collected in two reaches. Microsatellite and mitochondrial DNA data established that 58% of these hybrids were first-generation (F₁) progenies between male brook trout and female white-spotted charr. Our results suggest potential negative impacts of nonnative brook trout on native charr populations in Hokkaido through interspecific interactions.     

Do stocked hatchery‐reared juveniles ecologically suppress wild juveniles in Salvelinus leucomaenis?

The dominancy of semi‐wild and hatchery‐reared white‐spotted charr Salvelinus leucomaenis juveniles was evaluated using pair‐wise enclosure tests and field stocking tests. The semi‐wild S. leucomaenis originated in a hatchery, being stocked into the test stream as eyed‐eggs. In the pair‐wise enclosure test, the semi‐wild S. leucomaenis dominated the hatchery S. leucomaenis that were of a similar standard length (L_S). The semi‐wild S. leucomaenis were subordinate to hatchery S. leucomaenis that were > 11% larger in L_S. In the field stocking test, the abundance and growth of semi‐wild S. leucomaenis was decreased in the presence of larger hatchery S. leucomaenis (14% larger L_S). Taken together, these results suggest that larger hatchery S. leucomaenis ecologically suppress the smaller semi‐wild S. leucomaenis. Salvelinus leucomaenis juveniles that are stocked with the intention of supplementing natural populations should be < 10% larger than their wild counterparts at the time of stocking to minimize their competitive advantage. The semi‐wild and hatchery S. leucomaenis used in both tests were genetically similar individuals, suggesting that the differences are due to the early rearing environment of either a natural stream or hatchery. The hatchery S. leucomaenis have lower levels of aggression as a result of selection in the hatchery rearing environment. Rearing in a natural stream from the eyed‐egg stage is likely to increase their lowered aggression.     

Displacement of native white‐spotted charr Salvelinus leucomaenis by non‐native brown trout Salmo trutta after resolution of habitat fragmentation by a migration barrier

After resolution of habitat fragmentation by an erosion‐control dam, non‐native brown trout Salmo trutta invaded the upstream side of the dam and displaced native white‐spotted charr Salvelinus leucomaenis in Monbetsu stream, Hokkaido, northern Japan.     

Frequent infections of mountain stream fish with the amphibian acanthocephalan,Pseudoacanthocephalus toshimai (Acanthocephala: Echinorhynchidae)

Pseudoacanthocephalus toshimai is an intestinal acanthocephalan parasite of amphibians in Hokkaido, the northernmost island of Japan. In this study, common freshwater fish of the families Salmonidae and Cottidae in mountain streams around the Kamikawa basin of Hokkaido were examined for acanthocephalan infections with P. toshimai. A total of 160 salmonids and 14 cottids were caught in 4 streams by bait fishing during summer and autumn seasons of 2019. Adult acanthocephalans were found only from the salmonids, namely, Salvelinus leucomaenis leucomaenis, Salvelinus malma krascheninnikovi, Oncorhynchus masou, and Oncorhynchus mykiss. The maximum prevalence reached 58.1% in S. leucomaenis, but the mean worm burden was at low levels (e.g., 3.1 in S. leucomaenis and 2.2 in S. malma). All of the acanthocephalans were identified to P. toshimai by morphological observation and DNA barcoding. Although the male acanthocephalans became sexually mature, the females never reached the gravid adult stage, suggesting that salmonids are unsuitable or aberrant hosts for P. toshimai. The infected fish were found exclusively from a small stream with bush, in which a large habitat of amphibians is included. Ligidium japonicum, a terrestrial isopod, collected from the habitat was highly infected with cystacanth larvae of P. toshimai. The observation of fish stomach contents directly demonstrated that small salmonids eat L. japonicum. The terrestrial isopods, which are washed away by rain into a stream, seem to be a source of salmonid infections with P. toshimai. The habitat of intermediate hosts should be emphasized in the taxonomy of the closely related genera Acanthocephalus and Pseudoacanthocephalus.     

Effect of ozone exposure on the compositions of gill and erythrocyte membrane lipids and proteins of Japanese charr (Salvelinus leucomaenis)

• 1.1. Compositions of lipids and proteins of erythrocytes (RBC) and gills from Japanese charr (Salvelinus leucomaenis) which were exposed to 0.4 and 0.7 ppm ozone for 30 min were compared with those of the control.
• 2.2. On exposure to ozone, both RBC and gill membrane phospholipid content, especially phosphatidylethanolamine (PE), dropped.
• 3.3. The decrease of PE was brought about by the decrease of docosahexaenoic acid content which comprised the major component of PE.
• 4.4. RBC membrane protein with 215 and 225 kDa, which is equivalent to cytoskeletal protein, selectively disappeared on exposure to ozone.

     

Redd superimposition by introduced rainbow trout,oncorhynchus mykiss, on native charrs in a japanese stream

Spawning redd superimposition of introduced, spring-spawning rainbow trout,Oncorhynchus mykiss, on native, fall-spawning Dolly varden,Salvelinus malma, and white-spotted charr,S. leucomaenis, were examined in a small stream in Hokkaido, Japan. The stream reaches in which Dolly Varden and white-sported charr redds were observed in fall 1997 greatly overlapped with the reaches in which rainbow trout redds were recorded in spring 1998. Spawning microhabitats were also similar between trout and the two charr species. Thirteen and 3% of Dolly Varden and white-spotted charr redds, respectively, were superimposed by rainbow trout redds. The eggs or alevins in the disturbed charr redds were potentially damaged because charrs were not likely to have emerged from the redds before the superimposition occurred. In sufficiently great abundance, introduced rainbow trout may negatively impact native charr populations by dislodging the latter’s spawning redds.     

Genetic Differentiation of Three Sympatric Charr Species from the Genus SalvelinusInferred from PCR–RFLP Analysis of Mitochondrial DNA

We examined differentiation of three sympatric charr species Dolly Varden charr Salvelinus malmaWalbaum, white-spotted charrS.leucomaenisPallas, and Levanidov charrS. levanidovi Chereshnev, Scopetz, Gudkov. Using restriction fragment length polymorphism analysis (RFLP), three mitochondrial DNA fragments (ND1/ND2, ND5/ND6, and Cytb/D-loop) amplified in PCR were compared. The divergence of mtDNA nucleotide sequences betweenS. levanidovi and S. leucomaenis was about 9.7%, between S. levanidovi and S. malma, 8.7%, and between S. malma andS. laecomaenis, 7.5%. These results indicate genetic isolation of the species examined and support the earlier suggestion on closeness of Levanidov charr to the common ancestor of the genus Salvelinus.     

Distribution of two congeneric charrs in streams of Hokkaido Island,Japan: considering multiple factors across scales

Salvelinus leucomaenis (white-spotted charr) and S. malma (Dolly Varden) are distributed throughout Hokkaido Island, Japan, but sites where they occur in sympatry are rare. In general, S. malma inhabit upstream reaches and S. leucomaenis extend downstream to the ocean. Factors influencing their distribution were analyzed at four spatial scales ranging from the whole island to individual stream pools. At the island scale, S. leucomaenis were found in the warmer south-west region and at lower altitudes elsewhere, whereas S. malma were found in the colder north-east and at higher altitudes. At a regional scale, the downstream limit of S. malma and upstream limit of S. leucomaenis shifted to lower altitude from south-west to north-east across the island, coincident with the decrease in temperature. Further analysis showed that transition points from S. leucomaenis or sympatry to S. malma in individual watersheds were closely related to an index of cumulative mean monthly temperatures exceeding 5°C. However, at the scale of a single watershed, the transition occurred at different altitudes, gradients, and temperatures in two tributaries, apparently because stream discharge, habitat, and disturbances from floods interacted with these abiotic factors to limit distribution. The two charr species developed interspecific dominance hierarchies in individual pools, and there was strong complementary density compensation among stream pools that could be explained by interspecific competition but not by differences in habitat. However, patterns at watershed and regional scales suggested that interspecific competition interacts with temperature in complex ways. We conclude that the importance of various abiotic and biotic factors in shaping Hokkaido charr distributions depends on the scale at which they are viewed.     

Isolation and characterization of tri‐ and tetra‐repeat microsatellite loci in the white‐spotted charr Salvelinus leucomaenis (Salmonidae)

Tri‐ and tetra‐motif repeat microsatellite marker loci were developed for the white‐spotted charr Salvelinus leucomaenis. The 454 pyrosequencing was used to discover repeat arrays, and eight microsatellite‐primer sets, available for the estimation of polymorphisms, were identified. The number of alleles in a wild population ranged from two to four and the observed and expected heterozygosities were 0·180–0·600 and 0·188–0·599, respectively.     

Reproduction efficiency and some characteristics of the spawning grounds of the pink salmon <Emphasis Type="Italic">Oncorhynchus gorbuscha</Emphasis> in the small salmon watercourse in southern Sakhalin

The peculiarities of the distribution of the freshwater ichthyofauna, bottom sediments and conditions at the spawning grounds, and the egg survivability rate of Oncorhynchus gorbuscha were studied in 2003?2012 in a typical salmon river on Sakhalin Island (Goluboi Ruchei brook, Aniva Bay, southern Sakhalin). The sites characterized by the highest survivability rate of the embryos of the pink salmon are inhabited by the freshwater fish community where the juveniles of masu salmon O. masu and whitespotted char Salvelinus leucomaenis dominate. The lengthway bed slope at this site is steeper compared to the sites with lower survivability rates (0.010?0.020 vs. 0.004?0.020?). The maximal positive correlation of the egg survivability rate to the flow velocity of the underflow has been registered for the depth of 30?40 cm, and the maximal negative correlation of the egg survivability rate has been registered to the bottom sediment temperature.     

Karyological Differentiation of Northern Dolly Varden and Sympatric Chars of the Genus <Emphasis Type="Italic">Salvelinus</Emphasis> in Northeastern Russia

In many cases the taxonomic status of sympatric chars (with exception of white-spotted char Salvelinus leucomaenis) is not clear and is actively debated. We karyotyped three pairs of sympatric chars inhabiting the Russian Far East-northern Dolly Varden, S. malma malma, and Lavanidov's char, S. levanidovi, from the Yama River (northern coast of the Sea of Okhotsk, Magadan Region), northern Dolly Varden and Taranetz's char, S. taranetzi, from Lake Achchen (east Chukotka), and northern Dolly Varden and white char, S. albus, from the Kamchatka River (Kamchatka Peninsula). Three of them had similar chromosome numbers. But all chars studied had an individual and discrete set of karyotypic characters, which enabled reliable identification each of them by chromosome number, chromosome arm number, and number and location of active nuclear organizer regions.     

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.     

Size at maturity of fluvial white-spotted charr, <Emphasis Type="Italic">Salvelinus leucomaenis</Emphasis>, around the Lake Biwa water system varies with habitat size

Size at maturity of fluvial white-spotted charr, Salvelinus leucomaenis, was studied in small headwater tributaries of nine rivers around the Lake Biwa water system, Japan. Threshold size at maturity in both sexes showed significant positive relationships with water discharge, indicating that smaller threshold sizes at maturity of fluvial white-spotted charr occurred in smaller habitats. These results provide a link between size at maturity and habitat size and have important implications for the management of both habitats and white-spotted charr populations.     

On brook chars of the southern Kuril Islands and a possible mechanism of formation of dwarf forms of Dolly Varden trout Salvelinus malma curilus

The specific morphological and biological features of dwarf chars Salvelinus malma curilus from three isolated populations of the southern Kuril Islands Kunashir and Iturup were studied. It was shown that brook dwarfs, in comparison with the migratory form of Salvelinus malma curilus, are characterized by a smaller diameter of spawned eggs (which corresponds to smaller yolk reserves and shorter embryos at hatching), retarded growth and morphogenesis of early juveniles, a mosaic pattern of paedomorphic and peramorphic morphological transformations, and a short lifespan. The population and age variability of the relative sizes and shape of otoliths was revealed. Dwarf populations are typically characterized by considerable morphological differences between males and females corresponding to those in migratory fish. The strategy of dwarfism is assumed to be built into the genome of the migratory ecotype of S. malma curilus.     

Experimentally induced foraging mode shift by sympatric charrs in a Japanese mountain stream

Foraging mode shifts may allow animals flexibility to adaptto a variety of ecological conditions. Theory holds that ectothermssuch as fishes should shift from ambush to active search modeswhen prey density declines, to maintain a minimum encounterrate. Salvelinus malma (Dolly Varden) sympatric withS. leucomaenis(white-spottedchirr) in a northern Japan mountain stream were observed toshift from ambushing drifting invertebrates at fixed focal pointsto picking benthic invertebrates from the substrate along circuitousroutes throughout pools, as drift declined throughout summer.Experimentally reducing drift in two pools during early summerwhen all charr were drift foragers caused subordinate malmato make marked shifts from drift to benthic foraging within1 h, whereas nearly all leucomaenis remained drift foragers.Some charr of both species responded to reduced drift by emigratingfrom pools. Combined results of three replicate experimentsrevealed that malma shifted to benthic foraging when their rateof drift forays was reduced below a specific threshold, therebyupholding predictions of the theory. Adaptive foraging modeshirts may promote coexistence of these congeneric charrs inreaches of Japanese mountain streams     

Life history traits of white-spotted charr in an alpine environment: Implications for local adaptation along an altitude gradient

As a case study of local adaptation, we compared the life history traits of white-spotted charr Salvelinus leucomaenis between populations isolated in an alpine environment (altitude above 2000 m) and a normal environment (ca. 1000 m) in the Fuji River basin, near the southern limit of its distribution (35° N, 138° E). Our results showed that white-spotted charr in alpine streams had lower growth rate, longer lifespan, earlier spawning season, and were older and larger size at maturity, compared with those habiting a normal mountain stream. We concluded that charr in alpine streams were adapted to low water temperatures and long starvation periods by specialized life history traits.     

Effect of female size on fecundity and egg size in white-spotted charr: comparison between sea-run and resident forms

The relationships between fecundity, egg size and female size of sea-run form were compared with resident form, using white-spotted charr, Salvelinus leucomaenis. Both fecundity and egg size increase with female size. However, the relationship between egg size and female size differed significantly between the resident and sea-run forms. Egg sizes of sea-run and resident were similar even though sea-run fish were much larger. ? 1998 The Fisheries Society of the British Isles     

Phylogeography of mitochondrial DNA in South Asian Dolly Varden char <Emphasis Type="Italic">Salvelinus curilus</Emphasis> Pallas, 1814 (Salmoniformes,Salmonidae): Mediated gene introgression?

In 41 individuals of South Asian Dolly Varden char Salvelinus curilus, nucleotide sequences of tRNA-Pro gene fragment (27 bp) and mtDNA control region (483–484 bp) were analyzed. The fish were collected in 20 localities covering virtually the whole range of the species: Kuril Islands, Sakhalin Island, and Primorye. In addition, six individuals of three other char species (S. albus, S. malma, and S. leucomaenis), which are closely related to S. curilus and inhabit the Russian Far East, were examined. In all, we detected 12 different variants of mtDNA haplotypes that formed three distinct groups differing in 14–20 nucleotide positions. The first group consisted of six haplotypes found in S. curilus in Kuril Islands, Sakhalin, and Primorye (mtDNA phylogroup OKHOTSKIA). The second group comprised four haplotypes representing the mtDNA phylogroup BERING, which had been described earlier (Brunner et al, 2001); they were found in S. curilus in Kuril Islands and Sakhalin, as well as in S. albus and S. malma in Kamchatka and northern Kurils. The third group included two haplotypes detected in S. leucomaenis. The existence of two mtDNA lineages (OKHOTSKIA and BERING) in S. curilus from Kurils and Sakhalin was explained by hybridization and mtDNA transfer from S. malma to S. curilus. The absence of the BERING haplotypes in S. curilus from Primorye water reservoirs is related to the physical isolation of the Sea of Okhotsk and Sea of Japan basins in past epochs. On the basis of comparing phylogenetic trees, constructed from the data on allozyme and mtDNA variation, we suggest that in this case, a mediated transfer of mtDNA in Alpinoid chars → S. malma → S. curilus chain could occur.     

Comparing competitive ability and associated metabolic traits between a resident and migratory population of bull trout against a non-native species

Juvenile bull trout Salvelinus confluentus from two geographically and ecologically distinct populations were compared with regard to their ability to compete with non-native brook trout Salvelinus fontinalis in an artificial stream, and with respect to their rates of oxygen consumption. Bull trout collected from a migratory population foraged more successfully against brook trout competitors than those from a resident population, capturing more of a limited amount of food items presented. The migratory population was also more aggressive (measured by the number of nips, chases and lateral threat displays) against brook trout competitors than the resident population. Bull trout from the migratory population had a higher oxygen consumption rate (203 mg O₂ kg · hr^-1) in the field than similar sized fish from the resident population (183 mg O₂ kg · hr^-1). These results suggest native bull trout have population-level variation in competitive ability against a non-native species and such competitive ability is positively associated with metabolism and migratory life history.