Variation in migratory history of Dolly Varden in a stream with an artificial dam in the Shiretoko Peninsula,Hokkaido, Japan

The variation of migration patterns in Dolly Varden Salvelinus malma in a stream with an artificial dam (erosion-control-dam) in the Shiretoko Peninsula, Hokkaido Island, Japan, at the southernmost part of its distribution, was examined by otolith Sr:Ca ratio analysis. All specimens from the above-dam area showed consistently low Sr:Ca ratios (<5.0 × 10⁻³) throughout the otolith. In contrast, many specimens from the below-dam area had higher ratios (>5.0 × 10⁻³) throughout the otolith or only at the outer part than do those from the above-dam area. This higher ratio is probably due to salinity effects. Specimen from the below-dam area could be divided into three types: (1) Consistently low Sr:Ca ratios throughout the otolith, being freshwater residents. (2) Low Sr:Ca ratios around the inner part of the otolith, and thereafter higher ratios toward the outer part, being typically anadromous. (3) Relatively higher Sr:Ca ratios throughout many or in some parts of the otolith, indicating that these have migrated from the freshwater to brackish water or seawater from the early life stage. These findings suggest that Dolly Varden has a high degree of plasticity in its migratory behavior.     

Stream-dwelling Dolly Varden (<Emphasis Type="Italic">Salvelinus malma</Emphasis>) density and habitat characteristics in stream sections installed with low-head dams in the Shiretoko Peninsula,Hokkaido, Japan

Numerous low-head dams have been constructed for erosion control and installed in almost all mountainous streams in Japan. Shiretoko Peninsula, Hokkaido, is considered as one of the most intact areas in Japan, however, more than 331 low-head dams have been installed in 39 streams of the peninsula since the 1960s. In this study, the density of stream-dwelling Dolly Varden (Salvelinus malma) and the habitat characteristics in dam-installed sections were investigated in Shiretoko streams and compared with unaltered sections in which no dams have been installed as a reference. Fish density in dam-installed sections was significantly lower than reference sections. Canopy cover, maximum temperature, wetted width, frequencies of pebble, bedrock and boulder, and areas of rapid, glide and riffle was significantly differed between dam-installed and reference sections. High stream temperature, occurrence of glides, and loss of boulder in dam-installed sections may reduce the suitability of habitats for fish and minimize the population size. We suggest that negative effects of dam installations on Dolly Varden populations have occurred in Shiretoko streams.     

Introgressive hybridization between Dolly Varden Salvelinus malma and white‐spotted charr Salvelinus leucomaenis on Hokkaido Island, Japan

Intra‐ and interspecific phylogenetic analysis of Dolly Varden Salvelinus malma and white‐spotted charr Salvelinus leucomaenis throughout Hokkaido Island was conducted using nucleotide sequences of the mitochondrial DNA control region and three nuclear DNA markers [ribosomal DNA (ITS‐1), microsatellite ( u ‐85), SINE ( Fok ‐223)]. A total of 19 mtDNA haplotypes from 271 individuals of Dolly Varden, nine haplotypes from 134 white‐spotted charr were defined, and identified two well‐supported monophyletic clades for each species. Two haplotypes of Dolly Varden, however, were clustered together in the white‐spotted charr clade. Those haplotypes were found only from several rivers in the Shiretoko Peninsula, and a neighbouring river of that region. Analyses of ribosomal DNA and Fok ‐223 loci revealed that both species are characterized by having completely species‐specific diagnostic sequence and fragment patterns. Dolly Varden of the Shiretoko populations are typically allopatric in distribution where white‐spotted charr do not currently occur. In addition, incongruence in genetic relationships between mtDNA and nuclear DNA markers give strong evidence of historical mtDNA introgression between Dolly Varden and white‐spotted charr. Some white‐spotted charr diagnostic alleles in a nuclear microsatellite locus ( u ‐85) were found in some Shiretoko Dolly Varden populations, suggesting that introgressive hybridization might have also occurred in relatively recent contact and potentially ongoing evolutionary event. The present study presents an example of historical hybridization and introgression at the southernmost distribution limits of Dolly Varden.     

Morphophysiological patterns of life history strategy adoption in Dolly Varden <Emphasis Type="Italic">Salvelinus malma</Emphasis> in Kamchatka

Growth, age composition, gonad maturity and patterns of life history strategy adoption in the population of Dolly Varden from the Kol River (West Kamchatka) are studied. Major factors controlling differentiation of juveniles and trajectories of ontogenetic developments, growth rate and gametogenesis in generations in particular years. The differentiation in a generation into anadromous and resident groupings is completed mainly at the age of 4 years. The process of formation of resident and migratory life history strategy in Dolly Varden is epigenetic. Bifurcation in the life of one specimen is observed once in life, and that in a generation is observed four times: at the first, the second, the third, or the fourth year. The life cycle of females from the Kol River is invariant until they reach the age of 1 year, and that in males is during the 4 years of the freshwater phase. In Kamchatka, all spawners, including precocious males, may reproduce several times during life.     

Effects of forestry on the thermal habitat of Dolly Varden (<Emphasis Type="Italic">Salvelinus malma</Emphasis>)

Forestry activities in riparian areas are known to affect stream communities considerably. Not only do riparian deforestation resulting from agriculture or urbanization developments affect stream communities but extensive commercial plantation and forestry practices can alter stream environments adjacent to remaining, intact or secondary forests. Because forestry often includes the construction of logging roads through the riparian zone, this can directly degrade stream environments. Twelve streams in the Shiretoko Peninsula, Hokkaido were investigated so as to determine the effects of forestry practices on stream temperature, periphyton biomass, grazer (benthic invertebrates) biomass and Dolly Varden (Salvelinus malma Walbaum) biomass. The greater the proportion of planted area in the catchment, the higher the stream temperature. Stream temperature directly affects periphyton biomass and Dolly Varden biomass negatively. Neither stream temperature nor periphyton biomass predicted grazer biomass, whereas a positive correlation was found between grazer biomass and Dolly Varden biomass that forage on invertebrates. The overall results indicated that Dolly Varden in the Shiretoko streams were negatively affected by forestry practices and the resultant stream temperature increases. Without effective future riparian forest management, the complex effects of both riparian disturbance and ongoing global warming could further reduce Dolly Varden populations in the region.     

Potential negative effects and heterogeneous distribution of a parasitic copepod Salmincola edwardsii (Copepoda: Lernaeopodidae) on Southern Asian Dolly Varden Salvelinus curilus in Hokkaido,Japan

The genus Salmincola is an ectoparasitic copepod group commonly infesting the branchial and buccal cavities of salmonids. While negative impacts on hatchery fishes have been reported, their impacts on wild fish populations and distribution patterns are critically understudied. In the Shiretoko Peninsula, Hokkaido, Japan, we found parasites belonging to this genus on the branchial cavity of a stream salmonid, Southern Asian Dolly Varden Salvelinus curilus. All parasites recovered were identified as Salmincola edwardsii based on morphological characteristics and partial 28S rDNA sequences. Prevalence was highly heterogeneous even among neighboring streams (0–54.8%, < 10 km) with the mean intensity among streams being generally low (2.19 parasites/infeted fish). Despite the low intensity, quantile regression analysis showed negative trends between parasite intensity and host condition, suggesting that the infestation of S. edwardsii has a potential negative impact on the host salmonid. In addition, a single copepod was found from an anadromous fish, which could indicate some salinity tolerance of the copepods. It is important to evaluate the effects of Salmincola spp. on host species and determine the limiting factors on the parasite's distribution for proper management.     

Karyotype and divergence of stream Dolly Varden from the Southern Sakhalin

The karyotype of stream Dolly Varden inhabiting a tributary of the Belaya River (the basin of Naiba River, southern Sakhalin) was determined (2n = 82 and NF = 98 + 2). According to the main characteristics (chromosome number and arm number, the presence of a pair of marker submeta-subtelocentric chromosomes with nucleolus organizer regions (NORs), one pair of large acrocentric chromosomes, and one pair of subtelocentric chromosomes), this karyotype is identical to the karyotype of anadromous southern Dolly Varden from Salvelinus malma krasheninnikovi of Primorye and Japan. However, in most stream Dolly Varden individuals, additional active nucleolus organizer regions (NORs) located in telomeric and paracentric regions of two to three pairs of acrocentric chromosomes were revealed. It is suggested that the stream and anadromous southern forms of Dolly Varden are evolutionarily related NORs that are silent in the anadromous souther form are active in the stream form. Possible causes of these differences in NOR activity are discussed.     

Is isolation by adaptation driving genetic divergence among proximate Dolly Varden char populations?

Numerous studies of population genetics in salmonids and other anadromous fishes have revealed that population structure is generally organized into geographic hierarchies (isolation by distance), but significant structure can exist in proximate populations due to varying selective pressures (isolation by adaptation). In Chignik Lakes, Alaska, anadromous Dolly Varden char (Salvelinus malma) spawn in nearly all accessible streams throughout the watershed, including those draining directly to an estuary, Chignik Lagoon, into larger rivers, and into lakes. Collections of Dolly Varden fry from 13 streams throughout the system revealed low levels of population structure among streams emptying into freshwater. However, much stronger genetic differentiation was detected between streams emptying into freshwater and streams flowing directly into estuarine environments. This fine‐scale reproductive isolation without any physical barriers to migration is likely driven by differences in selection pressures across freshwater and estuarine environments. Estuary tributaries had fewer larger, older juveniles, suggesting an alternative life history of smolting and migration to the marine environment at a much smaller size than occurs in the other populations. Therefore, genetic data were consistent with a scenario where isolation by adaptation occurs between populations of Dolly Varden in the study system, and ecological data suggest that this isolation may partially be a result of a novel Dolly Varden life history of seawater tolerance at a smaller size than previously recognized.     

Offshore Dolly Varden charr (<Emphasis Type="Italic">Salvelinus malma</Emphasis>) in the North Pacific

Many studies have investigated the ecology of charrs in freshwater, however, little is known about charrs in the ocean. This study examined the distribution, seasonal abundance, and some biological features of Dolly Varden (Salvelinus malma) in the Pacific Ocean. An analysis of by-catch data of Japanese offshore salmon monitoring showed that Dolly Varden were distributed across a wide range in the offshore waters of the Pacific Ocean, including the Japan Sea, Bering Sea, and Okhotsk Sea. The catch per unit effort showed a sharp increase from May to August, followed by a sharp decrease in September. Offshore areas served as an important summer habitat for anadromous Dolly Varden.     

Innate predator recognition and fright response in related populations of Oncorhynchus mykiss under different predation pressure

Innate predator recognition and fright response behaviours were compared in a laboratory study between second generation offspring from two related populations of steelhead trout Oncorhynchus mykiss from Sashin Creek, Alaska. The stream population was anadromous and co-occurred with Dolly Varden Salvelinus malma , a piscivore and salmonid predator. Sashin Lake, formerly fishless, was stocked with fish from the stream population in 1926 and that population has been isolated from heterospecific piscine predation ever since. Fish from the lake population were predicted to show diminished innate fright response to Dolly Varden scent relative to the stream population. The behaviour of 60 individual juvenile O. mykiss from each population was measured and observed in aquaria before and after exposure to chemical cues of Dolly Varden, conspecific skin extract, or a control of distilled water. The alarm substances caused significant behavioural changes in both populations in the amount of time spent motionless, time spent in the lower water column and feeding frequency. No significant differences were observed between the stream and lake populations in the change in behaviour between pre- and post-stimulus observation periods for any of the measured fright responses, indicating that the sequestered lake population has not lost the ability to detect or respond to conspecific alarm substances or Dolly Varden scent.     

Physiological Adaptations in Juvenile Dolly Varden <Emphasis Type="Italic">Salvelinus malma</Emphasis> (Salmonidae) Dwelling in Polluted Rivers of Kamchatkan Volcanic Territories

Biochemical status of riverine juvenile Dolly Varden was defined under the dissolved toxicants and mineral suspension excess concentration impact. The processes of toxicants bioaccumulation, metabolism activation, dynamics of oxidative stress and detoxification were examined in a wide range of natural chronic pollution intensity. Background conditions variability and critical toxicants levels in the polluted habitats were determined. Physiological response specificity was found for juveniles of anadromous and landlocked Dolly Varden.     

Microsatellite genetic variation of Asian populations of Dolly Varden char

Genetic variation at eight microsatellite loci was examined in 21 populations of Dolly Varden charrs, Salvelinus malma, representing five geographical regions (Kamchatka Peninsula, Sea of Okhotsk coast, Sea of Japan coast, Sakhalin Island, and Kuril islands). Hierarchical analysis of molecular variance showed that 11% (58% in terms of R-statistics) of the variation was distributed among of northern subspecies of Dolly Varden, Salvelinus malma malma and southern Asian Dolly Varden, S. m. krascheninnikovi while similar values were attributed to the among-regional level within northern Dolly Varden 9% (7%) and southern Asian Dolly Varden 11% (14%). Permutation-based tests indicated a mutational component to genetic differentiation based on allelic size variance and suggested that divergence of the two subspecies had occurred at least 3,000 generations ago. On large spatial scales (within the Asian range of the species), populations clustered according to their geographical location. On smaller scales (within regions and subregions) correlation between genetic and geographic distances was not significant. Northern Dolly Varden has higher allelic diversity and more private alleles than southern subspecies, this probably indicating differences in demographic history.     

Genetic structure of the <Emphasis Type="Italic">Salvelinus</Emphasis> genus chars from reservoirs of the Kuril Islands

Genetic resemblance of chars Salvelinus alpinus krasheninnikovi (Salvelinus malma krasheninnikovi) of 35 samples collected in five Kuril Islands--Shumshu, Paramushir, Onekotan, Iturup, and Kunashir--has been studied by the PCR-RAPD method. In the limits of each island, both resident isolates and anadromous forms give strictly supported clusters distinct from samples from the other islands. The samples from five islands form three superclusters: the first from Kunashir and Iturup Islands, the second from Paramushir and Onekotan Islands, and the third from Shumshu Island. The possible reasons for genetic similarity of resident and anadromous forms of Dolly Varden chars inhabiting reservoirs of a definite island are considered (the founder effect, homing, limited migration).     

Nuclear DNA identification of migrating bull trout captured at the Puget Sound Energy diversion dam on the White River,Washington State

Bull trout (Salvelinus confluentus) is a char listed as threatened under the United States Endangered Species Act throughout its range in the coterminous United States. Substantial morphological similarities between bull trout and Dolly Varden (S. malma) make field identification difficult. This has resulted in an incomplete understanding of their distribution and abundance in Washington State where these two species occur sympatrically. We used three diagnostic nuclear loci to determine the species of char collected at a trap on the White River in southern Puget Sound (Washington State, USA). Each of the 104 samples revealed the expected bull trout genotype at all three loci. This work presents three principle results: (i) the presence of a migratory bull trout population in southern Puget Sound; (ii) no evidence of migratory Dolly Varden over 3 years; and (iii) no evidence of hybridization was detected. These results also demonstrate how molecular markers can provide information essential to the conservation and management of these species.     

On the Dolly Varden’s <Emphasis Type="Italic">Salvelinus malma</Emphasis> (Salmonidae) biology in Kamchatkan spawning rivers of the volcanic areas

Anadromous and stream resident Dolly Varden S. malma were compared in the contaminated and reference rivers across Kamchatka region. Anadromous Dolly Varden’s fry from the polluted and clean rivers were correspondently different by reduced growth rate and narrow length variability. It was observed that juveniles prefer to migrate from the polluted river sections; only seldom fry reaches the smoltification stage at the contaminated sites. The volcanogenic environmental pollution causes paedomorphosis and accelerated sexual maturation in the landlocked brook-dwelling populations. Either the growth rate or the length variability within the age groups were not reduced during the maturation period in the landlocked groups comparing with fish from reference streams. However the weakened individuals with an extremely low body weight were observed among the landlocked fish during maturing. Gonadosomatic index and relative fecundity were comparable for fish from polluted and clean rivers, though relatively high fecundity for the first group was attained by the oocytes size decreasing. Skin cover was damaged; Clark’s condition index and muscle fatness were reduced while liver size was enlarged in either landlocked or anadromous fishes from the polluted water-courses.     

Female‐biased migration of stream‐dwelling Dolly Varden in the Shiisorapuchi River, Hokkaido, Japan

The first evidence for female‐biased migration in a partially migratory stream‐dwelling salmonid the Dolly Varden Salvelinus malma , a phenomenon well known in sea‐run and lake‐run populations, is presented. Dolly Varden in the Shiisorapuchi River in central Hokkaido, Japan, used both tributaries, of which there are many, and the main stem, but spawned only in tributaries. The size structures of Dolly Varden (≥age 1 + years) in tributaries were unimodal (<100 mm fork length, L _F) during non‐spawning seasons but changed to bimodal during spawning seasons (lower mode <110 mm, upper mode >120 mm L _F). Mature individuals were observed in both modal groups. From the trapping and census data, the small group appeared to be tributary resident and the large group main stem migrant. Males were common in both resident and migrant components. Most females, however, migrated to the main stem to mature, indicating female‐biased migration.     

Diversity of life strategies of pikepech <Emphasis Type="Italic">Sander lucioperca</Emphasis> (L.) in the Lower Volga (by the data of microelement composition of otolithes)

Strontium (Sr) and calcium (Ca) contents and Sr/Ca ratios in otoliths of pikeperch Sander lucioperca have been studied by X-ray fluorescent microanalysis. A sample of 95 specimens from the Lower Volga region are studied. The fish were obtained in a section of the Akhtuba River at a distance of 250–279 km upstream from the Caspian Sea. Some specimens in the sample have low strontium content throughout the otolith. The other fish have increased both Sr content and Sr/Ca ratios in core zones of otolith or near its outer edge: the Sr/Ca ratio is over 6.00 × 10^–3, with a maximum at 10.02 × 10^–3. The fish with a low Sr/Ca ratio live in freshwater and demonstrate a resident life history strategy. Pikeperch that have increased ratios of Sr/Ca in outer zones of otolith demonstrate a migratory life history strategy. These fish leave the freshwater of the Volga and feed in brackish water of the Northern Caspian Sea. Some migratory fish migrate to the sea as underyearlings, stay in a brackish water for 1 year or less, and then return back to fresh water for the rest of its life. The other group migrates back and forth from freshwater to the sea several times during their life. Finally, some fish leave freshwater for 1–2 years, spending this time in the Northern Caspian Sea. The conclusion is that the pikeperch stock in the Lower Volga has a complicated composition and consists of freshwater (residents and rheodromic ones) and migratory (anadromous and semianadromous) fish.     

Variation of the mitochondrial DNA control region in the populations of southern form of Dolly Varden (<Emphasis Type="Italic">Salvelinus malma krascheninnikovi</Emphasis>) from Sakhalin

Analysis of a 551-bp segment of the mitochondrial DNA control region in 23 individuals from nine populations of Dolly Varden from Sakhalin and three individuals from the Shikaribetsu Lake (Hokkaido) revealed the presence of seven haplotypes of southern form, along with one haplotype of northern form of Dolly Varden. All seven haplotypes of southern Dolly Varden were earlier described in the populations from Hokkaido. Hierarchical analysis of molecular variance (AMOVA) based on the haplotype frequencies, performed using literature data, suggested that, during the glacial epoch, there were three regional population groups of Dolly Varden (from eastern and western coasts of Sakhalin, and from Southern Primorye). Population groups from Sakhalin and Primorye were clearly separated. The differences between two Sakhalin population groups in the mtDNA haplotype frequencies were not statistically significant. However, relative to the earlier obtained data on microsatellite loci, these differences were statistically significant. For the populations of Sakhalin Dolly Varden, the data on mitochondrial and microsatellite DNA variation supplement each other.     

Migratory patterns of anadromous white-spotted charr Salvelinus leucomaenis in Eastern Hokkaido, Japan: The solution to a mystery?

We evaluated the migratory patterns of white-spotted charr in eastern Hokkaido, Japan using: (1) field observation of fish, (2) salinity-recording archival tags, and (3) analysis of otolith Sr and Ca concentrations. Field observations suggest that the majority of anadromous white-spotted charr outmigrate to the sea in spring (April to June) and ascend the river between late summer and autumn (August to November). Salinity records from archival tags revealed a fluctuating pattern consisting of both low and high values within a month, indicating frequent short-term movements between freshwater (including non-natal rivers) and brackish/salt water habitats. Otolith Sr:Ca ratios exhibited a sharp rise at about 40–50% of the otolith radius, which was followed by several spikes consisting of both low and high values, indicating that fish migrated between freshwater and marine environments multiple times during their life history. However, the peaks in Sr:Ca ratios were generally associated with annulus zones on the otolith, indicating that the anadromous migration was generally an annual event.     

Variability of microsatellite DNA and genetic differentiation of populations in the resident form of Dolly Varden Salvelinus malma krascheninnikovi from Sakhalin

Variability in 11 microsatellite loci is followed for nine populations of the resident southern form of Dolly Varden Salvelinus malma krascheninnikovi from Sakhalin. In all studied populations, the level of genetic differentiation is significant with global values of F _st and R _st 0.182 and 0.329, respectively. On the NJ tree, two clusters are separated significantly: the former is represented by the populations from southwestern Sakhalin (the Novoselka River basin), and the latter includes all populations from southern and eastern Sakhalin. Abrupt size variations (bottleneck events) are suggested for several studied populations, and 50% reductions of allelic richness and average heterozygosity are observed in two lacustrine populations of the Novoselka River basin in comparison to the riverine populations of this basin. The results suggest an occurrence of a comparatively recent gene flow between the populations of resident Dolly Varden from Sakhalin and absence of reproductive isolation between the anadromous and resident forms. The degradation of the majority of Dolly Varden populations can be expected in the near future, and conservation projects should be developed.