Salvelinus Leucomaenis Research Articles

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.

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.

Susceptibility of various Japanese freshwater fish species to an isolate of viral haemorrhagic septicaemia virus (VHSV) genotype IVb

Genotype IVb of viral haemorrhagic septicaemia virus (VHSV) was isolated for the first time in the Great Lakes basin in 2003, where it spread and caused mass mortalities in several wild fish species throughout the basin. In order to prevent further spreading of the disease and to assess risks of new genotypes invading new watersheds, basic microbiological information such as pathogenicity studies are essential. In this study, experimental infections were conducted on 7 indigenous freshwater fish species from Japan by immersion with a VHSV genotype IVb isolate. In Expt 1, cumulative mortalities in bluegill Lepomis macrochirus used as positive controls, Japanese fluvial sculpin Cottus pollux, and iwana Salvelinus leucomaenis pluvius were 50, 80 and 0%, respectively. In Expt 2, cumulative mortalities of 100, 100 and 10% were observed in Japanese fluvial sculpin C. pollux, Japanese rice fish Oryzias latipes and yoshinobori Rhinogobius sp., respectively. No mortality was observed in honmoroko Gnathopogon caerulescens, akaza Liobagrus reini or Japanese striped loach Cobitis biwae. VHSV was detected by RT-PCR from samples of kidney, spleen, and brain from all dead fish, and virus re-isolation by cell culture was successful from all dead fish. We detected the virus in the brain from a few surviving bluegill 50 d post exposure by both cell culture and RT-PCR. These results revealed that VHSV IVb could become a serious threat to wild freshwater fish species in Japan, and that some surviving fish might become healthy carriers of the virus.

Effects of Flow Reduction on a Whitespotted Char Population in a Japanese Mountain Stream

AbstractI evaluated the effects of long‐term (about 270 d/year) and large‐volume (83.3% at mean flow) reductions in stream flow on a population of Whitespotted Char Salvelinus leucomaenis. I compared a range of biological parameters (density, biomass, condition factor, and age composition) between populations of char in the free‐flowing (above dam) and regulated (below dam) sections of a Japanese mountain stream over a 4‐year period. The density and biomass of age‐1 and older fish was significantly lower in the regulated section than in the free‐flowing section: 32.8% reduction in density and 42.5% in biomass. The mean condition factor of age‐1 and older fish was significantly lower in the regulated section. In addition, the percentage of age‐2 and older fish in the total catch was significantly lower in the regulated section. Except for flow, the physical environment was similar in both the free‐flowing and regulated sections. Thus, the changes I observed in the regulated section were likely caused by flow reduction. I hypothesize that a decrease in food availability associated with the reduction in flow caused the decrease in density and condition factor in the regulated section. I also speculate that an increase in density in the pools due to flow reduction resulted in increased aggression among conspecifics. In turn, this results in an increase in the emigration of individuals, particularly older and larger fish, in the regulated section. The decreases in the density, condition factor, and the number of older and larger fish following the reduction in flow probably explain the decrease in biomass in the regulated section.Received November 20, 2012; accepted July 15, 2013

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.

Cloning, molecular characterization, and expression analysis of the signal transducer and activator of transcription 3 (STAT3) gene from grass carp (Ctenopharyngodon idellus)

Signal transducer and activator of transcription 3 (STAT3) binds to Janus kinase 2 (JAK2) to initiate the JAK2/STAT3 signal transduction pathway, which plays an important role in cancer cell proliferation, immune regulation, reproduction, lipid metabolism, and other physiological processes of the organism. In this study, the cDNA sequence of the STAT3 gene from grass carp was cloned using RACE (rapid-amplification of cDNA ends). Twelve characteristics of the STAT3 gene and its encoded protein sequence were predicted and analyzed using bioinformatics methods; these features included the general physical and chemical properties, the hydrophobicity, the secondary structure and the three-dimensional structure of the protein. Quantitative real-time PCR was employed to detect grass carp STAT3 expression pattern in different tissues. The results showed that the full-length STAT3 gene from grass carp is 2739-bp long and contains a 216-bp 5′UTR, a 300-bp 3′UTR, and a 2223-bp open reading frame (ORF) that encodes a 740-amino acid peptide. The deduced protein exhibited 99%∼94% homology to the STAT3 protein of zebrafish (Danio rerio), medaka (Oryzias latipes), turbot (Scophthalmus maximus), white-spotted char (Salvelinus leucomaenis), mandarin fish (Siniperca chuatsi), rainbow trout (Oncorhynchus mykiss), and green pufferfish (Tetraodon fluviatilis). The deduced grass carp STAT3 protein contains a protein interaction domain, an alpha domain, a DNA binding domain, and an SH2 domain. The STAT3 protein of grass carp is a hydrophilic and non-secretory protein, and its molecular mass and isoeletronic point were found to be 98,5412.1 Da and 6.39, respectively. The structural elements of STAT3 included α-helixes, β-sheets, and loops. The grass carp STAT3 is expressed in all of the six tissues tested, which were the liver, spleen, gill, muscle, heart, and brain. The highest expression level was found in the liver (P < 0.05), whereas a significantly lower expression level was found in the spleen, gills, brain, and muscle (P < 0.05), and the lowest expression level was found in the heart (P < 0.05). This study provides a basis for further structural and functional exploration of the STAT3 from grass carp, including its deduced protein and its signal transduction function.

Microsatellite variation in white-spotted char Salvelinus leucomaenis from Sakhalin oblast

A panel of 12 polymorphic microsatellite markers was developed for the population genetic studies of white-spotted char Salvelinus leucomaenis. The four population samples examined consisted of 48 individuals each, and were collected in different geographical regions, including Sakhalin Island, Kunashir Island, and Iturup Island (two samples). The total number of different-sized alleles at different loci varied in the range of 2-31. In the population of white-spotted char subjected to strong anthropogenic pressure allelic diversity and expected heterozygosity indices were found to be lower than in wild populations of this species. The considerable genetic subdivision of different insular populations of white-spotted char observed was consistent with isolation by the distance model.

Strategies for the conservation and management of isolated salmonid populations: lessons from Japanese streams

Summary1. Endangered native populations of stream salmonids in Japan face three major threats: (i) negative interactions with introduced hatchery‐reared fish, (ii) fragmentation of habitat by impassable dams and (iii) recreational angling.2. To prevent imminent extinction of many local populations, we evaluated these threats and possible conservation actions for red‐spotted masu salmon (Oncorhynchus masou ishikawae) and white‐spotted charr (Salvelinus leucomaenis japonicus) in the Fuji River system in central Japan.3. Red‐spotted masu salmon and white‐spotted charr occupied only 0.73 and 2.4% of suitable thermal habitats, respectively, with masu salmon typically occupying habitats closer to human population centres.4. Population viability analysis resulted in a 100‐year probability of extinction of 78.1% for masu salmon and 48.1% for charr. However, extinction risk of both species was predicted to be &lt;5% if the carrying capacity increased from 141 to 303 for masu salmon and from 94 to 125 for charr, by allowing fish passage at the lower end of the habitat, and if annual adult survival rate increased by 0.04. Adult survival rate was the principal factor associated with population persistence.5. To conserve isolated populations of stream‐dwelling salmonids, we recommend (i) assessing the distribution of remnant native and non‐native fish populations, (ii) that fishing regulations are modified to improve adult survival and population persistence and (iii) that fragmented reaches be reconnected to adjacent habitat, for example by removing or modifying artificial barriers to increase the carrying capacity of the isolated populations. Reconnection of fragmented reaches should, however, be avoided if it results in non‐native fish invading isolated populations.

Bioaccumulation of organochlorines in relation to the life history in the white-spotted charr Salvelinus leucomaenis

The bioaccumulation of organochlorines (OCs) in the muscle tissue of sea-run (anadromous) and freshwater-resident (fluvial) white-spotted charr (Salvelinus leucomaenis) was determined to assess the ecological risk related to intraspecies variations in diadromous fish life history as they migrate between sea and freshwater. Generally, there were significant correlations between the accumulation of OCs such as DDTs, HCB, HCHs and CHLs. In addition, various biological characteristics, such as total length (TL), body weight (BW) and age, and number of downstream migration (NDM) were correlated. A positive correlation occurred between the lipid content and the OC concentrations. Close linear relationships were found between TL, BW and NDM and the lipid content. Although they are both the same species, the OCs concentrations in the anadromous fish were significantly higher than those in the fluvial individuals. These results suggest that anadromous S. leucomaenis have a higher ecological risk for OCs exposure than the fluvial fish.

Relationships between Physical Characteristics of Pools and the Residency of Stream-dwelling White-spotted Charr

Relationships between Physical Characteristics of Pools and the Residency of Stream-dwelling White-spotted Charr

Using rainbow trout Oncorhynchus mykiss as self-feeding actuators for white-spotted charr Salvelinus leucomaenis: Implications for production and welfare

Self-feeding systems, where fish actuate a trigger to obtain food, can be a useful feed management tool for aquaculture. However, some species such as the white-spotted charr Salvelinus leucomaenis can be poor self-feeders. The current experiment evaluated the production and welfare effects of growing a single competent self-feeding ‘demonstrator’ species, rainbow trout Oncorhynchus mykiss, in tandem with groups of inexperienced, ‘observer’ white-spotted charr. During Part I (PI, 50 days), all demonstrator groups (n=4) utilised the self-feeders from day one, whilst no naïve charr successfully actuated the self-feeders. This enhanced utilisation had a significant and positive effect upon the growth and condition of observer charr. When demonstrator trout were removed during Part II (PII, 26 days), only one group of observer and one group of naïve charr started actuating the trigger, on the 1st and 21st day of PII, respectively. This resulted in poor growth performance in both observers and naïve charr, and there were no significant differences between treatments. However, observer fish still retained a significantly better condition factor than naïve fish at the end of PII. There were no significant differences in the levels of fin erosion, opercular erosion and mortality between observer and naïve charr throughout the experiment.This study confirms the previous assumption that white-spotted charr are poor self-feeders, but their production performance and welfare can be improved by growing charr in tandem with experienced and proficient self-feeding rainbow trout.

Residential form of white-spotted char Salvelinus leucomaenis inhabiting the warm stream discharging into Semlyachikskii Firth (Kronotskii natural reserve, Kamchatka)

Residential form of white-spotted char Salvelinus leucomaenis appears in volcanic stream characterized by stable water and temperature regime. The maximal body length of fish is 285 mm and body mass is 245 g; the oldest specimen is 7 years old. The somatic growth does not relax, and the annual growth rate is 30–40 mm. The maturation begins at the age of 4 years after the fish reaches 175 mm length and 60 g in weight. The spawning takes place in autumn. Sex dimorphism and nuptial coloration are not observed, and the “spotted” coloration remains through the year. Vomer is toothless, or only one tooth is presented (in 15% of sampled specimens). Sagittal otoliths are characterized by deformation granular texture of ventral area, the layering is broken. The food spectra of a mature specimen comprises gammarids, large-size larvae, and imagoes of amphibiotic insects during the summer period.

Curative and Preventive Measures for Edema in Juvenile Japanese Char Salvelinus leucomaenis

Curative and Preventive Measures for Edema in Juvenile Japanese Char Salvelinus leucomaenis

Virulence of Yersinia ruckeri for Four Indigenous Fish Species in Japan

Enteric redmouth disease (ERM), which is caused by Yersinia ruckeri, has not been reported in Japan. In the present study, virulence of the bacterium were assessed by experimental chal­ lenges with the rainbow trout Oncorhynchus mykiss and 4 indigenous fish species in Japan: yamame (masu salmon parr) O. masou masou, amago O. masou macrostomus, whitespotted char Salvelinus leucomaenis and ayu Plecoglossus altivelis. When intraperitoneally (ip) injected with the bacterium at a dose of 7.1 x 10 2 CFU/g fish body weight (BW), rainbow trout, char, yamame, and amago showed the cumulative mortalities of 100%, 60%, 30% and 30%, respectively. The cumulative mortalities of ip­ injected ayu with doses of 1.5 x 10 6 , 1.5 X 10 5 , 1.5 X 10 4 and 1.5 x 10 3 CFU/g BW were 87%, 47%, 13% and 0%, respectively. In addition, the cumulative mortalities of ayu immersed in water containing 1.7 x 10 8 and 1.7 x 10 7 CFU/mL of the bacterium were 60% and 6.7%, respectively. Typical clinical signs of ERM, such as reddening of the wall of the oral cavity, tongue, upper jaw, lower jaw, operculum, bases of fins, or skin around the anus, were observed in all dead salmonids but not in ayu. Instead, exophthal­ mos, hemorrhage in the eyes, ascites or hypertrophy of the kidney were often observed in dead ayu. These results indicate that Yersinia ruckeri is a potentially dangerous bacterium to freshwater aquacul­ ture in Japan.

Size at maturity of fluvial white-spotted charr, Salvelinus leucomaenis, 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 the Eggs, Alevins, and Fry Identified as the Anadromous Char Salvelinus leucomaenis

On the Eggs, Alevins, and Fry Identified as the Anadromous Char Salvelinus leucomaenis

Salvelinus leucomaenis with Atypical Color Patterns, Collected in the Mogami and Nikko River Systems, Yamagata Prefectur

Salvelinus leucomaenis with Atypical Color Patterns, Collected in the Mogami and Nikko River Systems, Yamagata Prefectur

Seasonal changes in stream salmonid population densities in two tributaries of a boreal river in northern Japan

We examined seasonal changes in population densities of stream salmonids (masu salmon Oncorhynchus masou, white-spotted charr Salvelinus leucomaenis, and rainbow trout O. mykiss) in two tributaries of the Shoro River, eastern Hokkaido, Japan. In one small tributary, water temperature was relatively high during the winter, and populations of salmon and trout increased through immigration at this time of the year, becoming dominant components of the salmonid assemblage; the density of charr in this stream decreased during the winter, but charr was dominant during the summer. In another medium-sized tributary, the water temperature fell to close to 0°C during the winter, and densities of salmon and charr decreased in this season, through emigration; trout were very rare in this stream. Seasonal patterns of stream salmonid densities vary among species and between localities, resulting in seasonal changes in species composition. For a comprehensive understanding of population processes, a whole-river survey across seasons will be necessary.

Nematomorph parasites drive energy flow through a riparian ecosystem

Parasites are ubiquitous in natural systems and ecosystem-level effects should be proportional to the amount of biomass or energy flow altered by the parasites. Here we quantified the extent to which a manipulative parasite altered the flow of energy through a forest-stream ecosystem. In a Japanese headwater stream, camel crickets and grasshoppers (Orthoptera) were 20 times more likely to enter a stream if infected by a nematomorph parasite (Gordionus spp.), corroborating evidence that nematomorphs manipulate their hosts to seek water where the parasites emerge as free-living adults. Endangered Japanese trout (Salvelinus leucomaenis japonicus) readily ate these infected orthopterans, which due to their abundance, accounted for 60% of the annual energy intake of the trout population. Trout grew fastest in the fall, when nematomorphs were driving energy-rich orthopterans into the stream. When infected orthopterans were available, trout did not eat benthic invertebrates in proportion to their abundance, leading to the potential for cascading, indirect effects through the forest-stream ecosystem. These results provide the first quantitative evidence that a manipulative parasite can dramatically alter the flow of energy through and across ecosystems.

ミトコンドリア DNA 分析による信越地方産イワナの遺伝的集団構造

信越地方の大川，三面川，信濃川，関川の日本海に流入する 4 水系 8 つの在来イワナ集団を対象にミトコンドリア DNA シトクロム b 領域 557 bp の塩基配列分析を行い，遺伝的特徴を把握した。107 個体を分析した結果，9 種類のハプロタイプが観察された。三面川水系では，これまで報告がなかった 2 つのハプロタイプが検出され，これらは琵琶湖周辺域で認められるハプロタイプと遺伝的に極めて近縁であった。また，信濃川水系では，同一水系内であってもハプロタイプ組成が大きく異なる集団が存在することが明らかになった。