Salvelinus Leucomaenis Research Articles

Interaction between hatchery and wild juvenile white‐spotted charr Salvelinus leucomaenis in a stream enclosure experiment

The competitive interactions between hatchery and wild juvenile white‐spotted charr Salvelinus leucomaenis were examined in enclosure experiments in a natural stream. A total of 24 enclosures (1·0 × 1·0 × 0·7 m height) were arranged in stream in an array for randomized block design with replicates of three treatments (wild fish only, hatchery fish only, wild plus hatchery fish). Three experiments were conducted in 2006, using different densities and sizes for each experimental trial. When densities in enclosures were controlled to be equal among treatments (4 individuals m−2: substitutive design), wild fish in the presence of hatchery fish had significantly higher growth rates than the wild fish alone treatment. When densities in enclosures were controlled to be 4 individuals m−2 hatchery fish only treatment, 4 individuals m−2 wild fish only treatment and 8 individuals m−2 in the hatchery plus wild fish treatment (additive design), wild fish in the presence of hatchery fish had significantly lower growth rate than the wild fish alone treatment. Hatchery fish in the presence of wild fish also grew significantly slower than the hatchery fish alone treatment. When densities in enclosures were controlled to be equal among treatments (4 individuals m−2) but hatchery fish were 1·1 times longer than wild fish, growth of wild fish in the presence of the larger hatchery fish did not differ significantly from growth of the wild fish alone treatment. These results suggested that relative size of hatchery fish in relation to wild fish and increased fish density are two important factors influencing the growth of wild juvenile S. leucomaenis.

A simple technique for remote identification of individual spawning fishes

A robust method to identify individual spawning Japanese charr Salvelinus leucomaenis japonicus using visible implant elastomer (VIE) and commercial binoculars was developed. Successful individual identification was c. 80% for 1693 observation trials, and successful pair recognition was c. 70% for 337 pairs of spawning fish.

Synchronous Female Spawning and Male Mating Behavior in a Land-Locked Population of Japanese Charr, Salvelinus leucomaenis japonicus

In resource-based promiscuous mating systems, synchronous spawning of females affects competition among males and variation in the reproductive success of males. We documented the mating behavior of Japanese charr (Salvelinus leucomaenis japonicus) through an annual breeding season to examine the relationship between female spawning synchrony and male mating behavior. Females spawned highly synchronously in the population studied, i.e., approximately half the spawning was finished within the first three days of the entire spawning season (11 days). The daily operational sex ratio (OSR) was nearly 1:1 through the spawning period. The number of males around a spawning female was very small (1.21+/-0.49 males per female) over the spawning ground and period, suggesting that a competitive male could effectively chase subordinate males away from a spawning female. A few males attempted to sneak near the oviposition site of females (16%; 9 of 57 breeding groups), while some males adopted sneaking tactics in the initial phase of females' spawning (24%). We did not observe any males to succeed in sneak fertilizations. We conclude that in this Japanese charr population, the synchronous spawning of females was related to the unbiased daily OSR, male aggregation around females, and consequently whether and how efficiently males engaged in sneak mating behavior.

Relationships among tributary length, census population size, and genetic variability of white-spotted charr, Salvelinus leucomaenis, in the Lake Biwa water system

The relationships between census population size and tributary length and between haplotype diversity of the mitochondrial DNA and census population size in ten white-spotted charr populations in the Lake Biwa water system and its adjacent basins were investigated. The census population size (number of fish with ≥100 mm in standard length) significantly increased with the tributary length. In the eastern part of the Lake Biwa water system, haplotype diversity increased with the census population size. On other hand, in the western part of the water system and adjacent basins, haplotype diversity was zero irrespective of the census population size. These results suggest that white-spotted charr populations in the eastern and western part of the Lake Biwa water system have undergone different levels of bottlenecks related to the habitat size in the postglacial warming.

Phylogenetic relationships of Sakhalin taimen Parahucho perryi inferred from PCR-RFLP analysis of mitochondrial DNA

RFLP analysis of three amplified mtDNA fragments (Cytb/D-loop, ND1/ND2, and ND3/ND4L/ND4) was performed in the following taxa: Parahucho perryi, Hucho taimen, Brachymystax lenok, B. tumensis, Salmo salar, Salvelinus leucomaenis, and S. levanidovi. For mtDNA of P. perryi, a substantial decrease in the haplotype and nucleotide diversity was observed as a result of random genetic drift, caused by a reduction in the effective population size. Nucleotide divergence estimates between the mtDNA haplotypes were determined. Sakhalin taimen P. perryi was found to be approximately equally diverged from S. salar and from the charrs of the genus Salvelinus, by 11.0 and 10.0%, respectively. The divergence between P. perryi and H. taimen constituted 14.6%, between P. perryi and lenoks of the genus Brachymystax, 14.2%, and between H. taimen and Brachymystax, 7.7%. The analysis of possible phylogenetic relationships of the mtDNA from P. perryi among the group of taxa examined confirmed validity of the genus Parahucho. Phylogenetic reconstructions performed showed that robustness of the trees constructed for the complex of phylogenetically informative characters over three mtDNA fragments was considerably higher than that of the trees constructed for individual genes.

Potential of habitat complexity for mitigating interference competition between native and non-native salmonid species

This study aimed to confirm the mitigation effect of structurally complex habitat on interspecific interference competition between native and non-native salmonid species. We evaluated the effects of habitat complexity (number and size of aggregates of large woody debris and length of undercut banks) and other habitat components that were related to the local abundance of salmonids (dimension and mean depth of pool, mean particle size, and mean current velocity) on the local abundance of native white-spotted char ( Salvelinus leucomaenis (Pallas, 1814)) in allopatry and sympatry with non-native brown trout ( Salmo trutta L., 1758). The field survey was conducted in a Japanese montane stream. The number of char in pool habitats in the allopatric area correlated positively with habitat size, i.e., pool dimension. The number of char in the sympatric area with trout was positively correlated with habitat complexity, while it was negatively correlated with number of trout. In this study, we found that structurally complex habitats might be effective in mitigating interspecific competition between native white-spotted char and non-native brown trout in a montane stream.

Effects of instream structures on Kirikuchi charr, southernmost population of genus Salvelinus, in a small mountain stream of Japan

The changes in physical habitats and responses of fish, e.g. the Kirikuchi charr Salvelinus leucomaenis japonicus, were examined by placing instream structures in a stream on the upper drainage of the Totsu River system of the Kii Peninsula, Japan, over a two-year period. Instream structures created pools below the structures, and these pools have maintained their functions as fish habitats over two years. In two treatment sections, sections A and B (some red-spotted masu salmon were removed in advance in section B), mean water depth increased soon after placing the structures, but decreased over two years. Mean water velocity slowed after placing the structures in both sections. Total fish abundance has been relatively high at the two treatment sections compared with a control section after placing the structures. Age 1 Kirikuchi charr, however, increased only in section B. These results indicate that instream structures can serve as habitat enhancement for fish, including Kirikuchi charr, in the study area if other appropriate habitat factors for respective species are taken into consideration.

Loss of genetic variation and effective population size of Kirikuchi charr: implications for the management of small, isolated salmonid populations

AbstractSmall, isolated populations may face extinction due to a combination of inbreeding depression and other threats. Effective population size (Ne) is one comprehensive measure that allows us to evaluate the genetic status of a population, and to make management decisions regarding genetic viability. We simulated loss of genetic variation and estimated Ne for two small, isolated populations of Kirikuchi charr Salvelinus leucomaenis japonicus, the endangered, southernmost local populations of the genus Salvelinus in the world, using VORTEX, an individual‐based stochastic PVA model. Approximately half of the genetic variation was lost over 200 years regardless of census population size and demographic parameters, and Ne estimates were roughly 50 in each of the two populations, suggesting the possibility of inbreeding depression. The target population size of Ne>500, by securing long‐term viability, is several times that of the present size of each of the populations studied, and no local habitats maintaining such a target number are considered to exist. The results strongly indicate a need for recovering natural connections and potential gene flow among local populations. However, the impending threat to these populations from non‐native charr widely distributed throughout the drainage has prevented the recovery of the connections. Given the small Ne of the two populations, it would be necessary to retain gene flow artificially within or across local populations. This will be true of many other salmonid populations that have been isolated or fragmented recently.

Parasite-mediated allochthonous input: Do hairworms enhance subsidized predation of stream salmonids on crickets?

Energy and nutrients flow in diverse pathways across heterogeneous landscapes and tightly link the discrete food webs in local habitats. However, parasitism that enhances allochthonous resource input has not been previously documented. In a well-known example of parasite manipulation of host behaviour, crickets infected by mature hairworms (Nematomorpha) seek and jump into water when the worms reach the free-living stage. We found that a large number of trout (22%–61%), an aquatic predator, preyed on camel crickets (genera Diestrammena Brunner von Wattenwyl, 1888 and Tachycines Adelung, 1902) in September in five Japanese mountain streams where this host–parasite system exists. Trout (Kirikuchi charr, Salvelinus leucomaenis japonicus (Oshima, 1961); red-spotted masu salmon, Oncorhynchus masou ishikawae Jordan and McGregor, 1925) that preyed on crickets frequently ingested hairworms, whereas trout that did not prey on crickets did not ingest hairworms. Our results strongly suggest that hairworms enhance stream salmonid predation on camel crickets. This is the first documentation of parasitism enhancing allochthonous resource input in nature. Trout ingested a greater mass of crickets than other prey species in September, and this energy influx may play an important role in food-web dynamics in headwater streams.

Genetic diversity and population structure of white-spotted charr, Salvelinus leucomaenis, in the Lake Biwa water system inferred from AFLP analysis

The genetic variations—and the time dependence of such variations—of natural populations of the white-spotted charr ,Salvelinus leucomaenis, in the Lake Biwa water system as well as those of a hatchery-reared population were inferred from AFLP. Upon the application of principal coordinate analysis using 118 polymorphic AFLP fragments based on the Jaccard similarity index, specimens of each of six natural local populations from the inlet rivers of Lake Biwa grouped roughly together, suggesting that each local population was genetically differentiated. The hatchery-reared population was shown to be closely related to the local population in the Seri River, suggesting that the Seri River population originated from hatchery-reared charr due to extensive stocking. Furthermore, specimens of the Yasu River grouped in a somewhat different position from the other natural populations, agreeing well with its geographic distance from the other populations. The nucleotide diversities of six natural populations (Harihata River, Ishida River, two reaches of the Takatoki River, Ane River, and Yasu River) in 2002 or 2003 were relatively low (π = 0.067–0.146%) compared with that of the Seri River (0.278%) and the hatchery-reared charr (0.316%). The nucleotide diversity in the five local populations (Ishida River, two reaches of the Takatoki River, Ane River, and Yasu River) remained at a low level from 1994 to 2002/2003, but only the nucleotide diversity in the Harihata River actually decreased. From 1994 to 2002/2003, the nucleotide diversity in the Seri River remained at a higher level among the natural populations from 1994 to 2002/2003; it was enhanced by the artificial release of hatchery-reared charr before 1994. In order to conserve the genetic diversity of the white-spotted charr in the Lake Biwa water system, it is necessary to prevent the stocking of hatchery-reared charr in reaches where hatchery-reared charr have not previously been stocked.

Mitochondrial DNA Population Structure of the White-Spotted Charr (Salvelinus leucomaenis) in the Lake Biwa Water System

A phylogeographic analysis of mitochondrial DNA sequences was performed in order to elucidate the origin, dispersal process, and genetic structure of white-spotted charr in the Lake Biwa water system. Two haplotypes were most common in the Lake Biwa water system, and were also common in the adjacent inlet rivers of the Sea of Japan. These results suggest that in the glacial periods of the Pleistocene, white-spotted charr dispersed into the northern inlet rivers of Lake Biwa from adjacent inlet rivers of the Sea of Japan by watershed exchanges, colonizing the whole of the Lake Biwa water system. Mitochondrial DNA diversity contrasted sharply between the western and eastern parts of the system, suggesting that the populations in the western part might be more reduced than those in the eastern part in relation to the smaller habitat size. The high overall FST estimate (0.50), together with pairwise comparisons of FST, indicated significant genetic divergence between populations due to isolation and small population size. Hierarchical analysis (AMOVA) also showed that genetic variation was more pronounced among regions (28.39%) and among populations within regions (47.24%) than within populations (24.37%). This suggests that each population in and around the Lake Biwa water system should be treated as a significant unit for conservation and management.

Relationships between Catch per Unit Effort, Catchability, and Abundance Based on Actual Measurements of Salmonids in a Mountain Stream

AbstractThe relationships between catch per unit effort (CPUE), catchability, and abundance were examined in a mountain stream (Ara Stream, Japan) using actual measurement data from two sympatric salmonids, the white‐spotted char Salvelinus leucomaenis and red‐spotted masu salmon Oncorhynchus masou ishikawae. We counted the number of individuals of each species by underwater observations after effort‐regulated baitfishing in 92 pools that were considered to be short‐term closed systems. Catch per unit effort increased with increasing abundance for both species, but the relationships were different. For white‐spotted char, a linear relationship (i.e., proportional increase) was a better fit than a power curve relationship, whereas for red‐spotted masu salmon a power curve relationship was a better fit. The shape parameter (β) was estimated to be less than 1.0 for red‐spotted masu salmon, suggesting that CPUE declines more slowly than abundance (i.e., hyperstability). The relationship between catchability and abundance also differed between the species. For white‐spotted char, catchability was constant and independent of abundance, whereas red‐spotted masu salmon catchability increased with decreasing abundance. This corresponds to the relationship between CPUE and abundance for each species. We conclude that the CPUE‐abundance relationship differs between species, even when the same fishing method is used in the same habitat. The relationship may be fundamentally species specific, determined by the vulnerability of each species to fishing gear and fishing methods.

Intergeneric Hybridization between Sympatric Kirikuchi Char and Red‐Spotted Masu Salmon in a Small Japanese Mountain Stream

AbstractHybridization occurs widely across salmonid species. Intergeneric hybridization of salmonid species in nature, however, has been rarely reported. Using microsatellite and mitochondrial DNA (mtDNA) markers, we obtained evidence of intergeneric hybridization between threatened, naturally sympatric Kirikuchi char Salvelinus leucomaenis japonicus and red‐spotted masu salmon Oncorhynchus masou ishikawae in an upper drainage of the Totsu River system, which is located on Kii Peninsula, central Honshu, Japan. Fifteen suspected hybrid juveniles were captured in August 2005 in a tributary within a surveyed drainage, where an intergeneric pair consisting of a female Kirikuchi char and a male red‐spotted masu salmon was observed during the preceding spawning season. The suspected hybrids all appeared to be F1 on the basis of microsatellite genotypes at five loci, which is consistent with the previously reported infertility of such hybrids. The maternal parent species was presumed to be the Kirikuchi char, since all hybrids had this species' mtDNA haplotype. The estimated number of hybrids was equivalent to that of age‐0 Kirikuchi char, suggesting that at least half of the annual reproduction of Kirikuchi char in the tributary was disturbed by the present hybridization. Six of nine hybrid recaptures were collected from the same tributary in 2006, indicating that hybrids could survive and stay in their nursery tributary at least until age 1. This study suggests that intergeneric hybridization negatively affects long‐term persistence of both parental species, especially Kirikuchi char, through reproductive disturbances and competition for resources.

ミトコンドリア DNA 分析に基づく関東地方産イワナの遺伝的集団構造

ミトコンドリア DNA 分析に基づく関東地方産イワナの遺伝的集団構造

Differences in allele frequency at ME-1 locus among four subspecies of Japanese white-spotted char Salvelinus leucomaenis

Differences in allele frequency at ME-1 locus among four subspecies of Japanese white-spotted char Salvelinus leucomaenis

Genetic identification of native populations of fluvial white-spotted charr Salvelinus leucomaenis in the upper Tone River drainage

Stocking of exogenous, hatchery-reared white-spotted charr Salvelinus leucomaenis has been conducted throughout much of their range in Honshu Island, Japan, to increase angling opportunities. Although the native char populations are thought to have declined because of hybridization with introduce fish, their distribution and genetic status have been uncertain. Fine population structures of charr in the upper Tone River drainage were examined using mitochondrial DNA and microsatellite analyses so as to clarify the presence of native populations. One common mtDNA haplotype was detected in all populations in the Ohashi River and Watarase River, and four and one tributary populations were monomorphic for such haplotypes, respectively. However, several haplotypes, considered to have originated from stocked hatchery fish, were observed in the stocked and the remaining populations. Judging from the genetic integrity over a fine geographic scale, the former were considered as indicative of native populations and the latter as admixtures with hatchery fish. Comparisons of genetic diversity, deviations from the Hardy-Weinberg equilibrium, principal component analysis, and relatedness estimations based on microsatellite DNA can also provide evidence for distinguishing native populations from those influenced by hatchery fish.

Systematics and biology of the East Siberian char Salvelinus leucomaenis

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.

Dramatic decline in population abundance of Salvelinus leucomaenis after a severe flood and debris flow in a high gradient stream

A dramatic change in population abundance of Salvelinus leucomaenis following a catastrophic flood event was investigated. Population density declined by c. 98% after the flood in a river section affected by debris flow. The isolation of the affected population and habitat change caused by flooding may have impeded population recovery.

Effect of Habitat Components on Competitive Interaction between Native White-Spotted Charr and Introduced Brown Trout

ABSTRACT In salmonid species, interspecific competition has been affirmed as the major mechanism of the replacement of native species by introduced species. However, competitive interactions are variable according to various habitat components. Our study on native white-spotted charr and introduced brown trout in a small creek in southwestern Hokkaido, Japan indicates that the intensity of the interspecific competition was reduced in structurally complex habitats, areas with numerous woody debris, because the native species were able to survive in those environments. Therefore, the replacement may be inhibited in structurally complex habitat.

Threatened fishes of the world: Kirikuchi charr, Salvelinus leucomaenis japonicus (Oshima 1961) (Salmonidae)

Common name: Kirikuchi (Japanese). Conservation status: Kirikuchi char (Salvelinus leucomaenis japonicus) is the southernmost population of the genus Salvelinus. Isolated from the main rivers in the drainages (Endangered, IUCN 1996; Threatened local populations, Tanaka 2003 Red Data Book of Japan 2003). Parts of the natural habitat have been designated as the natural protected area of Nara Prefecture. Identification: Kirikuchi char constitute geographically and genetically distinct local populations of Yamato char S. leucomaenis japonicus, a subspecies of the typical Japanese char S. leucomaenis leucomaenis, which belongs to a different clade of the Yamato char in a maximum parsimony tree of haplotypes (Yamamoto et al. 2004). Kirikuchi char differ morphologically from other Japanese chars: they have reddish golden bodies, few white spots on the lateral sides, darkish squash spots around the lateral lines, and relatively short snouts (Hosoya 2000). Photograph by Yuichi Kano. Distribution: Originally, Kirikuchi char were common in the Totsu and the Hidaka River systems in the Kii Peninsula, western Japan. However, only six small populations remain in the two upper drainages of the Totsu River system (34 5¢N, 135 33¢E; 34 13¢N, 135 53¢E), isolated from the main rivers in the drainages (Tanaka 2003, Sato & Watanabe 2004). Abundance: Its largest population comprises approximately 600 fish (100 mm and over in SL); the smallest, which might become extinct in the near future, comprises a few dozen individuals. Estimated effective population sizes of the largest two populations are not more than 100 individuals (Sato unpublished data). Habitat and ecology: Adapted to cold-water high mountain streams in which maximum temperatures are less than 18 C. Only the stream resident form has been observed. Specimens rarely reach 300 mm SL, and the average body size is approximately 160 –180 mm SL. Kirikuchi char preferably inhabit pools with refuges, woody debris and/or rocks, and feed mainly on aquatic and terrestrial insects. Reproduction: They spawn during October–November. Threats: Kirikuchi char face a high risk of extinction primarily from: (1) habitat deterioration by riparian forest logging or habitat fragmentation; (2) hybridization and competition with introduced non-native Nikko char S. leucomaenis pluvius, which has been commonly cultured and stocked in Japan; and (3) overharvesting, including poaching, by fishermen (Sato & Watanabe 2004). Moreover, because of their small isolated population structures, inbreeding depression might affect their viability. Conservation actions: Effective management measures have not been implemented, but a few volunteers are carrying out surveillance for prevention of poaching. Conservation education programs have also been launched for children of local communities. Conservation recommendations: Practical preservation techniques are urgently required for remaining populations. Habitat restoration, removal of non-native char, and re-establishment of new populations would be effective. Furthermore, rehabilitation of riparian forest is essential for conserving self-sustaining populations in the future. Remarks: Kirikuchi char is of biogeographical, evolutionary, and ecological interest.