We conducted a thorough investigation of the natural range of the species through contacts with experts familiar with Sakhalin taimen distribution. We would particularly like to identify the following individuals for providing input into this process: Dr. Sergei Zolotukhin (TINRO), Dr. Anatoly Semenchenko (TINRO), Mr. Sergei Makeev (Sakhalin Wild Nature Fund), Dr. S. N. Safranov (Sakhalin State University), and Dr. Michio Fukushima (JMOE).
We relied on the stream network developed in ArcGIS based on the Digital Chart of the World, based on a resolution of 1:1,000,000 (ESRI 1992). We generated a convex polygon that contained all the rivers known to support the species currently. The estimate of area delineated by this polygon is 332,153 km, excluding marine waters greater than 1 km offshore. We estimated the area of occupancy based on the sum of the individual basin areas that support the species, and marine waters extending 1 km offshore. Our estimate for the area of occupancy is 233,498 km. We assumed in both cases that the area is continuing to decline, but the species does not exhibit extreme fluctuations.
Habitat and Ecology
IUCN Red List Assessment
Red List Category
Red List Criteria
The IUCN criteria used to estimate the population size reduction for a species can include the following: direct observations, indices of abundance, declines in area of occupancy or extent of occurrence and/or quality of the habitat, actual or potential levels of exploitation, or effects of introduced taxa, hybridization, pathogens, pollutants, competitors or parasites. We relied on four primary sources of information to document declines in population abundance (in Russia) and habitat (in Japan). Below we include documentation of our data sources and our analytical approaches:
1. Khabarovsk bycatch time series
We obtained data on bycatch of Sakhalin taimen in commercial fisheries (primarily gill net captures) along the Sea of Japan coast in Khabarovsk during 19511998. These data have been reported in a number of publications (Zolotukhin et al. 2000, Zolotukhin et al. 2002). Data are reported as weight (in 1,000 kg) of landed biomass of taimen (see Figure 2 in the Supplementary Material). We parsed the data into three discrete periods to account for different prevailing social and economic conditions for the fishery. We identified the first period (19511964) as the most reliable time series, where bycatch reporting rate was high and consistent. We fit a exponential model to these data and estimated a rate of decline of the regional population at -9% yr-1. Assuming an average weight of captured taimen at 5 kg, the total harvest during this period ranged from ~800 to ~4,000 individuals yr-1, most likely representing the peak bycatch fishery yield for the species in this region. We fit an exponential model to a second time series that extended from 19721979, a period marked by a growing black market for the species, resulting in under-reported bycatch. The rate of decline during this period was estimated at -23% yr-1. We fit the remaining data in the time series (19801998) to a separate exponential model. This period can be characterized by continued under-reporting of bycatch, and includes recreational landings beginning in the mid-1990s. The model fit to these data suggested the regional population declined by -12% yr-1.
2. Sakhalin bycatch time series
We obtained data on bycatch of Sakhalin taimen in the commercial fishery located in the Nogliki region of Sakhalin Island during 19711997. These data were compiled by SakhNIRO, the regional fisheries agency on Sakhalin. Data are reported as weight (in 100 kg) of landed biomass of taimen (see Figure 3 in the Supplementary Material). Assuming an average weight for captured taimen at 5 kg, peak harvest during this time series was ~ 3,000 individuals yr-1, occurring in 1974. We fit these data to an exponential model, and estimated the slope of the regression of log(catch) vs. year. This time series suggests a rate of reduction of the population of 11% yr-1 over the period of record (26 yr). The rate of decline of the older members of the population in the region is thought to be even more dramatic (S.N. Safronov, Sakhalin State University, pers. comm.).
3. Estimate of exploitation rate on the Koppi River population
Catch and age composition data from the Koppi River population was obtained during 2000-2002. Gill nets and angling were the primary methods of capture. Captured individuals were aged by scale analysis (N = 131). We fit a regression of log (catch) vs. age for individuals aged 3-16 to estimate Z, total instantaneous mortality rate of the population (see Figure 4 in the Supplementary Material). This assumes that taimen are fully recruited to the fishing gear by age 3, and that the age composition of the catch is representative of the true population in the river. Our estimate for Z is 0.307 (or -26 % yr-1). Assuming natural mortality (M) to be 0.11 (see above), we estimated fishing mortality by difference (F = Z - M, F = 0.197). The resulting value for fishing mortality is ~ two times the rate of natural mortality of the population. Annual rate of fishing mortality is estimated at -18% yr-1. This mortality rate is within the range of estimated population loss rates based on the bycatch time series for Khabarovsk estimated above (-9, -12, and -23% yr-1). While this may be an overestimate of fishing mortality based on difficulties associated with sampling older, mature individuals in the Koppi River population, it does represent the most comprehensive effort to date to provide a reliable sample of the age composition and relative abundance of a river population of Sakhalin taimen.
4. Hokkaido taimen fry survey
Trend data for the species abundance in Hokkaido, Japan are not available. A comparison of results from redd surveys conducted during 1991 and 1998 in the Sarufutsu River in northern Hokkaido indicated no marked changes over time in spawner abundance for this population (M. Fukushima, JMOE unpubl. data). We feel that that this data set is not representative given the short period of observation, and that the region has seen much less change in land use compared to other regions in Hokkaido. Here we rely on a study on presence/absence for the species in Hokkaido to scale the magnitude of habitat loss for the species. Edo (2001) concluded that the range of the species has been reduced by 57% based on an extensive survey of juvenile taimen (fry, or young-of-the-year) during 2000. The survey involved electrofishing reaches in a total of 30 study streams that were thought to support the species historically (Edo 2001). Fry were observed in a total of 13 study streams, representing 43% of the historic range currently occupied. We acknowledge the likelihood of error by relying on fry absence based on a one-time survey as evidence of extirpation, but we feel this is the best available data to allow us to gauge habitat loss in this region. While numerous anecdotes exists for declining adult abundance in some river systems, we lack reliable time series data. One river, the Shiribetsu (located in southwestern Hokkaido), was recognized historically for it prized receational taimen fishery, but no longer supports adult spawners. Surveys for redds conducted since 1995 have indicated that this population has been extirpated (H. Kawamura, Hokkaido Fish Hatchery, pers. comm.).
Based on results of these analyses, and assuming a generation time of 14 yrs, we estimated regional population reductions over three generations (42 yr period) of 98% in Khabarovsk (based on -9% yr-1 using the most reliable time series), 99% in Sakhalin, and 57% in Hokkaido (based on range reduction using results of fry survey).
In 2012, Hucho perryi was included among the world's 100 most threatened species in a report by the IUCN Species Survival Commission and the Zoological Society of London.
We relied on best expert judgment, and consideration of the magnitude of bycatch of taimen in the commercial salmon fishery, to gauge levels of abundance for taimen in the Russian portion of the species range. Ranges of abundance were provided for 10 rivers along the Sea of Japan coast (1-100,101-1000,1001-10000 adults per basin), and 61 rivers on Sakhalin (1-50, 51-100, 101-1000 adults per basin). Because ranges were provided in this case, we estimated densities by basin (2.9-29.6 taimen km-1, see Table 1 in the Supplementary Material) using the low and high value in each abundance strata. We assumed the density range estimated for Sakhalin applied to the Kuril Islands portion of the species range. Populations in five basins on Sakhalin Island are presently considered extirpated. To arrive at a total population for each region, we summed the population estimates (both low and high values in each strata) for the rivers where we had estimates, and extrapolated abundances based on total stream km in basins where we lack data. Our estimates for total population by region are as follows: Primorye: 2,796-28,323 adults, Khabarovsk: 3,351-33,520 adults, and Sakhalin (including Kuril Islands): 1,591-12,024 (see Table 1 in the Supplementary Material). The historic peaks of bycatch landings in the time series (Khabarovsk at ~ 4,000 adults yr-1 and Sakhalin at ~3,000 adults yr-1, estimated by converting landed biomass to adult numbers assuming average weight of landed adult at ~ 5kg) fall within the range of abundances estimated here.
1. We recommend expanding and/or modifying the network of conservation rivers designated by the government in Hokkaido to provide protection to Sakhalin taimen. The existing network was established originally for protection of commercial species (e.g. Oncorhynchus masu cherry salmon and O. keta chum salmon), and has been expanded in recent years to protect rare salmonids. However, a recent effort to identify prime habitat for Sakhalin taimen based on habitat modeling suggests the existing protected area network provides little protection for this species (Fukushima and Kameyama 2006). We strongly encourage the Hokkaido government to consider extending conservation river protection to the rivers identified by Fukushima and Kameyama (2006), particularly those in the Soya peninsula that still support healthy taimen populations.
2. We recommend new regulations on recreational fishing, particularly during the spawning season. While the species has been recognized as endangered (red book species) in several regions (Primorye, Sakhalin and Hokkaido), the regulations triggered by these listings are not always sufficient or properly enforced (see #3). While establishing a ban on fishing is clearly needed in some circumstances, we think establishing exemptions in certain basins would be prudent if there is sufficient evidence that the exploited populations are stable or increasing. A key virtue of these exemptions is that the presence of recreational fishers, particularly in rivers in remote regions in the Russian part of the species range, could help deter illegal fishing practices. Where recreational fishing is allowed, we feel there should be a set of regulations enforced, including explicit creel limits and gear restrictions to reduce release mortality. These fish tend to become aggregated and vulnerable to heavy fishing pressure during the spring spawning season, so we feel it is especially important to enact regulations during this critical period in their life history.
3. We recommend increased enforcement of existing fishing regulations in the Russian part of the species range. Recent observations by research scientists have revealed illegal fishing operations, and much of the take, beginning in the 1980s and continuing to present, have gone unreported. Our observations have indicated that fisheries officers that are hired to enforce existing regulations have been ineffectual, largely due to a lack of presence on the rivers, particularly during the critical spawning period. We recommend increased vigilance to enforce fishing regulations intended to protect the species.
4. We recommend investigating the role of habitat and population fragmentation, particularly in Japan. Habitat fragmentation has been most widespread in Hokkaido, and we encourage actions that reduce and minimize further habitat loss, and restore habitat where possible. We are aware of ten individual, local efforts in Hokkaido to raise awareness of lost and degraded taimen habitat (e.g., Obirame Restoration Group), but we feel much more can be done through a broader scale assessment of salmonid species diversity, threats, and cumulative aquatic habitat loss across Hokkaido. A formal investigation by key public agencies into how to better balance flood plain development with conservation of rare species is critically important. A key step has recently been taken to form the Committee of Critically Endangered Species (CCES) by the Hokkaido government, and we encourage this group to focus on habitat related issues involving conservation of Sakhalin taimen.
5. We recommend formulating and enforcing best practices for infrastructure development, particularly related to resource extractive industries. While much of the habitat for Sakhalin taimen in Russia is intact, there are a number of threats that exist. Logging, road construction and pipeline development present threats to spawning habitat, in the form of increased bank instability, leading to accelerated erosion and sedimentation. Road construction also leads to increased illegal fishing activities by providing easier access to rivers. Sound best practices (e.g., riparian buffers, pipeline river crossings, culvert designs) need to be established and enforced to reduce erosion and allow unimpeded movement of fish throughout the watershed.
6. While there has been some preliminary efforts in both Japan and Russia at captive breeding for the species, we feel these activities should proceed with great caution. Inter-basin transplants could contribute to loss of locally adapted gene complexes. We encourage basic research on the degree of geneflow that exists between river populations to understand phylogeographic patterns that could help guide future reintroductions. Although there is some evidence that captive propagation can help reduce short-term extinction risk for critically endangered species, there is virtually no empirical evidence to indicate whether propagation can promote long-term sustainability. Therefore, captive propagation efforts, to the extent that they exist, are at best stop-gap measures and are in no way a substitute for conserving the species in the wild.
7. Finally, given the myriad threats to the species, it's dramatic rate of decline, and it's cross border, limited distribution, we feel it is important to establish an intergovernmental working group to consider formally our proposed conservation actions and draft an implementation plan to conserve the species.
Relevance to Humans and Ecosystems
Hucho perryi is one of largest, most ancient salmon species and primarily inhabits the lower to middle reaches of lakes and rivers. Fish over 30 cm long are almost exclusively piscivores, while the young feed mostly on aquatic insects. Females typically lay between 2,000 and 10,000 eggs in the spring on the sandy or gravelly river bottom. The average specimens caught have weighed around 5 kg (11 lb). The largest fish caught was recorded at 9.45 kg / 20 lb 13 oz (IGFA world record). According to the unauthorized record of Japan, a fish with length of 2.10 cm was captured in 1937 from the Tokachi River, Hokkaidō. This species of fish is able to change its own sex for mating.
Hucho perryi are found in the Northwest Pacific: Sakhalin Island (Russia), the Island of Hokkaidō (Japan), and parts of the far eastern Russian mainland. An anadromous form lives near the eastern shores of Hokkaido.
The global population of the species has dwindled in recent years for a variety of reasons. The loss of more than 50% of their original habitat due to agriculture, urbanization, and more recently, oil and gas development, is a major factor. Other considerable pressures include bycatch in the commercial salmon fisheries of Russia and Japan, as well as illegal fishing practices in Russia. The fish are also prized as trophies by Japanese recreational anglers.
In Japan, this species is bred for game-fishing at managed fishing sites, and raised fish are available for purchase. However, the species remains critically endangered.
In 2006, the IUCN listed Hucho perryi as critically endangered based on the assessment completed by the Salmonid Specialist Group. This designation represents the highest potential risk of global extinction to the species. The assessment revealed that the range-wide population has dropped in size to less than 5% of historic levels.
- Froese, Rainer and Pauly, Daniel, eds. (2014). "Parahucho perryi" in FishBase. September 2014 version.
- Robins, C.R., R.M. Bailey, C.E. Bond, J.R. Brooker, E.A. Lachner, R.N. Lea and W.B. Scott, 1991. World fishes important to North Americans. Exclusive of species from the continental waters of the United States and Canada. Am. Fish. Soc. Spec. Publ. (21):243 p.(from fishbase, Hucho perryi)
- "Hucho perryi". IUCN Red List of Threatened Species. Version 2007. International Union for Conservation of Nature. 2006. Retrieved 11 November 2007. Listed as Critically Endangered (CR A4abcd v3.1)
- Rand, Pete. "Ancient, Giant Salmon in Asia Edging Towards Extinction" Wild Salmon Center, May 23, 2006.
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