Oncorhynchus nerka (HECATE STRAIT-Q.C. SOUND: Atnarko R)http://dx.doi.org/10.2305/IUCN.UK.2011-2.RLTS.T135354A4107038.en
|Scientific Name:||Oncorhynchus nerka (HECATE STRAIT-Q.C. SOUND: Atnarko R)|
|Species Authority:||(Walbaum, 1792)|
|Taxonomic Notes:||A total of 93 extant and five extinct subpopulations were identified across the natural range of O. nerka. The assessors used a combination of ecoregional information (i.e., based on differences in marine and freshwater habitat) and the degree of genetic divergence between known spawning locations, using an Fst value of 0.04, representing a threshold level of gene flow between putative subpopulations of less than or equal to one effective migrant per year. The five extinct subpopulations were based on Gustafson et al. 2007. While the assessors acknowledge that it is not straightforward to ascribe demographic or geographic distinctness to a subpopulation based on observed genetic distances, they feel it is the most appropriate methodology given the scale of the assessment and the paucity of observations of stray rates among the spawning locations considered in this assessment. For the amendment completed in 2011, we split a number of British Columbia subpopulations described in the original 2008 assessment based on additional input from experts. For a complete description of the approach and methods used for identifying units and the underlying assumptions, please refer to the Supplementary Material.
Subpopulation naming convention:
Subpopulation names consist of an ecoregion name in upper case with any subdivision of the ecoregion by other criteria (e.g. genetic divergence) indicated in proper case after a colon.
|Red List Category & Criteria:||Least Concern ver 3.1|
|Reviewer(s):||Ruggerone, G. & English, K.|
This subpopulation was evaluated against relevant criteria A, B and D. Recent escapement trends at individual monitoring sites were analysed and results were scaled upwards to characterize the Red List status of the subpopulation against criterion A2 (i.e., based on the rate of change in adult abundance over three generations, or 12 years for this species). The rate of change applied to this subpopulation, assessed over 1 site(s), was -27%. It therefore qualifies as Least Concern against criterion A2. For evaluation against criterion B2 we determined that the subpopulation does not quality for listing given stable or increasing adult abundance. The current abundance of mature adults in the subpopulation qualifies it as Least Concern against criterion D1. See Supplementary Material for data sources, trend model parameters, complete description of methods and assumptions, key threats specific to each threatened and Near Threatened subpopulation and general conservation measures.
|Previously published Red List assessments:||
|Range Description:||The current distribution of Oncorhynchus nerka extends from approximately 45-70°N to 140°E-125°W longitude. The species has been recorded from Russia, United States, Canada, and Japan, although the Japanese populations are likely to have resulted from introductions; Japan is therefore not considered to be part of this species' natural range.
See the Supplementary Material (particularly Figures 1 & 2, and Appendices 1 & 2) for details on the range of this species and of each of the 98 subpopulations identified.
Native:Canada (British Columbia)
|FAO Marine Fishing Areas:||
Pacific – northeast
|Estimated area of occupancy (AOO) - km2:||50|
|Lower elevation limit (metres):||152|
|Upper elevation limit (metres):||1472|
|Lower depth limit (metres):||30|
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||At the species level, the population is believed to be stable; however, some subpopulations are declining. For more details on subpopulaiton size estimates and trends, see the additional supporting documentation (particularly Appendix 2). Follow the link below for a PDF of the additional supporting documentation.|
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||The species exhibits a great variety of life history patterns. It has a genetically diverged life history form called “kokanee” that lives its entire life within freshwater, but this assessment includes only anadromous populations commonly referred to as “sockeye” or “red salmon”. Sockeye are born in gravel nests in rivers or lakes and the majority of life history forms rear as juveniles for one to three years in freshwater before migrating to the ocean. Some sockeye assume a river-type life history and rear in a river channel, while others are lake-type and rear in a lake environment. Primary prey during this life history stage include zooplankton and stream invertebrates. Some sea-type populations migrate within one to three months following emergence, and these make extensive use of estuaries. Most populations spend one to three years in offshore feeding areas where they grow to maturity (ca. 50-60 cm total length, 2.5-3.0 kg weight). Diet in the ocean consists primarily of zooplankton (copepods and euphausiids), but their diet also includes squids and fishes. Natural predators during this period in their life history include salmon sharks (Lamna ditropis) and Daggertooth (Anotopterus nikparini). Foraging individuals mix among populations both within and between Asia and North America, but at maturity they all migrate back toward their natal freshwater habitat where they spawn and die. The return to natal habitat and the isolation of spawning populations results in considerable genetic differentiation and adaptation to local conditions. Many fish are intercepted by fishers during the homeward, spawning migration, and natural predators include seals, sea lions and bears. Spawning occurs in late summer and autumn, in lake outlet or lake tributary streams or along lake beaches in finer sediments where subterranean upwelling occurs or among boulders on wave-aerated shores. River-type sockeye spawn in river channels not associated with lakes. Adults display bright red bodies and green heads. Males compete with each other for access to females. Females compete with each other for gravel sites where they build nests, deposit eggs (fecundity typically ranges from 2,000-5,000 eggs), and briefly guard the redd. Median population size for the species is ca. 6,000 individuals. Reviews of life history and ecology of the species appear in Smith et al. (1987), Burgner (1991), Wood (1995) and Quinn (2005).|
|Movement patterns:||Full Migrant|
|Use and Trade:||A certain percentage of sockeye are captured and killed exclusively for their roe (eggs, caviar). This occurs primarily in the Russian portion of their natural range, and the fishery is illegal and the take is unreported.|
General threats to O. nerka
The key threats to the species identified by the IUCN SSC Salmon Specialist Group were:
a) Mixed stock fishing leading to over fishing small, less productive populations
b) Changing river and ocean conditions that are likely linked to global climate change, expressed in poor marine survival rates and increased incidence of disease in adult spawners
c) Negative effects of hatcheries and construction of artificial spawning habitat
It is important to note that in many cases, the causes for declines in some specific sockeye salmon subpopulations remain unknown.
1. Many subpopulations of sockeye in British Columbia were found to be threatened based on this assessment. Fisheries and Oceans Canada (DFO) is responsible for salmon management and is currently formulating conservation units (Holtby and Ciruna, unpublished manuscript) and initiating new policy (e.g,. Wild Salmon Policy) and procedures to stem the loss in diversity (DFO 2005, Irvine and Fraser 2008). Two locations of sockeye salmon, Sakinaw Lake and Cultus Lake, have been assessed and listed as Endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). However, the federal government has declined protection under the Species at Risk Act (SARA) due to the social and economic costs of closures to the fishery (Irvine et al. 2005). We encourage COSEWIC and DFO to focus attention on those subpopulations that we identified as threatened in this IUCN assessment.
2. We considered Ozette Lake, Lake Pleasant and Quinault Lake sockeye salmon as individual spawning sites in a larger subpopulation (SEASONAL UPWELLING). These lake systems are recognized individually as Evolutionarily Significant Units (ESUs) by National Oceanic and Atmospheric Administration (NOAA). The latter two sites were not included in the genetic baseline applied in this assessment, thus we assumed all sites are members of a larger, parent subpopulation. Further, we did not include Ozette Lake in our assessment given the recent escapement data available for the native beach-spawning population at that location is obscured by repeated attempts at establishing a tributary spawning population originating from broodstock taken from outside the basin. We encourage efforts at expanding the range-wide microsatellite-DNA baseline to include Lake Pleasant and Quinault Lake, and to investigate the status of the native beach-spawning sockeye in Ozette Lake.
3. Most of the data used in our assessment, particularly in Alaska, were from large aggregate stocks that may contain many (sometimes 100s) of individual spawning sites, and hence may mask important dynamics occurring at small scales. While a number of recent studies have shown that there is a significant degree of coherence among populations within a given region, it is important to acknowledge that a majority of the variability in vital rates are not explained by regional, environmental drivers, and may result from localized threats, for example road or other infrastructural development, or by different life history characteristics which affect productivity. Where possible and feasible, we recommend a more comprehensive monitoring approach that addresses dynamics at the scale of individual spawning sites. An excellent example of this approach is the Wood River system in Alaska’s Bristol Bay region, where a combination of sampling approaches provides a more integrated monitoring system that translates into a robust assessment of the status of the species in that basin.
4. Mixed-stock fishing is likely to be a key factor in the decline observed at many sites and subpopulations in our assessment. We feel a key priority is filling a gap in knowledge about composition of mixed-stock harvest in coastal sockeye salmon fisheries. While a great deal of resources has been invested in developing weak-stock management for Fraser River sockeye salmon through the Pacific Salmon Commission and DFO, there has been much less attention placed in other regions along the west coast of North America, particularly in the regions where we found the greatest diversity of subpopulations. We encourage continued investment in developing methods and protocols to account for subpopulation composition of coastal fisheries targeting sockeye salmon to help track harvest pressure at a biologically and ecologically meaningful scale. Further, we encourage fisheries management agencies to explore restructuring fisheries in a way that would result in shifting fishing pressure from coastal regions to more terminal locations, thus providing a more effective means of controlling fishing pressure at the scale of individual subpopulations.
5. Another leading factor threatening sockeye salmon are poor marine survival rates. This has been documented in cases where smolt-to-adult survival rates are estimated through intensive monitoring programs. This appears to be a significant factor explaining declines in adult abundance across many locations in the southern range of the species in North America. While marine conditions have been shown to cycle based on climate forcing and may, in fact, improve in future years, we feel it is important for those managing salmon in this region to acknowledge that poor marine survival may persist, particularly given projections based on global climate change. Reversing declining trends in those subpopulations affected may require increased attention to agents of mortality that are occurring at other life history stages over which we have more local control.
6. Many previous attempts at re-introductions of sockeye salmon have been unsuccessful, and we feel any effort at captive breeding or inter-basin transfers for re-introduction purposes should proceed with great caution. These 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. The lack of success from the captive breeding of endangered Sakinaw sockeye salmon by DFO, and endangered Redfish Lake sockeye by NMFS, are examples of the limitations to these expensive measures. Recent evidence of re-establishment of anadromous runs of sockeye from remnant, isolated kokanee populations following dam removal or modification (e.g., Allouette Lake in British Columbia) may offer hope in re-establishing anadromous life histories in cases where dams have prevented passage.
7. Enhancement activities (particularly hatchery releases and spawning channel construction) is likely to be a key factor in reducing abundance in neighboring, small wild populations. In our assessment, we were unable to functionally track both wild and enhanced sockeye salmon where they intermingle. We strongly recommend adoption of integrated monitoring programs that includes a robust marking program and monitoring efforts targeted toward wild sockeye salmon populations that would provide the data necessary to address the degree to which enhancement practices threaten wild sockeye salmon. It is important to note that two large basins in our assessment (Fraser and Skeena) are all strongly. influenced by enhancement activities, and these activities likely represent a key factor threatening many neighboring subpopulations.
8. While not addressed in the present assessment due to lack of data, we feel there should be more focused research attention on sea-and river-type sockeye that may serve as colonizers in the future. This line of research is particularly important given expected habitat alterations from climate change.9. Very few data were available to assess population viability of sockeye salmon in the Russian Far East, and we document a significant reduction in escapement in recent years at a site within the Kamchatka River basin that warranted an endangered listing for this subpopulation. The leading threat recognized for this subpopulation is overfishing. The situation has been exacerbated by an increase in illegal fishing practices. We encourage the leading agencies in this region to provide more open access to data, and supporting meta-data, for assessment purposes. We also encourage development of new monitoring efforts throughout the region and increased enforcement to reduce poaching. Many populations of river-type sockeye exist, particularly in western Kamchatka, and focused research on these populations will provide important insight into the status of the species there.
|Citation:||Rand, P.S. 2011. Oncorhynchus nerka (HECATE STRAIT-Q.C. SOUND: Atnarko R). The IUCN Red List of Threatened Species 2011: e.T135354A4107038. http://dx.doi.org/10.2305/IUCN.UK.2011-2.RLTS.T135354A4107038.en . Downloaded on 10 October 2015.|