Pyper B.J.,Cramer Fish science |
Cramer S.P.,Cramer Fish science |
Ericksen R.P.,Cramer Fish science |
Ericksen R.P.,Wild Salmon Center |
Sitts R.M.,Cramer Fish science
Marine and Coastal Fisheries | Year: 2012
The need to protect imperiled salmon stocks along the Pacific coast of North America has led to an increasing use of mark-selective fisheries (MSFs) as a management strategy to reduce harvest mortality of wild salmon while allowing harvest of abundant hatchery salmon. However, MSFs remain untested in ocean fisheries for Chinook salmon Oncorhynchus tshawytscha off the coasts of California and Oregon, where hatchery fish have been estimated to compose the majority of Chinook salmon but where harvests have been restricted to protect several imperiled stocks. We developed a quantitative framework based on conventional cohort models to examine how aggregate ocean harvest and in-river escapement of Sacramento River fall-run Chinook salmon, the numerically dominant stock in the region, would have differed under MSF scenarios compared with the historic, traditional fishery. At historic contact rates (fishing effort) for 1988-2007, we estimated that annual in-river escapement of natural-origin fish would have increased by 119% on average under MSF scenarios, while reductions in harvest would have been inversely proportional to the fraction of hatchery-origin fish. During the more recent period of constrained fishing (2001-2007), we estimated MSF outcomes for a range of plausible contact rates (40-60% of age-4 fish) and hatchery fractions (40-80% of Chinook salmon). The combination of these factors determined the magnitude of estimated harvest reductions or gains underMSFs, with totalMSF harvest (2001-2007) ranging from 46% lower to 48% higher than historic harvest. Increases in total escapement of natural-origin fish (2001-2007) underMSFs ranged from 24% to 48% depending on the contact rate. Comparisons between the traditional fishery and simulated MSF outcomes were robust to a wide range of cohort parameter values, suggesting that our aggregate results provide useful insights into potential MSF outcomes and the effects of key uncertainties. © American Fisheries Society 2012.
Fukushima M.,Japan National Institute of Environmental Studies |
Rand P.S.,Wild Salmon Center |
Kaeriyama M.,Hokkaido University
Transactions of the American Fisheries Society | Year: 2011
The Sakhalin taimen Parahucho perryi is an endangered salmonid with a natural range limited to the Russian Far East and Japan. We constructed a classification tree to determine the environmental factors shaping the historical global distribution of this species and then predicted its potential geographic range. The distribution wasmost strongly influenced by a spatial autocorrelation term, indicating that it is highly contiguous. Large drainage basins with low topographic relief and large floodplains had a higher probability of taimen occurrence. The boundary of the global distribution was delineated by mean monthly precipitation within the range of 54-96 mm. The presence of Sakhalin taimen was predicted in many drainage basins where it has never been recorded. We also modeled the status of 48 taimen populations in Japan, where it was possible to classify them into three categories: currently stable (7), endangered (5), and extinct (36). The most significant factor differentiating the 12 extant populations from the 36 extinct populations was mean annual air temperature, the extant populations being distributed exclusively in areas where the air temperature is below 5.2°C and agricultural development is minimal. The extant populations were found in drainages with significantly lower elevations and a smaller percentage of farmland compared with drainages where populations have been extirpated. The presence of lagoons was a common characteristic of the drainages with the 7 stable populations, suggesting that lagoons represent critical refugia for the species. The implications of this study for taimen conservation are discussed. © American Fisheries Society 2011.
Zhivotovsky L.A.,Russian Academy of Sciences |
Yurchenko A.A.,Russian Academy of Sciences |
Nikitin V.D.,Sakhalin Research Institute of Fisheries and Oceanography |
Safronov S.N.,Sakhalin Research Institute of Fisheries and Oceanography |
And 5 more authors.
Conservation Genetics | Year: 2015
Hierarchical population structure can result from range-wide geographic subdivision under conditions of environmental heterogeneity and weak gene flow. While a lower level of structure can be formed by local populations within eco-geographic regions, an upper level can be characterized by variation between populations from different regions, and thus, be represented by evolutionarily significant units (ESUs) defined by environmental, ecological and genetic variation. Selection of ESUs may depend on the sequence of using these three sources of variation. We propose to determine ESUs by first using non-genetic, ecological and geographical gradients for defining preliminary population groups (eco-geographic units, EGUs) and then testing whether the boundaries of these units are genetically coherent and thus represent ESUs or warrant their further modification. We evaluate this approach using Sakhalin taimen, an East Asian endangered endemic fish. Forty-one samples (473 fish) were drawn from thirty populations across the species range and genotyped at microsatellite DNA markers. We assign the populations into ESUs based on geographic and life history criteria and subsequent application of genetic diversity analyses. The ESUs appeared to be greatly diverged genetically. Within ESUs, local populations are genetically differentiated, have low effective sizes, show signatures of demographic decline and extremely restricted gene flow. Conservation plans aimed to restore or maintain a specific threatened population should take into account such hierarchical structure, and in particular be based on the genetic resources drawn from each population or using ecologically and genetically similar populations from the same ESU as donors for restoration of the population. © 2014, Springer Science+Business Media Dordrecht.
Rand P.S.,Wild Salmon Center |
Fukushima M.,Japan National Institute of Environmental Studies
Global Ecology and Conservation | Year: 2014
Sakhalin taimen Parahucho perryi, an east Asian fish noted to be one of the largest salmonids in the world, is threatened throughout its range in northern Japan and neighboring Russian Federation. We report here on the first effort to enumerate and characterize the spawning run of a river population. We applied sonar and video methods in a tributary of the Sarufutsu River in Hokkaido, Japan, and evaluated environmental controls on migration. Over two years we estimated the tributary population to range from 335 to 425. We found passage rate by our site to increase with temperature and decrease with river discharge, and migratory cues were reinforced by strong diel fluctuations in environmental conditions. Finally, we report evidence of males arriving early to the spawning grounds in this species. Given our results and data on the recreational fishery, we conclude that a substantial number of individuals in the population are affected by angling, underscoring the need to establish fishing regulations. Further, our study indicates passage success can vary over the migration period, and efforts at modifying or removing impediments, and devoting more research to factors controlling passage, could ultimately improve the status of this species. © 2014 The Authors.
Rand P.S.,Wild Salmon Center
PloS one | Year: 2012
Concern about the decline of wild salmon has attracted the attention of the International Union for the Conservation of Nature (IUCN). The IUCN applies quantitative criteria to assess risk of extinction and publishes its results on the Red List of Threatened Species. However, the focus is on the species level and thus may fail to show the risk to populations. The IUCN has adapted their criteria to apply to populations but there exist few examples of this type of assessment. We assessed the status of sockeye salmon Oncorhynchus nerka as a model for application of the IUCN population-level assessments and to provide the first global assessment of the status of an anadromous Pacific salmon. We found from demographic data that the sockeye salmon species is not presently at risk of extinction. We identified 98 independent populations with varying levels of risk within the species' range. Of these, 5 (5%) are already extinct. We analyzed the risk for 62 out of 93 extant populations (67%) and found that 17 of these (27%) are at risk of extinction. The greatest number and concentration of extinct and threatened populations is in the southern part of the North American range, primarily due to overfishing, freshwater habitat loss, dams, hatcheries, and changing ocean conditions. Although sockeye salmon are not at risk at the species-level, about one-third of the populations that we analyzed are at risk or already extinct. Without an understanding of risk to biodiversity at the level of populations, the biodiversity loss in salmon would be greatly underrepresented on the Red List. We urge government, conservation organizations, scientists and the public to recognize this limitation of the Red List. We also urge recognition that about one-third of sockeye salmon global population diversity is at risk of extinction or already extinct.