Hokkaido National Fisheries Research Institute
Hokkaido National Fisheries Research Institute
Hasegawa K.,Hokkaido National Fisheries Research Institute
Journal of Fish Biology | Year: 2017
After resolution of habitat fragmentation by an erosion-control dam, non-native brown trout Salmo trutta invaded the upstream side of the dam and displaced native white-spotted charr Salvelinus leucomaenis in Monbetsu stream, Hokkaido, northern Japan. © 2017 The Fisheries Society of the British Isles.
Saito T.,Hokkaido National Fisheries Research Institute
Fisheries Science | Year: 2017
Linear discriminant analysis (LDA) based on scale patterns was used to develop a methodology of estimating regional origins of chum salmon. Age-4 fish were sampled in 2004–2006 from 12 river stocks of the Okhotsk and Sea of Japan (SJ) regions from Hokkaido to Honshu. The scale radius at the first annulus of each fish was separated into i intervals and the radius of each interval was divided by the number of scale circuli within the interval to quantify scale patterns. The i variables and five other morphometric measurements were used in a stepwise LDA to classify the following regional groups: Hokkaido and Honshu (I), Okhotsk and SJ (II), Okhotsk, Hokkaido SJ and Honshu SJ (III). Percentages of correctly classified fish (hit rates) improved with increased i but tended to be close to asymptotic values in all cases. Hit rates for each river stock in case (I) ranged from 74.3% to 100% (mean 97.2%), estimated by direct maximum likelihood methods using predictor variable sets from the best models for LDAs. Hit rates were lower in cases (II) and (III). This study demonstrated that scale patterns are useful for classifying the origins of chum salmon, at least between Hokkaido and Honshu. © 2017, Japanese Society of Fisheries Science.
Watanabe K.,Hokkaido National Fisheries Research Institute
Fisheries Oceanography | Year: 2017
Based on generalized linear models, interspecific interactions were identified between chum and pink salmon. In addition, the effects of sea surface temperature and location on the variability of catch per unit effort (CPUE) of chum salmon from gill-net surveys carried out between 1972 and 2010 were investigated. In the optimal model, interspecific interactions between CPUEs of chum and pink salmon on a year scale were positive for approximately half of all years in the central Bering Sea. In addition, interspecific interactions on a multi-year scale were positive in even-numbered years. The effects of location on the CPUE of chum salmon were significant variables in the optimal model. The CPUEs of chum salmon located near the continental shelf in the Bering Sea were higher than those of other locations. This study provides new evidence of positive interspecific interactions between the CPUEs of chum and pink salmon. The results also suggest that the standardized CPUE of chum salmon from the gill-net surveys reflects relative chum salmon abundance in the North Pacific Ocean in the following year. © 2017 John Wiley & Sons Ltd
Morita K.,Hokkaido National Fisheries Research Institute |
Nagasawa T.,Fisheries Research Agency
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2010
We examined latitudinal variation in riverine growth and parr maturation of an endemic Asian salmonid, masu salmon (Oncorhynchus masou), in 12 rivers located between 36.6°N and 45.4°N. Masu salmon parr showed considerable variation in growth and maturation patterns among populations. Body sizes were generally larger, and parr maturation was common at southern latitudes. Male parr matured at smaller sizes at more southern latitudes. Latitudinal variation in riverine growth and maturation of masu salmon parr was largely attributed to latitudinal changes in temperature and population density. Parr size at age increased with increasing temperature and decreased with population density. Riverine growth conditions were an important environmental factor determining parr maturation for both males and females; however, the occurrence of mature female parr required extremely favorable growth conditions. Water temperature in May, approximately four months before maturation, was the most important environmental factor affecting the maturation of male parr. Our study supports the hypothesis that freshwater residency was promoted by favorable growth conditions at southern latitudes.
Whitney F.A.,Canadian Department of Fisheries and Oceans |
Bograd S.J.,Southwest Fisheries Science Center |
Ono T.,Hokkaido National Fisheries Research Institute
Geophysical Research Letters | Year: 2013
At the end of the global thermohaline circulation, the subarctic Pacific is the richest nutrient repository in the world oceans. Trends towards lower oxygen and higher nutrients in waters below the surface layer (the pycnocline) have been observed in recent decades. We assess these trends using data from four programs and suggest the enrichment of pycnocline nitrate (200 Gmol y -1) is essential in keeping supply to the surface ocean constant, despite increasing upper ocean stratification. A nitrate budget helps identify possible vertical processes that could account for nutrient redistribution. We hypothesize that warming and oxygen loss in the deeper pycnocline, arising from ice loss in the Okhotsk Sea, have initiated a largely vertical redistribution of nutrients due to compression of vertical migrator habitat and/or changes in dissolution of sinking particulates. Coupled climate-ecosystem models will need to incorporate these processes to more fully understand projected changes in the subarctic Pacific. © 2013 American Geophysical Union. All Rights Reserved.
Irvine J.R.,Canadian Department of Fisheries and Oceans |
Fukuwaka M.-A.,Hokkaido National Fisheries Research Institute
ICES Journal of Marine Science | Year: 2011
Understanding reasons for historical patterns in salmon abundance could help anticipate future climate-related changes. Recent salmon abundance in the northern North Pacific Ocean, as indexed by commercial catches, has been among the highest on record, with no indication of decline; the 2009 catch was the highest to date. Although the North Pacific Ocean continues to produce large quantities of Pacific salmon, temporal abundance patterns vary among species and areas. Currently, pink and chum salmon are very abundant overall and Chinook and coho salmon are less abundant than they were previously, whereas sockeye salmon abundance varies among areas. Analyses confirm climate-related shifts in abundance, associated with reported ecosystem regime shifts in approximately 1947, 1977, and 1989. We found little evidence to support a major shift after 1989. From 1990, generally favourable climate-related marine conditions in the western North Pacific Ocean, as well as expanding hatchery operations and improving hatchery technologies, are increasing abundances of chum and pink salmon. In the eastern North Pacific Ocean, climate-related changes are apparently playing a role in increasing chum and pink salmon abundances and declining numbers of coho and Chinook salmon. © 2011 International Council for the Exploration of the Sea.
Katsumata K.,Japan Agency for Marine - Earth Science and Technology |
Yoshinari H.,Hokkaido National Fisheries Research Institute
Journal of Oceanography | Year: 2010
We used Argo float drift data to estimate average ocean currents at 1000 dbar depth from early 2000 to early 2010. Our estimates cover the global oceans, except for marginal seas and ice-covered regions, at a resolution of 1 degree in latitude and longitude. The estimated flow field satisfies the horizontal boundary condition of no flow through the topography, and is in geostrophic balance. We also estimated the uncertainty in the average flow field, which had a typical magnitude of 0.03 ms-1. The uncertainty is relatively large (>0.03 ms-1 in both the zonal and meridional directions) near the Equator and in the Southern Ocean. The array bias, which is the bias due to the horizontal gradient in the spatial density of the float data, is generally negligible, with an average magnitude outside the equatorial region of 0.007 ms-1, becoming relatively large (>0.01 ms-1) only near the coastal regions. The measurement uncertainty is assumed to be spatially uniform and includes errors due to the Argos positioning system, internal clock drift, unknown surface drift before submerging or after surfacing, and unknown drifts during ascent and descent between the surface and the parking depth. We found that the overall uncertainty was not sensitive to the assumed value of the measurement uncertainty (εm)1/2 when (εm)1/2 < 0.01 ms-1 but it increased with (εm)1/2 for (εm)1/2 > 0.01 ms-1. © 2010 Springer Science+Business Media B.V.
Sahashi G.,Hokkaido University |
Sahashi G.,Hokkaido National Fisheries Research Institute
Proceedings. Biological sciences / The Royal Society | Year: 2013
Partial migration of some, but not all, members of a population is a common form of migration. We evaluated how migration costs influence which members migrate in 10 populations of two salmonid species. The migratory patterns of both species were evaluated based on the size at maturity for resident males, which is the threshold trait that determines the migratory tactics used within a population. In both species, this size was smaller in males located further from the sea, where migration costs are presumably higher. Moreover, the threshold sizes at maturity in males were correlated between both species. Our results suggest that migration costs are a significant convergent selective force on migratory tactics and life-history traits in nature.
Funamoto T.,Hokkaido National Fisheries Research Institute
Fisheries Oceanography | Year: 2011
Recruitment of the northern Japan Sea stock (JSS) of walleye pollock has been decreasing since around 1990. In this study, I analyzed the factors causing this decrease in recruitment by investigating the relationship between recruitment, spawning stock biomass (SSB) and environmental factors using a generalized additive model (GAM). GAM fit to the data showed the importance of SSB, sea surface temperature (SST), ocean current strength (Tsushima Warm Current) and wind intensity (Asian monsoon) in determining the recruitment. Of these, the relationship between SSB and recruitment was positive and not negatively density-dependent. On the other hand, the recruitment was negatively related to SST and ocean current strength, and a dome-shaped relationship was observed between wind intensity and recruitment. Since around 1990, the values of SST and ocean current strength have mostly been high and that of wind intensity mostly low. In addition, SSB has been decreasing since the late 1990s. It is likely that the recruitment decline of JSS after approximately 1990 has been caused by warm water temperature, strong Tsushima Warm Current and weak Asian monsoon, and that the recent decrease in SSB has amplified this recruitment decline. According to the model's estimation, a recruitment recovery due to environmental improvement will be highly restricted as long as SSB remains at its current low level. Significant recovery of SSB is urgently needed for JSS. © 2011 Blackwell Publishing Ltd.
Morita K.,Hokkaido National Fisheries Research Institute
Fisheries Oceanography | Year: 2011
Relationships between the vertical distribution and thermal habitat, and body size of chum salmon Oncorhynchus keta were studied in the Bering Sea in summer using trawl surveys at various depths. Chum salmon abundance decreased with increasing depth, but the patterns of decrease differed between size groups. The abundance of small salmon fell rapidly with depth, whereas that of large salmon decreased gradually to 40m depth, and abruptly below that. The average fork length of chum salmon collected from each trawl correlated positively with trawl net depth and negatively with water temperature. Since the optimal temperature for growth decreases with body size in this species, the observed body size-related vertical habitat use by chum salmon may indicate size-dependent thermal preferences. © 2011 Blackwell Publishing Ltd.