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Kasugai K.,Salmon and Freshwater Fisheries Research Institute | Hayano H.,Salmon and Freshwater Fisheries Research Institute | Mano S.,Salmon and Freshwater Fisheries Research Institute | Watanabe T.,Salmon and Freshwater Fisheries Research Institute | And 5 more authors.
Ichthyological Research | Year: 2014

Otolith Sr:Ca ratios of 11 masu salmon (Oncorhynchus masou) in Lake Kussharo and its tributaries, of which outlet river has no barriers to the ocean, were analyzed to estimate their migration histories. The Sr:Ca ratios of all masu salmon generally fluctuated below 2. Masu salmon from Lake Kussharo presumably do not migrate to the ocean. However, more specimens must be analyzed to clarify the migration history of masu salmon in this lake. © 2014, The Ichthyological Society of Japan. Source

Shimada H.,Central Fisheries Research Institute | Sakaguchi K.,Kushiro Fisheries Research Institute | Sakaguchi K.,Central Fishries Research Institute | Mori Y.,Kushiro Fisheries Research Institute | And 3 more authors.
Bulletin of the Plankton Society of Japan | Year: 2012

To evaluate the seasonal/annual changes and regional variations in biomass structure,175 zooplankton samples were collected from the 0-150 m layer and the 0-500 m or the 0-300 mlayer using a modified NORPAC net at four areas around Hokkaido (Doto and the Donan area of the North Pacific, the northern Japan Sea and the southern Okhotsk Sea) every one-three months during February 2008 to December 2011. Seasonal zooplankton biomass peaks were found from April to June every year, with the exception of the southern Okhotsk Sea. Large cold water copepods (.Neocalanus spp., Eucalanus bungii and Metridia spp.) dominated the biomass throughout the areas, composing ca. 40-50% of the total zooplankton biomass in terms of wet weight. The most dominant species varied with area; i.e. E. bungii (Doto and Donan area), N. plumchrus/flemingeri (northern Japan Sea) and M. pacifica/okhotensts (southern Okhotsk Sea). The biomass of large copepods, especially N. plumchrus/flemingerit showed significant year-to-year changes. In the northern Japan Sea (Tsushima Warm Current area), N. plumchrus/flemingeri were abundant during spring 2010, when the current was less warm and high chlorophyll-a values were observed. In the Doto and Donan area of the North Pacific, N. plumchrus/flemingeri were less abundant during spring 2009, when their was less Oyashio water and lower chlorophyll-a concentrations were found Our results suggest that the biomass of large cold-water copepods fluctuates year-to-year, being influenced by the physical/biological environment-especially in spring. © 2012 Plankton Society of Japan. Source

Sugawara M.,Hokkaido National Fisheries Research Institute | Yamashita N.,Hokkaido National Fisheries Research Institute | Sakaguchi K.,Hokkaido Research Organization HRO | Sato T.,Kushiro Fisheries Research Institute | And 5 more authors.
Nippon Suisan Gakkaishi (Japanese Edition) | Year: 2013

To identify factors affecting the somatic growth of the winter-spawning stock of Japanese common squid, the somatic growth of squid caught in the East China Sea, the Pacific Ocean and the Tsushima Strait from 2000 to 2011 was estimated using age determination from statolith microstructure analysis. The relationship between estimated age in days and dorsal mantle length was fitted using a Gompertz growth equation. The residuals of dorsal mantle length from the growth equation differed among year classes, hatch months, and sexes. Although no environmental factors correlated with the annual difference in growth, increased sea water temperature in spring in the Kuroshio-Oyashio transition region corresponded to increased growth with hatch month. Growth was smaller in males than in females during the southward migration, which suggested depressed growth in males due to earlier sexual maturation than in females. Source

Liu Y.,Hokkaido University | Saitoh S.-I.,Hokkaido University | Ihara Y.,University of Tokyo | Nakada S.,Kobe University | And 5 more authors.
ICES Journal of Marine Science | Year: 2015

The Japanese scallop (Patinopecten (Mizuhopecten) yessoensis) is an important commercial species in Funka Bay, Japan, where it is farmed using the hanging culture method. Our study was based on 6 years (from 2006 to 2011) of monthly in situ observations of scallop growth at Yakumo station. To produce a basic spatial distribution dataset, we developed an interpolation solution for the shortage of Chl- A concentration data available from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite. Additionally,we integrated four-dimensional variational (4D-VAR) assimilation water temperature data from ocean general circulation models (OGCMs), with four vertical levels (6, 10, 14, and 18 m) from the sea surface. Statistical models, including generalized additive models (GAMs) and generalized linear models, were applied to in situ observation data, satellite data, and 4D-VARdata to identify the influence of environment factors (interpolated Chl-a, temperature, and depth) on the growth of scallops, and to develop a three-dimensional growth prediction model for the Japanese scallops in Funka Bay. We considered three methods to simulate the growth process of scallops (accumulation, summation, and product), and used them to select the most suitable model. All the interpolated Chl- A concentrations and 4D-VAR temperature data were verified by shipboard data. The results revealed that GAM, using an accumulation method that was based on a combination of integrated temperature, integrated log Chl-a, depth, and number of days, was best able to predict the vertical and spatial growth of the Japanese scallop. The predictions were verified by in situ observations from different depths (R2 = 0.83- 0.94). From the distribution of three-dimensional predicted scallop growth maps at each depth, it was suggested that the growth of the Japanese scallop was most favourable at 6 m and least favourable at 18 m, although variations occurred in each aquaculture region in different years. These variations were probably due to the ocean environment and climate variation. © 2015 International Council for the Exploration of the Sea. All rights reserved. Source

Nishikawa T.,Toho University | Oohara I.,Japan National Research Institute of Fisheries Science | Saitoh K.,Japan National Research Institute of Fisheries Science | Shigenobu Y.,Japan National Research Institute of Fisheries Science | And 5 more authors.
Zoological Science | Year: 2014

The solitary ascidian Ascidiella aspersa (Müller, 1776) has sometimes been regarded as conspecific with A. scabra (Müller, 1776), although previous detailed morphological comparisons have indicated that the two are distinguishable by internal structures. Resolution of this taxonomic issue is important because A. aspersa has been known as a notoriously invasive ascidian, doing much damage to aquaculture e.g. in Hokkaido, Japan. We collected many specimens from European waters (including the Swedish coast, near the type localities of these two species) and Hokkaido, Japan (as an alien population) and made molecular phylogenetic analyses using the mitochondrial cytochrome c oxidase subunit I (COI) gene, and found that in terms of COI sequences all the analyzed specimens were clustered into two distinct groups, one of which is morphologically referable to A. aspersa and the other to A. scabra. Thus, these two species should be regarded as distinct from each other. © 2014 Zoological Society of Japan. Source

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