Time filter

Source Type

Sano M.,Wakkanai Fisheries Research Institute | Bando T.,Soya Fishery Cooperative | Mihara Y.,Central Fisheries Research Institute
Nippon Suisan Gakkaishi (Japanese Edition) | Year: 2011

Seasonal changes in sexual maturity of the Pacific giant octopus Enteroctopus dofleini from the Soya/La Perouse Strait were examined in order to determine a biological index for stock assessment. In addition, the body weight and organ weight of more than 100 specimens were measured at monthly intervals from October 2003 to December 2004. Comparisons of body and gonad weight in females revealed the existence of two groups in the period between autumn and spring. The group with the relatively heavier gonads consisted of mature females containing spermatozoa. A similar relationship was observed in male octopuses between autumn and winter. The group with the heavier gonads consisted of mature males with spermatophores. Based on the assumption that the spawning season was in early summer, the stage of maturity could be used as a biological index for assessing the spawning biomass of Pacific giant octopus in this area.


Sano M.,Wakkanai Fisheries Research Institute | Bando T.,Soya Fishery Cooperative
Nippon Suisan Gakkaishi (Japanese Edition) | Year: 2015

The seasonal migration of North Pacific giant octopus Enteroctopus dofleini in the Soya/La Peá rouse Strait was investigated using GPS location information of octopus catches by drift fishery boats. Body weight and stage of maturity of the collected octopuses were recorded. Immature octopuses were found at depths of 40 to 60 m in summer and 10 to 30 m in autumn to spring. Although mature octopuses were observed at the same depths as juveniles in most months, in June and July, mature males and females migrated to deeper areas immediately before death and spawning, respectively. Based on bottom water temperatures in areas where the octopus was distributed, it appears that this species migrates to deeper areas to avoid water temperatures above 18°C.


Yamaguchi H.,Central Fisheries Research Institute | Goto Y.,Wakkanai Fisheries Research Institute | Hoshino N.,Central Fisheries Research Institute | Miyashita K.,Hokkaido University
Fisheries Science | Year: 2014

We examined growth of northern shrimp Pandalus eous in the Sea of Japan, off western Hokkaido, to improve estimations of catch-at-age for stock assessment. Multiple length frequency analysis based on length frequency data collected by a scientific research vessel was conducted to examine length-at-age in the shrimp population. Multi-normal distributions estimated using maximum likelihood indicated a good fit to length distributions. AIC values and regression analyses revealed annual growth variation and a decreasing trend in the length at several age classes in the shrimp population. We revised the method for estimating catch-at-age from the age-conversion table (ACT), which is a simple method for age determination, to age-length keys (ALK) calculated from the results of multiple length frequency analysis. Abundant year classes caught successively year after year could be more easily identified from the catch-at-age data computed using ALK than by using ACT. Our results suggested not only that the mean size of commercial landings fluctuated based on changes in age composition but also that a decrease in the length-at-age in the population influenced the consistent size decrease of commercial landings. © 2014 The Japanese Society of Fisheries Science.


Funamoto T.,Hokkaido National Fisheries Research Institute | Yamamura O.,Hokkaido National Fisheries Research Institute | Shida O.,Central Fisheries Research Institute | Itaya K.,Wakkanai Fisheries Research Institute | And 3 more authors.
Fisheries Science | Year: 2014

The Japanese Pacific stock (JPS) and the northern Japan Sea stock (JSS) of walleye pollock Theragra chalcogramma are mainly distributed in the Pacific Ocean and the Sea of Japan off northern Japan, respectively. This paper summarizes and compares the factors affecting the recruitment variability of these two stocks. Spawning season is from December to March for both stocks. JPS recruitment has a positive relationship with the water temperature in January and February, whereas that of JSS has a negative relationship with the water temperature in January, February, and April. One possible reason for this is that pollock larvae have an optimum growth temperature of approximately 5 °C in the field. Drift of early life stages also appears to be an important influence on the recruitment of both stocks. Because the current generated by the northwest wind carries eggs of JPS into the main larval nursery ground, JPS recruitment is enhanced in years when the northwest wind is predominant in February. On the other hand, early life stages of JSS are transported into the nursery ground by the Tsushima Warm Current. However, this current also carries early life stages into the Sea of Okhotsk and offshore, resulting in poor JSS recruitment in years when this current is strong in March. In contrast to JPS, the recruitment of which is significantly impacted by cannibalism, young pollock have not been found in the stomachs of adult JSS. Warm temperatures in the Sea of Japan seem to induce the separation of young and adult pollock, and the shape of the stock-recruitment relationship also suggests that cannibalism is not important for JSS. Based on this knowledge, and on the hatch date distributions of larvae and juveniles, we propose mechanisms that can explain the recruitment fluctuations for JPS and JSS pollock. © 2014 The Japanese Society of Fisheries Science.


Fukamachi Y.,Hokkaido University | Ohshima K.I.,Hokkaido University | Ebuchi N.,Hokkaido University | Bando T.,Soya Fishery Cooperative Society | And 2 more authors.
Journal of Oceanography | Year: 2010

Time-series data of the vertical structure of the Soya Warm Current (SWC) were obtained by a bottom-mounted acoustic Doppler current profiler (ADCP) in the middle of the Soya Strait from September 2006 to July 2008. The site of the ADCP measurement was within the coverage of the ocean-radar measurement around the strait. The volume transport of the SWC through the strait is estimated on the basis of both the vertical structure observed by the ADCP and the horizontal structure observed by the radars for the first time. The annual transport estimates are 0.62-0.67 Sv (1 Sv = 106 m3s-1). They are somewhat smaller than the difference between the previous estimates of the inflow and outflow through other straits in the Sea of Japan, and smaller than those obtained in the region downstream of the strait during 2004-05 (0.94-1.04 Sv). The difference in the two periods may be attributed to interannual variability of the SWC and/or the different measurement locations. © 2010 Springer Science+Business Media B.V.


Saville R.,Tokyo University of Agriculture | Hatanaka K.,Tokyo University of Agriculture | Sano M.,Wakkanai Fisheries Research Institute | Wada M.,Future University Hakodate
Ocean and Coastal Management | Year: 2015

In this paper, we propose an automatic computation and data sharing scheme to support management system in coastal fishery using real-time fishery information through information and communication technology (ICT). In Japan, several species of fisheries commodity have not been specified in Total Allowable Catch policy, causing a lot of confusion on fishery cooperatives and fishermen on how to set the catch limit. To deal with the problem, in the previous study, we developed catchable stock index, a method to estimate a certain extent of resource via the swept area method. However, as the calculation of the index was computed on a GIS software manually, it was very time consuming, costly and unable to give an immediate evaluation of the fishing operation. This study aims to support management system in a coastal fishery through the development of automatic catchable stock index algorithm. In this study, ICT was utilized to obtain and transmit the real-time data sharing of fishery information as well as to distribute the computation results to the fishermen and fishery cooperative. The data used were vessels' trajectories and catch records, which included the start/end time and catch amount of each fishing operation. The catchable stock index was automatically computed in an originally developed cloud computing service. We have conducted the test run of the present method in sea cucumber dredge-net fishery on the coast of Rumoi City, Hokkaido, Japan. Data were collected from the entire vessels in Rumoi (16 vessels) during the 2012 and 2013 fishing seasons. The results were returned to the fishermen via the Internet each day during the fishing season, therefore, fishermen were able to immediately evaluate their catch. The estimated catchable stock index for the 2012 and 2013 seasons was 85.5tons and 92.3tons, respectively. By referring to the present system, fishermen voluntarily stopped the 2012 and 2013 fishing season several weeks earlier than their initial schedule to avoid overfishing. Moreover, in the previous study, the spacing of the grid has been decided empirically, but in this study, the adequate grid size could be evaluated due to the fast computation through ratio of the area of a grid cell to the total dredged area. In light of the evidence, the present automatic algorithm provided useful information for supporting the self-management of this coastal fishery. © 2015 Elsevier Ltd.


Wada T.,Fukushima Prefectural Fisheries Experimental Station | Kamiyama K.,Fukushima Prefectural Fisheries Experimental Station | Shimamura S.,Fukushima Prefectural Fisheries Experimental Station | Murakami O.,Mariculture Fisheries Research Institute | And 3 more authors.
Fisheries Science | Year: 2014

Commercial landings of a rare pleuronectid flatfish, barfin flounder Verasper moseri, recovered drastically after large-scale stock enhancement in Hokkaido conducted since 2006. This study investigated commercial landings, fishing grounds, size distributions, and sex and age compositions of barfin flounder during 2007–2011 in southern Tohoku, their major spawning ground, which is over 700 km south of Hokkaido. Landings, mostly comprising stocked fish, increased drastically in southern Tohoku: from 2.0 tons in 2007 to 20.8 tons in 2010. Over 98 % of them were landed during January–April, with the peak period during February–March. Fishing logbook data of offshore bottom-trawl vessels during 2007–2010 revealed the upper continental slope off southernmost Tohoku as the main fishing ground (35°40′–36°50′N, annual weighted mean depth 267–299 m). Two size modes in the landings consisted of males (ca. 40 cm) and females (ca. 60 cm). The main age at fishery recruitment in southern Tohoku was younger for males (age 2+) than for females (ages 3+ and 4+), the result of which was that the female percentage was lowest at 1.5 % in 2009 and highest at 7.9 % in 2011. Our results showed clearly how the effectiveness of large-scale stock enhancement in Hokkaido extended to southern Tohoku in association with spawning migration of stocked barfin flounder. © 2014, Japanese Society of Fisheries Science.


Ikeda K.,Hokkaido University | Doi H.,University of Hyogo | Tanaka K.,Hokkaido University | Kawai T.,Wakkanai Fisheries Research Institute | Negishi J.N.,Hokkaido University
Conservation Genetics Resources | Year: 2016

The freshwater crayfish, Cambaroides japonicus, is endangered in Hokkaido, Japan and inhabits burrows. Here, we applied environmental DNA (eDNA) method for evaluating the species distributions with comparing hand-capture method in the headwater streams. We detected the eDNA of C. japonicus from all sites, where we collected C. japonicus, and confirmed that eDNA can be applied to detect burrowing aquatic freshwater crayfish without disturbing their habitats. © 2016, Springer Science+Business Media Dordrecht.


Koizumi I.,Hokkaido University | Usio N.,Niigata University | Kawai T.,Wakkanai Fisheries Research Institute | Azuma N.,Tokyo University of Agriculture | Masuda R.,Hokkaido University
PLoS ONE | Year: 2012

Intra-specific genetic diversity is important not only because it influences population persistence and evolutionary potential, but also because it contains past geological, climatic and environmental information. In this paper, we show unusually clear genetic structure of the endangered Japanese crayfish that, as a sedentary species, provides many insights into lesser-known past environments in northern Japan. Over the native range, most populations consisted of unique 16S mtDNA haplotypes, resulting in significant genetic divergence (overall F ST = 0.96). Owing to the simple and clear structure, a new graphic approach unraveled a detailed evolutionary history; regional crayfish populations were comprised of two distinct lineages that had experienced contrasting demographic processes (i.e. rapid expansion vs. slow stepwise range expansion) following differential drainage topologies and past climate events. Nuclear DNA sequences also showed deep separation between the lineages. Current ocean barriers to dispersal did not significantly affect the genetic structure of the freshwater crayfish, indicating the formation of relatively recent land bridges. This study provides one of the best examples of how phylogeographic analysis can unravel a detailed evolutionary history of a species and how this history contributes to the understanding of the past environment in the region. Ongoing local extinctions of the crayfish lead not only to loss of biodiversity but also to the loss of a significant information regarding past geological and climatic events. © 2012 Koizumi et al.


Yotsukura N.,Hokkaido University | Nagai N.,Hokkaido University | Kawai T.,Wakkanai Fisheries Research Institute
Botanica Marina | Year: 2016

The taxonomy of Saccharina longipedalis, a kelp species endemic to the brackish Lake Akkeshi in eastern Hokkaido, was reviewed. The external morphology of sporophytes collected from seven sites around the distribution boundary of S. longipedalis and Saccharina japonica var. diabolica were compared; it was confirmed that the diagnostic morphology of S. longipedalis, such as a long stipe and thin blade, was not solely characteristic of individuals that grew in and around the center of the lake, which is thought to be the unique distribution area of S. longipedalis. Sequence comparisons of a 5S rDNA spacer and four microsatellite regions and AFLP analysis revealed that genetic similarity was high between S. longipedalis and S. japonica var. diabolica. Also based on observations that the early development in hybrids of sporelings from the seven sites was normal, we conclude that S. longipedalis should be treated as S. japonica var. diabolica. © 2016 by De Gruyter 2016.

Loading Wakkanai Fisheries Research Institute collaborators
Loading Wakkanai Fisheries Research Institute collaborators