Fukushima Prefectural Fisheries Experimental Station

Fukushima, Japan

Fukushima Prefectural Fisheries Experimental Station

Fukushima, Japan

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Yoshida K.,Hiroshima University | Sato T.,Fukushima Prefectural Fisheries Experimental Station | Narita K.,Fukushima Prefectural Fisheries Experimental Station | Tomiyama T.,Hiroshima University
Plankton and Benthos Research | Year: 2017

The moonsnail Laguncula pulchella (Naticidae, formerly known as Euspira fortunei) is an invasive species that has had a negative impact on the Manila clam (Ruditapes philippinarum) population in northern Japan. In southern Japan, few records of L. pulchella exist; furthermore, the knowledge concerning the ecology of this organism is currently limited. Unexpectedly, we found many L. pulchella individuals in the Misuji River estuary, located in Hiroshima in southern Japan, during May 2015. We conducted a field survey on the density and body size of L. pulchella at a tidal flat in the Misuji River estuary (Site H) and compared those to L. pulchella in Matsukawaura Lagoon, located in Fukushima in northern Japan (Site F). The adult population of L. pulchella in a clam fishing ground (40,500 m2) at Site H was estimated to be 2,048 individuals in 2015. Densities of both surfaced individuals and egg collars of L. pulchella were lower at Site H than at Site F. Sizes of L. pulchella individuals and their egg collars as well as the somatic weight of the individuals at Site H were significantly smaller than those at Site F. These results suggest that the biological characteristics of L. pulchella largely differ between the two sites. © The Japanese Association of Benthology.


Wada T.,Fukushima Prefectural Fisheries Experimental Station | Chiyokubo T.,Fukushima Prefectural Fisheries Experimental Station | Aritaki M.,Seikai National Fisheries Research Institute
Fisheries Science | Year: 2010

Morphological characteristics and body pigmentations of juvenile slime flounder Microstomus achne were described from one specimen [27.8 mm total length (TL)] collected off Niigata Prefecture from the Sea of Japan (35 m depth) in May 1993 and from three specimens (30.1, 36.2, and 40.9 mm TL) collected off Fukushima Prefecture on the Pacific coast of northern Japan (15 and 50 m depths) during April-May 2008 and 2009. These age-0 juveniles had a characteristically slenderly oval-shaped body and slightly protruded front nostrils. Sparsely distributed melanophores and xanthophores were clearly visible throughout the ocular side of one specimen, which was judged as a newly settled juvenile, whereas several spots aggregated by small melanophores were found in the others with elongated pectoral fins and small cycloid scales. Melanophores were only slightly detectable on the blind side. Comparisons of the depth distributions of slime flounder juveniles and sympatrically collected age-0 pleuronectids (Pseudopleuronectes herzensteini, Pseudopleuronectes yokohamae, Platichthys bicoloratus, and Dexistes rikuzenius) suggested that slime flounder can settle on broad nursery areas of coastal and offshore pleuronectid flatfishes, probably depending on local oceanic conditions during the protracted pelagic phase. © 2010 The Japanese Society of Fisheries Science.


Thornton B.,University of Tokyo | Ohnishi S.,Japan National Maritime Research Institute | Ura T.,University of Tokyo | Odano N.,Japan National Maritime Research Institute | Fujita T.,Fukushima Prefectural Fisheries Experimental Station
Deep-Sea Research Part I: Oceanographic Research Papers | Year: 2013

Instrumentation and data processing methods to continuously map the distribution of radionuclides on the seafloor have been developed and applied to survey radioactive discharge from the Fukushima Dai-ichi Nuclear Power Plant following the M9.0 earthquake and tsunami that struck the east coast of Japan on March 11 2011. The instrument consists of a flexible rubber hose with an integrated gamma ray spectrometer that measures the full gamma spectrum between 0.1 and 1.8MeV while being towed along the seafloor by a ship. The data processing methods described allow for quantification of 137Cs and 134Cs concentration in marine sediments, and a technique has been developed to optimize the spatial resolution of the measurements for each radioactive species for a given level of statistical uncertainty. The system was deployed during August and November 2012 to measure the distribution of radionuclides along three transects within an 80km radius of the plant. Increased levels of 137Cs and 134Cs were recorded and their distributions mapped continuously over distances of 1.6, 12.5 and 22km respectively. The levels of 137Cs and 134Cs were found to vary significantly with location. The in situ measurements show good agreement with laboratory analyzed samples obtained during the surveys. The results demonstrate that the instrument and data processing techniques described enable high resolution, quantitative measurements of 137Cs and 134Cs in marine sediments, and provide an effective solution for rapid, low cost monitoring of radioactive material on the seafloor. © 2013 Elsevier Ltd.


Tomiyama T.,Fukushima Prefectural Fisheries Experimental Station | Tomiyama T.,Hiroshima University | Uehara S.,Tohoku National Fisheries Research Institute | Uehara S.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Kurita Y.,Tohoku National Fisheries Research Institute
Marine Ecology Progress Series | Year: 2013

Juvenile Japanese flounder Paralichthys olivaceus inhabit shallow sandy areas and consume chiefly mysids. Hatchery-reared P. olivaceus (ca. 100 mm in total length) released in stock enhancement programs also consume mysids. To examine whether stocking is implemented within the available carrying capacity, we assessed the feeding relationships among fishes, based on the stomach contents of fishes collected off the coast of Fukushima, Japan. Similarity in diet suggested that 10 species, particularly the poacher Occella iburia and nibe croaker Nibea mitsukurii were potential competitors of P. olivaceus juveniles for food. Large inter-annual variability in the abundance of these competitors was observed, suggesting variability in their consumption of mysids. The predominant mysid Orientomysis mitsukurii was abundant every year, and growth rates of wild P. olivaceus, estimated from otolith microstructure, were mostly high (>1 mm d-1), even in the year when wild P. olivaceus were highly abundant. In our statistical model, abundance of mysids and consumption of mysids by fishes significantly affected the growth rates of wild P. olivaceus but only accounted for a small proportion (i.e. explained 2.2 and 2.4% of variance, respectively) of the total compared to the body size of juveniles (30.0%) and bottom water temperature (4.5%). These results suggest that the productivity of mysids is usually high enough to support the production of mysid consumers, but exceptionally high abundances of wild P. oliva ceus or other competitors can reduce the available carrying capacity. In such a situation, stocking should be restricted so as not to reduce productivity of wild fishes. © Inter-Research 2013.


Tomiyama T.,Fukushima Prefectural Fisheries Experimental Station | Kurita Y.,Tohoku National Fisheries Research Institute
Aquatic Biology | Year: 2011

We investigated the diet and somatic condition of 5129 individual Japanese flounder Paralichthys olivaceus, 20 to 92 cm in total length, in the Joban area along the Pacific coast of Japan (36° 40' N to 38° 00' N) from 2001 to 2007. Japanese flounder with food in their stomachs (1668 individuals) consumed chiefly fishes (92% of stomach contents by weight). Predominant prey species were Japanese anchovy Engraulis japonica (54% of fishes by weight) and Japanese sandlance Ammodytes personatus (22%). Japanese anchovy were consumed by Japanese flounder year round except in March and April, when the anchovy migrate from the Joban area. In March and April, Japanese flounder frequently consumed Japanese sandlance, but only in the northern part of the Joban area (37° 20' N to 38° 00' N); Japanese flounder did not feed on this species and had less content in their stomachs in the southern area (36° 40' N to 37° 20' N), where the sandlance is absent. Somatic and hepatosomatic conditions of Japanese flounder in the northern area were better than those in the southern area in March and April, suggesting that such spatial and seasonal heterogeneities in prey availability affect the nutritional status of predators © Inter-Research 2011.


Wada T.,Fukushima Prefectural Fisheries Experimental Station | Nemoto Y.,Fukushima Prefectural Fisheries Experimental Station | Shimamura S.,Fukushima Prefectural Fisheries Experimental Station | Fujita T.,Fukushima Prefectural Fisheries Experimental Station | And 5 more authors.
Journal of Environmental Radioactivity | Year: 2013

After the release of huge amounts of radionuclides into the ocean from the devastated Fukushima Dai-ichi Nuclear Power Plant (FDNPP), safety concerns have arisen for marine products in Fukushima Prefecture. As of October 2012, we had inspected the radionuclide (131I, 134Cs and 137Cs) concentrations in 6462 specimens within 169 marine species collected off the coast of Fukushima Prefecture from April 2011. Only two species exceeded the Japanese provisional regulatory limit for 131I (2000Bq/kg-wet) immediately after the FDNPP accident. In 2011 and 2012, 63 and 41 species respectively exceeded the Japanese regulatory limit for radioactive Cs (100Bq/kg-wet). The overall radioactive Cs concentrations of the total marine products have decreased significantly. However, the time-series trends of radioactive Cs concentrations have differed greatly among taxa, habitats (pelagic/demersal), and spatial distributions. Higher concentrations were observed in shallower waters south of the FDNPP. Radioactive Cs concentrations decreased quickly or were below detection limits in pelagic fishes and some invertebrates, and decreased constantly in seaweed, surf clams, and other organisms. However, in some coastal demersal fishes, the declining trend was much more gradual, and concentrations above the regulatory limit have been detected frequently, indicating continued uptake of radioactive Cs through the benthic food web. The main continuing source of radioactive Cs to the benthic food web is expected to be the radioactive Cs-containing detritus in sediment. Trial fishing operations for several selected species without radioactive Cs contamination were commenced in Soma area, 50km north of the FDNPP, from June 2012. Long-term and careful monitoring of marine products in the waters off Fukushima Prefecture, especially around the FDNPP, is necessary to restart the coastal fishery reliably and to prevent harmful rumors in the future. © 2013 Elsevier Ltd.


Tomiyama T.,Fukushima Prefectural Fisheries Experimental Station | Watanabe M.,Fukushima Prefectural Fisheries Experimental Station | Kawata G.,Fukushima Prefectural Fisheries Experimental Station | Ebe K.,Fukushima Prefectural Fisheries Experimental Station
Journal of Fish Biology | Year: 2011

The feeding and growth of hatchery-reared (HR) Japanese flounder Paralichthys olivaceus of c. 100 mm total length (LT) released off the coast of Fukushima, Japan, were investigated. From 2 to 15 days after release, the HR P. olivaceus frequently exhibited high empty-stomach frequency (>40%), low stomach-content mass (<1% of body mass), reduced somatic condition from release (c.-10%) and negligible growth. Thereafter, empty-stomach frequency decreased, the stomach-content mass of HR fish increased to 2-8% of body mass, the somatic condition recovered and growth rate increased to 0·5-1·5 mm day-1. Prey items were initially mysids, shifting thereafter to fishes such as the Japanese anchovy Engraulis japonica, as observed similarly in wild counterparts. The proportion of mysids decreased with time after release irrespective of size at release, indicating the importance of mysids for adaptation to natural food. Recapture rates at age 1 year, derived from fish market surveys, varied greatly among release years (4-11%). The variation in the recapture rates was largely accounted for by the post-release growth rates (r2 = 0·5), suggesting a relationship between the post-release growth of HR fish and their survival and subsequent stocking effectiveness. © 2011 The Authors. Journal of Fish Biology © 2011 The Fisheries Society of the British Isles.


Freeman M.A.,University of Malaya | Yokoyama H.,University of Tokyo | Osada A.,Fukushima Prefectural Fisheries Experimental Station | Yoshida T.,Fukushima Prefectural Fisheries Experimental Station | And 2 more authors.
Journal of Fish Diseases | Year: 2011

Anglerfish from the genus Lophius are a globally important commercial fishery. The microsporidian Spraguea infects the nervous system of these fish resulting in the formation of large, visible parasitic xenomas. Lophius litulon from Japan were investigated to evaluate the intensity and distribution of Spraguea xenomas throughout the nervous system and to assess pathogenicity to the host and possible transmission routes of the parasite. Spraguea infections in L. litulon had a high prevalence; all fish over 403mm in standard length being infected, with larger fish usually more heavily infected than smaller fish. Seventy percent of all fish examined had some gross visible sign of infection. The initial site of development is the supramedullary cells on the dorsal surface of the medulla oblongata, where all infected fish have parasitic xenomas. As the disease progresses, a number of secondary sites typically become infected such as the spinal, trigeminal and vagus nerves. Fish with infection in the vagus nerve bundles often have simultaneous sites of infection, in particular the spinal nerves and along the ventral nerve towards the urinary bladder. Advanced vagus nerve infections sometimes form xenomas adjacent to kidney tissue. Spraguea DNA was amplified from the contents of the urinary bladders of two fish, suggesting that microsporidian spores may be excreted in the urine. We conclude that supramedullary cells on the hindbrain are the primary site of infection, which is probably initiated at the cutaneous mucous glands where supramedullary cells are known to extend their peripheral axons. The prevalence of Spraguea infections in L. litulon was very high, and infections often extremely heavy; however, no associated pathogenicity was observed, and heavily infected fish were otherwise normal. © 2011 Blackwell Publishing Ltd.


Variation of scales on the blind side of Pseudopleuronectes yokohamae in relation to sex, maturity and body size was examined. Immature males often have cycloid scales, while mature males have mostly ctenoid scales. Large females also often have ctenoid scales (but with fewer spines compared with males), and small females have mostly cycloid scales. The number of spines (ctenii) on the blind-side scale increases with body size in both sexes, indicating an ontogenetic change in scale morphology. As P. yokohamae spawn demersal eggs with males positioning themselves above the females on the ocular side, it is hypothesized that ctenoid scales on the blind side in mature males function for maintaining contact with females during spawning. © 2013 The Fisheries Society of the British Isles.


Wada T.,Fukushima Prefectural Fisheries Experimental Station | Kamiyama K.,Fukushima Prefectural Fisheries Experimental Station | Shimamura S.,Fukushima Prefectural Fisheries Experimental Station | Mizuno T.,Fukushima Prefectural Fisheries Experimental Station | Nemoto Y.,Fukushima Prefectural Fisheries Experimental Station
Aquaculture | Year: 2012

The effectiveness of stock enhancement trials of a rare flatfish Verasper variegatus was evaluated through assessment of fishery statistics, geographical distributions of catches, and intensive market surveys in Fukushima Prefecture, Japan. In all, 426,704 cultured individuals within 23 age-0 cohorts and 4 older cohorts (7.5-10.8. cm and 20.0-51.0. cm total length, respectively) were released at six coastal sites off Fukushima between 1993 and 2007. Commercial landings before the release trials decreased from 5.3. metric tons (MT) in 1987 to 1.0. MT in 1993. After the release trials, commercial landings increased rapidly to 2.7. ±. 0.6. MT during 1996-2010 (maximum of 3.8. MT in 2008). Fish of 25-70. cm total length (mainly 1-3. years old) were caught equally by gillnet and trawl fisheries at different depth ranges (mainly <. 50. m and 100-150. m), corresponding respectively to those of feeding and spawning grounds. The numerical contribution of released fish increased rapidly, exceeding 70% during the mid-2000s; up to 91% in 2004. Multiple regression analysis revealed two factors (number released and release date from first January) that significantly and negatively affected the recapture rates of age-0 cohorts (0-24.8%, mean 6.0%). Our results demonstrate that local stocks of a rare species can be augmented through the release of cultured juveniles. In addition, the strong direct impacts of hatchery releases (rapid increase of landings and contribution rate) suggest that stocking effectiveness of a rare species were less influenced by the fluctuating natural populations than common species are. Results also suggest that the long-term and comprehensive assessments of release trials from release, to fishery catches, and to market landings are necessary to detect potential factors affecting recapture rates and to clarify the ecological characteristics of a rare species. The release strategy can be refined based on the feedback process of these results. © 2012 Elsevier B.V.

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