Japan Fisheries Research and Education Agency (FRA) Repository
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Application of the Shimonoseki local traditional vegetable ‘Hikoshima-haruna’ powder to fish paste products
Full text link‘Hikoshima-haruna’ (Brassica rapa var. narinosa) is a local traditional vegetable in Shimonoseki (Yamaguchi, Japan). The mature leaves are edible and much of the harvest is processed into pickles for consumption in the Shimonoseki area. To expand the consumption of ‘Hikoshima-haruna’, we verified the use of ‘Hikoshima-haruna’ powder in fish paste products as a part of the utilization research. We prepared heated gels (Kamaboko) mixed with 0-10% ‘Hikoshima-haruna’ powder and measured their breaking strength. The Kamaboko containing 1.0-4.0% powder exhibited a bright green color, preserving the characteristics of ‘Hikoshima-haruna’ as a plant with bright green leaves. Although the breaking strength of the two-step heating (30℃ for 30 min followed by 85℃ for 20 min) gels tended to decrease with increasing powder concentration, the 1.0% powder concentration exhibited a slightly greater breaking strength than the other concentrations. Therefore, when applying ‘Hikoshima-haruna’ powder to fish paste products, its use as Kamaboko at a powder concentration of 1.0% was considered appropriate.編集：水産大学校departmental bulletin pape
Methods for monitoring abalone Young-of-the-Year in the Japan Sea: Habitat utilization and depth distribution of Haliotis species
No full textThe four abalone species Haliotis discus discus, H. madaka, H. gigantea, and H. diversicolor are important fisheries resources in Japan. However, the stock abundance of these species has declined. Fluctuations in abalone young-of-the-year (YOY) stocks may significantly influence adult stock abundance. Monitoring methods for YOY are proposed which clarify habitat shifts associated with growth, particularly in H. discus discus and H. diversicolor. While only partial trends could be inferred for H. madaka and H. gigantea. For all four species, YOY were frequently observed in gaps between rocks or beneath sea urchins in these gaps. In H. discus discus and H. diversicolor, a habitat shift was observed with growth, transitioning from cryptic habitats (e.g., rock gaps and areas under sea urchins) to more exposed habitats. The depths at which YOY were found varied each year. However, H. discus discus and H. diversicolor were found in shallower waters than H. madaka and H. gigantea; the former two species appeared to migrate from deeper to shallower areas as they grew. These findings provide essential insights for improving abalone YOY survey methods. Additionally, it was recognized that, since catch-per-unit-effort trends varied among the four species, precise YOY species identification is crucial for effective monitoring.journal articl
Spatial distribution, microhabitat association, dependence to live corals, and habitat partitioning among five grouper species (family Epinephelidae) in an Okinawan coral reef
Full text linkSpecies-specific spatial distribution in relation to diverse environmental characteristics regulates the species diversity and coexistence of coral reef fishes. This study aims to clarify: (1) broad-scale spatial variation in fish density, (2) microhabitat-scale substrate association, (3) degree of dependence to live corals, (4) habitat partitioning, and (5) fish size variations (smaller size vs. larger size) in these four ecological aspects of five grouper species (Epinephelus ongus, E. fasciatus, Cephalopholis miniata, C. urodeta, and, C. argus). Three species (E. ongus, E. fasciatus and, C. miniata) and two species (C. urodeta and C. argus) showed significantly greater densities in inner reefs and exposed reefs, respectively. Smaller-sized and larger-sized individuals of E. ongus showed significantly positive associations with bottlebrush Acropora and staghorn Acropora, respectively. For E. fasciatus, smaller-sized individuals showed a significantly positive association with bottlebrush Acropora, whereas larger-sized individuals showed no significant association with any substrates. For C. miniata, smaller-sized individuals showed no significant association with any substrates, whereas larger-sized individuals showed a significantly positive association with rock. Smaller-sized and larger-sized individuals of C. urodeta and C. argus showed a significantly positive association with rock. The degree of dependence on live corals varied among the five species and between the two size classes. Inter-specific habitat partitioning was found among the five species in broad and/or microhabitat scales, whereas two size classes of E. ongus and E. fasciatus overlapped in intra-specific habitat use at both broad and microhabitat scales. These ecological aspects should be considered for the effective management of grouper assemblages.journal articl
Importance of input image size on the performance of automatic age determination of chum salmon Oncorhynchus keta using deep learning
Full text linkManual determination of fish age using hard tissues demands considerable effort. However, reliable and high-performance automatic alternative methods are not widely available. The aim of this study was to investigate the influence of input image size on the performance and the image areas used for automatic age determination. To this end, we used input images with sizes of 240 × 240–960 × 960 or 170 × 340–679 × 1358 pixels, either whole or trimmed in half, of 3- to 5-year-old chum salmon scales (n = 1835), as well as deep convolutional neural networks (CNN). In entire-scale images, high accuracy was achieved when the input image size exceeded 679 × 679 pixels, reaching a maximum of 94.7%. Below this size, accuracy decreased significantly, and overfitting became pronounced. At sizes exceeding 480 × 480 pixels, the CNN consistently based its determinations on areas outside the first annulus, similar to visual inspection. Conversely, at sizes below 480 × 480 pixels, where the circuli become indistinguishable, the CNN focused on a wide range around the focus. In trimmed-scale images, CNN accuracy plateaued at a lower level (80.8–88.7%) than in entire-scale images, even for large-sized images. These results suggest that using sufficiently large entire-scale images which retain detailed information about the circulus pattern is important for achieving high performance of frameworks for automatic age determination.journal articl
Variations in sea surface water temperature and nutrient concentrations in Ono Seto, Hiroshima Bay -trends from 2012 to 2023
Full text linkLong-term changes in sea surface water temperature (SST) and nutrient concentration were investigated in Ono Seto, Hiroshima Bay. SST increased by approximately 0.8°C over a 10-year period of observation from 2013 to 2022. Nutrient concentrations fluctuated widely during the survey period, with silicic acid, nitrate, and nirite tending to decrease, and phosphate and ammonium tending to increase. In addition, the fluctuations in silicic acid, nitrate, and nirite concentrations, which showed a decreasing trend, were strongly influenced by the flooding of Ota River.広島湾大野瀬戸の観測定点において，表面水温と栄養塩濃度の長期変動を調査した。観測期間中，2013～2022年の10年間で表層水温は約0.8°Cの上昇であった。調査期間中の栄養塩濃度は大きな変動幅を示し，ケイ酸塩，硝酸塩および亜硝酸塩は減少傾向，リン酸塩とアンモニウム塩は増加する傾向であった。また，減少傾向を示したケイ酸塩，硝酸塩および亜硝酸塩濃度の変動は，太田川の出水の影響を強く受けていた。ファイル名末尾に”_abs_j”のファイルは和文要旨journal articl
Giant viruses specific to deep oceans show persistent presence and activity
Full text linkGiant viruses (GVs) of the phyla Nucleocytoviricota and Mirusviricota are large double-stranded DNA viruses that infect diverse eukaryotic hosts and impact biogeochemical cycles. Their diversity and ecological roles have been well studied in the photic layer of the ocean, but less is known about their activity, population dynamics, and adaptive strategies in the aphotic layers. Here, we conducted eight seasonal time-series samplings of the surface and mesopelagic layers at a coastal site in Muroto, Japan, and integrated 18S metabarcoding, metagenomic, and metatranscriptomic data to investigate mesopelagic GVs and their potential hosts. The analysis identified 48 GV genomes including six that were exclusively detected in the mesopelagic layer. Notably, these mesopelagic-specific GVs showed persistent activity across seasons. To further investigate the distribution and phylogenomic features of GVs at a global scale across broader depths, we compiled 4,473 species-level GV genomes from the OceanDNA MAG project and other resources and analyzed 1,890 marine metagenomes. This revealed 101 deep-sea-specific GVs, distributed across the GV phylogenetic tree, indicating that adaptation to deep-sea environments has occurred in multiple lineages. One clade enriched with deep-sea-specific GVs included a GV genome identified in our Muroto data, which displayed a wide geographic distribution. Seventy-six KEGG orthologs and 74 Pfam domains were specifically enriched in deep-sea-specific GVs, encompassing functions related to the ubiquitin system, energy metabolism, and nitrogen acquisition. These findings support the scenario that distinct GV lineages have adapted to hosts in aphotic marine environments by altering their gene repertoire to thrive in this unique habitat.Open Peer Reviewjournal articl
Behavioral responses to sound in smallmouth bass, brown trout, and channel catfish.
Full text linkA aquarium experiment was conducted to examine the responses of smallmouth bass, brown trout and channel catfish to pure tones at frequencies (sound pressure: dB re 1μPa) of 30 Hz (> 120.1), 150 Hz (> 148.4), 300 Hz (> 141.2), 600 Hz (> 133.7), and 900Hz (> 97.1). Smallmouth bass did not exhibit any avoidance behavior to 150 Hz, which is considered highly sensitive, or to any other pure tone. Brown trout exhibited a moderate reactive response to pure tones of 150 Hz and 300 Hz, which were in the audible range; however, it did not exhibit any avoidance behavior toward any other pure tone. Channel catfish did not exhibit any avoidance behavior such as 600 Hz or 900 Hz, which are considered highly sensitive.研究ではコクチバス，ブラウントラウト，チャネルキャットフィッシュを対象に水槽実験を行い，周波数（音圧：dB re 1μPa）が30Hz（>120.1），150Hz（>148.4），300Hz（>141.2），600Hz（>133.7），900Hz（>97.1）の純音に対する反応行動を調べた。コクチバスは感度が高いと考えられる150Hzや，その他の純音に対して忌避行動を示さなかった。ブラウントラウトは可聴域である150と300Hzの純音に対して緩やかな反応行動を示したが，その他の純音に対して忌避行動を示さなかった。チャネルキャットフィッシュは感度が高いと考えられる600と900Hzや，その他の純音に対して忌避行動を示さなかった。journal articl