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Estimation of hemolymph CO2 solubility coefficient for acid-base balance in Pinctada fucata martensii Crassostrea gigas and Mimachlamys nobilis
No full textThe influence of temperature on the hemolymph CO2 solubility coefficient (αco2 , µM/L/torr) was investigated in the marine bivalves, akoya pearl oyster Pinctada fucata martensii, Pacific oyster Crassostrea gigas and noble scallop Mimachlamys nobilis. Hemolymph samples were equilibrated with standard CO2 gas mixtures to obtain expressions for αco2 as a function of temperature. Relationships between hemolymph αco2 and temperature (T) were expressed as follows: αco2 = 76.88145 − 2.62637 ･ T + 0.036203 · T2 (for P. fucata martensii), αco2 = 94.2109 – 3.6252 · T + 0.0554 · T2 (for C. gigas), αco2 = 70.4591 – 1.5253 · T + 0.0103 · T2 (for M. nobilis). In the distribution of hemolymph αco2 values, there was no statistical significance across an interspecies comparison of αco2 . From this result, the regression was fitted using all values of αco2 and temperature across the species, and the relationship was expressed as follows: αco2 = 182.3717 – 24.3932 · T + 1.6396 · T2 – 0.0492 · T3 + 0.000536 · T4. This polynomial is versatile equation and would yield the hemolymph αco2 at arbitrary temperature, even with different species.アコヤガイPinctada fucata martensii, マガキ Crassostrea gigas，ヒオウギ Mimachlamys nobilis から採取したヘモリンパ液を用いて二酸化炭素溶解度係数 (αco2，µM/L/torr) に及ぼす温度 (T，°C) の影響について調べ，αco2 とT の関係を明らかにした。アコヤガイで得た関係式は，αco2 = 76.88145 − 2.62637 · T + 0.036203 · T2 であった。同様にマガキとヒオウギはαco2 = 94.2109 – 3.6252 · T + 0.0554 · T2 (マガキ)，αco2 = 70.4591 – 1.5253 · T + 0.0103 · T2 (ヒオウギ) だった。これら３種のαco2 の分布を比較すると統計的有意差は認められなかったことから，３種のαco2 と温度の全ての結果に対して多項式回帰を適用し，以下の関係式を得た。αco2 = 182.3717 – 24.3932 · T + 1.6396 · T2 – 0.0492 · T3 + 0.000536 · T4。この式により，種が異なっても，任意の温度で海産二枚貝のαco2 を容易に得られ，酸塩基平衡，二酸化炭素動態および呼吸生理の評価に有効と考えられる。編集：水産大学校departmental bulletin pape
The significance of direct sales utilizing multiple sales channels for f ishing households: A case study of Tabuse Fisheries Improvement Group “Shinsen Tabuse”
No full textThere are various types of farmers' markets; depending on the type used, the markets have both advantages and disadvantages for fishing households. In reality, fishing households utilize multiple farmers’ markets as sales channels because utilizing multiple markets offers advantages for fishing households. However, previous research on direct sales using multiple different types of farmers' markets are limited. Taking the Tabuse Fisheries Improvement Group “Shinsen Tabuse” as a case and confirming the benefits and drawbacks of direct sales using multiple farmers’ markets as sales channels, we examined the significance of direct sales using multiple sales channels. The results revealed that there were both advantages and disadvantages for fishing households, depending on the characteristics of the farmers' markets that fishing households utilized. We also found that utilizing multiple sales channels in direct sales helped avoid the accumulation of product stock, and fishing households acquired more customers.直売所には様々なタイプがあり，利用する直売所のタイプによっては，漁家にとって利点だけでなく欠点も存在すると考えられる。ただし，実際，販売チャネルとして複数の直売所が利用されている現状からすると，複数の販売チャネルの利用にはそれなりの意義があると考えられる。しかし，タイプの異なる複数の直売所を利用した直売に関する先行研究は，限られたものしかない。本論文は田布施漁業改善グループ「新鮮田布施」を事例として，販売チャネルとして複数の直売所を利用した直売に関して利点と欠点を確認したうえで，複数の販売チャネルを利用した直売の意義について検討した。その結果，利用する直売所の特性に応じて，漁家にとって利点と欠点があることが明らかになった。また，直売において複数の販売チャネルを利用することで，当初懸念された商品在庫の蓄積を回避し，より多くの顧客を獲得することができていることが明らかになった。編集：水産大学校departmental bulletin pape
Age and growth estimated by Bayesian methods for largescale blackfish Girella punctata in the southwestern Sea of Japan
No full textThis study presents a comprehensive re-evaluation of growth patterns in largescale blackfish (Girella punctata) using otolith cross-sections and compares conventional and Bayesian analytical approaches. Previous growth studies relied on scale-based age determination, which underestimates maximum age and shows poor model fitting for older individuals. We analyzed 425 specimens collected between 2021 and 2022 from the southwestern Sea of Japan. Using otolith cross-sections, we documented individuals up to 23 years old—nearly three times the maximum age reported in previous scale-based studies. Age determination confirmed annual ring formation in May through marginal increment analysis. We implemented von Bertalanffy and Richards growth models using JAGS, and conducted back-calculation analyses using Bayesian hierarchical methods. The Richards model provided better fit than the von Bertalanffy model, estimating higher L∞ values, though both conventional approaches demonstrated poor fitting for individuals exceeding 400 mm FL. Back-calculation analyses revealed that excluding younger age classes improved growth estimates, with significant changes observed when restricting data to ages ≥ 5 for females and ≥ 3 for males, suggesting timing-specific shifts in energy allocation between somatic growth and reproduction. Size-selective mortality and fishing-induced selection likely bias our understanding of "natural" growth patterns, as faster-growing individuals showed differential survival. A methodological concern is that linear otolith measurements may underestimate growth in older specimens due to curvilinear growth trajectories. While the Bayesian hierarchical approach provided insights into individual growth variation and encompassed larger individuals, results primarily reflect faster-growing survivors rather than average population growth. Our findings demonstrate the importance of combining improved age determination methods with appropriate statistical approaches, while highlighting the need for targeted sampling of larger individuals and consideration of gear selectivity for robust stock assessment of this commercially important species.Complimentary accessjournal articl
An attempt at the outdoor mass-cultivation of a marine euglenophyte Eutreptiella eupharyngea during winter
No full textTo ensure the stable supply of the euglenophyte Eutreptiella eupharyngea in the seed production of bivalves during the winter, we evaluated the growth potential of E. eupharyngea under low water temperatures through laboratory and outdoor experiments. In laboratory experiments, no significant difference was found in the maximum yield of E. eupharyngea between water temperatures of 10 and 20°C, whereas the maximum yield of the diatom Chaetoceros neogracile known as a common diet alga for the seed production of bivalves significantly decreased at 10℃ compared with 20℃. In an outdoor experiment on a 150-L scale at a salinity of 25, furthermore, E. eupharyngea grew well in mid-winter, and reached the maximum cell density of 3.7 × 105 cells mL–1. During the outdoor experiment, water temperatures ranged from 0.5 to 23.7℃, with a mean of 10.7℃. Although the water temperature in the mass-culture tank fluctuated significantly with the weather and day or night, E. eupharyngea maintained more than 2.2×105 cells mL-1 for 12 days. Therefore, E. eupharyngea may contribute to the stable supply of the feed throughout seed production of bivalves in late fall and spring.冬季の二枚貝類種苗生産における新規餌料候補種である海産ミドリムシ類 Eutreptiella eupharyngea の安定供給体制の構築を目的として，冬季の屋外において，十分な日射量を確保可能な水槽を用いた150 L 規模の E. eupharyngea の大量培養実証試験を試みた。また，屋外大量培養時の最大到達密度の到達目標の参考値を得るために，低水温環境下における2 L 規模での室内培養試験を実施した。2 L 規模での室内培養試験では，既報の50 mL 規模の培養実験結果と同様に，10℃区におけるC. neogracile の最大到達密度が20℃区の48%程度にまで顕著に低下した。これに対して，10℃区における E. eupharyngea の最大到達密度 (3.6 × 105 cells mL-1) は20℃区の73%程度であったものの，両試験区の最大到達密度に有意差は認められなかった。さらに，塩分25 に調整した培地を用いて実施した150 L 規模の屋外大量培養試験において，E. eupharyngea の最大細胞密度は2 L 規模での室内培養と同等の3.7 × 105 cells mL-1 に到達した。また，屋外大量培養試験期間中の水温は，気温の変化に同調して0.5-23.7℃の範囲で変動し，平均水温は10.7℃であった。このように，大量培養水槽内の水温は天候や昼夜によって大きく変動したにもかかわらず，E. eupharyngea は2.2 × 105 cells mL-1 以上の細胞密度を12 日間維持した。したがって，E. eupharyngea は晩秋から翌年の早春期に行われるアサリなどの二枚貝類種苗生産における餌料の安定供給に寄与する可能性がある。編集：水産大学校departmental bulletin pape
Effects of input-image size on performance of fish detection and species classification using deep learning
Full text linkDeep learning has been extensively used in fisheries science, as it enables the acquisition of information regarding the body length and stock-abundance index of target fish from images, thereby facilitating stock assessment and management. However, generally, multiple species appear together in images obtained from fisheries, necessitating the classification of fish species before extracting relevant biological information.
Improving the performance of fish detection and species classification is crucial as it affects the quality of biological information that could be inferred from images. Previous studies have reported that increasing the inputimage size can affect the classification accuracy. Identification characteristics of fish are small in comparison with their body size, and increasing the image size can affect the classification accuracy; however, there are no reports on the effect of image size on fish species-classification accuracy. Herein, different input-image sizes were taken to evaluate the effect of input-image size on the performance of fish detection and species classification.
Fish images (41,922 fish across 41 classes) were acquired from conveyor belts to sort set-net fish catches. Fish were detected and classified using a mask region-based convolutional neural network. The effect of input-image size on performance was examined using nine datasets in three image sizes of 1333 × 888, 2000 × 1333, and 2666 × 1777 pixels, obtaining an average mAP50–95 value of 0.586, 0.612, and 0.609, respectively. Larger image sizes offered improved performance compared with that of the smallest, averaging 0.026 and 0.023 improvements in mAP50–95 at two larger image sizes. However, when comparing the degree of improvement between image sizes of 2000 × 1333 pixels and 2666 × 1777 pixels under fine-tuning conditions, the former size resulted in higher performance. Performance was observed to improve for species with low performance at the smallest image size; therefore, we can say that increasing the input-image size is a simple and effective way for improving detection and classification performance for these species.journal articl
Broad-scale spatial distribution, microhabitat association and habitat partitioning of damselfishes (family Pomacentridae) on an Okinawan coral reef
No full textSpatial distribution of coral reef fishes is related to diverse environmental variables. This study aimed to elucidate the (1) broad-scale spatial distribution, (2) microhabitat-scale substrate association, (3) degree of dependence on live corals and (4) habitat partitioning of 26 damselfish species on an Okinawan coral reef. Broad-scale analysis revealed that fish assemblages could be divided into three groups in relation to the degree of wave exposure, and the coverage of live corals as well as non-coralline substrates: (1) 11 species that were found in exposed reefs with greater coverage of rock; (2) nine species that that were found in inner reefs with greater coverage of live corals, dead corals and macroalgae; and (3) six species that were found in inner reefs with a greater coverage of sand. Microhabitat-scale analysis revealed that fish assemblages could be divided into six groups in relation to diverse microhabitat availability: (1) 12 species showed significant positive associations with rock; (2) two species showed significant positive associations with coral rubble; (3) two species showed significant positive associations with corymbose Acropora, Pocillopora and branching corals; (4) three species showed significant positive associations with branching Acropora; (5) three species showed significant positive associations with branching Acropora, branching Isopora and branching Porites; and (6) two species showed significant positive associations with staghorn Acropora and branching Millepora. The microhabitat-scale analysis also revealed that Pomacentrus amboinensis showed a significant positive association with branching Millepora, whereas Neopomacentrus anabatoides showed significant positive associations with branching Porites, foliose coral and dead branching Porites. Among the 26 species, nine species were categorized as obligate coral dwellers (>80% of the individuals were associated with live corals), and three species showed a greater degree of dependence on acroporid corals (>60% individuals were associated with acroporid coral). Niche overlap analysis revealed that 14 species showed relatively greater habitat partitioning with other species, whereas the remaining 12 species showed greater habitat overlaps among some species. These results suggest that broad-scale and microhabitat-scale habitat partitioning is one of the factors supporting coexistence in at least 14 species among the 26 species, and the effects of habitat diversity on the species coexistence of damselfishes should be incorporated to establish effective marine protected areas to preserve damselfish species diversity.journal articl
Staining principle in the mixtures of acidic and basic dyes
Full text linkPreviously, we speculated on the staining principle of triacid staining solution (neutral mixture) containing a dye complex. The principle could be explained solely by the relationship between the stained object and the dye complex. We propose here to extend the staining principles of triacid stain to explain the staining principles of other dye mixtures such as May-Grünwald (MG), Giemsa and MG-Giemsa. In a mixture of acidic and basic dyes, the staining characteristics of the object were presumably determined by the degree of stainability (degree of acidophilicity or basophilicity) of the object, the degree of stainability of both dyes (degree of basophilicity of the acidic dye and degree of acidophilicity of the basic dye), and the ratio and concentration of each dye編集：水産大学校departmental bulletin pape
Development and evaluation of statistical methods for fisheries resource analysis and their implementation in management practices
No full textFisheries stock assessment is a collaborative effort requiring expertise from multiple disciplines, such as modeling, statistics, fish biology, oceanography, and fisheries. No single researcher can conduct a comprehensive assessment alone; it is achieved through teamwork. In this context, I consider my award a recognition of the collective efforts of all the researchers and collaborators with whom I have worked over the years. My research journey in fisheries science has covered several key areas. One of my earliest major contributions was the introduction of Stock Synthesis (SS) for Pacific bluefin tuna assessments. This required methodological adjustments, international cooperation, and computational tool development to support implementation. Subsequently, I worked on Maximum Sustainable Yield (MSY) -based stock assessment, responding to the global emphasis on sustainable fisheries and the revision of Japanese fisheries policy since 2017. Our team developed standardized MSY estimation methods for Japanese fisheries stock, aligning assessments with international standards and contributing to global stock databases. More recently, I have focused on production models, which do not require age-structured data, for application to Japanese data-limited stocks. Our team has established standard guidelines and procedures for management strategy evaluation. Throughout my career, the most valuable experience has been the long discussions with supervisors and colleagues to solve the challenging tasks at hand. These debates, often across different disciplines, have deepened my understanding and shaped my research approach. Open and in-depth discussion with diverse people is key to addressing the challenges of fisheries resource assessment and its management practices. The Japanese Society of Fisheries Oceanography provides an ideal platform for fostering such discussions, and I would like to contribute to its continued fulfillment of this important role.宇田賞受賞記念講演journal articl
