Japan Fisheries Research and Education Agency (FRA) Repository
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Reproduction and development of the Amazon puffer Colomesus asellus in captivity
Get PDFTo induce breeding of the freshwater pufferfish Colomesus asellus, artificial maturation by hormone injection (hCG, 10 IU per gram) and insemination were performed, and subsequent development observed. The rearing environment for the parental fish was freshwater, maintained at 26.0 ± 1.5 ℃ under L12:D12 lighting cycle. Two hormone treatments were applied, one month apart, to two females and four males, ovulation being confirmed 47 hours after the second treatment. Three hundred and sixty-three and 548 eggs with a mean diameter of 1.11 mm (n = 20) were collected from the two females, 334 (92.0 %) and 395 (72.1 %) being fertilized, respectively. The larvae and juveniles were fed with S-type Brachionus sp. fortified initially with freshwater chlorella, followed by Artemia larvae and Chironomid sp. larvae. The pufferfish were reared in a salinity of 7 ‰ for 24 days after hatching, the water then being gradually changed to freshwater over the following 10 days. Two individuals survived for 225 days after hatching, growing to average standard and total lengths of 29.24 mm and 38.72 mm, respectively.
The Gonperz growth formulae were as follows：
SL：Lt = 29.4075×exp (-exp (-0.02301(t-39.1213)))
TL：Lt = 38.51177×exp (-exp (-0.023253(t-41.25841)))
Further investigations of rearing conditions, such as salinity, are required to improve the breeding techniques for this species.編集：水産大学校departmental bulletin pape
Spawning aggregation of blacktail snapper (Lutjanus fulvus) in an Okinawan coral reef: lunar-phase periodicity of aggregation formation, seasonal consistency in fish spatial distribution, and fish size and age frequency in the aggregation site
Get PDFSnappers (family Lutjanidae) are main fishery target species and some fish species in this family form spawning aggregations on coral reefs. This study aimed to clarify the ecological characteristics of fish aggregation of Lutjanus fulvus: (1) lunar-phase periodicity of aggregation formation, (2) seasonal consistency of the aggregation site, (3) differences in fish density between inside and outside the aggregation site, (4) gonad development of fish individuals inside the aggregation site, (5) frequency distribution of size and age of fish individuals at the aggregation site, and (6) to determine if the aggregation is a spawning aggregation. Time-lapse still photography and data plotted with a correlogram revealed that fish aggregations were observed only around the 20th day of the moon. Underwater observations revealed greater fish density (42–2042 individuals per 600 m × 5 m) between April and September. Plotting fine-scale fish spatial distributions revealed consistent spatial patterns from May to September. The fish density inside the aggregation site was about 7960.5-fold greater than that outside the aggregation site. Most females inside the aggregation site had hydrated eggs. The average fork length and age of fish individuals inside the aggregation site were 241.8 mm and 12.2 years for males and 247.8 mm and 13.4 years for females, respectively. This study revealed that the aggregation of L. fulvus on an Okinawan coral reef could be regarded as spawning aggregation. The results can provide insights into the precise setting position of marine protected area to effectively protect the spawning ground of L. fulvus.journal articl
Morphological and cytochemical characteristics of monocytes from inshore hagfish Eptatretus burgei
Get PDFMonocytes were observed in the blood of inshore hagfish Eptatretus burgei. The monocytes were round or oval, high nucleus/cytoplasm ratio, and have several round or oval eosinophilic granules, which show dark red or blackish red color when stained with May-Grünwald (MG), Giemsa, and MG-Giemsa stain. The granules were positive for alkaline phosphatase, acid phosphatase, andα-naphthyl butyrate esterase. Also, the granules show metachromatic (reddish purple) with toluidine blue. However, ꞵ-glucuronidase,α-naphthyl acetate esterase, naphthol AS-D chloroacetate esterase and peroxidase were not detected in the monocytes, and negative for periodic acid Schiff reaction, alcian blue, Sudan black B, Sudan III, and oil red O. The monocytes engulfed many yeast particles (zymosan).編集：水産大学校departmental bulletin pape
キャベツ給餌によるサザエの長期飼育と棘形成に関する考察
Get PDFJuveniles of the Japanese turban shell Turbo sazae were reared under static and flowing water conditions by feeding cabbage alone for two years. The growth of the reared individuals was comparable to that of reared juveniles fed formulated diets and/or algae and to that of wild juveniles, indicating that the cabbage could be an alternative or supplemental food source for rearing the turban shells. Survival rates were approximately 60 % after one year and decreased to 20 % after two years. Spine formation was not observed in all individuals. Factors involved in the spine formation were discussed.journal articl
Candidate orexigenic peptide hormone-related genes in yellowtail Seriola quinqueradiata: cloning and tissue distribution of two distinct agouti-related protein genes and response of five candidate appetite-related genes to fasting, fishmeal soluble fraction addition, and a fishmeal-based diet
Get PDFAgouti-related protein (Agrp) is an orexigenic peptide hormone found in fish and other vertebrates. Understanding appetite regulation is important for improving production performance in aquaculture systems. However, information on appetite-related hormones in yellowtail is still fragmentary. In this study, two distinct agrpgenes (i.e., agrp1 and agrp2) were cloned from the yellowtail brain. Brain distribution and response of the agrp genes to fasting, along with other candidate orexigenic peptide hormone-related genes including neuropeptide Y (npy) and melanin-concentrating hormones (mch1 and mch2), were studied. The highest expression level of those genes was observed in the hypothalamus, except for npy. After fasting, agrp1 and npy increased significantly in the hypothalamus, whereas agrp2 in the olfactory bulb and cerebellum decreased significantly. After feeding with a fishmeal (FM)-based diet and addition of a fishmeal soluble fraction (FMS), hypothalamic agrp1, agrp2, mch1, and mch2 increased, whereas hypothalamic npy decreased significantly. From the fasting experiment, agrp1 and npy may function as orexigenic hormones in yellowtail; however, the function of other hormones warrants further research. Expression of all the analyzed appetite-related hormonal genes might respond to the smell/taste of fishmeal through sensory organs. Furthermore, npy and agrp1 may enhance appetite through different mechanisms in yellowtail.journal articl
Consumer preference for label presentations of freshness, taste, and serving suggestion on fresh fish packages of Japanese flounder Paralichthys olivaceus
Get PDFUnderstanding consumer choice behavior for seafood is important for the efficient and sustainable use of marine resources and the improvement of human health. This study aims to identify the information content that effectively motivates Japanese consumers to purchase fresh fish products. Group interviews with 12 consumers were conducted in September 2021 to collect qualitative information on consumer evaluations of the presentation of package labels for freshness, taste, and serving suggestion. Subsequently, data were collected through a web-based survey, administered to 3651 consumers in the Kanto area, Japan from October to November 2021. A latent class logit model was applied to the data to estimate the influence of product attributes and personal characteristics on the choice and willingness-to-pay for each product attribute. The consumers gave the highest rating to freshness labels. The taste label was evaluated highly by consumers in one class. The group interview showed that when the serving suggestion label recommending meunière use was presented, consumers associated it with the recommendation to heat the fish because of less freshness. The results of the choice experiment also showed that the “meunière” label was evaluated negatively. The consumer segment characterized by a high income and frequent purchases of fish tended to respond to all types of labels.journal articl
海面養殖サーモンの生産性向上に向けた研究開発の現状と展望
Get PDF国内の水産物消費量が減少する中にあって，サーモンの国内需要は年々拡大傾向にある。しかし，国内市場の大部分は輸入サーモンに依存しており，国産サーモンの生産量は伸び悩んでいる。海面養殖サーモンの場合では，淡水で飼育した種苗を沖出した時の斃死やその後の成長停滞により歩留まりが低いこと，我が国特有の海面養殖形態に適した育種系統がないことが制限要因であると考えられている。ここでは，2019年度より始まった養殖業成長産業化技術開発事業のうち，サーモン養殖推進技術開発課題で取り組んでいる海水馴致技術の高度化や海面養殖サーモンの高成長育種について紹介する。journal articl
シオミズツボワムシへの毒性を指標とした Karenia mikimotoi 赤潮の貝類へい死リスクの評価
Get PDFThe dinoflagellate Karenia mikimotoi, recognised as a harmful algal bloom (HAB) species, induces mass mortality among aquacultured fish and molluscan shellfish in coastal areas worldwide. Despite numerous studies examining the mechanism behind the lethal effects of K. mikimotoi on marine organisms, the exact toxicity mechanism remains unclear. Therefore, developing a method for readily assessing the toxicity of dinoflagellates collected from the field is crucial. While previous investigations have used the rotifer Brachionus plicatilis to evaluate the toxicity of HAB species, a comprehensive verification of K. mikimotoi, especially in its natural cell state, has not been conducted. Therefore, we aimed to demonstrate the efficacy of the rotifer toxicity test for K. mikimotoi. Initially, we investigated the toxic effects of three culture strains of K. mikimotoi (IMR4, KU9, and Km69-9ax) on juvenile abalones (Haliotis discus discus and H. gigantea) and the rotifer B. plicatilis. Exposure tests with juveniles of abalone (exposure density: 5.0–5.3×104 cells mL-1) and rotifers (exposure density: 103 cells mL-1) revealed that IMR4 significantly reduced the survival rate of juvenile H. discus discus (p<0.05) and H. gigantea (p<0.01), whereas KU9 and Km69-9ax exhibited no toxicity. The rotifer survival rate was lowest in the group exposed to the IMR4 strain (p<0.001), followed by those exposed to KU9 (p<0.001) and Km69-9ax strains (p<0.01). Rotifer survival decreased in an exposure density-dependent manner during IMR4 toxicity tests, and rotifers were killed even at a cell density of 10 cells mL-1. Consequently, we classified the IMR4 strain as virulent and the KU9 and Km69-9ax strains as attenuated. Subsequently, no toxicity to rotifers was observed in groups exposed to the culture supernatant, ruptured cell suspension, heat-treated cell suspension, or non-contact conditions. However, the rotifer survival rate significantly decreased in the group exposed to the intact cell suspension of the IMR4 strain (p<0.001). Finally, we investigated the effects of natural seawater collected on 5th and 6th August, 2022 from the Yatsushiro Sea, which contained K. mikimotoi cells on H. discus discus and rotifers. Both juvenile H. discus discus and rotifers died rapidly after exposure to red-tide seawater of K. mikimotoi. Our findings indicate that the rotifer toxicity test can assess the toxicity of K. mikimotoi on mollusc shellfish with high sensitivity.journal articl