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Volume 69, Issue 4
Displaying 1-9 of 9 articles from this issue
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Original paper
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Ayako Yokoyama, Nobuaki Arai, Hiromichi Mitamura, Hideaki Nishizawa, Y ...2021 Volume 69 Issue 4 Pages 237-244
Published: 2021
Released on J-STAGE: January 21, 2023
JOURNAL FREE ACCESSThe Mekong giant catfish Pangasianodon gigas is distributed in Southeast Asia and one of the largest freshwater fish in the world. Due to river basin development and overfishing, the catfish is endangered at present. In Thailand, zero- and one-year-old hatchery-reared juveniles have been released into local reservoirs for more than 30 years for stock enhancement. However, their habitat use and movement patterns after the release have been poorly understood even though such knowledge would contribute to their successful stock enhancement. In addition to our previous acoustic telemetry study on the habitat use and movement patterns of zero-year-old Mekong giant catfish, in this study we studied habitat use and movement patterns of four hatchery-reared, one-year-old catfish by acoustic telemetry in Kaeng Krachan Reservoir, Thailand. The objective of the paper is to describe the movement, horizontal distribution, and diel movement of the tagged fish. We succeeded in monitoring the tagged fish for 57, 24, 350, and 12 days, respectively. Three of the four tagged catfish possibly died from unknown causes or were unintentionally captured (bycatch) by fishermen during the experiment. The tagged catfish utilized almost the entire reservoir after their release, and then the horizontal utilization area gradually decreased. No significant diel horizontal movements were observed. These movement patterns were similar to those of zero-year-old catfish. These findings are important for their successful stock enhancement, and further comprehensive studies using a larger number of the tagged catfish are imperative in the near future.View full abstractDownload PDF (509K) -
Ryosuke Watanabe, Kinuko Ito, Satoshi Katayama, Keisuke Matsuzaki2021 Volume 69 Issue 4 Pages 245-254
Published: 2021
Released on J-STAGE: January 21, 2023
JOURNAL FREE ACCESSTo clarify the factors affecting growth variation of ayu Plecoglossus altivelis altivelis, which swam upstream in the Hirose River, Miyagi Prefecture, fish were caught at three survey points in May and June 2020. Standard length and wet weight of the fish were measured, and otolith and muscle samples were extracted to count daily increments and to analyze carbon and nitrogen stable isotope ratios, respectively. The Sr:Ca ratio was also analyzed in otoliths of 15 individuals caught on 19 May. Standard length varied from 74 to 139 mm among individuals of the almost same age in day. Most of the nitrogen stable-isotope ratios were less than 13‰, indicating that food of the fish had already switched from zooplankton to the attached algae in the river. The carbon stable-isotope ratios which varied from -28 to -13‰ were positively correlated with standard length. Through the analysis on the Sr:Ca ratio, it is suggested that the variation in body size of the ayu (which were the same age in days) is caused by differences in the time spent living in freshwater area. Additionally, we consider that larger ayu fed on more algae with higher productivity, resulting in increase of its body size variation.View full abstractDownload PDF (809K) -
Tadashi Imai, Tatsuo Tsuzaki, Toyohiro Nishioka, Tetsuo Morita, Yoshih ...2021 Volume 69 Issue 4 Pages 255-263
Published: 2021
Released on J-STAGE: January 21, 2023
JOURNAL FREE ACCESSThe propose of this study is to show the effect of addition of seed filter materials (SFM) to reduce the time required to achieve full nitrification by new filter materials (NFM). Experiments were performed using ceramic filter materials in artificial seawater at 25°C. Used SFM has ammonia oxidation ability of about 6 mg-N/h/kg. The relative proportions of SFM were 0, 12.5, 25 and 50% in the first experiment, and 0, 0.1, 1 and 10% in the second. Total weight of filter materials (NFM + SFM) used was 1,000 g in each experiment. After the addition of total ammonia-nitrogen 10 mg/l, we determined the acquisition of nitrification as the time required until ammonia and nitrite were not detected. Although the time taken for NFM to acquire nitrification was about 50 days, after addition of SFM the time required was reduced to 4-30 days. Increase of the proportion of SFM was accompanied by a decrease in the time. Moreover, we put SFM (100 g) on NFM (1,000 g), and retrieved the SFM after one week. In this case, oxidation of ammonia and nitrite continued. Therefore, addition of SFM is an effective method to acquire nitrification, even if the addition is only temporary.View full abstractDownload PDF (1242K) -
Takashi Takeda, Naotaka Yasue2021 Volume 69 Issue 4 Pages 265-273
Published: 2021
Released on J-STAGE: January 21, 2023
JOURNAL FREE ACCESSThe seasonal variabilities in lipid content of muscle, intraperitoneal fat-body ratio and hepatosomatic index of Japanese scad were examined in the Kii Channel and the outer waters adjacent to the Kii Channel to clarify the relationship between nutritional condition and spawning. The fatty acid content of muscle was also examined in the spawning and non-spawning seasons. The spawning season was from April to August based on the gonadosomatic index. Lipid content of muscle was relatively low from July to August, and intraperitoneal fat-body ratio was nearly zero in the spawning season. Lipid content of muscle and intraperitoneal fat-body ratio increased after the spawning season. These results suggest that the seasonal variabilities in lipid content of muscle and intraperitoneal fat-body ratio are related to the spawning cycle. Hepatosomatic index was relatively high from April to June. The fatty acid compositions were similar between the spawning and non-spawning seasons. The individuals with higher lipid content tended to have higher fatty acid content such as C16 : 0 and C18 : 1.View full abstractDownload PDF (816K) -
Yuta Yagi, Hiroyuki Takeuchi, Makoto Nitta, Naoki Iida, Tomoaki Iseki, ...2021 Volume 69 Issue 4 Pages 275-280
Published: 2021
Released on J-STAGE: January 21, 2023
JOURNAL FREE ACCESSThe age and hatching period of wild-caught Doederleinia berycoides larvae in the coastal waters off Niigata Prefecture, Japan were estimated based on the recorded daily increment formation in the otoliths of laboratory-reared specimens. The relationships between the increments on sagittae (Is) or lapilli (Il) and age (Ac, day) of the laboratory-reared larvae were expressed using linear regression (sagittae: Is = 0.998 Ac + 0.044; lapilli: Il = 0.999 Ac + 0.001). Regression slopes and intercepts did not differ significantly from 1 and 0, respectively, indicating that the increments were formed daily after hatching. The majority of wild-caught larvae were estimated to be less than 10 days old. The hatching period was estimated to range from early September to late October, with a peak in mid- to late-September. The findings showed that this species reproduces in the waters off Niigata Prefecture.View full abstractDownload PDF (528K) -
Satoshi Yamamoto, Tsutomu Tsutsui, Tomoyuki Saguchi, Naoaki Tsutsui, T ...2021 Volume 69 Issue 4 Pages 281-290
Published: 2021
Released on J-STAGE: January 21, 2023
JOURNAL FREE ACCESSThe development of an easy and inexpensive indicator to estimate the health condition of cultured Japanese pearl oyster has been needed for early detection of debilitation and decreased growth. The present study conducted the 6-week rearing experiment of pearl oysters under fed or non-fed conditions and examined the relationship between the shell repair process and the health status of newly developing the valid physical indicator on pearl oyster. Pearl oysters in the fed group showed better somatic growth and higher glycogen content in an adductor muscle conventionally used as health indicators of cultured pearl oysters than that in the non-fed group throughout the experiment. The prismatic layer length (PLL) ratio showed no significant difference between both groups at the beginning of the experiment, but after the ablation of the shell, the shell in the fed group regenerated quickly, resulting in a higher PLL ratio than that in the non-fed group. Besides, a significant positive correlation between glycogen content in an adductor muscle and the PLL ratio was detected during the shell repair process after the ablation. This study indicates the correlation between glycogen content and shell repair process and the availability of shell repair process as the health indicator of cultured Japanese pearl oyster.View full abstractDownload PDF (1176K) -
Atsushi Urabe, Riou Nagaiwa, Kazu Sumikawa, Tetsu Ishikawa, Yugo Okamu ...2021 Volume 69 Issue 4 Pages 291-298
Published: 2021
Released on J-STAGE: January 21, 2023
JOURNAL FREE ACCESSThe genetic diversity and structure of amphidromous populations of ayu Plecoglossus altivelis altivelis (n = 383) from eight rivers in Kochi Prefecture were investigated using microsatellite DNA analysis. The levels of genetic diversity in amphidromous populations in Kochi Prefecture showed that allelic richness and expected heterozygosity ranged from 11.4 to 12.4, and from 0.718 to 0.746, respectively. Using pairwise FST values, we detected significant genetic differentiation between the amphidromous form in Kochi Prefecture and the landlocked form (n = 43) in Lake Biwa, but no significant differentiation among populations of the amphidromous form in Kochi Prefecture. Amphidromous populations in the eight rivers in Kochi Prefecture were grouped as a genetically single regional unit as estimated from pairwise FST, principal component analysis, and an unrooted neighbor-joining tree. These results provide important information to assist with management, conservation, and enhancement of the stock in amphidromous populations of ayu in Kochi Prefecture.View full abstractDownload PDF (556K)
Note
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Takanobu Goto, Kotarou Ooya, Syogo Yamamoto, Kan Onoda, Tarou Kobayash ...2021 Volume 69 Issue 4 Pages 299-305
Published: 2021
Released on J-STAGE: January 21, 2023
JOURNAL FREE ACCESSWe studied the characterization of cysteine dioxygenase (CDO) in the liver of bluegill Lepomis macrochirus. The content of cysteinesulfinic acid (CSA) produced by enzymic reaction was determined by means of OPA-prelabeling and reverse-phase HPLC using homocysteic acid (HCA) as an internal standard.
Production of CSA from cysteine was elevated when the liver homogenate was incubated with increases in reaction time and concentration of protein and cysteine, respectively. The CSA production reached maximum velocity when the incubation was conducted at pH of 6.1 and temperature of 27°C. At the same pH, phosphate buffer resulted in higher CSA formation than 2-morpholinoethanesulfonate buffer. As demonstrated in mammals, an addition of hydroxylamine into the reaction mixture was needed for CSA formation but the higher concentration of this amine decreased the amino acid production. Same phenomenon was observed in the case of ferrous ion added into the reaction mixture. Neither NAD+ nor bathocuproinedisulfonic acid exhibited any significant effects on the CSA production in bluegill homogenate.
Our present data indicated a conclusion that the characterization of CDO in the liver of bluegill was basically similar to those in mammals but the enzyme in this fish is sensitive to chemicals and temperature than that in mammals.View full abstractDownload PDF (804K)
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2021 Volume 69 Issue 4 Pages 307-316
Published: 2021
Released on J-STAGE: January 21, 2023
JOURNAL FREE ACCESS
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