DSpace Collection: 2016-08-10
http://hdl.handle.net/2115/62644
2016-08-102024-03-29T05:34:56ZSeasonal changes in mesozooplankton swimmer community and fecal pellets collected by sediment trap moored at the Northwind Abyssal Plain in the western Arctic Ocean
http://hdl.handle.net/2115/62649
Title: Seasonal changes in mesozooplankton swimmer community and fecal pellets collected by sediment trap moored at the Northwind Abyssal Plain in the western Arctic Ocean
Authors: Matsuno, Kohei; Yamaguchi, Atsushi; Fujiwara, Amane; Onodera, Jonaotaro; Watanabe, Eiji; Harada, Naomi; Kikuchi, Takashi
Abstract: In the western Arctic Ocean, the long sea ice coverage period prevents year-round seasonal zooplankton sampling by ordinary ship-board observation. To overcome these problems, the analysis of zooplankton swimmers in samples collected by a year-round moored sediment trap may be a powerful tool. In this study, we studied seasonal changes in zooplankton swimmer community and fecal pellets collected by a sediment trap moored at fixed depths(180-260m) of the Northwind Abyssal Plain in the western Arctic Ocean from October 2010 to September 2012. The fecal pellets were separated into four types : oval, cylinder, spherical and brown-colored pellets. The occurrence of brown-colored pellets was limited to the open water period(July-August) and reached 80% of the total at that time. Ship-board experiments showed that the brown-colored fecal pellets were egested by amphipods(Themisto libellula). The high occurrence of brown-colored fecal pellets during the open water period might be a reflection of the massive feeding activity of amphipods. Zooplankton swimmer flux ranged from 35-739 ind m-2 day-1, and poecilostomatoid copepods were the most abundant(accounted for 69% of the annual mean). Seasonally, barnacle and bivalve larvae were abundant during August-September and August-November, respectively. These meroplanktionic larvae were considered to be transported by current flow from the southern continental shelf, whereas they were absent from summer to autumn 2012. The annual changes in meroplanktonic larvae occurrence would be a reflection of the annual changes in water mass formation at the upper layer of the sediment trap moored station.2016-08-09T15:00:00ZMatsuno, KoheiYamaguchi, AtsushiFujiwara, AmaneOnodera, JonaotaroWatanabe, EijiHarada, NaomiKikuchi, TakashiIn the western Arctic Ocean, the long sea ice coverage period prevents year-round seasonal zooplankton sampling by ordinary ship-board observation. To overcome these problems, the analysis of zooplankton swimmers in samples collected by a year-round moored sediment trap may be a powerful tool. In this study, we studied seasonal changes in zooplankton swimmer community and fecal pellets collected by a sediment trap moored at fixed depths(180-260m) of the Northwind Abyssal Plain in the western Arctic Ocean from October 2010 to September 2012. The fecal pellets were separated into four types : oval, cylinder, spherical and brown-colored pellets. The occurrence of brown-colored pellets was limited to the open water period(July-August) and reached 80% of the total at that time. Ship-board experiments showed that the brown-colored fecal pellets were egested by amphipods(Themisto libellula). The high occurrence of brown-colored fecal pellets during the open water period might be a reflection of the massive feeding activity of amphipods. Zooplankton swimmer flux ranged from 35-739 ind m-2 day-1, and poecilostomatoid copepods were the most abundant(accounted for 69% of the annual mean). Seasonally, barnacle and bivalve larvae were abundant during August-September and August-November, respectively. These meroplanktionic larvae were considered to be transported by current flow from the southern continental shelf, whereas they were absent from summer to autumn 2012. The annual changes in meroplanktonic larvae occurrence would be a reflection of the annual changes in water mass formation at the upper layer of the sediment trap moored station.北海道近海産マイナー魚28種の脂質特性
http://hdl.handle.net/2115/62647
Title: 北海道近海産マイナー魚28種の脂質特性
Authors: 中塚, 美紀子; 安藤, 靖浩
Abstract: Lipid content, lipid class composition, and fatty acid composition were determined for 28 minor marine fish species caught from the waters around Hokkaido, Japan. The samples include some rare fish such as dusky rockfish Sebastes variabilis "nagamenuke" and prowfish Zaprora silenus "bouzuginpo." Most samples had low lipid contents, and therefore, can be used in low-fat fish foods. In contrast, the fish of four species and the liver of eight species were rich in lipid as they contained triacylgycerols or diacylglycerylethers as major lipid classes. Such fatty fish can be used as a source of marine lipids. The liver of brown hakeling Physiculus maximowiczi "donko" and ocean sunfish Mola mola "manbou" was found to be useful for including EPA and DHA. Prowfish and other two species were shown to contain tetracosahexaenoic acid in their fatty flesh and/or liver. These findings are useful fundamental information on the minor marine fish.2016-08-09T15:00:00Z中塚, 美紀子安藤, 靖浩Lipid content, lipid class composition, and fatty acid composition were determined for 28 minor marine fish species caught from the waters around Hokkaido, Japan. The samples include some rare fish such as dusky rockfish Sebastes variabilis "nagamenuke" and prowfish Zaprora silenus "bouzuginpo." Most samples had low lipid contents, and therefore, can be used in low-fat fish foods. In contrast, the fish of four species and the liver of eight species were rich in lipid as they contained triacylgycerols or diacylglycerylethers as major lipid classes. Such fatty fish can be used as a source of marine lipids. The liver of brown hakeling Physiculus maximowiczi "donko" and ocean sunfish Mola mola "manbou" was found to be useful for including EPA and DHA. Prowfish and other two species were shown to contain tetracosahexaenoic acid in their fatty flesh and/or liver. These findings are useful fundamental information on the minor marine fish.アサリの定位方向が摂食効率に与える影響
http://hdl.handle.net/2115/62646
Title: アサリの定位方向が摂食効率に与える影響
Authors: 岩城, 里奈; 田村, 亮輔; 五嶋, 聖治
Abstract: The substratum of Tateno fishing ground of the short-necked clam, Ruditapes philippinarum, Hakodate Bay, Hokkaido, Japan is characterized by higher percentage of cobbles and pebbles compared with other regions. The shell growth rate of the adult clam in this region is slower than that of other fishing grounds. In this study, the relationship between the uncommon sediment composition and the depressed growth was examined from the viewpoint of feeding efficiency of the clam. Infaunal bivalves usually stay with vertically directed siphons up to the sediment surface in suspension feeding, but in this region the clams often burrow into the sediment at an angle when they cannot burrow into sediment deeper. In the laboratory experiment the clam could not turn its valves but often extended its siphons up under condition of restricted burrowing. Filtration rate of the clam, which was estimated by changes in the chlorophyll-α concentration of the diatom Chaetoceros gracilis as an algal diet, was the highest in the vertical position of siphons among all setup directions. Therefore, the short-necked clam cannot keep their body the most effective direction by restricted burrowing due to many cobbles and pebbles, which may cause food intake reduction. It seems one of the reasons for depressed growth of the short-necked clam in this region.2016-08-09T15:00:00Z岩城, 里奈田村, 亮輔五嶋, 聖治The substratum of Tateno fishing ground of the short-necked clam, Ruditapes philippinarum, Hakodate Bay, Hokkaido, Japan is characterized by higher percentage of cobbles and pebbles compared with other regions. The shell growth rate of the adult clam in this region is slower than that of other fishing grounds. In this study, the relationship between the uncommon sediment composition and the depressed growth was examined from the viewpoint of feeding efficiency of the clam. Infaunal bivalves usually stay with vertically directed siphons up to the sediment surface in suspension feeding, but in this region the clams often burrow into the sediment at an angle when they cannot burrow into sediment deeper. In the laboratory experiment the clam could not turn its valves but often extended its siphons up under condition of restricted burrowing. Filtration rate of the clam, which was estimated by changes in the chlorophyll-α concentration of the diatom Chaetoceros gracilis as an algal diet, was the highest in the vertical position of siphons among all setup directions. Therefore, the short-necked clam cannot keep their body the most effective direction by restricted burrowing due to many cobbles and pebbles, which may cause food intake reduction. It seems one of the reasons for depressed growth of the short-necked clam in this region.Anatomical Features of the Pelvic Girdle in the Family Ateleopodidae(Pisces: Ateleopodiformes)
http://hdl.handle.net/2115/62645
Title: Anatomical Features of the Pelvic Girdle in the Family Ateleopodidae(Pisces: Ateleopodiformes)
Authors: Atsumi, Keisuke
Abstract: The osteology and myology of the pelvic girdle in a deep sea ateleopodiform fish, Ateleopus japonicus, were studied. The pelvic girdle is characterized by four unique features : (1) a pelvis that consists of a cartilaginous plate with a pair of large openings, (2) a pelvic fin that is thread-like owning to a greatly elongated first fin ray and subsequent rays that are concealed under the skin, (3) a greater number of muscles inserted on the first pelvic ray than in other teleosts, and (4) a pelvis that supports fin rays laterally, allowing muscles to insert on the first pelvic ray both anteriorly and posteriorly. The latter three characteristics suggest that the pelvic fin of A.japonicus is highly flexible and mobile. As demonstrated in other fishes with thread-like pelvic fins, this fin may not function in swimming, but may function in other actions such an searching for prey or signaling.2016-08-09T15:00:00ZAtsumi, KeisukeThe osteology and myology of the pelvic girdle in a deep sea ateleopodiform fish, Ateleopus japonicus, were studied. The pelvic girdle is characterized by four unique features : (1) a pelvis that consists of a cartilaginous plate with a pair of large openings, (2) a pelvic fin that is thread-like owning to a greatly elongated first fin ray and subsequent rays that are concealed under the skin, (3) a greater number of muscles inserted on the first pelvic ray than in other teleosts, and (4) a pelvis that supports fin rays laterally, allowing muscles to insert on the first pelvic ray both anteriorly and posteriorly. The latter three characteristics suggest that the pelvic fin of A.japonicus is highly flexible and mobile. As demonstrated in other fishes with thread-like pelvic fins, this fin may not function in swimming, but may function in other actions such an searching for prey or signaling.