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Volume 70, Issue 3
Displaying 1-15 of 15 articles from this issue
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Jun NISHIHIRO, Miki OKAMOTO, Noriko TAKAMURA2009 Volume 70 Issue 3 Pages 183-190
Published: 2009
Released on J-STAGE: February 16, 2011
JOURNAL FREE ACCESSThe macrophytic communities in Lake Shirarutoro were investigated in August 2007. Twenty-three species including 4 found on the Japanese Red List were recorded in the survey. Communities of submerged plants were observed in the northern area of the lake. In the southern area, the distribution of submerged plants was sparse, while a floating leaved plant, Trapa japonica, was dominant. Although the lake still maintains a relatively high floristic diversity, their abundance may have decreased in recent years.View full abstractDownload PDF (610K) -
Yukiko TANABE, Sakae KUDOH2009 Volume 70 Issue 3 Pages 191-199
Published: 2009
Released on J-STAGE: February 16, 2011
JOURNAL FREE ACCESSBathymetric maps yield important information for lake research. However, a study of bathymetric features has almost never been carried out on lakes around Syowa Station, Antarctica. This is due to a variety of factors; ice covers the lakes almost all year long, and the transportation of ships/boats and bulky instruments is extremely difficult, impeding access to the lakes. In this study, explorations were carried out in the summer of 2007-8 at two lakes, Lake Naga Ike and Lake Skallen Ô-Ike, near Syowa Station. Data related to water depths and geolocations were obtained using a portable sonar or plumb line, and GPS. We then completed two bathymetric maps, the first ever made for this area. We were able to create maps that would facilitate lake study in convenient and efficient ways without resorting to heavy surveying equipment or boats/ships. An effort planned for the near future is to apply this study method to investigate the bathymetric features of more than 100 other Antarctic lakes located near Syowa Station.View full abstractDownload PDF (1159K)
Limnological record
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Yoshimasa YAMAMOTO, Hajime TSUKADA, Daisuke NAKAI2009 Volume 70 Issue 3 Pages 201-207
Published: 2009
Released on J-STAGE: February 16, 2011
JOURNAL FREE ACCESSHeavy cyanobacterial blooms have formed in recent years in Hirosawa-no-ike Pond (Kyoto, Japan). Although the pond water is drained during winter and the sediment is exposed to air for over two months, cyanobacterial blooms appear annually each summer. Moreover, the dominance of Microcystis aeruginosa during the summer months cannot be accounted for solely by cell division. These findings suggest that colonies and resting spores of cyanobacteria in the sediment play a critical role as seed populations for blooms. Numerous colonies of Microcystis species are present in the top layers of the sediment with a water content of over 40 % during winter. Accordingly, the formation of cyanobacterial blooms may be controllable by removing the top layers of the sediment containing the inocula of bloom-forming cyanobacteria. To examine the effectiveness of the removed sediment in crop cultivation, 20 crops were cultured using the sediment from March 2006 to April 2007. Culturing with the removed sediment substantially increased the final yields of ten crops. These results suggest that sediment removal may not only be effective in controlling the development of cyanobacterial blooms, but also in increasing the yields of many crops.View full abstractDownload PDF (598K)
Features
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Satoshi KOBAYASHI, Kiyoshi SATAKE2009 Volume 70 Issue 3 Pages 209-224
Published: 2009
Released on J-STAGE: February 16, 2011
JOURNAL FREE ACCESSThe Ogasawara mitten crab Eriocheir ogasawaraensis is a varunid species endemic to the Ogasawara (Bonin) Islands. Although this crab undertakes catadromous migration to the sea for reproduction, little is known about its ecological characteristics. Therefore, we carried out field surveys on the distribution patterns of E. ogasawaraensis and other brachyuran crabs in the rivers and streams of Chichi-jima, Ogasawara Islands, from June to July and in November, 2007. Although, the streams and rivers of Chichi-jima are generally small and the range of the tidal river area is usually very short, the upper tidal river area is an extremely important habitat for the recruitment and maintenance of the mitten crab population. The present survey revealed that E. ogasawaraensis settled in a narrowly limited area nearly dozens of meters long at the rivermouth. Juvenile crabs (13-23 mm carapace width) with relatively longer legs migrated upstream to the headwaters at a high altitude. Though the distribution of E. ogasawaraensis covered the entire river area, it was strongly inclined toward the headwaters. The microhabitat of the crab was usually underwater, though an occasional adult crab wandering along the riverside wetland was also captured. This distribution pattern differs from that of its congener, E. japonica, which favors freshwater downstream areas in mainland Japan. In addition, the number of mitten crabs caught was too small for the effort made in the present survey, suggesting that the population of this species in Chichi-jima may be endangered. Three brachyuran species (Ptychognathus glaber, Varuna litterata and Chiromantes dehaani) were also widely distributed from the downstream area to the upper freshwater area in the river. Complexity of brachyuran species composition in the rivers and streams of Ogasawara Islands was generally poor compared to that in the Japanese mainland and the Ryukyu Islands.View full abstractDownload PDF (789K) -
Seiichi NOHARA, Kiyoshi SATAKE, Tomohiro TAKASE, Makoto KUROKAWA2009 Volume 70 Issue 3 Pages 225-238
Published: 2009
Released on J-STAGE: February 16, 2011
JOURNAL FREE ACCESSChemical analysis of river water and groundwater were carried out for the samples from Izu-Ohshima Island, Hachijyoujima Island and Ogasawara Islands from 1997 to 1999 and from 2005 to 2008. Concentrations of nitrate-N of inland water of Ogasawara Islands were higher than those in summer. The analytical results show that nutrient concentrations of the groundwater around the coastal area were increased from Ogasawara Islands to Izu Islands because of land use of agriculture and sewage water from human activity. The analytical results of nitrogen isotope ratio in seaweeds show that the nutrient supply from inland water was decreasing in Hachijyoujima Island. This indicates the importance of nutrient from groundwater seepage for seaweed vegetation in Izu Islands.View full abstractDownload PDF (1316K) -
Haruki KARUBE2009 Volume 70 Issue 3 Pages 239-245
Published: 2009
Released on J-STAGE: February 16, 2011
JOURNAL FREE ACCESSThe five endemic species of Odonata inhabiting the oceanic islands of Ogasawara have been rapidly declining from the mid-1980s. The reason for that decline is likely due to predation by an invasive alien species, ‘green anoles’. Currently, almost all the endemic Odonates have gone extinct from the main islands of Chichi-jima and Haha-jima. Although these endemic Odonates have still managed to survive in a few satellite islands, there are only small aquatic habitats which readily dry up when severe droughts hit Ogasawara.
Our recent efforts to construct artificial conservation ponds in these satellite islands appear to be effective. Three endemic species are currently breeding in those ponds, and the total population has increased.
Based on these encouraging results, we continue to stress the importance of an integrated action plan, including the development of areas protected from green anoles predation and the construction of more permanent ponds.View full abstractDownload PDF (842K)
Features
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USIO N., Kimiko UCHII2009 Volume 70 Issue 3 Pages 247-248
Published: 2009
Released on J-STAGE: February 16, 2011
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Kenzi TAKAMURA2009 Volume 70 Issue 3 Pages 249-253
Published: 2009
Released on J-STAGE: February 16, 2011
JOURNAL FREE ACCESSThe highly endemic fish fauna of Lake Biwa has not only been a source of invasive species to other Japanese freshwaters through the activities of fish stocking, but has also itself been threatened by invasive species from other freshwaters as well as by habitat destruction. In rivers of the Kanto region, an analysis of the mitochondrial cytochrome-b gene revealed that populations of the freshwater fish Zacco platypus are composed of two distinct lineages, i. e., the native Kanto and the non-indigenous L. Biwa lineage. The latter was inadvertently introduced along with the stock of the ayu Plecoglossus altivelis from the lake. Since the stocking has been reported as not contributing to the recruitment of the next generation in the rivers, terminating the stocking is advisable for preventing invasive species as well as for sustaining the ayu stock.View full abstractDownload PDF (438K) -
Yoko OKI2009 Volume 70 Issue 3 Pages 255-260
Published: 2009
Released on J-STAGE: February 16, 2011
JOURNAL FREE ACCESSThe spread of alien organisms has drastically increased in the past few years, and alien plants have directly damaged our living space and caused ecosystem imbalances. The Ministry of Environment of Japan has enforced the Invasive Alien Species Act since 2006, by which specific alien plants are identified, and is focusing its efforts towards the breeding prevention and their eventual extermination. However, the environmental factors that nourish the luxuriant growth of alien aquatic plants remain largely unknown and the attendant risks are poorly understood. In this paper, I proposed how we might cope with the problems caused by alien aquatic plants based on a survey of their distribution and the relevant environmental factors of aquatic plants in the water of the southern Okayama area. This survey revealed that the habitats of alien species were characterized by water that was heavily enriched, and that they were distributed mostly in irrigation and drainage canals with artificial banks near urban districts. This suggested that their preferred habitats were places where disturbances occurred. Further more, even though Trapa sp. is native to Japan, they also showed invasive tendencies and habitat preferences similar to those of alien species. Therefore, when we are faced with alien aquatic plants, it is necessary to accurately determine the risk and to define the direction of risk management, instead of making blind assumptions that the alien species are harmful. Moreover, alien species are sometimes introduced repeatedly, as exemplified by Pistia stratiotes. Thus, we must keep in mind the concept of a time-axis.View full abstractDownload PDF (626K) -
USIO N., Miho IMADA, Munemitsu AKASAKA, Noriko TAKAMURA2009 Volume 70 Issue 3 Pages 261-266
Published: 2009
Released on J-STAGE: February 16, 2011
JOURNAL FREE ACCESSBiological invasion is one of the major threats to farm pond biodiversity. Farm ponds may serve as biodiversity hot spots because they provide refuge sites for a variety of animals and plants inhabiting floodplain marshes. Developing effective management methods with regard to the multifunctionality of farm ponds is one of the major concerns among environmental managers. Here, we investigated through a field survey and interviews the effects of pond management on the presence/absence of alien species in 64 farm ponds in Hyogo Prefecture, Japan. The result of the field survey indicated that bluegill sunfish (Lepomis macrochirus) and red swamp crayfish (Procambarus clarkii) are the most widespread and abundant aquatic invaders in the study region. Although it is generally believed that pond draining is effective in eradicating alien fish, pond draining showed no effect on the presence/absence of bluegill sunfish, but influenced the occurrence of red swamp crayfish, with crayfish generally found in drained ponds. The presence/absence of bluegill sunfish was generally high where dam water or agriculture draining is used as the major water supply. Thus, the alien bluegill sunfish probably immigrate into farm ponds from dams or irrigation systems even though they may temporarily disappear following pond draining. If the (mutually exclusive) distributions of bluegill sunfish and red swamp crayfish are determined at least in part by interspecific interactions between the two species, eradication of one species may lead to an increased density of the other.View full abstractDownload PDF (529K) -
Kimiko UCHII, Zen’ichiro KAWABATA2009 Volume 70 Issue 3 Pages 267-272
Published: 2009
Released on J-STAGE: February 16, 2011
JOURNAL FREE ACCESSCyprinid herpesvirus 3 was first isolated from cultured koi and common carp that were undergoing mass mortality in the USA and Israel in 1998. The first outbreak of this virus in Japan occurred in 2003, and had spread to various lakes and rivers by 2004. In the same year, the virus killed more than 100,000 wild common carp in Lake Biwa, while those that survived infection would become carriers of the virus, possibly serving as a source of the virus in Lake Biwa after the initial outbreak. Transmission of the virus might well occur during the group spawning of common carp.View full abstractDownload PDF (636K) -
Sawako EGUSA, Hiroshi SAKATA2009 Volume 70 Issue 3 Pages 273-276
Published: 2009
Released on J-STAGE: February 16, 2011
JOURNAL FREE ACCESSThe alien rodent coypu (Myocastor coypus) was introduced into Japan as a domestic animal for its fur. Here we report on its rapid range expansion and the agricultural damage it has caused in Hyogo Prefecture. According to the results of a questionnaire survey, coypu have inflicted damage or been sighted in 2349 of 4195 agricultural communities in 2007. This year, 1007 individuals were culled mainly for nuisance control. The efforts at nuisance control have been less intense than that those against the raccoon (Procyon lotor), a more destructive alien mammal.View full abstractDownload PDF (747K) -
Katsuki NAKAI2009 Volume 70 Issue 3 Pages 277-280
Published: 2009
Released on J-STAGE: February 16, 2011
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Satoko NAKAYAMA2009 Volume 70 Issue 3 Pages 281-283
Published: 2009
Released on J-STAGE: February 16, 2011
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Kimiko UCHII, USIO N.2009 Volume 70 Issue 3 Pages 285-286
Published: 2009
Released on J-STAGE: February 16, 2011
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