The Japanese pond smelt (Hypomesus nipponensis) stock has been observed to fluctuate quite rigorously over the years with sustained periods of low catch in Lake Kasumigaura and Kitaura of the Ibaraki prefecture, Japan...The Japanese pond smelt (Hypomesus nipponensis) stock has been observed to fluctuate quite rigorously over the years with sustained periods of low catch in Lake Kasumigaura and Kitaura of the Ibaraki prefecture, Japan which would adversely affect the socioeconomic livelihood of the local fishermen and fisheries industry. This study was aimed at determining the factors affecting the stock fluctuation of the pond smelt through the different years in the two lakes. Through exploratory analysis it was found that the pond smelt had significant relationship with total phosphorus (TP) level in both lakes. The global mean land and ocean temperature index (LOTI) was also found to be indirectly related to the pond smelt stock in lake Kasumigaura and Kitaura at the latitude band of 24°N to 90°N (l). Both TP and LOTI had inverse relationship with pond smelt trajectory in both lakes. For both Lake Kasumigaura and Kitaura, TP for the individual lakes and LOTI (l) were used as independent variables using generalized linear model and response surface methods for modeling the stock dynamics of the pond smelt in the two lakes. Model selection was based on significant parameter estimates (p < 0.05), Akaikes Information Criterion and R2 values. Phosphorus loading is an indication of increasing anthropogenic activities in the surrounding area having negative impact on the pond smelt population. When management decisions are being made regarding pond smelt fishery and sustainability plans in the Ibaraki prefecture, the effects of TP and LOTI should be taken into account. Future research needs to be directed towards deeper understanding the mechanisms by which TP and LOTI affect pond smelt population in Lake Kasumigaura and Kitaura for more effective management.展开更多
Lake Kasumigaura,the second largest lake in Japan,has faced water quality challenges since the 1970s owing to rapid economic growth,land use changes,and increased wastewater discharge.Moreover,severe cyanobacterial bl...Lake Kasumigaura,the second largest lake in Japan,has faced water quality challenges since the 1970s owing to rapid economic growth,land use changes,and increased wastewater discharge.Moreover,severe cyanobacterial blooms,particularly those of Microcystis,were observed in the 1980s,emphasizing the urgent need for comprehensive ecological monitoring.We present the results of phytoplankton monitoring by the Ibaraki Kasumigaura Environmental Science Center(IKESC)since 2005 and the publication of information on cyanobacterial blooms for citizens since 2012.Our monitoring surveys identified distinct phytoplankton communities in Nishiura and Kitaura,the two main water bodies of Lake Kasumigaura,emphasizing the need for monitoring surveys at various sites in Lake Kasumigaura.Analysis of long-term phytoplankton data from the Lake Kasumigaura Database(National Institute of Environmental Studies,NIES)revealed that Planktothrix is the predominant cyanobacteria in Lake Kasumigaura.At IKESC,we have responded to these potentially socially problematic phytoplankton blooms by releasing the“Bulletin of Cyanobacteria Blooms”in 2012 and the“Bulletin of Cyanobacteria Forecast”in 2020.展开更多
文摘The Japanese pond smelt (Hypomesus nipponensis) stock has been observed to fluctuate quite rigorously over the years with sustained periods of low catch in Lake Kasumigaura and Kitaura of the Ibaraki prefecture, Japan which would adversely affect the socioeconomic livelihood of the local fishermen and fisheries industry. This study was aimed at determining the factors affecting the stock fluctuation of the pond smelt through the different years in the two lakes. Through exploratory analysis it was found that the pond smelt had significant relationship with total phosphorus (TP) level in both lakes. The global mean land and ocean temperature index (LOTI) was also found to be indirectly related to the pond smelt stock in lake Kasumigaura and Kitaura at the latitude band of 24°N to 90°N (l). Both TP and LOTI had inverse relationship with pond smelt trajectory in both lakes. For both Lake Kasumigaura and Kitaura, TP for the individual lakes and LOTI (l) were used as independent variables using generalized linear model and response surface methods for modeling the stock dynamics of the pond smelt in the two lakes. Model selection was based on significant parameter estimates (p < 0.05), Akaikes Information Criterion and R2 values. Phosphorus loading is an indication of increasing anthropogenic activities in the surrounding area having negative impact on the pond smelt population. When management decisions are being made regarding pond smelt fishery and sustainability plans in the Ibaraki prefecture, the effects of TP and LOTI should be taken into account. Future research needs to be directed towards deeper understanding the mechanisms by which TP and LOTI affect pond smelt population in Lake Kasumigaura and Kitaura for more effective management.
基金Supported by the Kasumigaura Long-Term Environmental Monitoring Program。
文摘Lake Kasumigaura,the second largest lake in Japan,has faced water quality challenges since the 1970s owing to rapid economic growth,land use changes,and increased wastewater discharge.Moreover,severe cyanobacterial blooms,particularly those of Microcystis,were observed in the 1980s,emphasizing the urgent need for comprehensive ecological monitoring.We present the results of phytoplankton monitoring by the Ibaraki Kasumigaura Environmental Science Center(IKESC)since 2005 and the publication of information on cyanobacterial blooms for citizens since 2012.Our monitoring surveys identified distinct phytoplankton communities in Nishiura and Kitaura,the two main water bodies of Lake Kasumigaura,emphasizing the need for monitoring surveys at various sites in Lake Kasumigaura.Analysis of long-term phytoplankton data from the Lake Kasumigaura Database(National Institute of Environmental Studies,NIES)revealed that Planktothrix is the predominant cyanobacteria in Lake Kasumigaura.At IKESC,we have responded to these potentially socially problematic phytoplankton blooms by releasing the“Bulletin of Cyanobacteria Blooms”in 2012 and the“Bulletin of Cyanobacteria Forecast”in 2020.
