Spatial and temporal variation in fish community structure of a marine embayment in Zanzibar, Tanzania
Spatial and temporal variation in fish community structure of a marine embayment in Zanzibar, Tanzania
复制标题
坦桑尼亚桑给巴尔海湾鱼类群落结构的时空变化
作者：
B. R. Lugendo;B. R. Lugendo;B. R. Lugendo;A. D. Groene;A. D. Groene;I. Cornelissen;I. Cornelissen;A. Pronker;A. Pronker;I. Nagelkerken;I. Nagelkerken;G. Velde;Y. Mgaya
研究了桑给巴尔（坦桑尼亚）Chwaka湾热带非河口湾鱼类群落结构的时空变化。从一系列海湾栖息地，从海湾深处的红树林到靠近海湾口的海草床，每两个月（在每个春季低潮）收集1年（2001年11月至2002年10月）的鱼类样本。此外，环境变量进行了检查，以确定其与鱼类群落结构的关系。作为一个非河口湾，环境变量以及在每个栖息地的鱼类群落结构保持相对稳定的大部分时间的一年，但在雨季（4月至5月）观察到显着下降。在雨季期间，所有生境的鱼类群落变量（密度、生物量和物种丰富度）以及水温和盐度都有显著变化，红树林和泥/沙滩生境的变化大于海草床。然而，水的透明度和溶解氧的季节性变化并不显著。在雨季，许多物种从红树林和泥/沙滩生境中消失，而那些持续存在的物种的密度则显着下降。此外，研究结果表明，红树林是首选的定居栖息地Gerres filamentosus，Gerres oyena，Lethrinus lentjan和Monodactylus argenteus，特别是在旱季（12月至2月）前的雨季。这一观察结果与其他一些热带地区的报告相反，在这些地区，雨季的数量和物种丰富度更高。鱼类密度与温度、盐度和浊度有显著的相关性。由于盐度是最显着的变化与季节的环境变量，我们建议，盐度，单独或结合低能见度和温度，可能是最重要的环境因素结构的鱼类组合在红树林和泥/砂滩栖息地，特别是在雨季。
Spatial and temporal variation in the fish community structure were studied in a tropical non-estuarine embayment in Chwaka Bay, Zanzibar (Tanzania). Fish samples were collected bi-monthly (at each spring low tide) for 1 year (November 2001–October 2002) from a range of bay habitats ranging from mangroves deep inside the bay to seagrass beds close to the mouth of the bay. Additionally, environmental variables were examined to determine their relationship with the fish community structure. Being a non-estuarine embayment, the environmental variables as well as the fish community structure in each habitat remained relatively constant for most part of the year; however, a marked decline was observed during the rainy period (April–May). Significant variations in fish community variables (density, biomass and species richness) and in water temperature and salinity were observed during the rainy season in all habitats, with larger changes in the mangrove and mud/sand flats habitats than in the seagrass beds. Seasonal variations in water clarity and dissolved oxygen were not significant, though. Many species disappeared from the mangrove and mud/sand flats habitats during the rainy season and those which persisted showed a remarkable decrease in density. Moreover, the results indicate that mangroves were the preferred settling habitats for Gerres filamentosus, Gerres oyena, Lethrinus lentjan and Monodactylus argenteus, especially during the dry period (December–February) before the rainy season. This observation is contrary to what has been reported from some other tropical regions where greater abundance and species richness was observed during the rainy season. A significant relationship was found between density of fish and temperature, salinity and turbidity. Since salinity was the most conspicuously changing environmental variable with seasons, we propose that salinity, alone or in combination with low visibility and temperature, was probably the most important environmental factor structuring the fish assemblage in the mangrove and mud/sand flats habitats, particularly during the rainy season.