Ortaz Mario, Martín Ricardo, López-Ordaz Adriana
Instituto de Biología Experimental, Universidad Central de Venezuela, Apartado postal 48170, Caracas 1041A, Venezuela.
Rev Biol Trop. 2011 Sep;59(3):1217-31.
Invertivores fishes are an important component of neotropical streams and they represent a link between aquatic invertebrates and piscivorous species. This study evaluated the breadth diet and interspecific food overlap of nine invertivores fish species during three consecutive hydrological phases: falling (December/07, January/08, February/08 and March/08), low (April/08) and rising waters (June/08), in two sections of a Venezuelan neotropical stream, which were located at different elevation, high watershed (HW) and low watershed (LW). The fishes were collected with a beach seine (5mm mesh) between 8:00 and 11:00 hours. The diet of each species was evaluated using an index of relative importance (IRI), which includes as variables the number, weight and occurrence frequency of food items consumed. The Levin' index (B ) and Morisita (IM) were used to estimate the breadth diet and interspecific food overlap, respectively. All estimations were made using the numeric proportion of preys. Nine fish species were captured, eight Characiformes, of which three were captured in HW (Knodus deuteronoides, Creagrutus bolivari and C. melasma) and five in LW (Thoracocharax stellatus, Moenkhausia lepidura, Cheirodon pulcher, Ctenobrycon spilurus and Aphyocharax alburnus), and one Cyprinodontiformes (Poecilia reticulata), which was also found in HW. In HW aquatic insects were the main resource consumed by fishes while plant material and terrestrial arthropods were secondary resources. In LW the fishes ingested all of these items in addition to zooplankton (Copepoda, Cladocera and larval stages of Decapoda). However, there was a temporal replacement with a predominance of zooplankton in falling and low water. In general, the breadth diet decreased during the falling water in both sections and increased in rising water. However, the average breadth diet was higher in HW. The interspecific food overlap was high in HW while low values were more frequent in LW and its temporal variation was opposed in both sections during almost all the sampling period.
食虫鱼类是新热带溪流的重要组成部分，它们是水生无脊椎动物和食鱼物种之间的一个环节。本研究评估了委内瑞拉一条新热带溪流两个不同海拔区域，即高流域（HW）和低流域（LW）的九个食虫鱼类物种在三个连续水文阶段：落水期（2007年12月、2008年1月、2月和3月）、低水位期（2008年4月）和涨水期（2008年6月）的食物广度和种间食物重叠情况。在8:00至11:00之间用沙滩围网（5毫米网目）采集鱼类。使用相对重要性指数（IRI）评估每个物种的食物组成，该指数将所消耗食物项目的数量、重量和出现频率作为变量。分别使用莱文指数（B）和森下指数（IM）来估计食物广度和种间食物重叠。所有估计均使用猎物的数量比例。共捕获了九个鱼类物种，其中八个是脂鲤目，三个在高流域捕获（德氏裸项脂鲤、博氏溪脂鲤和黑斑溪脂鲤），五个在低流域捕获（星点胸斧脂鲤、细纹穆尔脂鲤、美丽细脂鲤、斯氏栉齿脂鲤和艾氏真唇脂鲤），还有一个鲤齿目（网纹食蚊鱼），在高流域也有发现。在高流域，水生昆虫是鱼类消耗的主要资源，而植物材料和陆生节肢动物是次要资源。在低流域，鱼类除了摄食这些项目外，还摄食浮游动物（桡足类、枝角类和十足目幼虫阶段）。然而，在落水期和低水位期浮游动物占主导，存在时间上的替代现象。总体而言，两个区域的食物广度在落水期均下降，在涨水期增加。然而，高流域的平均食物广度更高。高流域的种间食物重叠程度高，而低流域的值较低且在几乎所有采样期两个区域的时间变化相反。
