Merino Regina Sánchez, Benítez Miriam Y Fermín, Estrada Angélica Mendoza
Facultad de Estudios Superiores Iztacala, Tlalnepantla, estado de México, México.
Rev Biol Trop. 2009 Mar-Jun;57(1-2):187-94.
The Menidia humboldtiana silverside is considered one of the most important species in fisheries in some states of Mexico. Knowing the choice that this species exercises over its food gives us an understanding of the behavior of zooplankton in presence of zooplanktonic fish, and tells us if the silverside choose amongst bigger prey fish, and if there is competition for food between the native and introduced fish in the reservoir. The purpose of this study was to determine if M. humboldtiana selects its food, and in which genera, and to establish whether there was an overlap in the diet of the different sizes of silverside. The fish were catched with a 88 mm mesh net, in six sampling points during one year, from Danxh6 (19 degrees 5'17" - 53'46" N, 99 degrees 32'42" - 35'40" W) reservoir. Samples of filtered zooplankton were also taken with a 125 micron net. The analysis of stomach contents was carried out in fish grouped by regular size intervals during each season of the year, using the volumetric method and Chesson's selectivity coefficient. To evaluate the trophic overlap between the different size groups, the Morisita index, modified by Horn, was used. The zooplankton community was represented by twelve genera: Mastigodiaptomus and Cyclops (Copepoda); Bosmina, Diaphanosoma, Daphnia, Ceriodaphnia, Moina, Alonopsis and Camptocercus, (Cladocera); Asplanchna, Conochillus and Filinia (Rotifera). Mastigodiaptomus was the most abundant throughout the year. The silverside consumed only four genera: Bosmina, Mastigodiaptomus, Daphnia and Ceriodaphnia; the group measuring 5 to 8.9 cm consumed a high percentage of Bosmina, Mastigodiaptomus and Daphnia, and a lesser percentage of Ceriodaphnia. The larger fish (9 to 10.9 cm) consumed only Mastigodiaptomus and Daphnia. In accordance with the selectivity values, the small and medium size silverside selected their prey, with more intensity on the genera Bosmina and Daphnia, while the bigger fish concentrated on Daphnia and Mastigodiaptomus. During spring, the silverside between 3 to 8.9 cm showed overlap in diet; in summer the bigger size group (7-10.9 cm) showed the overlap. In autumm the overlap ocurred in all sizes, and in winter it was shown only in the medium size fish (5-8.9 cm).
洪堡银汉鱼被认为是墨西哥一些州渔业中最重要的物种之一。了解该物种对食物的选择，能让我们了解浮游动物在浮游鱼类存在时的行为，并告诉我们银汉鱼是否会在较大的猎物鱼中进行选择，以及水库中本地鱼和引入鱼之间是否存在食物竞争。本研究的目的是确定洪堡银汉鱼是否会选择食物、选择哪些属的食物，并确定不同大小的银汉鱼在食物选择上是否存在重叠。在一年中的六个采样点，使用88毫米网目的渔网从丹什6号水库（北纬19度5分17秒至53分46秒，西经99度32分42秒至35分40秒）捕获鱼类。还使用125微米网目的渔网采集过滤后的浮游动物样本。在一年的每个季节，按照常规大小间隔对鱼进行分组，采用体积法和切森选择性系数对胃内容物进行分析。为了评估不同大小组之间的营养重叠情况，使用了经霍恩修正的森下指数。浮游动物群落由十二个属代表：鞭毛镖水蚤属和剑水蚤属（桡足类）；裸腹溞属、透明溞属、水蚤属、角突网纹溞属、裸腹水蚤属、异尾溞属和弯尾溞属（枝角类）；长刺溞属、双突轮虫属和细簇轮虫属（轮虫类）。鞭毛镖水蚤属全年最为丰富。银汉鱼只摄食四个属：裸腹溞属、鞭毛镖水蚤属、水蚤属和角突网纹溞属；体长5至8.9厘米的组摄食裸腹溞属、鞭毛镖水蚤属和水蚤属的比例较高，摄食角突网纹溞属的比例较低。较大的鱼（9至10.9厘米）只摄食鞭毛镖水蚤属和水蚤属。根据选择性值，中小型银汉鱼会选择猎物，对裸腹溞属和水蚤属的选择更为强烈，而较大的鱼则集中在水蚤属和鞭毛镖水蚤属。在春季，体长3至8.9厘米的银汉鱼在食物选择上存在重叠；在夏季，较大尺寸组（7至10.9厘米）出现重叠。在秋季，所有大小的鱼都出现重叠，而在冬季，只有中等大小的鱼（5至8.9厘米）出现重叠。
