Atobatele Oluwatosin Ebenezer, Ugwumba Alex Obih
Department of Biological Sciences, Bowen University, P.M.B. 284, Iwo, Osun, Nigeria.
Rev Biol Trop. 2011 Sep;59(3):1233-44.
Chrysichthys nigrodigitatus and C. auratus are important, highly valued and threatened freshwater species. To contribute with their ecological knowledge, the condition factor and diet of these two congeneric species were studied between April 2005 and April 2006. Food items of fish were evaluated by occurrence and numerical abundance methods, and the possible changes among sexes, seasons and sizes were considered. Results showed that generally C. nigrodigitatus were better conditioned than C. auratus. The males of C. nigrodigitatus and females of C. auratus were in better condition than their respective opposite sex throughout the year, and during the wet season compared to the dry. The food items of C. nigrodigitatus and C. auratus were similar and comprised twelve species belonging to five groups: Insecta (three species), Crustacea (five species), Arachnida (one species), Rotifera (one species) and Mollusca (two species). Other food items included fish scales, unidentified green eggs, plant parts, detritus and sand. Insecta and Crustacea dominated the food items in both species. For C. nigrodigitatus, insect consumption increased with fish size, while Crustacea items decreased (from 89.59% for 8.1cm - 12.0cm size class to 1.58% for 20.1cm - 26.0cm size class). However, while C. auratus smaller sized fish preferred Crustacea (98.72% for 8.1cm -12.0 cm size class), larger sized fish had both groups in relatively similar amounts. Schoener Overlap Index for both species and between seasons is 1.00. Diet breadth ranged from 0.00-1.47 for C. nigrodigitatus and 0.00-1.32 for C. auratus. Food Richness ranged from 0.00-1.44 for both species. Gut Repletion Index for C. nigrodigitatus and C. auratus are 76.39% and 76.27% respectively. Although, there is considerable similarity and overlap in the utilization of food resource for both coexisting species, condition factor and feeding behavior suggest strategies to reduce intra- and interspecific competition.
黑指金鲿和金色金鲿是重要的、具有很高价值但面临威胁的淡水物种。为增进对它们生态知识的了解，于2005年4月至2006年4月对这两种同属物种的肥满度和食性进行了研究。通过出现频率和数量丰度法评估鱼类的食物种类，并考虑了性别、季节和体型之间可能的变化。结果表明，总体而言，黑指金鲿的身体状况比金色金鲿更好。黑指金鲿的雄性和金色金鲿的雌性在全年以及雨季相比旱季时，身体状况都比各自的异性更好。黑指金鲿和金色金鲿的食物种类相似，包括属于五个类群的12个物种：昆虫纲（3种）、甲壳纲（5种）、蛛形纲（1种）、轮虫纲（1种）和软体动物门（2种）。其他食物种类包括鱼鳞、不明绿色卵、植物部分、碎屑和沙子。昆虫纲和甲壳纲在两种鱼的食物种类中占主导地位。对于黑指金鲿，昆虫类食物的消耗量随鱼的体型增大而增加，而甲壳纲食物则减少（从8.1厘米 - 12.0厘米体长组的89.59%降至20.1厘米 - 26.0厘米体长组的1.58%）。然而，金色金鲿较小体型的鱼更喜欢甲壳纲食物（8.1厘米 - 12.0厘米体长组为98.72%），而较大体型的鱼对这两类食物的摄取量相对相似。两种鱼之间以及不同季节间的谢纳重叠指数为1.00。黑指金鲿的食物广度范围为0.00 - 1.47，金色金鲿为0.00 - 1.32。两种鱼的食物丰富度范围均为0.00 - 1.44。黑指金鲿和金色金鲿的肠道饱满指数分别为76.39%和76.27%。尽管共存的这两个物种在食物资源利用上有相当大的相似性和重叠，但肥满度和摄食行为表明了减少种内和种间竞争的策略。
