Abstract

Morphological variations of the Asian sheat catfish, Wallago attu (Bloch and Schneider, 1801) sampled from the rivers Gomti, Ganga, Yamuna at Lucknow, Kanpur and Agra districts in Northern India, river Hooghly at Kolkata in Eastern India and river Pampa at Kerala in Southern India were analyzed in the present study. Images of 261 specimens of W. attu were taken without harming the fish to evaluate the morphometric variation using 8 digitized homologous landmarks for truss analysis and geometric morphometrics. Size corrected morphometric variables were analyzed using analysis of variance (ANOVA), multivariate analysis of variance (MANOVA), principal component analysis (PCA) and discriminant function analysis (DFA). Coefficients of all PCs were positively and negatively correlated to 31 significant (p < 0.001) truss measurements due to variations in size and shape. Morphometric measurements lying in the head region such as head length (HL), eye diameter (ED), inter-orbital length (IOL) and snout length (SNL) contributed most to differentiate the populations in truss analysis. The ED, HL, SNL and IOL of Yamuna fish was significantly (p < 0.001) smaller than the other fish populations. This could be attributed to the heavy pollution load in the Yamuna River and differences in the feeding regimes of fish. PCs and relative warps depicted differences in geometric analysis because of body shape variations among different river populations. The scatter plot in DFA revealed the presence of three distant and different phenotypic groups of W. attu among five wild river populations of fish with 70.5% and 83.9% of correct classification of fish into their original groups in truss and geometric analysis respectively. A single homogenous stock of fish was found to be in the rivers Gomti, Ganga and Hooghly because of a high level of intermixing (maximum misclassification) among the three river populations, whereas Yamuna and Pampa populations were two non-overlapping isolated groups due to negligible intermixing. These variations in the present study might be the effect of geographical isolation and river fragmentation due to the change in habitat that restricts fish movements. This is the first report on the morphometric assessment of W. attu that provides base line data for further confirmatory stock studies that would be useful for conservation and sustainable management of this vulnerable fish.

中文翻译：

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印度五条河流的亚洲鲶鱼 Wallago attu（鲶科）种群形态变异的评估

摘要

亚洲鞘鲶的形态变异，Wallago attu（Bloch 和 Schneider，1801 年）从 Gomti、Ganga、Yamuna 河采样本研究分析了印度北部的勒克瑙、坎普尔和阿格拉地区，印度东部加尔各答的胡格利河和印度南部喀拉拉邦的潘帕河。 261 个 W 标本的图像。 attu 在不伤害鱼的情况下进行，使用 8 个数字化同源地标进行桁架分析和几何形态测量来评估形态变化。使用方差分析（ANOVA）、多变量方差分析（MANOVA）、主成分分析（PCA）和判别函数分析（DFA）对尺寸校正的形态计量变量进行分析。由于尺寸和形状的变化，所有 PC 的系数与 31 个显着 (p < 0.001) 桁架测量值呈正相关和负相关。头部区域的形态测量，如头长 (HL)、眼直径 (ED)、眼眶间长度 (IOL) 和吻部长度 (SNL) 对桁架分析中的种群区分贡献最大。亚穆纳鱼的 ED、HL、SNL 和 IOL 显着小于其他鱼类种群 (p < 0.001)。这可能是由于亚穆纳河的严重污染负荷和鱼类摄食方式的差异造成的。 PC 和相对扭曲描绘了几何分析中的差异，因为不同河流种群之间的体形差异。 DFA 中的散点图揭示了 W 的三个远距离且不同表型组的存在。 attu 在五个野生河流鱼类种群中，在桁架和几何分析中将鱼类正确分类到其原始类群中的正确率分别为 70.5% 和 83.9%。在 Gomti、Ganga 和 Hooghly 河中发现了单一同质鱼类种群，因为这三个河流种群之间存在高度混合（最大错误分类），而亚穆纳河和潘帕种群则由于可忽略不计而成为两个不重叠的孤立群体。混合。本研究中的这些变化可能是地理隔离和河流破碎化的影响，这是由于栖息地的变化限制了鱼类的运动。这是第一份关于W形态测量评估的报告。 attu 为进一步验证种群研究提供基线数据，这将有助于保护和可持续管理这种脆弱鱼类。