Biology of the ornamental cyprinid fish Danio dangila (Hamilton, 1822) from the North-eastern hill region of India

Abstract

The moustache danio Danio dangila (Hamilton, 1822) is one of the most popular native ornamental fishes of the
North-eastern hill region of India. The species needs immediate attention owing to its reduced abundance in the wild. The length-weight relationship of D. dangila indicated an isometric growth in general and was found to follow the cube law. The L-W relationships derived for the species were: log W = -5.009 + 3.00 log L (male and female combined); log W = -5.542 + 3.31 log L (male) and log W = -5.462 + 3.26 log L (female). The 41-50 mm size group was found to be predominant (44.25%) in the wild. The fish predominantly feeds on phytoplankton (97.12%), with Myxophycea forming 68%, followed by Zygnemophyceae 25%, Ulvophyceae 3%, Zygnematophyceae 2%, Cryptophyceae 1% and Bacillariophyceae 1%. The major zooplankton group in the diet was Rotifera. Nematodes and other similar worms also formed a part of their diet. The sex ratio (female: male) estimated was 1:1.77. The gonadosomatic index (GSI) for gravid females ranged from 2.55 to 24.12 with an average value of 7.65. The minimum and maximum fecundity were 400 and 2000 in females having a length of 52 and 64 mm and weight of 2.52 and 3.15 g respectively.