Maturity, breeding cycle, and fecundity of Mastacembelus armatus (Actinopterygii: Synbranchiformes: Mastacembelidae) in the sub-tropical waters of the river Ganga

Abstract

Background. The investigation on different aspects of the reproductive biology is valuable information in the development of breeding technologies towards initiating conservation and other management measures of the indigenous fish stocks. Mastacembelus armatus (Lacepede, 1800) is a commercially important fish species in the river Ganges of India. But, the data on the reproductive biology of this species is limited. Hence, this study was done to gather information on some aspects of the reproductive biology of M. armatus to address the gap in the current knowledge. Materials and methods. Some biological traits relating to the reproduction of the Zig-zag eel M. armatus were examined from the Ganga River through the monthly sampling for one year from April 2015 to March 2016. About 286 fish specimens were collected comprising 167 males and 119 females. Weight-Length- relations for both the sexes were estimated employing regression analysis. The fecundity was calculated following the gravimetric method. The length at 50% maturity (L50) for the male and female were assessed employing maturity status data. The spawning season was predicted employing Gonado-somatic index and maturity status data. Results. Monthly sex ratio (F ÷ M) ranging between 0.22 ÷ 1 and 2.75 ÷ 1 with a mean of 0.71 ÷ 1 observed in the population was significantly different from 1 ÷ 1. Analysis of mean monthly Gonado- Somatic Index (GSI) and the existence of matured (IV and V) and spent (VI) individuals, indicated year-round spawning with two breeding seasons. The first breeding season occurred between February to May, and the other between July to November in the Ganga River. The L50 of Mastacembelus armatus female and male were determined as 362.2 and 385.6 mm total length (TL), respectively. The reproductive potential in terms of absolute fecundity ranged between 2546 and 6058 with a mean of 3962 ova. Conclusion. The current investigation helps to report the size at maturity in the female and the male for the first time from Indian waters. This species has got a low fecundity indicated that this species possess a comparatively lower reproductive potential, making it more vulnerable to the fishing operation. For the sustainable management of this species, it is necessary to utilise the resources wisely and avoid overfishing in the River Ganga.