Comparative Study of Reproductive Traits in Gangetic Hairfin Anchovy, Setipinna phasa (Hamilton, 1822) from Estuarine and Freshwater Ecosystems

The Gangetic hairfin anchovy, Setipinna phasa (Hamilton, 1822) were collected from river Ganga (Kanpur) and Hooghly estuary (Kolkata) to study the comparative reproductive traits (sex ratio, spawning season, gonado-somatic index, fecundity and egg diameter). Female outnumbered the male in the population of river Ganga but it was non-significant in the population of the estuary. Five maturity stages were identified in males and females of the fish of both ecosystems. Occurrence of multimodal (immature, maturing and mature) and uni-modal (matured) type of ova in the ovary of the fish of Hooghly estuary and river Ganga respectively and the values of gonado-somatic index confirmed the double and single spawning in a year in the fish in estuary and river respectively. The absolute fecundity was found to be higher in the fish of river Ganga compared to that of the estuary (P < 0.05). Linear and positive correlations between fecundity and the total length, body weight, ovary length and ovary weight were noted in the fish of both ecosystems (R2 > 0.90). The present study provides the comparative account of the reproductive and spawning strategies of S. phasa for the first time in favour of the proper management and conservation of the fish.

Application of artificial neural network for predicting water levels in Hooghly estuary, India

Hydrodynamic models for morphodynamic studies in estuaries require continuous tidal water level data as boundary conditions. However, for the Hooghly estuary in India, measurement of continuous tidal water elevation data at the most downstream point is a very difficult task because of the remote location and the confluence with the deep sea. The tidal water level data at this station are measured for a half tidal cycle which is not useful for hydrodynamic modeling. However, at other upstream stations, tide water level data are measured continuously. Accordingly, in this study, an attempt is made to generate continuous tidal water level data at the remote station, using the data of the neighboring stations as input to an artificial neural network (ANN) model. A three-layered feed-forward backpropagation (FFBP) network with two hidden layers is selected and five different combinations of input vectors are used. Simulated water level data obtained from each model are compared with the observed data graphically as well as by estimating the standard error parameters. The best model suitable for prediction of continuous tidal elevation during any time of the tidal cycle and applicable throughout the year is then identified. It is found that tidal data from the nearest neighboring station are more suitable for training.

Prevalence and Ecotoxicological significance of heavy metals in sediments of lower stretches of the Hooghly estuary, India

The concentration and distribution of selected eight heavy metals in five stations from lower stretches of the Hooghly estuary were studied to ascertain the level of anthropogenic contaminant loading resulting from the development of the region. Atomic absorption spectroscopy showed that the mean concentration of Fe, Zn, Cu, Ni, Pb, Cr, Cd and As (mg kg-1, dry weight,) ranged from 29950.70 – 39567.94, 61.45 – 98.83, 40.65 – 54.46, 25.44 – 42.78, 36.93 – 48.56, 29.07 – 46.35, BDL – 3.48 and 1.18 – 6.44 respectively. Pollution load index (PLI) and Index of geoaccumulation (Igeo) revealed overall low values but the enrichment factors (EFs) for Cd was typically high for three of the stations. Calculations based on Effect Range Low (ERL) and Threshold Effect Level (TEL) showed that the mean concentration of Cu, Ni and Cd and to some extent Pb exceeded these levels, indicating that there is chance of ecotoxicological effects on benthic organisms dwelling in this region. Inter-elemental relationship and cluster analysis revealed identical behavior of the elements during transport and distribution. The study will help to further the cause of environmental protection of this sensitive biorealm in conjunction with the need for development of the region.