BIOLOGY, POPULATION DYNAMICS AND FISHERY OF PUNTIUS CONCHONIUS (HAMILTON) IN A FLOODPLAIN WETLAND IN GANGA RIVER BASIN, INDIA

Abstract

The biology, population parameters and fishery of Puntius conchonius (Hamilton) in a floodplain wetland in Ganga river basin, India was studied during 2004-06. Investigations on the food habit showed that it feed mainly on phytoplankton, belonging to Chlorophyceae and Bacillariophyceae. Male female ratio in the population was 1:1. Females attained sexual maturity at 6 cm in total length. The fecundity ranged from 320 (6 cm and 3.78 g fish) to 11045 (7.9 cm and 8.98 g fish). The fish breed year round with peaks during May-July and November-January. Fitting the von Bertalanffy growth function (VBGF) revealed the asymptotic length (L8 ) as = 9.45 cm, growth coefficient (K) as = 0.71/year. Other population parameters such as length at maximum yield possible (Lopt) was 5.5 cm, the instantaneous total mortality coefficient (Z) was 2.53 year-1, natural mortality coefficient (M) was 1.89 year-1, fishing mortality coefficient (F) was 0.64 year-1, exploitation rate (E) was 0.25, length at recruitment (Lr ) was 3.3 cm and length at first capture (Lc or L50) was 3.7 cm. The recruitment pattern was continuous and year-round. The estimated exploitation rate needed for obtaining maximum yield/recruit (Emax) was 0.52, indicating low fishing pressure on the stock as E < Emax. About 34.43% of the fishes caught were smaller than their length at first maturity (Lm= 6 cm). Only 17.75% of the catch was at Lopt (5.5 cm), while 51.53% was above Lm. Occurrence of immature specimens in the population was high during July-November, while the abundance was high during December-June. Capture at mean lengths nearer to Lopt and Lm (say at 5-6 cm TL) would help sustain stock while increasing exploitation to reach E>0.25 and = 0.52 to attain higher yield.

Key words: Biology, population dynamics, fishery, floodplain wetland, growth, mortality, recruitment, exploitation, Puntius conchonius, Ganga, India