Abundance and Diversity of Plankton in Different Stocking Densities of Mola (Amblypharyngodon mola) in Prawn-Carp Gher Culture System

Abstract

The present study was conducted to assess the abundance and diversity of plankton among the ponds of three different stocking densities of mola fish (Amblypharyngodon mola) at Dumuria upazilla, Khulna, from September to December, 2015. The present experiment consists of three treatments each of which has three replications. Stocking density of mola fish 1, 2 and 4 indv./m² were considered as Treatment-1, Treatment-2 and Treatment-3 respectively. Plankton samples were collected fortnightly by conical shaped monofilament nylon net (Phytoplankton net) and Lugol’s solution was used for preservation. In the present study 25 genera belong to 5 groups of phytoplankton namely Chlorophyta, Cyanophyta, Bacillariophyta, Euglenophyta, Chrysophycophyta were found. Among all groups Chlorophyta was the dominant and the average percentages of Chlorophyta, Cyanophyta, Bacillariophyta, Euglenophyta, Chrysophycophyta in the three treatments were 34.72%, 21.67%, 18.81%, 14.15% and 10.55% respectively. The mean (±SD) values were 4506.5±803.49, 4308.25±771.91 and 4097±774.46 indv./l of total phytoplankton in T₁, T₂ and T₃ respectively. During the study 8 genera belong to 5 groups of zooplankton were observed. These are copepod, rotifer, cladocera, ostracoda and crustacean larvae. Among all groups, Copepod was the dominant and the average percentages of Copepoda, Rotifera, Cladocera, Ostracoda and Crustacean, Larvae were 55.84%, 28.18%, 10.39%, 3.57% and 1.98% respectively. The mean (±SD) values were 1462.5±203.32, 1376.75±160.16 and 1288.25±156.75 indv./l of total zooplankton in T₁, T₂ and T₃ respectively. Chlorophyta was significantly higher than other groups of phytoplankton and Copepoda was significantly higher than other groups of zooplankton. This experiment indicates that the abundance of various groups of Plankton was significantly fluctuated by the three different stocking densities of mola fish (Amblypharyngodon mola).