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Ecological Assessment of Hilsa (tenualosa Ilisha, Hamilton) Resources with Special Reference to Juvenile Hilsa (jatka )in the Lower Meghna.

Dr. Khan Kamal Uddin Ahmed
Senior Scientific Officer
Riverine Station, Bangladesh Fisheries Research Institute, Mymensingh

Md. Rabiul Awal Hossain
Scientific Officer
Riverine Station, Bangladesh Fisheries Research Institute, Mymensingh

Mrs. Tayfa Ahmed
Scientific Officer
Riverine Station, Bangladesh Fisheries Research Institute, Mymensingh

Abstract/ Executive Summary:

The clarity of water was found higher at the upper stretch of the river than that of lower stretch. Dissolved oxygen content was found gradually decreasing from the upper to lower stretches of the river system. The values of DO ranged from 5.6 and 9.75 mg/l. The values of pH in the river water remained on the alkaline side (8.5-9.5) at the sampling stations. During the investigation 22 genera of phytoplankton belonging to 14 families and 8 genera of zooplankton belonging to 6 families were recorded. Of the total identified genera, 95.1% were Chlorophyceae, 3.9% Myxophyceae, 0.6% Bacillariophyceae and 0.4% Euglenophaeceae. Largely available zooplanktons were represented by the members of the group Rotifers (52.1%) followed by Copepoda (25.8%) and Cladocera (22.1%). The mean contribution of phytoplankton was 95.2% of the total and zooplankton contributed the rest. The net primary production (gC/m3/h) in the euphotic zone (15 cm below) of the Meghna river ranged from 0.041 (Tetulia) to 0.140 (Kalabadar) during the investigation period. Gross primary production fluctuated between 0.062 and 0.307). Primary productivity showed that the upper stretches of Meghna river had high productivity compared to estuarine zones.

Keywords: Ecological assessment, Hilsa, Jatka

Location: Chandpur

Start Date: 01-07-2004

End Date: 31-06-2005

Program Area: Resource Development and Management

Commodity: Hilsa

Objectives:

1. To study the limno-biological characteristics in the major rivers and estuaries; estimation of primary production and fish yield and landing status of hilsa/juvenile hilsa in the lower Meghna areas; 2. To study the age and gonad development of undersized hilsa and relevant factors and impact assessment of juvenile hilsa (jatka) ban program in the lower Meghna; and 3. To identify the causes of reduction in hilsa catch from selected river systems.

Methodology:

Year round experimental fishing was done by gill net of medium and big mesh sizes to know the production potential of hilsa resources. Hilsa landing data was record from major and small fish landing sites along the lower Meghna. Sampling, necessary preservation and analysis of the limno-biological parameters were carried out following APHA 1995. Temperature (air and water), transparency, dissolved oxygen, free carbondioxide, total hardness, total alkalinity, salinity, total dissolved solids (TDS) and chemical oxygen demand (CO) were studied following APHA 1995. Replicate plankton samples were collected by filtering 50L of water through bolting silk plankton net of 50µ. Qualitative and quantitative analysis of both phyto- and Zooplankton was done following drop count Method (APHA 1995). Continuous monitoring of gonads of undersized hilsa was attempted to check through their extent of maturity, gonado-somatic index (GSI) and fecundity. Age of the undersized was determined using length-frequency, scale and otolith study. Monitoring fishers' catch of different fishing gears were collected to estimate catch-effort and catch composition data of juvenile (jatka) and hilsa.

Source of Information: Annual Research Program 2004-05. BFRI, Mymensingh.

Article Link (Online Journal):

Funding Source:

1. Government

Budget: Five lakh

Total Budget (Tk.) : Five lakh

Achievement/Findings:

Ecological assessment of the rivers and estuarine environment related to hilsa resources will give a clear feature about the water quality and environmental aspects of the fishing, spawning and nursery grounds of hilsa; production potential of different rivers and estuarine systems can be estimated; extent of present abundance and distribution of juvenile (jatka)/hilsa at lower Meghna and compare them with previous condition. Impact assessment of fishing ban at lower Meghna; and major causes of reduction in the abundance hilsa resources can be identified from a number of rivers where once hilsa were abundant.

Knowledge Management: Report/Proceedings