Aquaculture Intervention in Seasonal Water Logged Areas in Southwest Region of Bangladesh

Bangabandhu Sheikh Mujibur Rahman Agricultural University

Background

Huge areas of agricultural land in the southwest regions, of Bangladesh are facing seasonal waterlogging. In the Blue Gold intervention areas, parts of Polder-2 in Satkhira have been identified with waterlogging problems for a period of 4-5 months each year. This recurring phenomenon has been resulting in low cropping intensity or no crop production, affecting all categories of farmers. Question rises, can this seasonal waterlogged condition be utilized to generate income and improve livelihoods of the affected farmers? The present project has been undertaken to explore the possibility of fish production through aquaculture in two selected beels in polder-2, Satkhira.

View of a pen fish culture site

Objectives

  1. To establish pen fish culture system in selected waterlogged areas in Polder 2.
  2. To establish pen fish culture system in selected waterlogged areas in Polder 2.
  3. To assess the growth and yield performance of tilapia and carps at different stocking rates in pen culture in a waterlogged environment.
  4. To engage Blue Gold WMG in the R&D process of fish culture in water logged rice fields in Polder 2.

Methodology

The study sites were selected through a few field visit and discussion with Water Management Group (WMG) members and local people. The selected sites are (i) Chaler Beel being managed by Degur Beel WMG and (ii) Kachur Beel, being managed by Jordia Eru Khal WMG.

Discussion with local farmer group


According to the local opinion, each of the selected sites has been affected by waterlogging, with a water depth of 2.5-4 feet during monsoon and lasts for a period of 4-5 months.

The WMG members who own the lands are the beneficiary farmers, whereas farmers in the project area who does not belong to WMG, are also taken in the beneficiary farmers group. Contract farmers have been trained on different aspects of pen fish culture and management.

Design of Experiment: The study has been designed with three different stocking rates (treatments) of tilapia (GIFT strain) and carps (Ruhu, Catla, Mrigal, Grass carp) maintaining a total fish stocking biomass of about 750-800 gm per decimal. Each treatment is replicated in two experimental sites.

Table 1. Treatment-wise stocking rates of fish species

Treatment Fish species (per ha)
  GIFT Ruhu Catla Mrigal Grass carp
1 44460 370
2 37050 740 247 123 370
3 29640 1235 370 247 370

The individual stocking weight of tilapia and carp was 3-5 gm and 45-50 gm, respectively.

Fish pen construction activity


Fish Pen Construction: A selected area at each site (1.94 and 2.16 ha in Chaler Beel and Kochur Beel, respectively) was enclosed and divided into three compartments with polyethylene knotless net to separate treatments. The net has been fixed 30 cm beneath the mud and tied with bamboo spilt. The height of the pen is maintained at least 3 meters.

Fish stocking, Feeding and Monitoring: Stocking of fishes commenced in between July 31 and August 03, 2017. A commercial feed (Mega Floating Feed) is used for feeding tilapia at the rate of 5-7% of fish biomass. No extra feed are being applied for carps. Feeding is done through broadcasting method. Fish growth and water quality are observed weekly. In addition, parameters are being monitored at time of sampling.

Results

Water quality: During the initial 60 days of fish culture period, variations in water temperature (29-31oC), dissolved oxygen (6.5-7.5 mg/l) and pH (5-6) were within the suitable limit in both sites. However, water depth has been reduced from an initial average of 80-90 cm to 30-54 cm.

Fish growth: During the 60 days of culture period, tilapia in Chaler Beel and Jordia Eru khal attained an average weight of 31.02-68.25 gm, 59.55-66.75 gm, respectively, with specific growth rate (SGR) of 3.82 to 5.44 (Fig. 4). Growth rate of tilapia has been found to vary among the treatments and between two experimental sites. After final harvest of fish, analysis of data will reveal if the variations are significant or not.

Speculation and Lesson Learnt

Considering higher growth rate of tilapia, pen fish culture may be feasible in waterlogged areas. The only most critical issue is the level of water retention. Due to re-excavation of Amodkhali khal, the water level has been reduced drastically in Chaler Beel that rendered the experimental site unsuitable for pen fish culture.

Pen fish culture could be a promising farming option in waterlogged rice fields. These fields are usually rich in nutrient that may provide the fish with natural food and reduced dependence on supplemental feed. There is opportunity of upscaling of this aquaculture technique in other waterlogged areas. However, it’s sustainability greatly depends on the community approached motivation of farmers.

Dr. Md. Jahangir Alam
Professor, Faculty of Fisheries, Bangabandhu Sheikh Mujibur Rahman Agricultural University

Download a PDF version: BSMR Aquaculture Intervention Polder 2 v4