• over-exploitation to support the growing population;
• siltation of river beds and inland water bodies;
• fish disease;
• irrigation for agriculture;
• application of agro-chemicals;
• ecological factors;
• application of poison in the deep ponds to kill SIS fish;
• reckless use of current jal;
• water scarcity due to changing environment; and impact of FCD/l projects for agro cropping.
In north-western Bangladesh, Bhuiyan (1997) cites the following reasons for the overall decline in SIS:
• over fishing;
• wide use of insecticides and pesticides; and · insufficient inundation and siltation in the rivers.
FAP 6 (1993) identified the following reasons for the decline in flood plain production in the north-east region:
• siltation of river beds and deeper beels;
• over exploitation of fish;
• fine-meshed nets used in tributaries affect SIS breeding and juvenile growth;
• fishing in the beels by complete de-watering;
• deforestation of the haor area;
• industrial effluents;
• barriers to fish migration during the breeding season caused by FCD/I projects.
An environmental impact of freshwater prawn cultivation in Bagerhat district was carried out by CARE-GOLDA (1997). Prawn
cultivation and Gher construction are considered to have negative environmental impacts and to have caused a reduction in
SIS. They cited the following consequences:
• reduced recruitment of riverine species migrating to coastal areas to spawn;
• reduced wetland habitat;
• reduced beel area;
• reduced grazing land;
• water pollution;
• blockage of water ways; and decline in snails
Biological, Seasonal and Physical Diversity: a Dynamic Equilibrium
The freshwater ecosystem is a valuable component of Bangladesh's biodiversity heritage.
A wide variety of habitats and ecosystems, geographically and seasonally isolated and varied, provide basis of a highly
diverse fauna and flora. This has adapted and evolved to fill the myriad of ecological niches. The seasonal cycle of flooding
and drying out of the flood plain provides for a seasonal enrichment of the soils. The linking of many water bodies at this
time, effectively forms a single (but highly diverse) biological production system. The migratory and reproductive behaviour of
freshwater fish is finely tuned and adjusted to rhythm and amplitude of this seasonal cycle of flooding.
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