Pond Construction (© MSSRF)
Construction of Integrated mangrove fish ponds
In the identified saline affected area, fish ponds where constructed with an innovative approach. Normally, fish ponds will have only four earthern bunds to hold water. In this model, apart from these four outer bunds, inner bunds are also created and the ponds look like a mitochandria. The inner bunds are created to provide more space for mangrove plantation. The water spread area is used for fish culture. Thus, in this system, nearly 60% to 70% is given for fish culture and nearly 40% is given for mangrove plantation. To create inner bunds a lot soil was dug from the pond and this makes the pond floor lower than the tidal level. As a result, tidal water enters the sysem during the high tide and drains out during the low tide by gravitation. Any amount of water can be kept in the system by placing tidal water inlet and outlet at appropirate hight. Due to regular tidal flushing, this systems requires no energy for pumping water in and out of the pond. Due to regular flushing by tides, no chemical treatement is necessary to maintain water quality. Since tidal water brings a lot of food, there is only a minium requirement for artificial feed. Thus, this system of fish farming is environment friendly.
Successful construction and implementation depends on:
- Acceptance of communities for brackish-water adapted fish species for cultivation as traditionally bred and conceivably preferred species are no longer economically viable
- Engagement and participation of village people to construct infrastructure and to plant mangrove seedlings
- Training in aquaculture for fish farmers
- Technical and capacity development support
- Village mangrove nursery
The selection of families done by the community to pilot the cultivation of brackish-water adapted fish species proofed successful as they established a model that will be replicated by other families in the community, and elsewhere.
The area selected for fish ponds and bunds should be carefully designed as to designate the major part (60-70% of the area selected) for fish, crab or shrimp farming without jeopardizing an effective regulation of the water spread by bunds (covering 30-40% of the area selected).
Fish ponds that are subject to tidal flow need to be protected against cyclones, storm surges and particularly sea water inundations that are likely to increase due to climate change induced sea level raise.
The combined systems of mangroves and halophytes proofed successful. The use of tidal flow makes redundant chemical additives and feed, thus reducing operational costs substantially.