Fisheries Dynamics of Modified Floodplains in Southern Asia, Final Technical Report.

Abstract

This final report outlines the project's background, purpose, data collection, results and outputs. Appendices contain a database user manual; a survey methodologies paper; and a PhD chapter on species assemblages as well as 6 sub-project report papers. The purpose of this project was to investigate the life history strategies of floodplain river fish (their spatio-temporal growth, reproduction and survival patterns), and the capture strategies of fishermen, to explain the impacts of hydrological modifications of floodplain rivers, and make recommendations on the management of floodplain river fisheries. The project was carried out at a hydrologically modified site in Pabna, NW Bangladesh and an unmodified site on the River Lempuing, Indonesia, in collaboration with the Bangladesh Agricultural University, Mymensingh, and the Central Research Institute for Fisheries, Indonesia. Research activities included 2-year surveys of catch/effort data, supported by length frequency, biological and mark-recapture studies on six key species at each site, in addition to six sub-projects on special topics. Comparative analyses were made between study years and among sampling regions, including floodplains inside and outside a flood control (FCD/I) scheme in Bangladesh. Fish catches were shown to be higher outside the Bangladesh FCD/I scheme, and species compositions to be richer, especially of the larger riverine species. Productive capacity was, however, undiminished inside the FCD/I scheme, with rates of growth, feeding, reproduction and survival all at least as good inside as outside. Lower catches inside the FCD/I scheme were concluded to be due to lower fishing effort (inhibited by agricultural production) and lower fish recruitment, due to reduced accessibility of migrant species. Inside production was mainly due to recruitment from fish surviving over the dry season inside the FCD/I scheme, but biodiversity and yield were also supplemented by fish immigration through sluice gates. Fishing access was incompletely licensed in Bangladesh, and fishing was intense and competitive at most times. In Indonesia all areas were licensed, and fishing was more efficient, employing ten times fewer people. Mostly due to fishing, mortality rates of fish were so high in Bangladesh, that very few fish were able to survive longer than one year. All the key species except the major carp Catla catla proved able to spawn by this age. It was recommended that licensing should be maintained at both sites, for its socio-economic benefits. Due to fish mobility, however, licensing holds little inherent value for fish conservation. As a precautionary measure, it was recommended that dry season reserves or fishing restraint should be used in both countries, in several deep waterbodies spread across each river catchment. Such reserves also have strong potential for enhancement of recruitment, for relatively small sacrifices in end-of-dry-season catches. In modified floodplains, catches may also be enhanced by simple management measures at FCD/I sluice gates, taking advantage of natural migratory instincts. Reserves were found to be traditionally used in Indonesia for the conservation of local fish stocks where waterbodies were clearly associated with communities. It was recommended that future management should encourage community participation, especially at a local level, with higher management agencies taking a coordinating and monitoring role.

Citation

Fisheries Management Science Programme, London, UK, 242 pp.

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