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Recruitment sources for fish stocks inside a floodplain river impoundment in Bangladesh
- HOGGARTH, D. D., DAM, R. K., DEBNATH, K., HALLS, A. S.
- Fisheries management and ecology 1999 v.6 no.4 pp. 287-310
- development projects, dry season, fish, fish behavior, fish production, fisheries, flood control, floodplains, irrigation management, lakes, migratory behavior, recruitment, rivers, rural development, species diversity, surface water, Bangladesh
- The sources of fish recruitment in the hydrologically modified, impounded Pabna Irrigation and Rural Development Project (PIRDP) flood control and irrigation scheme in NW Bangladesh were investigated. Catches at sluice gates were analysed to determine the migratory behaviour of fish. Fish attempted to migrate through the undershot sluice gates when they were opened, both with and against the currents, and both in and out of the PIRDP. Many fish were caught by the fishermen at such locations, but it is argued that some fish were probably able to enter the PIRDP from outside. One to two percentage of fish survived the dry season at the PIRDP, mostly in the deeper, perennial water bodies, both in rivers and lakes, and both inside and outside the flood control scheme. Fewer species survived inside the scheme, and the numbers of species remaining declined as the dry season progressed. It was shown in companion papers that fish production inside the PIRDP was lower than outside in both 1995 and 1996 even though the growth and reproductive potential of individual fish were at least as good inside as outside. The apparently negative impact of the PIRDP was explained by the reduced accessibility of the scheme to some migrant fish, as reflected by the inside/outside species compositions. It was concluded that fish catches within the PIRDP are sustained mainly from recruits produced by residing annual populations, while the biodiversity of the stocks was augmented by limited recruitment of fish migrating through the sluice gates from external sources. Two management approaches were proposed for increasing recruitment to the impounded PIRDP fishery as cheap alternatives to fish stocking: the use of dry season reserves to protect the residing spawning stocks; and the management of flood control sluice gates to maximise recruitment from external sources.