Assessment of ecological health status in selected haors with different degrees of interventions using fish indicators

Abstract

Haors are very important habitats for the unique and dynamic ecosystems, which have immense productive or ecological valuc. Importantly, haors provide suitable habitats for fisheries, a major component of the ecological resources. However, anthropogenic interfcrenccs, c.g. wetland encroachment and exploitation pressure, and water management infrastructures are causing decline of wetland habitats, especially during the dry season. Water management interventions bring about changes in natural systems of haors, and hence the impact of partial flood protection on the ecosystem of the haors is emerging as a significant concern. The study examined the ecosystem of three selected haors subject to varying physical effects of water management infrastructure. Fish has been selected as an indicator for ecosystem as fishes arc scnsltive to many changes in natural water quality and habitat structure caused by anlhrop<lgenic or by natural causes. Based on a set of pre-del ermined criteria, a tolal of three haors were selected, which represented three distinct physical characteristics: a relalhely undisturbed state (Chaptir haar), a moderately intervened state (fangua haor), and an extensively intervened state (Daram haer). A range of Participatory Rural Appraisal (PRA) tools (e.g. resource mapping, FGDs) were used in the srndy to obtain data relating to the status of the physical system of the haors and the status of fisheries ecosystem. The findings from' the field surveys showed that migration routes and fish habitat areas have been impacted to different degrees in the three haors by water management infrastructures. Fish migration routes are better in Chaptir haor, followed by Tanb'tJa haor. Migration routes in Baram haor are the worst. Habitat depths, e.g. depths of the river, khals and beels are highest in Chaptir haer, followed by Tangua haor. Habitat depths in Baram haor arc the lowest. The impact of water management interventions has also been reflected in the declines in fish catch compared to a period 10 years ago. A scoring and ranking method was used for analyzing habitat wise fish composition data obtained from the field survey. This exercise yielded three species (Rui, Catla, and Boal) which are indicative of different status of ecosystem health in the haors.