Impact of flood control schemes on river fish migrations and species assemblages in Bangladesh

Abstract

A mark-recapture programme at the Pabna Irrigation and Rural Development Project (PIRDP) site in NW Bangladesh showed that Catla catla, Channa striata and Wallago attu migrated through the sluice gates, both with and against prevailing currents in different season, while the smaller Anabas testudineus, Glossogobius giuris and Puntius sophore did not. Species assemblages were significantly different inside and outside the flood control, drainage and irrigation (FCDI) schemes, with up to 25 species absent or less abundant inside compared to outside. The majority of these species were large predators or conspicuous members of the highly prized migratory ' whitefish ' category, including silurid catfish, Indian major carps, mullets and clupeids. In their absence, species inside FCDI schemes were dominated by much smaller resident ' blackfish ' species. Assemblages inside FCDI schemes thus had both a reduced species richness, and a unit value reduced by up to 25%. It was concluded that FCDI schemes such as the PIRDP negatively affect fish species assemblages and stock values, by reducing the accessibility of impounded floodplains to migrant fish. Though some fish are capable of penetrating existing sluice gates, management measures are required to encourage the passage of more species. 1998 The Fisheries Society of the British Isles

Genetic structure of the snakehead murrel, Channa striata (channidae) based on the cytochrome c oxidase subunit I gene: influence of historical and geomorphological factors

“…This downstream migration pattern had already been documented in a study by Halls et al (1998) of C. striata in Bangladesh. Alternatively, the low variability observed in these three populations could also be the result of a historical bottleneck event that may have almost eradicated these populations.…”

Changes in the fish catches during a trial opening of sluice gates on a run‐of‐the river reservoir in Thailand

“…At the end of the monsoon, these fishes move in the opposite direction, from floodplains through the tributaries, and eventually to the Mekong mainstream, where many fishes spend the dry season in deep pools (Poulsen & Jørgensen 2001). Halls, Hoggarth & Debnath (1998) indicated that the floodplain habitat is necessary to the silurids to complete their life cycle. Thus, opening the sluice gates periodically is the recommended strategy to increase the accessibility of migrant fishes to the upstream, floodplain area (Hoggarth, Cowan, Halls, Aeron-Thomas, Garaway, Payne & Welcomme 1999).…”

Modified tide gate management for enhancing instream habitat for native fish upstream of the saline limit

“…However, as well as directly restricting fish passage, tide gates can indirectly affect fish behaviour and community composition through alterations to the instream environment, particularly upstream of the gates. By blocking the normal bi-directional movement of water the upstream hydrological regime is altered; the velocity, turbulence and pattern of freshwater drainage is modified; the normal gradual transition in salinity is disrupted; and the stagnation of freshwater above the tide gates can result in sedimentation and increased water temperatures (Pollard and Hannan, 1994;Kroon and Ansell, 2006;Halls et al, 1998). This is likely to interrupt rheotactic and olfactory cues for migrating fish species (e.g.…”