Long-Term Records of Fisheries Yield and Stocking in Kaptai Reservoir (Bangladesh)—Evidence for Regime Shift?

Regime shifts, abrupt switches between alternate states of ecosystems, have repeatedly been described for marine fisheries, but little evidence exists for regime shifts in freshwater fisheries systems.A 41-year long time series (from 1965 until 2005) of fisheries yielded 17 fish species, dried fish and miscellaneous species from Kaptai reservoir, Bangladesh, which were analyzed to detect major trends in fish assemblage composition.Annual rates of supplemental stocking were included to elucidate whether stocking modified fish assemblage structure.Indian major carp species (ruhu, catla, mrigal, kalibaus), which dominated initially, were replaced by pelagic clupeid species (chapila, kechki) after about 20 years.Ordination of time series by nonmetric multidimensional scaling indicated smooth transitions between 1965 and 1980, but demonstrated rather drastic jumps between 1980 and 1986.Afterward,…