Yield, growth and mortality rate of the Thai river sprat, Clupeichthys aesarnensis, in Sirinthorn Reservoir, Thailand

The Thai river sprat, Clupeichthys aesarnensis Wongratana, is a clupeid with a short life span, and supports artisanal fisheries in a number of reservoirs in the Mekong Basin. The growth parameters, mortality rates and the status of the Thai river sprat in Sirinthorn Reservoir (28 800 ha), NE Thailand (15&deg;N; 105&deg;E), are presented. The fishery is based on lured lift-nets, operated 7&ndash;14 days in the new moon period, September to April each year. It was shown that the von Bertalanffy growth function (VBGF) model was Lt (mm) = 78.43[1 &minus; exp{&minus;0.211[t &minus; (&minus;0.7996)]}] and its growth conformed to an isometric pattern. Natural mortality rate (month&minus;1) was 0.13 month&minus;1. Total mortality rates ranged from 0.69 to 1.53 month&minus;1 depending on the weather and the fishing season. Recruitment was continuous throughout the year but peaked in June and July. The yield per recruit model indicated that the exploitation rate of this fishery is probably too high.<br /

Fish biodiversity research in the Mekong Basin

The Mekong River is one of the great rivers of the world and is characterized by high fish biodiversity (Valbo-Jorgensen et al. 2009). The Mekong region is in fact a fish biodiversity hotspot whose richness is only now being revealed. During the last decade more than 279 new species of fish have been discovered in this basin alone (WWF 2009). An analysis of fish species present in 204 rivers worldwide recorded in FishBase (www.fishbase.org) (Fig. 1) and backed by a scientific study or publication. Baran (2010) recently showed that the Mekong River is the second richest river in the world for its fish diversity, after the Amazon River

Fish migration, dams, and loss of ecosystem service in the Mekong Basin

The past decade has seen increased international recognition of the importance of the services provided by natural ecosystems. It is unclear however whether such international awareness will lead to improved environmental management in many regions. We explore this issue by examining the specific case of fish migration and dams on the Mekong river. We determine that dams on the Mekong mainstem and major tributaries will have a major impact on the basin's fisheries and the people who depend upon them for food and income. We find no evidence that current moves towards dam construction will stop, and consider two scenarios for the future of the fisheries and other ecosystems of the basin. We conclude that major investment is required in innovative technology to reduce the loss of ecosystem services, and alternative livelihood strategies to cope with the losses that do occur