A preliminary study of fishes of Beris reservoir, Kedah, Malaysia AMIR SHAH RUDDIN MD SAH*, KHALID PUTIH and AHMAD SOFIMAN OTHMAN Abstract: The major impact in the damming of the river is the shift from lotic to lentic habitat associated with the reservoir development. As a result, there are major changes in the existing aquatic organism biodiversity especially fishes resulting to the changes in water quality and discharge regime. An intensive fish sampling study had been carried out from 14-21 August 2008 to assess the existing fish species at Beris Reservoir that had been in operation since 2004. Sampling design covered the existing lotic (upstream rivers) and lentic (reservoir) environment using active and passive sampling gears such as cast nets and gill nets. A total of 21 species consists of nine families had been recorded, lentic habitat recorded 11 species while 12 species in lotic habitat. The list includes three new records for the area, Barbodes altus, Oxyleotris marmorata and Oreochromis niloticus in comparison to the previous study that recorded 44 species in 15 families. This paper describes the distribution of freshwater fish species found in different habitats from the new man-made water body. Key words : Beris Reservoir; checklist; fishes; lotic; lentic INTRODUCTION After the impoundment there were major changes in the fish fauna attributing from the changes in the hydrological regimes and biological conditions from lotic (flowing water - river) to lentic (stagnant water - reservoir) environment. The sequence of ecological changes in a reservoir soon after the impoundment has been described by Tundisi and Straskraba (1999) and de Merona et al. (2003). Most of the fish colonizing reservoirs were riverine species as true lacustrine fish species were absent (Mohsin and Ambak, 1983; Yusoff and Gopinath, 1994; Zakaria-Ismail and Lim, 1995; Li and Xu, 1999). The information on fish diversity and its composition in Peninsular Malaysia prior to dam construction is still limited (Ali and Lee, 1995; Zakaria-Ismail and Lim, 1995; Zakariah and Ali, 1996). Although, a fewer fish studies were carried out in the respective reservoirs, as most of the studies concentrated were on fisheries purpose after the dam commissioning or operation (Khoo et al. 1982; Yap and Furtado, 1983; Yusoff and Gopinath, 1994; Zulkafli et al. 1996; Shah et al. 2002). Jackson and Marmulla (2001) had reported the decreasing fish landing in term of weight and species found in the reservoirs globally were due to a combination of factors, including river regulation, pollution, siltation, damming, illegal gear/methods, and overfishing. Chenderoh Reservoir, one of the oldest reservoir which was built in 1930’s also showed the disappearance of its important fish species such as temoleh (Probarbus jullienii) especially at dam downstream (Tan, 1980). Besides that the decreasing fish species at Chenderoh Reservoir had also been noted by Lee (1989) who recorded 63 species when compared to 42 species recorded in 1996 study (Kong and Ali 2000). However, there are several comprehensive studies on fish checklist undertaken by researchers such as Cramphorn (1983) prior to completion of Kenyir Reservoir. She noted that almost 70% of fish species diversity was impacted by the construction of Kenyir Reservoir. The only study on fish fauna before the impoundment of the Sungai Beris was done by Zahari et al. (2000) who recorded 44 species comprising of 15 families. The impact of this impoundment to fish biodiversity and population is still yet unknown. School of Biological Sciences, Universiti Sains Malaysia, 11800 Pulau Pinang, Malaysia. Email: amirshah@usm.my Malayan Nature Journal 2016, 68 (3), 73-81 73