Morphometric development in laboratory-reared larval and juvenile Puntioplites proctozysron (Cypriniformes: Cyprinidae)

Ichthyological Research - Several morphometric characters with observing general morphology of laboratory-reared larval and juvenile Puntioplites proctozysron (9–40-day-old, 6.8 to...     

Potential Effects of Hydroelectric Dam Development in the Mekong River Basin on the Migration of Siamese Mud Carp (Henicorhynchus siamensis and H. lobatus) Elucidated by Otolith Microchemistry

The migration of Siamese mud carp (Henicorhynchus siamensis and H. lobatus), two of the most economically important fish species in the Mekong River, was studied using an otolith microchemistry technique. Fish and river water samples were collected in seven regions throughout the whole basin in Thailand, Laos and Cambodia over a 4 year study period. There was coherence between the elements in the ambient water and on the surface of the otoliths, with strontium (Sr) and barium (Ba) showing the strongest correlation. The partition coefficients were 0.409–0.496 for Sr and 0.055 for Ba. Otolith Sr-Ba profiles indicated extensive synchronized migrations with similar natal origins among individuals within the same region. H. siamensis movement has been severely suppressed in a tributary system where a series of irrigation dams has blocked their migration. H. lobatus collected both below and above the Khone Falls in the mainstream Mekong exhibited statistically different otolith surface elemental signatures but similar core elemental signatures. This result suggests a population originating from a single natal origin but bypassing the waterfalls through a passable side channel where a major hydroelectric dam is planned. The potential effects of damming in the Mekong River are discussed.     

Life history of the riverine cyprinid Henicorhynchus siamensis (Sauvage, 1881) in a small reservoir

The riverine species, Henicorhynchus siamensis (Sauvage 1881), is an important source of protein and an economical fish for the rural population of inland Indochina. Investigated in the present study were the reproductive feeding aspects and growth of H. siamensis living in a lake system. The gonadosomatic index peaked in August, which was delayed compared to river fish, and individuals took 1.5 years to attain the length of 50% maturity (about 200 mm). Stomach contents were dominated by phytoplankton and showed considerable seasonal variation. Asymptotic length of H. siamensis was 264.2 mm, with a 0.75 year^?1 growth coefficient and slower growth during the winter. The role of the flood pulse as a major influence on the life history of the fish is also discussed.