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

Abstract

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.

Evidence for population genetic structure in two exploited Mekong River fishes across a natural riverine barrier

“…At Khone Falls, the recent completion of the Don Sahong dam on the Hou Sahong channel may restrict natural levels of gene flow and have detrimental impacts on migratory fishes known to use this corridor (Fukushima et al ., 2014). As sampling took place the same year as construction on the dam began, there is no evidence that damming has caused the genetic discontinuities observed by this study for H. lobatus or H. leptorhynchus as it is extremely unlikely that genetic drift could impact allele frequencies over such a short time span (Maruyama & Fuerst, 1985; Nei et al ., 1975; Tajima, 1989).…”

Spatial and temporal variation in fish community structure and diversity in the largest tropical flood‐pulse system of South‐East Asia

“…Henicorhynchus lobatus, are among ecological keystone species with critical roles in food security throughout the Lower Mekong Basin (LMB); additionally, these species are important prey for predatory species and Irrawaddy dolphins (Baird, 2011;Fukushima, Jutagate, Grudpan, Phomikong, & Nohara, 2014).…”

Changes in environmental salinity during the life of Pangasius krempfi in the Mekong Delta (Vietnam) estimated from otolith Sr : Ca ratios

“…Understanding the movement patterns of migratory fish is essential for fishery management and conservation across large spatial scales (Gillanders 2005a;Carlson et al 2017). In some major rivers, knowledge of these movements has become a priority for management because fish caught in one country may have migrated across several other countries (Hogan et al 2007;Fukushima et al 2014). Migratory fish in fresh water are particularly vulnerable because the water properties and the connectivity of different habitats may change (Poulsen et al 2004).…”

“…Fish otoliths (ear stones) are calcified structures that grow in regular cycles (daily and seasonal) and contain and reflect detailed changes in temperature and element concentrations in an individual fish's environment (Campana 1999). When combining microchemistry with age estimation, otoliths can provide valuable information about an individual fish's life history, including potential migrations for species that pass through different habitats (Wells et al 2003;Panfili et al 2009Panfili et al , 2012Fukushima et al 2014). Environmental conditions during a fish's life can be indicated by the composition of the otoliths, such as Sr, Zn, Pb, Mn, Ba and Fe concentrations, which can show differences, for example, between freshwater and marine environments (Campana 1999;Wells et al 2003).…”