Injury and mortality of two Mekong River species exposed to turbulent shear forces

Abstract

Global hydropower development is one solution proposed to address the increase in energy needs. However, hydropower-related impacts on riverine ecological systems are not well understood. The Mekong River Basin (MRB) is one of the world’s largest waterways and is presently experiencing significant hydropower expansion. It is also one of the most biodiverse rivers; serving as home to many species that are blocked or hindered by the development of dams. One source of injury and mortality for downstream moving fishes is passage through the turbine environment where fishes may be exposed to several physical stressors (e.g. shear forces, rapid decompression, blade strike and turbulence). The current study sought to understand the susceptibility of blue gourami (Trichopodus trichopterus) and iridescent shark (Pangasianodon hypophthalmus) to shear forces. Fishes were exposed to an underwater jet with velocities up to 21.3ms–1 (equating to strain rates of up to 1185s–1) and were assessed for behavioural effects, injuries and mortality. Overall, it was determined that both species were susceptible to the shear forces applied in this study and the effects were more pronounced at higher strain rates. Gouramis were more susceptible than sharks. To minimise impacts on these species, shear forces within turbines should not exceed critical limits.

Gambusia holbrooki Survive Shear Stress, Pressurization and Avoid Blade Strike in a Simulated Pumped Hydroelectric Scheme

“…In comparison to these species, our results indicate that gambusia are a relatively tolerant species to shear strain, owing perhaps to their small size and body morphology (Neitzel et al, 2000). Our results from the shear experiments and other similar laboratory studies (e.g., Neitzel et al, 2004;Deng et al, 2005Deng et al, , 2010Colotelo et al, 2018) have broadened our understanding of the effects of shear forces on a variety of fishes and indicate that there are species-specific responses, which generally relate to fish body morphology sensitivities. What is consistent from these other studies and the present study is, however, the probability of survival decreases with the severity of shear forces.…”

“…Elevated levels of shear are known to be harmful to other fish species (Neitzel et al, 2000) and mortality thresholds have been established under similar laboratory conditions for several species in the USA, such as salmonids [e.g., juvenile rainbow trout and steelhead (Oncorhynchus mykiss), juvenile Spring and Fall Chinook salmon (O. tshawytscha)], and American shad (Alosa sapidissima) (Johnson, 1970;Neitzel et al, 2004); and for Mekong species [e.g., blue gourami (Trichopodus trichopterus) and iridescent shark (Pangasianodon hypophthalmus) Colotelo et al, 2018]. Mortality thresholds for these species generally ranged between 800 and 1,200 s −1 , with blue gourami being the least tolerant (852 s −1 ) (Colotelo et al, 2018) and steelhead being the most tolerant [i.e., having no reported mortality at the highest strain tested (≥1,008 s −1 )] (Neitzel et al, 2004). In comparison to these species, our results indicate that gambusia are a relatively tolerant species to shear strain, owing perhaps to their small size and body morphology (Neitzel et al, 2000).…”

Priority knowledge needs for management of migratory fish species in Cambodia

“…Due to the many challenges of maintaining wild‐caught animals in captivity, laboratory studies of Mekong species are limited. Captive studies have been used to investigate swimming performance and tolerance to fish passageway design and effects of hydropower turbines for a few migratory species (Baumgartner et al, 2017; Colotelo et al, 2018). However, most captive studies for Mekong species have been conducted within an aquaculture or aquarium setting, such as growth and morphology studies (Morioka, Sano, Phommachan, & Vongvichith, 2009), effects of temperature on growth and behaviour (Baras et al, 2011) and reproductive studies (Zworykin, 2012).…”

Assessing turbine passage effects on internal fish injury and delayed mortality using X-ray imaging

“…Immediate and delayed fish mortality has commonly been observed after passage through river infrastructure and obstacles without any externally visible signs of severe injury (Mueller, Pander & Geist, 2017;Bierschenk et al, 2019). These fish may have sustained internal injuries that did not present external indications of the physical stressors they experienced during turbine or pump passage, such as injuries of the vertebral column or swim bladder rupture (Brown et al, 2013;Colotelo et al, 2018;Pflugrath, Boys & Cathers, 2018).…”