Suspended sediment causes annual acute fish mortality in the Pilcomayo River (Bolivia)

Abstract

Fish mortality in the middle reaches of the Pilcomayo River (Bolivia), locally called ‘borrachera’, can be observed almost every year at the onset of the rainy season. In order to study the potential causes of the ‘borrachera’, suspended sediment (SS) and selected water quality parameters have been monitored from mid‐September until mid‐December 2010. Gill samples were taken and analysed, before and during the ‘borrachera’ event on December 7th 2010. Data on river discharge were obtained from a database. During the sampling period, the river hydrology changed dramatically. At the day of the ‘borrachera’, heavy rains in upstream reaches of the river catchment changed the river from a quiet stream into a turbulent river with extremely high concentrations of SS (> 100 g l−1). This may be caused by the inundation of the entire riverbed, which causes easily erodible material, left on the riverbanks at the end of the former rainy season, to be transported by the river during the first peak discharges. As concentrations of heavy metals in filtered water samples did not show higher values during the ‘borrachera’, it is concluded that the ‘borrachera’ is unlikely to be caused by heavy metal toxicity. Results showed a strong association between the SS concentration and the ‘borrachera’. Gills of fish collected during the ‘borrachera’ were clogged with sediment to such an extent that oxygen uptake became virtually impossible. High SS concentrations are therefore considered to be the cause of this typical fish mortality phenomenon. Copyright © 2012 John Wiley & Sons, Ltd.

Acute impacts of reservoir sediment flushing on fishes in the Yellow River

“…Previous studies focused on relatively low sediment concentrations (<40 000 mg/l) and few families, notably salmonidae (Kemp and Sear, 2011). While, high sediment concentrations (>80 000 mg/l) and deceased fishes were reported in Europe, America, and China (Baoligao et al, 2013;Crosa et al, 2010;Newcombe and Jensen, 1996;Swinkels et al, 2012). Further studies on impacts of high sediment concentration on different fish species should be carried out.…”

Influence of Suspended Fluvial Sediments on the River Ichthyocene

“…Статья основана на литературных данных по острым эффектам и результатах собственных экспериментов по хроническим эффектам. При изучении влияния острых эффектов повышенной мутности использована база данных Агентства по охране окружающей среды США (United States Environmental Protection Agency), дополненная литературными данными [Ryan, 1991;Ardjosoediro, Ramnarine, 2002;Robertson et al, 2006;Swinkels et al, 2014]. Пороговые значения мутности проанализированы для 20 видов из 11 семейств: aтлантический шед Alosa sapidissima (сельдевые Clupeidae); арктический голец Salvelinus alpinus, атлантический лосось Salmo salar, радужная форель Oncorhynchus (=Parasalmo) mykiss, чавыча Oncorhynchus tshawytscha, горбуша Oncorhynchus gorbuscha, кета Oncorhynchus keta (лососевые Salmonidae); сибирский хариус Thymallus arcticus (хариусовые Thymallidae); обыкновенный сиг Coregonus lavaretus (сиговые Coregonidae); южноевропейская атерина Atherina mochon (атериновые Atherinidae); фундулюсы Fundulus majalis, Fundulus heteroclit и карпозуб Cyprinodon variegatus (карпозубые Cyprinodontidae); малиновая тиляпия Coptodon rendalli и ореохромис Oreochromis sp.…”

“…При изучении хронических эффектов использовались литературные данные [EIFAC, 1964*;Ryan, 1991;Swinkels et al, 2014] и собственные материалы, полученные на реках Камчатки [Чалов, Леман, 2014; Чалов и др., 2015]. Обобщалась вся доступная информация о видах из наиболее распространенных семейств ихтиофауны рек России: карповых Cyprinidae, лососевых Salmonidaе, хариусовых Thymallidaе, сиговых Coregonidae, окуневых Percidae, осетровых Acipeseridae и сомовых Siluridae.…”

Short informative title: Quantitative assessment of acute impacts of suspended sediment on carp in the Yellow River

“…Through field investigations, scholars found that the sediment concentration during the reservoir sediment flushing and natural floods reached tens or even hundreds of kilograms per cubic metre. This level of sediment concentration resulted in the deaths of fishes and drops in the biomass of the river (Baoligao, Xu, Chen, & Chen, ; Swinkels et al, ). In high sediment concentration flows, fishes must increase their amount of movement, respiratory rates, and oxygen demand.…”

“…Thus, the existing findings and principles require further verification. Experiments in tanks with fish species exposed to different SSCs are meant to provide more insight on the impacts of SSCs on fishes (Swinkels et al, ). Considering the diverse river habitats and the sediment tolerance capacity of different fish species, research in this field should be further expanded in terms of the range of sediment concentrations and affected fishes.…”