Migration and movement profiles of a potadromous fish (Brachymystax lenok Pallas 1773) in a highly connected river system (Mongolia)

Abstract

Understanding a species' spatial and temporal movements along with the way these shift under extreme environmental conditions is vital for developing scientifically sound conservation and management strategies. The aim of this research was to describe and quantify the seasonal migration patterns and fine-scale movement profiles of Brachymystax lenok, a threatened, potadromous salmonid that inhabits the highly connected, boreal river basins of Siberia and northern Asia. During this study 21 mature individuals were monitored over a 15 month period in the upper Eroo River basin, Mongolia, using passive acoustic telemetry. Mean (±SD) B. lenok home ranges were 19.1 ± 15.1 km (median = 11.5 km), with maximum longitudinal movements detected > 45.3 km. Two periods of increased movements were identified; the first in late summer/early autumn when 10 B. lenok moved into deeper, overwintering pools, with the second period occurring in late spring and early summer when nine B. lenok were detected entering the surrounding tributaries. Diel activity and depth typically increased during daylight hours followed by decreased activity or resting periods in shallower river sections at night. These results highlight the need to maintain a high level of river connectivity and adequate fishing season closures by implementing and enforcing an expansive spatiotemporal management plan that can better protect and recover the Mongolian B. lenok populations. Such measures should be transferable to other threatened, potadromous fish species residing throughout the world's boreal river basins. K E Y W O R D S acoustic telemetry, Brachymystax lenok, Mongolian fish fauna, potadromous fish, seasonal movements, spatial ecology

Fish conservation in the land of steppe and sky: Evolutionarily significant units of threatened salmonid species in Mongolia mirror major river basins

“…However, despite this shared haplotype, most of the genetic differentiation for B. lenok was distributed among basins (Froufe et al, 2008;Liu, Kunag, Tong, & Yin, 2011;Xia et al, 2006), which indicated large-scale, intrabasin gene flow within these vast, unfragmented river systems. However, B. lenok was the only species to demonstrate isolation by distance within both river basins, which is in line with the expectation of a reduced dispersal ability compared to the larger sized H. taimen (Yoon et al, 2014;Gilroy et al, 2010;Kaus et al, 2017).…”

“…This unique B. lenok phylogroup is genetically distinct and thus highly valuable in the context of genetic conservation for the species. Incidentally, this group has also been the focus of increased scientific research on B. lenok including studies on their feeding ecology (Olson, Jensen, & Hrabik, ), thermal tolerances (Hartman & Jensen, ), lotic and lentic growth comparisons (Tsogtsaikhan et al, ), and seasonal movements (Kaus, Büttner, Karthe, Schäffer, & Borchardt, ).…”

“…This unique B. lenok phylogroup is genetically distinct and thus highly valuable in the context of genetic conservation for the species. Incidentally, this group has also been the focus of increased scientific research on B. lenok including studies on their feeding ecology (Olson, Jensen, & Hrabik, 2016), thermal tolerances (Hartman & Jensen, 2016), lotic and lentic growth comparisons (Tsogtsaikhan et al, 2017), and seasonal movements (Kaus, Büttner, Karthe, Schäffer, & Borchardt, 2017 (Froufe et al, 2008(Froufe et al, , 2003Grosswald, 1998). However, despite this shared haplotype, most of the genetic differentiation for B. lenok was distributed among basins (Froufe et al, 2008;Liu, Kunag, Tong, & Yin, 2011;Xia et al, 2006), which indicated large-scale, intrabasin gene flow within these vast, unfragmented river systems.…”

Valley‐scale hydrogeomorphology drives river fish assemblage variation in Mongolia

“…Moreover, these rivers generally lack impoundments and introduced species. The available literature on fish assemblages in Mongolian rivers is scarce, with fish assemblages only being explored in a few publications, including identification and occurrences (Kottelat, 2006;Mendsaikhan et al, 2017), ecology (Kaus et al, 2018;Mendsaikhan et al, 2016;Mercado-Silva et al, 2008;Olson et al, 2016), conservation (Jensen et al, 2009), and genetics (Dulmaa et al, 2016;Kaus et al, 2019;Roman et al, 2018). However, variation of fish assemblages at the scale of entire river networks is largely unknown for most Mongolian drainages.…”

Locality of Forming Wintering Riverbed Depression in Irtysh River

“…Данная особенность может быть адаптивной поведенческой реакцией рыб на сложные сезонные условия водной среды [11]. Показано [11,22,31,32], что глубина, скорость придонных течений являются важными предикторами выбора среды обитания в зимний период для рыб, в том числе и представителей семейства Acipenseridae, поскольку глубоководная среда обитания обеспечивает убежище для этих рыб, а низкоскоростные участки обеспечивают сохранение энергии в состоянии покоя.…”