A Riparian Habitat Hypothesis for Successful Reproduction of White Sturgeon

Abstract

White sturgeon (Acipenser transmontanus) has recruitment failure or severe interannual variability in much of its range. Exceptions are Columbia River below Bonneville Dam, Snake River below Hells Canyon Dam, lower Fraser River, and Sacramento River. Since rivers were impounded or flows regulated, once-continuous populations now isolated by natural barriers or dams often have not reproduced successfully, despite successful spawning events. Research has not adequately explained recruitment failures or why certain populations are successful. This paper proposes that submerged riparian habitat during seasonal high water is needed for early development. Where recruitment is successful, channels are complex and floodable riparian vegetation or rocky substrate is abundant. There, spawning occurs in turbulent zones upstream (1-5 km) of seasonally submerged riparian habitat, eggs can disperse into inundated habitat and adhere to newly wetted surfaces for incubation, yolk-sac larvae can move to riparian crevices for prefeeding development, feeding larvae have food-rich flooded habitat for early growth, and larvae can transition to juveniles as water recedes to permanent channels. Such habitat is lacking where recruitment is low and present only in high-flow years where recruitment is sporadic. These observations suggest that management should rehabilitate riparian zones and provide high river flows during spawning to stimulate natural recruitment.

Missouri River Scaphirhynchus albus (pallid sturgeon) effects analysis—Integrative report 2016

“…The greatest influence would be on free embryos that emerge from spawning substrates closer to Gavins Point Dam where the influence of the reservoir releases is high, and lower velocities would have the greatest effect on drift distance. It is also possible that higher flows may contribute to retention of drifting larvae if the flow and channel hydraulics allow larvae to be transported into vegetated riparian zones or other areas of high roughness and low velocity (Coutant, 2004;Leeuw and others, 2006). Erwin and Jacobson (2014) used acoustic Doppler current profiler measures of longitudinal dispersion coefficients to document that dispersion-a measure of hydraulic characteristics that retard and retain particles-may increase with increasing discharge, depending on channel geometry.…”

The effect of substrate rearing on the growth, development, and survival of larval white sturgeon (Acipenser transmontanus) during early ontogeny.

“…Aside from spawning, the factor that may have the largest effect on year-class strength is the size of fish at the transition between endogenous and exogenous feeding, which is referred to as the critical period (Cushing 1972). The major bottleneck to white sturgeon recruitment is during the larval period (Gross et al 2002;Coutant 2004;Paragamain and Beamesderfer 2004); understanding the factors that affect growth and survival of larvae is therefore a prerequisite for improving survival of this stage, and ultimately year-class strength.…”

“…Understanding the causes of low recruitment (and recruitment failure) for white sturgeon are complicated by the lack of a detailed knowledge of the behavior, ecology, and habitat requirements of the early life history of this species. A major bottleneck for white sturgeon survival has been shown to be mortality prior to juvenile metamorphosis (Coutant 2004). For many fish, the larval period is the time of greatest mortality, which can be particularly high during the transition between endogenous to exogenous feeding.…”

“…The success of hatchery supplementation on the Nechako, Columbia, and Kootenay Rivers indicates that the bottleneck to recruitment may be associated with poor survival of wild spawned fish prior to 10 months post hatch (the age at which most hatchery sturgeon are released). The effect of incubation environment on growth and survival of larval sturgeon is a particularly critical stage of development as mortality prior to juvenile metamorphosis is a major bottleneck for white sturgeon survival (Coutant 2004). Factors affecting larval development, therefore, need to be determined to understand limits to recruitment.…”

Kootenai River White Sturgeon Recovery Implementation Plan and Schedule; 2005-2010, Technical Report 2004-2005.

“…Evaluate alternatives associated with the Riparian Habitat Hypothesis to characterize and restore sturgeon recruitment. The Riparian Habitat Hypothesis attributes the widespread collapse of resident white sturgeon populations in part to the loss of flooded riparian vegetation, which was hypothesized to provide critical incubation and feeding habitat conditions (Coutant 2004 …”