Modeling potential river management conflicts between frogs and salmonids

Abstract

Management of regulated rivers for yellow-legged frogs (Rana boylii) and salmonids exemplifies potential conflicts among species adapted to different parts of the natural flow and temperature regimes. Yellow-legged frogs oviposit in rivers in spring and depend on declining flows and warming temperatures for egg and tadpole survival and growth, whereas salmonid management can include high spring flows and low-temperature reservoir releases. We built a model of how flow and temperature affect frog breeding success. Its mechanisms include adults selecting oviposition sites to balance risks of egg dewatering by decreasing flow versus scouring by high flow, temperature effects on development, habitat selection by tadpoles, and mortality via dewatering and scouring. In simulations of a regulated river managed primarily for salmonids, below-natural temperatures delayed tadpole metamorphosis into froglets, which can reduce overwinter survival. However, mitigating this impact via higher temperatures was predicted to cause adults to oviposit before spring flow releases for salmonids, which then scoured the egg masses. The relative timing of frog oviposition and high flow releases appears critical in determining conflicts between salmonid and frog management.

Why It Is Time to Put PHABSIM Out to Pasture

“…One drawback of IBMs is that few "off-the-shelf" models are available (but see the trout, salmon, and frog models of Railsback et al 2009Railsback et al , 2013Railsback et al , 2014Railsback et al , and 2016 and developing new ones is nontrivial. New IBMs require digesting the literature on the target species' ecology, physiology, and behavior; specifying and testing model assumptions; and developing and testing software.…”

Seasonal growth potential of Oncorhynchus mykiss in streams with contrasting prey phenology and streamflow

“…Such interactions are pronounced in streams along the Pacific Coast of California, where aquatic consumers experience Mediterranean hydrologic seasonality and prey phenology. In these systems, the timing and rate of the annual spring–summer streamflow recession relative to seasonal fluctuations in food availability determine growth potential for many aquatic consumers, including Foothill Yellow Legged frog ( Rana boylii ) (Kupferberg et al, 2011; Railsback et al, 2016), Pacific salmon ( Oncorhynchus spp.) (Hayes et al, 2008; Smith & Li, 1983), and benthic macroinvertebrates (Beche et al, 2006; Gasith & Resh, 1999).…”

Hybridization between two parapatric ranid frog species in the northern Sierra Nevada, California, USA

“…To estimate divergence time between species, we used the & Yarnell, 2009;Railsback et al, 2016), while R. sierrae can have a greater range of generation times, between 3 and 6 years because tadpoles may overwinter as many as 3 years (Knapp et al, 2016;Knapp, Matthews, Preisler, & Jellison, 2003). We may assume the ancestral condition was derived from R. boylii (Macey et al, 2001;Vredenburg et al, 2007;Yuan et al, 2016), therefore we suggest a generation time of three years, which means R. sierrae probably diverged from R. boylii over 1.1 mya.…”