Newly published paper: Ecological niche models to predict effects of restoration activities along a desert river corridor

Species conservation efforts are often limited by funding for restoration activities, and time in the face of decreasing populations. Therefore, it is critical that restoration activities be prioritized such that the greatest benefit to target species and communities can be achieved. In a paper recently published in Transactions of the American Fisheries Society, co-author Phaedra Budy (Utah State University) and I describe a modeling effort to predict where different restoration activities would have the greatest benefit for imperiled native species in the San Rafael River (Utah).

Flannelmouth sucker, bluehead sucker, and roundtail chub are three imperiled species native to the Colorado River Basin. Populations of each of these species have declined dramatically in the last century in the face of habitat and flow alteration, and invasive species establishment. The states of the upper Colorado River Basin have signed agreements to conserve these three species, but in the face of numerous widespread threats, management agencies need to know where they should focus management and restoration efforts.

In this paper, we fit random forest models biotic and abiotic variables measured at sampling locations to determine the factors most limiting to each of the native species. We then used data from a longitudinal habitat survey of the lower 64 km of river to predict the effect of habitat restoration and non-native species removals at different locations along the San Rafael River. Expanding areas of high quality habitat was predicted to result in greater benefits for the native species than improving isolated patches of habitat. Additionally, the greatest benefit to the native species occurred when non-native species were removed to below about 10% of their current abundance. Non-native species present sources of predation and competition to the native species, and as such can limit the number of native species a habitat unit could support. In fact, our models predicted that habitat restoration without non-native species removals could reduce native species abundances in certain reaches, likely due to increased non-native species following habitat restoration.

Overall, this study highlighted the importance of considering both biotic and abiotic drivers of abundance and persistence of threatened species. Only considering abiotic drivers can lead to unexpected and even negative restoration results, wasting limited time, money, and opportunity. Additionally, river-scale ecological niche models can describe systems at the scale at which endemic species interact with their environment, and can allow for managers to obtain spatially-explicit information at the scale at which restoration activities will occur. Further, we recognize and discuss the importance of restoring the processes that shape river ecosystems (e.g., natural flow regime) in order to ensure the long-term success of any restoration strategy.

Timothy E. Walsworth & Phaedra Budy (2015) Integrating Nonnative Species in Niche Models to Prioritize Native Fish Restoration Activity Locations along a Desert River Corridor, Transactions of the American Fisheries Society, 144:4, 667-681

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Sockeye carcass collections

(Apologies for the long delay between posts)

Summer is turning to autumn here in Chignik Lake.  The air is taking on a chill and the berries are starting to ripen.  This also means that the rivers are low, the salmon are spawning, and the bears are feeding on the salmon in the shallow water.

Photo by Nick Sisson

Photo by Nick Sisson

The combination of salmon dying after spawning and being preyed upon by bears results in the banks of the rivers and streams in the area to be covered in dead salmon carcasses.  These carcasses, while pungent, can actually provide us with an incredible amount of data.DSC_0065

One research project we are working on is examining the otoliths (ear bones) of adult salmon to determine their habitat use as juveniles.  This may sound like a strange way to look at juvenile habitat use.  A more common approach to studying juvenile habitat use is to study, well, juvenile salmon and observe their behaviors.  However, one limitation of this approach is that is nearly impossible to follow the ultimate fate of individual juveniles, particularly for organisms with low survival rates such as fish.  When we sample otoliths from spawning salmon carcasses, we know their ultimate fate – they survived to reach the spawning grounds.

A cross-section of an otolith looks similar to a cross-section of a tree.  Material is laid down as a fish grows, with periods of slow growth making dark rings (usually in winter, an annual marker).  The otoliths also incorporate the chemistry of the water in which the fish resides.  Thus, the otolith contains a record of the water chemistry throughout its life.  If the water chemistry of different habitats varies in a consistent manner, we can determine what habitat an individual used throughout its life.  For the Chignik system, Black Lake, Chignik Lake, and the marine environment have significantly different water chemistry and we can determine which habitat an individual was located in at any point during its life.  From this, we can determine which habitats contribute most to the growth of individual fish.

We are currently drafting a manuscript describing the first round of results, which demonstrate that, even within a single population, there are a diversity of viable juvenile behavioral strategies that contribute to the spawning population.