Modelling competition and hybridization between native cutthroat trout and nonnative rainbow and hybrid trout

Abstract

Native salmonid fish have been displaced worldwide by nonnatives through hybridization, competition, and predation, but the dynamics of these factors are poorly understood. We apply stochastic Lotka-Volterra models to the displacement of cutthroat trout by rainbow/hybrid trout in the Snake River, Idaho, USA. Cutthroat trout are susceptible to hybridization in the river but are reproductively isolated in tributaries via removal of migratory rainbow/hybrid spawners at weirs. Based on information-theoretic analysis, population data provide evidence that hybridization was the primary mechanism for cutthroat trout displacement in the first 17 years of the invasion. However, under some parameter values, the data provide evidence for a model in which interaction occurs among fish from both river and tributary subpopulations. This situation is likely to occur when tributary-spawned cutthroat trout out-migrate to the river as fry. The resulting competition with rainbow/hybrid trout can result in the extinction of cutthroat trout even when reproductive segregation is maintained.

Using an Integrated Population Model to Evaluate Yellowstone Cutthroat Trout Responses to Management Actions

“…Rainbow Trout and hybrids have been suggested to have a competitive advantage over juvenile Yellowstone Cutthroat Trout, which could ultimately lead to lower survival of Yellowstone Cutthroat Trout in the presence of abundant adult and age‐0 Rainbow Trout (Seiler and Keely , ; Van Kirk et al. ).…”

Temporal Reproductive Separation of Fluvial Yellowstone Cutthroat Trout from Rainbow Trout and Hybrids in the Yellowstone River

“…Resistance of a native taxon to hybridization does not preclude its displacement (Utter 2001). Even if reproductive segregation is maintained between fluvial Yellowstone cutthroat trout and rainbow trout and hybrids, competition from these taxa can result in the extinction of Yellowstone cutthroat trout (Van Kirk et al 2009). Given the predominance of rainbow trout in the main-stem Yellowstone River, an understanding of how competition may affect cutthroat trout is likely to be a critical component to preserving the native taxon despite temporal reproductive separation.…”

Climate change vulnerability assessment of aquatic and terrestrial ecosystems in the U.S. Forest Service Rocky Mountain Region

“…Cutthroat trout (Oncorhynchus clarkii) populations have declined, as rainbow trout (O. mykiss) breed with native species . Nonnative brook (Salvelinus fontinalis), brown (Salmo trutta), and rainbow trout can hinder and outcompete native cutthroats (Van Kirk et al 2009). Leafy spurge (Euphorbia esula L.), purple loosestrife (Lythrum salicaria), cheatgrass (Bromus tectorum L.), and Canada thistle (Cirsium arvense) are particularly problematic in riparian areas, where they displace native species (Al-Chokhachy et al 2013b;Poff et al 2011).…”