Invasive crayfish in a high desert river: Implications of concurrent invaders and climate change

Patrick Martinez

doi:10.3391/ai.2012.7.2.008

Abstract

No crayfish species are native to the Colorado River Basin (CRB), including the portion of the state of Colorado west of the Continental Divide. Virile crayfish [Orconectes virilis (Hagen, 1870)], a recent invader in the middle Yampa River in northwestern Colorado, displayed an abrupt increase in abundance in the early 2000s, which coincided with a drought, a severe decline in the abundance of smallbodied and juvenile native fishes, and a dramatic increase in the abundance of nonnative smallmouth bass [Micropterus dolomieu (Lacepede, 1802)]. The annual density of virile crayfish was 6.4/m 2 in 2005 and 9.3/m 2 in 2006. The annual biomass density of virile crayfish was 9.0g/m 2 in 2005 and 15.8 g/m 2 in 2006, representing a riverwide biomass of 122 kg/ha, which equaled that of other macroinvertebrates and fish combined (120.7 kg/ha). Efforts to recover and preserve native fishes in the Upper Colorado River Basin (UCRB), particularly in the Yampa River, have been hampered by nonnative predatory fishes, but the implications of crayfish may have been overlooked and underestimated. Stream conditions during the drought apparently facilitated proliferation by virile crayfish in the middle Yampa River, likely contributing to hyperpredation on native fishes by invasive smallmouth bass. This trophic interaction between virile crayfish and smallmouth bass, in conjunction with regional projections for climate change, will likely make efforts to reduce the abundance and negative ecological impact of smallmouth bass in this ecosystem more difficult and costly. Given the nonnative status of all crayfishes in the CRB, and their invasive capacity and potential to negatively reconfigure native lotic food webs, all states in the UCRB should prohibit the importation, movement, sale, possession and stocking of any live crayfish.

Highlights

The Colorado River Basin (CRB) in western North America drains about one-twelfth of the land area of the 48 contiguous United States (Carlson and Muth 1989; Figure 1a)
Higher variability in the numbers of virile crayfish counted in individual quadrats in 2005 resulted in higher coefficients of variation (CV) for the three stations than in 2006 (Table 2)
18.5 sized substrates (Bovbjerg 1970; Daniels 1980; Mitchell and Smock 1991), which are common in the middle Yampa River, but they are tolerant of fine sediments (50–100% embeddedness; Clark and Lester 2005)

Summary

Introduction

The Colorado River Basin (CRB) in western North America drains about one-twelfth of the land area of the 48 contiguous United States (Carlson and Muth 1989; Figure 1a). The virile crayfish has a broad native distribution in North America where it occupies a wide variety of habitats in lotic and lentic systems (Bovbjerg 1970; Tierny and Atema 1988; Hobbs 1989; Richards et al 1996). It feeds on plants, detritus, and other animals (dead or alive), and displays grazing, scavenging, cannibalistic and predatory behaviors; its trophic status as an opportunistic rather than indiscriminate omnivore (Chambers et al 1990; Loughman 2010). These flexible habitat requirements and feeding habits categorize the virile crayfish as a generalist rather than specialist species (Charlebois and Lamberti 1996; Mead 2008; Larson and Olden 2010), which contributes to its success as an invasive species (Phillips et al 2009; Larson and Olden 2011; Gherardi et al 2011)

Methods

Results

Discussion

Conclusion