Effects of non-native crayfish on the structure & function of a stream food web in the lower Colorado River basin

Authors: Gregor Hamilton, Thomas Turner, Alesia Hallmark

Year: 2022

Abstract

Non-native crayfish evoke concern because they are explosive breeders, occur at high densities, and eat, or compete with native species, including fishes. In the lower Colorado River basin, aquatic communities are thought to be especially vulnerable to food web alteration from crayfish invasion. In this talk, we present a stable isotope analysis of carbon, nitrogen, and hydrogen to describe and understand food web interactions between crayfish and their host community (including aquatic and riparian plants, invertebrates, and vertebrates) in the Tularosa River in Catron County, NM. Specifically, we asked: Are there isotopic niche differences based on the sex and age of the crayfish? Do crayfish act as indiscriminate omnivores or do they preferentially feed on specific resources? Does the isotopic niche of crayfish overlap with other functional groups and, if so, to what degree? We found that there are differences in resource use depending on the sex and size of individual crayfish. Collectively, the isotopic niche of crayfish differs depending on crayfish density, and crayfish resource use overlaps considerably with secondary invertebrate consumers. We also comment on the relationship of crayfish density and isotopic niche shifts of other community members, including fishes and other sensitive aquatic and riparian species.