Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Temporal distribution modelling reveals upstream habitat drying and downstream non-native introgression are squeezing out an imperiled headwater fish.

Abstract

Aim: To review the conservation status of Headwater catfish Ictalurus lupus (Girard,1859) in the United States, including quantifying environmental correlates with range contraction and hybridization and introgression with Channel catfish Ictalurus punctatus (Rafinesque, 1818) to inform conservation prioritization. Location Texas and New Mexico, USA. Methods We used random forest models to construct species distribution models (SDMs) based on historical (1980-1999) and contemporary (2000-2019) data and 13 classes of remotely sensed stream network data. We measured hybridization and introgression with the widely introduced Channel catfish using external morphology, mitochondrial DNA (mtDNA), and a nuclear gene (RAG2). Results Species distribution models illustrated temporal reduction in suitability for Headwater catfish among the species' namesake headwater streams, including streams with steeper slopes, faster velocities, and higher elevations. Modelling also revealed reduced suitability of larger streams greater distances from groundwater springs, the same streams frequently occupied by non-native Channel catfish. A general pattern of increased use of streams draining watersheds with altered or developed land uses was apparent. Assessment of introgression and hybridization with non-native channel catfish at nine locations showed evidence of ongoing or past hybridization at six locations. Persistence of potentially non-introgressed populations were found at three locations with smaller sample sizes. Main conclusions Modelling temporal changes in Headwater catfish distribution provided critical insight into the types and locations of streams that should be targeted for habitat preservation or restoration. Conservation and management of Headwater catfish will require priority decisions based on existing levels of introgression and the practicality of preventing further contact with Channel catfish. Maintaining Headwater catfish populations in springs that are also heavily used by humans will be critical for conservation of the species in the United States.