State of the ART: Using Artificial Refuge Traps to Control Invasive Crayfish in Southern California Streams

Aquatic invasive species are a widespread and pervasive threat to stream ecosystems across the planet. In Southern California, the invasive red swamp crayfish (Procambarus clarkii) pose a significant threat to aquatic amphibian and invertebrate populations. To effectively remove invasive crayfish, some studies have suggested that artificial refuge traps (ARTs) that resemble crayfish burrows can be used but no studies have focused on optimizing ART design and deployment to maximize crayfish catch. This month long study tested the effect of modifications in ART diameter, color, and soak time across 160 traps. During the study period, a total of 240 crayfish were removed with no incidental bycatch. Larger crayfish (2 – 6 cm) were found more frequently in 5.1 cm traps and smaller crayfish (1 – 4 cm) were found more frequently in 2.5 cm traps. Crayfish catch significantly varied between trap types, with BLKTube5.1 traps removing the most amount of crayfish (mean = 0.27, stdev = 0.29; 35% of total crayfish caught) and BLKTube2.5 traps removing the least amount of crayfish (mean = 0.09, stdev = 0.55; 12% of total crayfish caught). Further, ART soak time was an important predictor variable for models, where ARTs that had 4- and 7-day soak times had lower catch per unit effort than traps with 1 and 2 day soak times. ARTs represent a valuable tool for conservation managers interested in restoring streams through invasive crayfish removal, especially if there are sensitive biological resources present.

Impact/Purpose

This manuscript describes a month-long field experiment evaluating the efficacy of bait-less artificial refuge traps (ARTs) to control the invasive red swamp crayfish in southern California stream systems. The invasive red swamp crayfish (Procambarus clarkii) pose a significant threat to aquatic amphibian and invertebrate populations in southern CA streams. To effectively remove invasive crayfish, some studies have suggested that artificial refuge traps that resemble crayfish burrows can be used to reduce populations, but no studies have focused on optimizing ART design and deployment to maximize crayfish catch. This study represents the first experimental use of ARTs in the continental US to investigate the effectiveness of these bait-less traps. Additionally, this is the first study to use a factorial design to investigate the specific ART features (e.g. color, opening/diameter size, soak time) that optimize invasive crayfish catch. The study found that ARTs with larger opening diameters caught more crayfish and a greater variety in crayfish sizes compared to ARTs with smaller openings. Catch-per-unit-effort was greatest in traps deployed for 24 hours compared to traps left for 7 days. ARTs during the study period did not result in a single instance of bycatch, further illustrating the reduced (if not completely eliminated) impact on native aquatic species. This study provides insights into a tool that can be extremely valuable for invasive species biologists, stream and lake managers, and benthic ecologists who are looking for an effective method for sampling or managing crayfish species while having little to no impact on sensitive native species co-existing in the same system.

Citation

Curti, J., C. Fergus, AND A. De Palma-Dow. State of the ART: Using Artificial Refuge Traps to Control Invasive Crayfish in Southern California Streams. The Society for Freshwater Science, Springfield, IL, 40(3):716185, (2021). [DOI: 10.1086/716185]

DOI: State of the ART: Using Artificial Refuge Traps to Control Invasive Crayfish in Southern California Streams