Sampling effort to detect Asian carps during response activities in the Great Lakes basin

Abstract

Response programs are designed to remove newly discovered, high priority aquatic invasive species from the wild. Advice is needed regarding sampling effort required to detect and remove Asian carps during response activities in the Great Lakes basin. Simulation models were developed to examine the relationship between fish abundance, the probability of capture, and sampling effort for detection and local removal under different sampling schemes (systematic, random, repeat, and informed sampling), response area sizes, and assumed fish behaviours (avoidance, aggregation, no emigration). The range in relative effort required for detection and local removal was strongly influenced by the probability of capture, which is poorly known for most gears and environmental conditions. Under the base simulation, the relative effort required for detection ranged from 0.07 to 13.48 complete passes of a response area, while relative effort for local removal ranged from 0.72 to 69.55 complete passes. For a modelled 75 ha response area, an electrofishing boat crew could require 5.8–1,120.7 sampling hours for detection, while local removal could require 59.9–5,782.1 sampling hours. Lower effort for detection was needed when the probability of capture was high, there was a higher abundance of Asian carps, and to a lesser degree if fish did not aggregate. Lower effort for local removal was needed when the probability of capture was high and there were fewer Asian carps. Total effort for detection and local removal was proportional to the size of the response area. Informed sampling, which involves only sampling habitats preferred by Asian carps, had the greatest decrease in effort for detection and local removal compared to the base model. The influence of informed sampling increased with higher habitat specificity and the ability of field crews to target such areas. Repeat sampling, when a fish was detected, reduced the effort for local removal when fish were aggregated, while random sampling generally increased effort for detection and local removal. Using information on species ecology and local habitat characteristics, field crews can use these results in real time to evaluate the likelihood that fish remain in the response area given the number of detections and assumptions about the probability of capture. General conclusions of this work can be applied to response efforts targeting other aquatic invasive species, but will require knowledge of the probability of capture of gears employed.