title: Intercalibration of hydroacoustic and mark-recapture methods for assessing the spawning population size of a threatened fish species.
abstract: Hydroacoustic counting and a three-year mark-recapture study with passive integrated transponders (PIT tags) were used to estimate the size of a spawning population of nase Chondrostoma nasus, a threatened potamodromous cyprinid that undertakes annual spawning migrations into a tributary of the Danube River. In 2005, the estimates of the size of the spawning population from the hydroacoustic counts (N = 2234, 95% CL 1929-2538) and from the Jolly-Seber model (N = 1198, 95% CL 461-5842) corresponded well. Estimates from the jackknife-estimator based on the hydroacoustic counts yielded slightly higher values (N = 2783, 95% CL 2529-3037), but were still in the same order of magnitude as those from the hydroacoustic and mark-recapture approach. At low run-size, hydroacoustic counting was more time consuming and technically demanding than mark-recapture studies. At the same time, it was non-invasive, provided real-time data on a fine temporal scale, and estimates showed less variability than the Jolly-Seber model. Mark-recapture of fish in spawning streams involved substantial disturbance at a sensitive stage of the life cycle. Hence, hydroacoustics is highly suited for population estimates of threatened potamodromous fishes, where interference needs to be minimized.
authors.affiliation: Department of Freshwater Ecology, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria. georg.rakowitz@univie.ac.at
authors.forename: G
authors.initials: G
authors.lastname: Rakowitz
authors.forename: J
authors.initials: J
authors.lastname: Kubecka
authors.forename: C
authors.initials: C
authors.lastname: Fesl
authors.forename: H
authors.initials: H
authors.lastname: Keckeis
mesh_terms: D000162:Acoustics; D000818:Animals; D003247:Conservation of Natural Resources / Q000379:methods*; D003530:Cyprinidae / Q000502:physiology*; D056727:Endangered Species; D005260:Female; D056127:Hydrobiology / Q000379:methods*; D011156:Population Density; D012098:Reproduction