Abstract
As concerns for amphibian decline continue, increased monitoring and accurate estimates are necessary to correctly assess developing population dynamics. Conservation management for salamanders in Norway is primarily based on count data with limited support from qualitative capture-recapture studies. By employing the standardized equation for estimating population size based on capture-per-unit-effort data, I investigate how this compares to estimates from a 7-year capture-recapture study on Norway’s two salamander species, Triturus cristatus and Lissotriton vulgaris in a small rural pond. I find that the CPUE Triturus cristatus population estimates are being consistently overestimated, and that the average CPUE population size estimates for Lissotriton vulgaris were double compared to adjusted capture-recapture estimates.
To reduce the risk of populations being overestimated, which could lead to overly optimistic condition assessments, less stringent conservation measures, and potentially neglecting habitat protection. I conclude that data from several capture-recapture studies is needed to increase knowledge about the relationship between capture-per-unit-effort and capture-recapture estimates. Data should be obtained from a larger variety of locations within the species' main biogeographical regions over longer periods of time.
Capture-recapture estimates for two syntopic salamander populations remain relatively stable through most years. With Triturus cristatus having an estimated average population size of 172,2 (± 29,4) between 2016 and 2023. But showing a potential decline in 2023. Excluding years with confounded estimates, the Lissotriton vulgaris population was estimated to number 583.7 individuals (±101.2).
Apparent annual survival estimates for Triturus cristatus averaged to 70% (± 9,7%), while annual survival for Lissotriton vulgaris males and females averaged to 42% (± 9,6%) and 42% (±12,7%) respectively. Low and uncertain capture probability affect the estimates for both species and sexes and was confounded for Lissotriton vulgaris females in 2020.
