PIT POP! Bursting the bubble on home-range bias with fine-scale PIT telemetry

Abstract

Context Improved tracking technologies increase understanding of fish movement, but care is required when comparing studies of different design. Aims We used an approach that allowed fine-scale tracking to compare results from individual-tracking designs to simulated batch-marking designs. Methods Adult Galaxias tantangara (a small freshwater fish) individuals were tagged with 9-mm PIT tags in a small headwater stream and tracked with an accuracy of 1 lineal metre. To evaluate differences between common study designs, data were re-analysed to simulate both batch-marking section size and tracking resolution between 1 and 250 m. Key results Home-range estimates decreased with a smaller section size and tracking resolution. Batch-marking simulations differed in 99% of cases, whereas individual tracking simulations differed in only 17% of comparisons. Comparisons between different methods were rarely statistically equivalent, being so only when section size or resolution was less than 4 m. Implications Importantly, batch-marking studies are often likely to overestimate home-range size, and results from different studies may be comparable only when resolution is very fine or identical, even if the same method was used.