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

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.