Integrated analysis of marked and count data to characterizefine-scale stream fish movement

Abstract

Immigration and emigration are key demographic processes of animal population dynamics. However, 3 we have limited knowledge on how fine-scale movement varies over space and time. We developed a 4 Bayesian integrated population model using individual mark-recapture and count data to characterize 5 fine-scale movement of stream fish at 20-m resolution every two months for 28 months. Our study 6 targeted small-bodied fish, for which imperfect capture was accounted for (bluehead chub Nocomis 7 leptocephalus, creek chub Semotilus atromaculatus and mottled sculpin Cottus bairdii). Based on 8 data from 2,021 individuals across all species, we found that proportions of immigrants averaged 9 30-42% among the study species, but they varied over space and time. Creek chub immigrants 10 increased during warmer intervals when individuals grew more and transitioned between body size 11 classes, suggesting that immigration was due to ontogenetic habitat shifts. There was a weak pattern 12 across the species that individuals were more likely to leave 20-m sections when flow was higher. 13 Water-column species (bluehead chub and creek chub) were more likely to immigrate into and stay 14 in deeper sections with more pool area. Across all species and occasions, number of immigrants 15 to stream sections did not decrease with number of individuals that survived and stayed in the 16 same sections. Thus, the habitat did not appear saturated, and our data provided no evidence that 17 intra-specific interactions affected fine-scale movement at our fish densities. In conclusion, high 18 turnover rates characterized fish movement among stream sections and their variation was associated 19 with temporal and spatial shifts in abiotic conditions.