2024/03/16 by Richard Kennedy, James Barry, Adele Boyd +1 · 1 voice · 1 citation
Environmental Science · Agricultural and Biological Sciences · #Fish Ecology and Management Studies #Hydrology and Sediment Transport Processes #Fish Biology and Ecology Studies
paper · pdf · doi:10.1111/jfb.15719
openalex publication_date 2024/03/16 · openalex created_date 2024/03/17 · openalex updated_date 2026/05/21
Abstract Acoustic tags fitted with predation sensors, which trigger following ingestion by piscivorous predators, were used to compare direct predation rates during downstream migration (out‐migration) of potamodromous (freshwater) brown trout ( Salmo trutta L.) parr from their natal river into a large freshwater lake system during spring and autumn. Thirty‐eight spring migrants were tagged across two study years (2021 and 2022) of which 13 individuals (34%) were predated. By contrast 40 autumn migrants were tagged (2020 and 2021) of which three individuals (7.5%) experienced predation. The overall predation loss rate for spring migrants was 0.342% day −1 and was 0.075% day −1 for autumn migrants. Most predation events during spring (77%) occurred within the lower river before tagged fish entered the lake, whilst no predation events were recorded within the river in the autumn. Predation events were significantly linked to tagging season (spring or autumn), with the probability of tags remaining untriggered (as a proxy for survival) being higher 93% (95% confidence interval [CI] [87%, 100%]) in autumn than in spring 66% (95% CI [53%, 83%]). The spring migration periods showed significantly lower river discharge (0.321 m 3 /s mean daily discharge, April 1 to May 31) to those measured during autumn (1.056 m 3 /s mean daily discharge, October 1 to November 30) (Mann–Whitney U ‐test, U = 1149, p < 0.001). Lower flows, clearer water, and longer sojourn in the river may have contributed to greater predation losses in the spring relative to the autumn.