Temporal analysis shows relaxed genetic erosion following improved stocking practices in a subarctic transnational brown trout population

Abstract

Maintaining standing genetic variation is a challenge in human-dominated landscapes. We used genetic (i.e., 16 short tandem repeats) and morphological (i.e., length and weight) measurements of 593 contemporary and historical brown trout (Salmo trutta) samples to study fine-scale and short-term impacts of different management practices. These had changed from traditional breeding practices, using the same broodstock for several years, to modern breeding practices, including annual broodstock replacement, in the transnational subarctic Pasvik River. Using population genetic structure analyses (i.e., Bayesian assignment tests, DAPCs, and PCAs), four historical genetic clusters (E2001A-D), likely representing family lineages resulting from different crosses, were found in zone E. These groups were characterized by consistently lower genetic diversity, higher within-group relatedness, lower effective population size, and significantly smaller body size than contemporary stocked (E2001E) and wild fish (E2001F). However, even current breeding practices are insufficient to prevent genetic diversity loss and morphological changes as demonstrated by on average smaller body sizes and recent genetic bottleneck signatures in the modern breeding stock compared to wild fish. Conservation management must evaluate breeding protocols for stocking programs and assess if these can preserve remaining natural genetic diversity and morphology in brown trout for long-term preservation of freshwater fauna.

Ecological Drivers of Mercury Bioaccumulation in Fish of a Subarctic Watercourse

“…In Vaggatem, brown trout had lower δ 13 C values than pike and the other piscivores, reflecting their predominant predation on small‐sized, zooplanktivorous pelagic fish dominated by the abundant invasive vendace (Jensen et al, 2015). The higher δ 13 C of brown trout in Skrukkebukta may be due to a higher proportion of the catch consisting of stocked brown trout (Jensen et al, 2004; Klütsch et al, 2021), which would include individuals having an isotopic signature influenced by fish‐feed pellets (typically in the −22 to −19 range for farmed salmonids; Dempson & Power, 2004) during the first 2–3 years of their life. Burbot had the lowest δ 13 C values among the piscivores in Skrukkebukta, reflecting a more profundal‐oriented diet in contrast to, for example, the littoral‐feeding pike, suggesting that burbot predominantly feed on the profundal‐dwelling small sparsely rakered whitefish.…”

Functional characteristics and habitat suitability of threatened birds in northeastern China

“…During this migration process, certain sensitive species may face local extinction, and populations may become highly fragmented (Ghehsareh Ardestani & Heidari Ghahfarrokhi, 2021 ). Prolonged habitat fragmentation may deplete genetic variation and lead to elevated levels of inbreeding, posing a threat to the survival of the remaining populations (Klütsch et al., 2021 ). Functional diversity and uniqueness describe the characteristics of multi‐species that influence their performance and contribute to ecosystem functionality (Cox et al., 2023 ; Violle et al., 2017 ).…”

“…Prolonged habitat fragmentation may deplete genetic variation and lead to elevated levels of inbreeding, posing a threat to the survival of the remaining populations (Klütsch et al, 2021). Functional diversity and uniqueness describe the characteristics of multi-species that influence their performance and contribute to ecosystem functionality (Cox et al, 2023;Violle et al, 2017).…”