Post-release exploration and diel activity of hatchery, wild and crossbred strain brown trout in semi-natural streams

Abstract

Behaviours that are adaptive in captivity may be maladaptive in the wild and hence compromise after-release survival of hatchery fish. Understanding behavioural differences displayed straight after the release could help improving hatchery protocols and developing behavioural tests for assessing the fitness of fish reared for releases. We characterized the post-release behaviour in two experiments using parr from wild, hatchery and crossed strains of brown trout (Salmo trutta): in small-scale channels and in high and low densities in mesocosm streams. Our results show that hatchery fish were more likely to disperse downstream from the natal stocking site compared to crossbred and wild fish. Small-scale experiment was not sufficient in discovering this ecologically pivotal difference in post-release performance between strains, and individual responses were inconsistent between experiments. Circadian activity patterns were not found to remarkably differ between strains. This detailed empirical evidence of post-release behaviour improves our understanding of the low success of captive-reared fish in the wild. Mixing locally adapted wild fish in the broodstock could rapidly mitigate some of the behavioural effects of hatchery selection.

Strong Parallel Differential Gene Expression Induced by Hatchery Rearing Weakly Associated with Methylation Signals in Adult Coho Salmon (O. kisutch)

“…Circadian rhythm may be subject to strong selective environmental pressures as, for example, feeding during day light highly increases the risk of predation and inversely feeding at night may decrease the food availability ( Yerushalmi and Green 2009 ). Alteration of the circadian rhythmicity occurring when food is continuously available in the hatchery environment can lead to maladaptative activity behavior of hatchery fish into the wild ( Alioravainen et al 2019 ). Finally, differential expression of genes implicated in hormonal production may also directly be related to the individual fitness as a seasonal production of gametes that mismatch the natural hatching period will result in a lower reproductive success ( Fregeneda-Grandes et al 2013 ; Christie et al 2014 ).…”

Life-history genotype explains variation in migration activity in Atlantic salmon ( Salmo salar )

“…The selected timing of the experiment overlaps with the natural smolt migration timing in Atlantic salmon [29,30]. Each stream was equipped with four RFID-antennas, positioned in quadrats of the circular stream [31]. Since the system had the capacity to record data from maximum 32 antennas at a time, streams were monitored periodically in two sets of eight streams: recording was swapped between the two sets of streams every three days until the end of the data collection period.…”

Enriched rearing environment enhances fitness-related traits of salmonid fishes facing multiple biological interactions

“…The antenna-specific ASCII data were further analyzed using AV Bio-Statistics v 5.2. (Alioravainen et al 2018;Vainikka et al 2012). The following variables were determined for each fish: 1) entry (yes/no) into pool, i.e.…”