Dispersal decisions and personality in a freshwater fish

Growth and physiological response of proactive and reactive juvenile "tambaqui" (Colossoma macropomum) in a recirculating aquaculture system

This study evaluated the growth and physiological response of proactive and reactive Colossoma macropomum juveniles in a recirculating aquaculture system (RAS). In Phase 1 of the experiment (50 days of cultivation), juveniles, weighing 2.16 ± 0.52 g, were stocked in 12 28-L tanks to test the following treatments: proactive (PT), reactive (RT) and mixed (MT) composed of reactive (MRT) and proactive (MPT) animals. In Phase 2 of the experiment (40 days of cultivation), the animals were transferred to 175-L tanks with the same treatments as Phase 1. The animals were fed twice a day with commercial diet during both phases. After Phase 1, MPT animals showed higher growth than MRT animals (P < 0.05), and higher weight gain and daily weight than PT animals (P < 0.05). After Phase 2, PT animals showed higher weight gain and daily weight gain than RT and MT animals (P < 0.05), as did MPT animals compared to PT animals. Performance for RT animals was superior (P < 0.05) to that of MRT animals. Glucose (P < 0.04) and cholesterol (P < 0.01) were higher for RT animals compared to PT animals. Cholesterol was higher for MPT animals compared to MRT animals (P < 0.01), while plasma protein was lower (P < 0.001). Glucose (P < 0.001) and cholesterol (P < 0.01) were higher for MPT animals compared to PT animals and for MRT animals compared to RT animals (glucose P < 0.02, cholesterol P < 0.01). After 90 days of cultivation, proactive animals cultivated separately presented better performance. When cultivated together, reactive animals experienced a decrease in performance and both stress coping styles showed more signs of stress.

Personality in juvenile Atlantic cod ecotypes and implications for fisheries management

Animals show among-individual variation in behaviors, including migration behaviors, which are often repeatable across time periods and contexts, commonly termed "personality." These behaviors can be correlated, forming a behavioral syndrome. In this study, we assessed the repeatability and correlation of different behavioral traits, i.e., boldness, exploration, and sociality, and the link to feeding migration patterns in Atlantic cod juveniles. To do so, we collected repeated measurements within two short-term (3 days) and two long-term (2 months) intervals of these personality traits and genotypes of the Pan I locus, which is correlated with feeding migration patterns in this species. We found high repeatabilities for exploration behavior in the short- and long-term intervals, and a trend for the relationship between exploration and the Pan I locus. Boldness and sociality were only repeatable in the second short-term interval indicating a possible development of stability over time and did not show a relation with the Pan I locus. We found no indication of behavioral syndromes among the studied traits. We were unable to identify the existence of a migration syndrome for the frontal genotype, which is the reason that the link between personality and migration remains inconclusive, but we demonstrated a possible link between exploration and the Pan I genotype. This supports the need for further research that should focus on the effect of exploration tendency and other personality traits on cod movement, including the migratory (frontal) ecotype to develop management strategies based on behavioral units, rather than treating the population as a single homogeneous stock.

Neuroendocrine correlates of juvenile amphibian behaviors across a latitudinal cline

We assessed the macrogeographic and neuroendocrine correlates of behavioral variation exhibited by juveniles, an important life stage for dispersal, across the expansive range of the wood frog. By rearing animals from eggs in a common garden then using a novel environment test, we uniquely demonstrated differential expression of juvenile behaviors among 16 populations spanning 8° latitude. On the individual level, cluster analysis indicated three major behavior profiles and principal component analysis resolved four unique axes of behavior, including escape, foraging, food intake, feeding efficiency. We found that increased escape behavior was associated with lower adrenocorticotropic hormone (ACTH)-induced circulating corticosterone (CORT) levels, however, foraging and food intake behaviors were not associated with either resting or ACTH-induced CORT. At the population level, the expression of foraging behaviors increased with latitude while food intake behaviors declined with latitude, which raised several hypotheses of eco-evolutionary processes likely driving this variation. Given that these behaviors covary along the same ecological gradient as locally adapted developmental traits, genomic studies in this species could provide deep insights into how HPA/I activity is associated with the eco-evolutionary processes that structure intraspecific variation in morphology and behavior.

Unravelling the causes and consequences of dispersal syndromes in a wild passerine

Evidence accumulates that dispersal is correlated with individual behavioural phenotype (dispersal syndrome). The evolutionary causes and consequences of such covariation depend on the degree of plasticity versus inheritance of the traits, which requires challenging experiments to implement in mobile organisms. Here, we combine a forced dispersal experiment, natural colonization and longitudinal data to establish if dispersal and aggression levels are integrated and to test their adaptive nature in pied flycatchers (Ficedula hypoleuca). We found that (forced) dispersers behaved more aggressively in their first breeding year after dispersal and decreased their aggression in following years. Strength of dispersal syndrome and direction of fecundity selection on aggression in newly colonized areas varied between years. We propose that the net benefits of aggression for dispersers increase under harsh conditions (e.g. low food abundance). This hypothesis now warrants further testing. Overall, this study provides unprecedented experimental evidence that dispersal syndromes can be remodelled via adaptive plasticity depending on the individuals' local breeding experience and/or year-specific ecological conditions. It highlights the importance of individual behavioural variation in population dynamics.

Lifetime movement history is associated with variable growth of a potamodromous freshwater fish

Directional or stabilising selection should drive the expression of a dominant movement phenotype within a population. Widespread persistence of multiple movement phenotypes within wild populations, however, suggests that individuals that move (movers) and those that do not (residents) can have commensurate performance. The costs and benefits of mover and resident phenotypes remain poorly understood. Here, we explored how the presence and timing of movements are correlated with annual somatic growth rates, a useful proxy for performance because it is easily measured and rapidly reflects environmental changes. We used otolith growth measurements and stable isotope analyses to recreate growth and among-reach movement histories of a partially migrating, long-lived freshwater fish, golden perch Macquaria ambigua. We compared the association between movement and growth at two temporal scales: (a) short-term (annual) differences in growth, in the years preceding, during or following movement; and (b) long-term (lifetime) differences in growth. Overall, 59% of individuals performed at least one among-reach movement, with these individuals subsequently more likely to move repeatedly throughout their lives. Movers grew faster than residents, with this difference most pronounced in the juvenile and early adult stages, when most movements occurred. Annual growth did not, however, change immediately prior to or following a specific movement event. Among-individual variation in growth was initially higher for residents than for movers but decreased with age, at a faster rate for residents than for movers, such that levels conformed after 5 years of age. Our results indicate that lifetime movement is linked to faster growth in the early years of a fish's life. These faster growing movers are likely to be larger at a given age, leading to numerous potential benefits. However, the persistence of resident phenotypes suggests that there is likely a cost-benefit trade-off to moving. The presence of multiple movement phenotypes may contribute to the resilience of populations by buffering against naturally and anthropogenically exacerbated environmental variability.

Consistent Behavioral Syndrome Across Seasons in an Invasive Freshwater Fish

Understanding the linkage between behavioral types and dispersal tendency has become a pressing issue in light of global change and biological invasions. Here, we explore whether dispersing individuals exhibit behavioral types that differ from those remaining in the source population. We investigated a feral population of guppies (Poecilia reticulata) that undergoes a yearly range shift cycle. Guppies are among the most widespread invasive species in the world, but in temperate regions these tropical fish can only survive in winter-warm freshwaters. Established in a thermally-altered stream in Germany, guppies are confined to a warm-water influx in winter, but can spread to peripheral parts as these become thermally accessible. We sampled fish from the source population and a winter-abandoned site in March, June and August. Fish were tested for boldness, sociability and activity involving open-field tests including interactions with a robotic social partner. Guppies differed consistently among each other in all three traits within each sample. Average trait expression in the source population differed across seasons, however, we could not detect differences between source and downstream population. Instead, all populations exhibited a remarkably stable behavioral syndrome between boldness and activity despite strong seasonal changes in water temperature and associated environmental factors. We conclude that random drift (opposed to personality-biased dispersal) is a more likely dispersal mode for guppies, at least in the investigated stream. In the face of fluctuating environments, guppies seem to be extremely effective in keeping behavioral expressions constant, which could help explain their successful invasion and adaptation to new and disturbed habitats.