Salmonid Jumping and Playing: Potential Cultural and Welfare Implications

Play behavior in ectothermic vertebrates

Until a few decades ago, play was considered a behavior unique to birds and mammals. Although play in other vertebrates is still a neglected research subject, data on it has been slowly accumulating, and are reviewed here. Now we know that animals as diverse as stingrays, cichlid fishes, monitor lizards, softshell turtles, and crocodiles can be unexpectedly playful. This knowledge has implications to broader theoretical problems, but much more research attention is needed to utilize its potential.

Towards a three-level neo-Tinbergenian approach to object play: Structure, causes and consequences of a behavioral puzzle

My main goal in this paper is to propose a reformulation of foundational models in behavioral research, including Tinbergen's (1963) well-known four levels of analysis (namely, ontogenetic, mechanistic, functional, and evolutionary questions) and Mayr's (1961) dichotomy between proximate and ultimate causations. After critically evaluating these influential but problematic models, I present a three-level neo-Tinbergenian approach to behavior that considers the triadic integration of behavioral causes, structure, and consequences along a single temporal continuum. I then argue that object-directed play is a good candidate behavior to apply this new paradigm by presenting significant examples of the combined analysis of at least two of these three levels. Finally, I show how stone handling, a form of culturally-transmitted object play in macaques, is perfectly amenable to this unified three-level explanatory framework. My proposed approach fits recent theoretical and empirical advances in behavioral biology, has a heuristic value, and may provide numerous benefits to a range of behavioral scientists.

Changes in Aggressive Behavior, Cortisol and Brain Monoamines during the Formation of Social Hierarchy in Black Rockfish (Sebastes schlegelii)

Aggressive interactions can lead to a social hierarchy and influence the responses of animal behavior and physiology. However, our understanding on the changes of fish behavior and physiology during the process of social hierarchical formation is limited. To explore the responses of fish behavior and physiology to social hierarchy, we examined the differences in the growth performance, aggression, cortisol level, brain serotonergic activity, and brain dopamine activity between the dominant individuals and the subordinate individuals of black rockfish (Sebastes schlegelii) in two time scenarios. In the short-term contest, the cortisol level and the ratio of telencephalic 5-hydroxyindoleacetic acid (5-HIAA)/5-hydroxytryptamine (5-HT) was significantly higher in subordinate individuals than in dominant individuals. In the long-term contest, the ratios of 5-HIAA/5-HT in all brain regions were significantly higher, and the frequency of aggressive acts were significantly lower in subordinate individuals than in dominant individuals. In contrast, no difference was detected in growth performance. Significant positive correlations between the cortisol level and serotonergic activity were observed in the short-term contest, but the serotonergic activity was negatively correlated with the aggressive behavior in the long-term contest. These results suggest that subordinate hierarchy inhibits aggression but does not impact growth in black rockfish. The cortisol-related change in brain monoaminergic activity could be a potential indicator to predict aggressive behavior in black rockfish in captivity with an obvious social hierarchy.

Positive Welfare for Fishes: Rationale and Areas for Future Study

Traditional animal welfare paradigms have focused on maintaining physical health and mitigating negative impacts to wellbeing. Recently, however, the field has increasingly recognized the importance of positive welfare (i.e., mental and physical states that exceed what is necessary for immediate survival) and accordingly introduced manipulations and indicators of positive welfare for use in agriculture, laboratories, and zoos/aquaria. The creation and monitoring of positive welfare requires an in-depth knowledge of species-specific behavior and biology, which necessitates species-specific or, at a minimum, taxa-specific standards. Research on positive welfare in fish is lagging in this regard and therefore merits further consideration. In this paper, we aim to merge what is already known about positive welfare with the existing fish behavior literature to develop a plan of action for fish welfare research that will ultimately contribute to the development of positive welfare standards and assessment strategies for fish. We begin by exploring the origins of positive welfare research and then outline the physical, psychological and species-specific areas of inquiry that can be investigated in fish. In addition to presenting current findings on fish motivation, emotion, potential sources of positive welfare such as fulfillment of motivational urges (establishing agency, engaging in exploration and learning), and play behavior, we also identify promising areas for future research aimed at developing accurate and appropriate indicators of positive welfare in fish.

Is Heightened-Shoaling a Good Candidate for Positive Emotional Behavior in Zebrafish?

Simple Summary

Despite increasing interest in fish welfare, we still know very little about positive emotions in fish. This study had two aims: (1) to characterize a previously undescribed social behavior in zebrafish, “heightened-shoaling”, and (2) to evaluate whether heightened-shoaling may be a good candidate for future research into positive emotional behavior in zebrafish. Observing six groups of zebrafish housed in 110 L tanks furnished with a sloping gravel substrate, rocks, and artificial plants (10 fish/tank), we found that heightened-shoaling is marked by tight group cohesion, high behavioral synchrony (all fish engaging in the same behaviors at the same time), and low agonism. Episodes of heightened-shoaling occurred in all six groups, but rarely at the same time (only once out of 31 episodes), suggesting that the onset of heightened-shoaling is driven by internal group dynamics rather than external influences. Heightened-shoaling also appeared to be self-reinforcing as it had sustained durations—typically lasting for over 7 min and sometimes lasting for nearly half-an-hour. Collectively, these results are similar to the patterns that typify positive emotional behavior in other animals, for example, social grooming and social play. As the first description of heightened-shoaling, this research extends our knowledge of the range of zebrafish social dynamics and suggests a promising area for future research on positive emotions in fish.

Abstract

Zebrafish, a highly-social species of freshwater fish, are widely studied across many fields of laboratory science including developmental biology, neuroscience, and genomics. Nevertheless, as standard housing for zebrafish typically consists of small and simplistic environments, less is known about their social behavioral repertoire in more naturalistic settings. In particular, spontaneously occurring, socio-positive affiliative behaviors (e.g., social coordination and cohesion) that may be indicative of positive emotional experiences have rarely been reported or studied deliberately in zebrafish. Housing adult zebrafish (10 fish/tank) in large semi-natural tanks (110 L; n = 6) with sloping gravel substrate, rocks, and artificial plants, we observed a previously undescribed behavior: Distinct periods of spontaneous, synchronized, compact aggregations, what we call “heightened-shoaling”. This project aimed to quantify the characteristics of this distinctive behavior and compare parameters of heightened-shoaling to baseline periods (normal behavior) and pre-feed periods (feed-anticipatory behavior). First, across 4 days, we selected video-clips (100 s each) from within (i) instances of heightened-shoaling (n = 9), (ii) baseline periods (n = 18), and (iii) pre-feed periods (n = 18). For each of these video clips, we scan sampled every 10 s to determine fish orientations and location within the tank and agonistic behavior. Next, we used an all-occurrence sampling method to record the timing and duration of all episodes of heightened-shoaling behavior when tank-lights were on (8:00 h to 18:00 h) across 10 days. From the scan-sampling data, we found that compared to baseline periods, heightened-shoaling was characterized by increased shoal cohesion (p < 0.0001), increased adherence to the horizontal plane (p < 0.0001), decreased agonism (p < 0.0001), and no diving behavior (lower positions within the water column signal negative effect in zebrafish, p > 0.1). From the all-occurrence sampling data, we found 31 episodes of heightened-shoaling with instances observed in all six tanks and only a single case in which heightened-shoaling occurred in two tanks at the same time. The median episode duration was 7.6 min (Range 1.3–28.6). As the first systematic description of heightened-shoaling behavior, this research contributes to our knowledge of the range of zebrafish social dynamics living in naturalistic environments. Moreover, as a spontaneously occurring, protracted, affiliative behavior, heightened-shoaling appears to be a good candidate for future research into positive emotional behavior in zebrafish.