Koi (Cyprinus rubrofuscus) Seek Out Tactile Interaction with Humans: General Patterns and Individual Differences

Abstract

The study of human–animal interactions has provided insights into the welfare of many species. To date, however, research has largely focused on human relationships with captive mammals, with relatively little exploration of interactions between humans and other vertebrates, despite non-mammals constituting the vast majority of animals currently living under human management. With this study, we aimed to address this gap in knowledge by investigating human–fish interactions at a community garden/aquaponics learning-center that is home to approximately 150 goldfish (Carassius auratus) and seven adult and two juvenile koi (Cyprinus rubrofuscus). After a habituation period (July–September 2019) during which time the fish were regularly provided with the opportunity to engage with the researcher’s submerged hand, but were not forced to interact with the researcher, we collected video data on 10 non-consecutive study days during the month of October. This procedure produced 18~20-min interaction sessions, 10 during T1 (when the experimenter first arrived and the fish had not been fed) and eight during T2 (20–30 min after the fish had been fed to satiation; two sessions of which were lost due equipment malfunction). Interactions between the researcher and the seven adult koi were coded from video based on location (within reach, on the periphery, or out of reach from the researcher) and instances of physical, tactile interaction. Analyses revealed that overall, koi spent more time than expected within reach of the researcher during both T1 (p < 0.02) and T2 (p < 0.03). There were also substantial differences between individuals’ overall propensity for being within-reach and engaging in physical interaction. These results show that koi will voluntarily interact with humans and that individual koi display unique and consistent patterns of interaction. By providing quantitative data to support anecdotal claims that such relationships exist around the world, this research contributes to the ongoing discoveries highlighting the profound dissonance between how humans think about and treat fish and who fish actually are, thereby emphasizing the necessity of stronger moral and legal protections for fishes.

Environmental enrichment in fish aquaculture: A review of fundamental and practical aspects

“…Recent studies on Nile tilapia suggest that, although tactile stimulation does not lower blood cortisol levels in the short‐term, it can reduce aggressiveness 204,205 and may also reduce the overall stress associated with social interactions in long‐term. Moreover, a recent study reported that koi carp ( Cyprinus rubrofuscus ) showed interest in physical contact (tactile interaction) with humans, suggesting that interacting with human skin, a novel substance and texture, might serve as a source of tactile and/or sensory enrichment 206 . However, further studies are still needed to test several effects of tactile stimulation on fish welfare 205 …”

“…Various studies identified three different play behaviour subtypes in fishes: locomotor (e.g. bubble jets/air stone), object manipulation (novel/stimulatory) and social (including human interaction) 206,252‐254 . Regarding species of aquaculture interest, it is known that salmonids and other fishes can jump into the air from the water, which is highly relevant in net‐pen culture since this behaviour can be related to buoyancy regulation, parasitic infections or stress.…”

“…), which already co-exist in natural conditions. 280,281 Finally, Fife-Cook and Franks 206 recently suggested the possibility of directed fish-human interaction. According to these authors, this kind of inter-specific interaction may be motivated by curiosity, presenting an opportunity to explore and exercise agency, which could serve as a source of cognitive stimulation for some species of captive fish.…”

“…bubble jets/air stone), object manipulation (novel/stimulatory) and social (including human interaction). 206,[252][253][254] Regarding species of aquaculture interest, it is known that salmonids and other fishes can jump into the air from the water, which is highly relevant in net-pen culture since this behaviour can be related to buoyancy regulation, parasitic infections or stress. However, Fagen 255 suggested that some salmonid jumping behaviour may be also a form of play.…”

“…Moreover, a recent study reported that koi carp (Cyprinus rubrofuscus) showed interest in physical contact (tactile interaction) with humans, suggesting that interacting with human skin, a novel substance and texture, might serve as a source of tactile and/or sensory enrichment. 206 However, further studies are still needed to test several effects of tactile stimulation on fish welfare. 205 There are other sensory systems, such as hydromechanical and electro-sensing, which are involved in diverse biological and ecological functions.…”