Life in captivity: varied behavioural responses to novel setting and food types in first-generation hybrids of farmed and wild juvenile Chinook salmon (Oncorhynchus tshawytscha)

Abstract

Aquaculture practices continuously seek to improve efficiency to produce larger fish at lower cost. Selective breeding within brood stocks can result in undesirable effects, promoting hatcheries to use outbreeding to increase or maintain genetic diversity. This practice however, could result in the introduction of wild behavioural phenotypes unable to adapt to captive-living conditions. Using four hatchery first-generation hybrid crosses and two fully domesticated stocks of Chinook salmon (Oncorhynchus tshawytscha) in British Columbia, we examined behavioural responses to common aquaculture practices such as abrupt environmental change and novel feed types in juvenile fish. Controlling for mass, we found crosses varied in their behaviours to a novel setting and preferences for natural versus commercial diets. These differences were furthermore associated with rearing environment and stock-level growth rate and body size. Our results suggest selecting for phenotypes that behaviourally exhibit better coping mechanisms and greater flexibility in response to change is possible, and when in combination with growth metrics, should be an integral part of producing the desired farmed fish. Behaviours that allow commercial anadromous fish to easily transition to captive environmental conditions can benefit production and also animal welfare.

Single generation exposure to a captive diet: a primer for domestication selection in a salmonid fish?

“…For example, high densities in captive environments, combined with feeding regimes that promote competitive behaviours such as dominance and boldness (e.g., repetitive, predictable access to highly nutritious pellet diet) may inadvertently select for growth differences between captive and wild fish (Einum & Fleming, 1997; McGinnity et al, 2003). Depending on the wild environments from which fish originate, behaviours may be fully engrained and inflexible (Huntingford, 2004; Canario et al, 2013; Janisse et al, 2019), resulting in poor adaptation to captivity. Put simply, other traits (e.g., behavioural traits) probably affect growth response in captivity and so it is hard to pin down exactly that only the novel captive diet leads to more rapid growth in captive fish.…”

“…Few studies have investigated how artificial pellet feed might induce genetic changes in wild salmonid populations that are reared in captivity (Dender et al, 2018; Janisse et al, 2019), even though there is now an extensive literature on how captivity affects salmonid phenotypes, genetic characteristics and individual fitness (Le Cam et al, 2015; Christie et al, 2018; Waters et al, 2018; Fraser et al, 2019). In nature, early juvenile salmonids feed on drifting and benthic invertebrates, and the availability, type and nutrient composition of such prey will depend on habitat characteristics such as a flow rate and substrate (Braithwaite and Salvanes, 2005; Jonsson & Jonsson, 2011; Naslund & Johnsson, 2016).…”

Premises for a digital twin of the Atlantic salmon in its world: Agency, robustness, subjectivity and prediction

“…The salmon digital twin shall represent an individual in an environment that differs from the one in which its behavioural mechanisms adapted through evolution (e.g. Janisse et al., 2019), for instance when there is a mismatch between a parr's physiological state and its evolutionary expectation due to cues of photoperiod, temperature, water flow or salinity. Some behavioural and developmental solutions parr find in the new environment would not emerge in life history optimization or bioenergetics models: These decisions are proximate traps rather than responses that are optimal for fitness.…”

Exploiting animal personality to reduce chronic stress in captive fish populations

“…We now think the potential for translation to applied contexts is clear, with the highest potential for short-term welfare gains likely to arise in the contexts of housing fish species for scientific research and developing novel species for food aquaculture. However, even in salmonid aquaculture—where genetically informed selection strategies are standard—the utility of behavioral biomarkers remains relatively unexplored [but see ( 48 , 49 ) for important exceptions]. Moreover, growing recognition of stress-related problems in the pet trade ( 50 , 51 ) has prompted the suggestion that improved understanding of natural behavior and ecology could greatly benefit welfare in ornamental species ( 52 ).…”