Group Behavioural Responses of Atlantic Salmon (Salmo salar L.) to Light, Infrasound and Sound Stimuli

Abstract

Understanding species-specific flight behaviours is essential in developing methods of guiding fish spatially, and requires knowledge on how groups of fish respond to aversive stimuli. By harnessing their natural behaviours, the use of physical manipulation or other potentially harmful procedures can be minimised. We examined the reactions of sea-caged groups of 50 salmon (1331±364 g) to short-term exposure to visual or acoustic stimuli. In light experiments, fish were exposed to one of three intensities of blue LED light (high, medium and low) or no light (control). Sound experiments included exposure to infrasound (12 Hz), a surface disturbance event, the combination of infrasound and surface disturbance, or no stimuli. Groups that experienced light, infrasound, and the combination of infrasound and surface disturbance treatments, elicited a marked change in vertical distribution, where fish dived to the bottom of the sea-cage for the duration of the stimulus. Light treatments, but not sound, also reduced the total echo-signal strength (indicative of swim bladder volume) after exposure to light, compared to pre-stimulus levels. Groups in infrasound and combination treatments showed increased swimming activity during stimulus application, with swimming speeds tripled compared to that of controls. In all light and sound treatments, fish returned to their pre-stimulus swimming depths and speeds once exposure had ceased. This work establishes consistent, short-term avoidance responses to these stimuli, and provides a basis for methods to guide fish for aquaculture applications, or create avoidance barriers for conservation purposes. In doing so, we can achieve the manipulation of group position with minimal welfare impacts, to create more sustainable practices.

Behavioural Differences in Tank-Held European Sea Bass under Dark/Light Environment

“…For example, studies in fisheries have already shown species attraction by shorter wavelength lights [4]. In parallel with fisheries, related studies have already shown promising results for salmon manipulation [17] and pathogen avoidance [5] through guidance in different swimming depths.…”

“…Particularly, biorhythms have been related to feeding time, either in nature or aquaculture as well as under restricted feeding conditions [3]. In recent years, artificial light has been introduced in both fisheries [4] and aquaculture [5] towards attraction to specific areas and population guide for manipulation and avoidance of unfavorable conditions [6,7].…”

“…Such studies are essential, since they promote welfare conditions for early domesticated species in aquaculture. However, they could further suggest light as another option to manipulate Mediterranean species in any field of the aquaculture production, a widely used technology in Atlantic salmon culture [4,5,21].…”

Oxygen gradients affect behaviour of caged Atlantic salmon Salmo salar

“…Finally, the use of environmental stimuli to alter fish distribution within cages has proven very successful , Bui et al 2013). Underwater lighting is commonly used to delay maturation in salmon aquaculture.…”

“…Salmon in sea cages alter their distribution and behaviour in response to numerous stimuli, including light ), temperature, salinity, feeding (Oppedal et al 2011a), water current velocity (Johansson et al 2014), sound (Bui et al 2013) and sea lice infestation level (Bui et al 2016). Given the myriad factors affecting salmon in sea cages, experimental testing within the marine cage environment is required to understand the behavioural trade-offs made by salmon in response to hypoxia and other environmental factors.…”