Samantha Bui

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

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.

Salmon lice evasion, susceptibility, retention, and development differ amongst host salmonid species.

Salmon lice evasion, susceptibility, retention, and development differ amongst host salmonid species Samantha Bui*, Elina Halttunen, Agnes M. Mohn, Tone Vågseth, and Frode Oppedal Institute of Marine Research, Matredal 5984, Norway Sustainable Aquaculture Laboratory – Temperate and Tropical (SALTT), School of BioSciences, University of Melbourne, Victoria 3010, Australia Institute of Marine Research, Tromsø 6404, Norway Department of Biology, University of Bergen, Bergen 7800, Norway *Corresponding author: tel: þ47 456 37 697; e-mail: samantha.bui@hi.no

Consistent melanophore spot patterns allow long‐term individual recognition of Atlantic salmon Salmo salar

The present study shows that permanent melanophore spot patterns in Atlantic salmon Salmo salar make it possible to use images of the operculum to keep track of individual fish over extended periods of their life history. Post-smolt S. salar (n = 246) were initially photographed at an average mass of 98 g and again 10 months later after rearing in a sea cage, at an average mass of 3088 g. Spots that were present initially remained and were the most overt (largest) 10 months later, while new and less overt spots had developed. Visual recognition of spot size and position showed that fish with at least four initial spots were relatively easy to identify, while identifying fish with less than four spots could be challenging. An automatic image analysis method was developed and shows potential for fast match processing of large numbers of fish. The current findings promote visual recognition of opercular spots as a welfare-friendly alternative to tagging in experiments involving salmonid fishes.

To treat or not to treat: a quantitative review of the effect of biofouling and control methods in shellfish aquaculture to evaluate the necessity of removal

Abstract The global growth of farmed shellfish production has resulted in considerable research investigating how biofouling compromises farm productivity. Shellfish fitness can be compared between fouled stock and stock which has undergone treatment. As treatment options are often harsh, they may deleteriously affect stock. The projected impact of biofouling may therefore be confounded by the impact of treatments. Given the substantial cost of fouling removal, some have questioned the necessity of biofouling mitigation strategies. Meta-analysis revealed that biofouling typically reduces shellfish fitness. However, the fitness of treated stock was often lower or equal to fouled control stock, indicating that many common antifouling (AF) strategies are ineffective at enhancing farm productivity. Overall, caution and diligence are required to successfully implement biofouling mitigation strategies. The need remains for increased passive prevention approaches and novel AF strategies suitable for shellfish culture, such as strategic siting of bivalve farms in areas of low biofouling larval supply.