The transport of live fish for aquaculture, either for food or as companion animals, presents a major issue for animal welfare. The stressors associated with live transportation are well documented with a focus on maintaining water quality during transport to reduce stress. Far less considered is our ability to enhance health and welfare during transport through the use of dietary and water additives prior to and during transport. With increasing interest in the use of plant essential oils as feed additives in food fish aquaculture and the increased availability of products claiming to alleviate stress in ornamental species, there is a need for scientific investigation into these potential welfare‐promoting methods. Here, we summarise current knowledge on the use of food additives, water conditioners, antibiotics, antimicrobials and probiotics to promote fish health during transport. This review aims to highlight the gaps in our knowledge surrounding promising ways of promoting fish health during transport and to stimulate new research in this area.

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Non-consumptive effects of predators can have important impacts on aquatic food webs, but there are few data on how predators change the behaviour of Caribbean reef fishes. Such changes may include behavioural responses to the invasive predatory lionfish (Pterois volitans / P. miles). This study used an aquarium experiment to examine the behaviour of herbivorous parrotfish (Scarus iseri) in the absence of other fish (control), with a non-piscivore present, and with a predatory threat from a native grouper or a lionfish. Treatments were repeated with and without additional parrotfish shelters to examine the potential effects of degraded reefs (loss of refuges). Using video, parrotfish behaviours (sheltering, swimming in open areas, foraging, aggressive interactions, bite rates, and shoaling behaviour) were recorded for groups of four parrotfish. Compared to the control, the average number of parrotfish hiding was reduced by 65% and foraging shoals were 10% larger when threatened by grouper, likely as a specific response to an ambush predator. When exposed to lionfish, parrotfish reduced their bite rates by 50%, possibly to be more vigilant of this predator's unique stalking behaviour. The absence of additional shelter had limited effects although parrotfish formed 10% larger shoals when swimming in open water, potentially as a defensive behaviour because of a perceived lack of refuges. The reduction in parrotfish bite rates caused by lionfish may have important demographic consequences. Furthermore, parrotfishes are important grazers of macroalgae, and these behavioural changes may exacerbate the direct effects of lionfish predation and potentially affect reef benthic dynamics.

The behavioural effects of supplementing diets with synthetic and naturally sourced astaxanthin in an ornamental fish (Puntius titteya). Research HighlightsAstaxanthin consumption caused subtle changes in fish colouration. Mate-choice associations were effected by dietary astaxanthin consumption. Red colouration and UV-reflectance influenced mate-choice association. Astaxanthin reduced mirror-image aggression in male fish, regardless of source. AbstractCarotenoids are routinely incorporated into ornamental fish diets with the aim of enhancing companion fish colouration which may concomitantly affect fish behaviour. Previously, colour enhancement has typically been achieved using synthetic carotenoids, however, there is now growing public demand for food additives such as carotenoids to be derived from natural sources, which can be acquired from microalgae and cyanobacteria. There has been very little research into whether natural carotenoids alter fish behaviour in a similar way to synthetic carotenoids; the present study aimed to determine whether behavioural changes typically associated with increased carotenoid consumption differed according to carotenoid source in the cherry barb (Puntius titteya).Cherry barbs were fed one of four diets (carotenoid-free, 20 ppm synthetic astaxanthin (AX) sourced from Carophyll pink®, 20 or 40 ppm of natural-AX sourced from Panaferd) over a 12 week period and then observed for colour changes, mate-choice and aggressive behaviours. The diets containing 20 ppm synthetic-AX and natural-AX enhanced male red colouration of the anal fin and anterior dorsal area, via a reduction in hue, in comparison to the carotenoidfree control diet whereas only the 20 ppm natural-AX altered the hue of female colour. In the mate choice trials, males spent more time with females fed the 20ppm synthetic-AX and 40ppm natural-AX compared with the carotenoid-free control and 20 ppm natural AX. Experiments conducted under red-blocking and UV blocking conditions demonstrated an effect of red colouration and ultraviolet reflectance on mate discrimination. Interestingly, males fed both the Page 4 synthetic and natural AX diets reduced aggressive interactions with a mirror image, even though they displayed enhanced red colouration, which is often used by fish as a signal of increased competitive ability. In conclusion, source of dietary AX affected the behaviour of cherry barbs, to the extent that synthetic AX exerted a stronger effect on mate-choice behaviour under full spectrum lighting in comparison to a similar concentration of natural AX. This therefore demonstrates that the behaviour of companion fish can be influenced by the source of carotenoids within their food.