Swimbladder hyperinflation in striped trumpeter Latris lineata is impacted by tank wall colour

Swim bladder hyperinflation, also known as ‘swim bladder stress syndrome’, has been reported during the larval rearing of a number of finfish species. It is associated with an overfilling of the swim bladder lumen with gas, in some cases after initial swim bladder inflation and after the pneumatic duct between the swim bladder and the oesophagus has closed. Hyperinflation is correlated with mortality of larvae, as they are positively buoyant and either become stuck at the water surface, or are unable to swim and feed efficiently. Several stress factors have been linked to hyperinflation, including the light conditions of larval culture tanks. In previous studies, we demonstrated that larval striped trumpeter (Latris lineata), formerly under investigation as a new species for aquaculture in Tasmania, require specific tank wall colours to minimise jaw abnormality. However, tank wall colour has a potential to impact swim bladder hyperinflation. In this study, striped trumpeter larvae were reared from the end of rotifer feeding through to metamorphosis, 16 to 44 days posthatching (dph), in twenty four 300 L hemispherical tanks with six different wall colours, black, blue, green, marble (a black, grey and white mottled pattern), red and white. Larvae were held at 15.9 ± 0.1 °C, light intensity was 10.0 ± 1.1 μmol s^-1 m^-2, and seawater was exchanged at 214 ± 4 l h^-1. Artemia enriched with Algamac 3050 were added at 0.25 nauplii ml^-1 four times daily, to feed the larvae. At stocking on 16 dph, 95% of larvae had inflated swim bladders and the overall proportion remained unchanged at 23 and 30 dph across treatments. In contrast, coloured tanks affected swim bladder hyperinflation. Almost 50% of larvae transferred to red tanks exhibited swim bladder hyperinflation at 23 dph. Hyperinflation occurred in significantly lower proportions and with reduced severity in other treatments. There was a significant positive relationship between fish dying at the water surface and swim bladder hyperinflation (Fig 1). For striped trumpeter, both black and white tanks were least affected by swim bladder hyperinflation. We recommend care in the selection of tank colour for marine fish larvae to avoid stress, which may induce hyperinflation, leading to subsequent mortality.