BRAZIL - The pacamã (Lophiosilurus alexandri) fish is a carnivorous fresh water fish of importance to Brazil which lives the sediments and rocks or the river bed, writes Lucy Towers, TheFishSite Editor.
In order to understand welfare in the growing conditions of pacamã, Delihane Costa has looked at how tank colour can affect stress levels in the fish and therefore welfare.
The experiment was conducted at the Federal University of Minas Gerais and pacamã juveniles from the same spawning were stocked at a density of 1.66 larvae/L in 24 tanks with a volume of 6 L and constant aeration.
After acclimatising in white tanks for 20 days, the fish were transferred into white, green, blue, yellow, brown, and black tanks.
Food was provided twice a day and uneaten feed and feces cleared out daily.
The study, which was presented at Aquaculture Europe 2014, showed that cortisol levels were affected by tank colour. Cortisol levels were highest in the black tanks and lowest in the yellow, blue and brown tanks.
Ms Costa stated that according to work by Sabbah et al. (2010) fish retinas contain rods and cones that must respond to the specific range of wavelengths found in the ecological niche of the species.
From the results of this experiment it can be seen that white, black, and green tanks should not be used for the farming of juvenile pacamã as they caused increased stress. Instead, yellow, brown and blue colours should be used.