AQUA 2012: Blue Gravel Enhances Welfare of Gilthead Seabream06 September 2012
CZECH REPUBLIC - Nafsika Karakatsouli from the University of Athen, Greece, has looked at fish preference to different coloured gravel substrate layers. This work has helped to understand fish welfare through prefernce tests which show what fish want and how much they work to get or avoid it, writes Lucy Towers, TheFishSite Editor at AQUA 2012, Prague, Czech Republic.
The study by Ms Karakatsouli looked at the preference of gilthead seabream to blue, green and red-brown coloured gravel.
The tanks were set out with a 2.5cm layer of gravel and laboratory raised fish of 0+ and 2+ years of age, with no previous exposure to gravel, were placed in the tanks over a period of three months.
The study examined the preference of both individual and groups of fish to gravel colour.
During the trial, fish were placed in a tank with two compartments so they could choose which colour gravel they preferred and spent more time over. It also showed whether fish would choose to move to a certain colour.
The results showed that fish with blue gravel had higher growth, were less aggressive and had better fillet quality.
Fish exposed to the red gravel also experienced the above apart from no growth benefit was seen.
Green gravel saw no benefits and was rejected by fish of all ages.
Age was seen to have a deciding affect on the trial, with the older fish choosing more often which part of the tank/colour to be in. The most popular colour of choice was blue
Overall blue gravel was the preferred colour and had the most positive affects on the fish. There was also no social affects indicated as fish in groups and alone tended to choose the blue gravel.