The size of a flatfish, and of its appetite, is influenced by the colour of its environment. Akiyoshi Takahashi of Kitasato University in Iwate, Japan, and his colleagues have discovered that the barfin flounder (Verasper moseri), a promising species for aquaculture, grows longer and heavier if kept under green light than under blue or unfiltered light. Red light seems to stunt its growth.
The team kept adult fish of the same approximate starting size for 14 weeks, giving them as many pellets as they were willing to eat twice a day. The different wavelengths of light the fish experienced may have modified the release of melanin-concentrating hormone, an appetite stimulant, in the brain, prompting the fish to eat more, the authors say. Like many fish, this species keeps growing throughout its life.