ILLUMINATION IN FIRST FEEDING TANKS FOR MARINE FISH LARVAE

Illumination levels were measured in three artificially illuminated ta nks (a black tank, a white tank and a tank with black sides and white bottom) in order to test how well normal tank illumination in differen t tank types corresponds to natural illumination conditions for first feeding of marine fish larvae. Measurements were made with clear water and with algae added ('green water'). The black tank had low wall and bottom illumination. The white tank had high wall and bottom illumina tion. The black-walled white-bottomed tank had low wall and high centr al and bottom illumination. Green water attenuated light substantially . The black tank seemed best suited to reproduce natural illumination conditions. The white tank was not suited. The black-walled white-bott omed tank had interesting properties, but species specific tests would have to be carried out to fine tune the reflective properties of the bottom. Green water seemed to be beneficial in all tests.