A Framework for Latitudinalcomparisons of Flatfish Recruitment*

Some major latitudinal trends in the physiology, population dynamics and ecology of flatfish are illustrated, and related to their ultimate cause: temperature-mediated difference of metabolic rate. The niche of tropical flatfish is then defined with some emphasis on Psettodes erumei in the Gulf of Thailand, and a hypothesis is derived to explain the generally low observed biomass-and hence recruitment of tropical flatfish. It is stated that flatfish are overadapted to feeding on zoobenthic inand epifauna. In combination with a trend of decreasing importance of the benthic system towards the tropics, this suggests an increasing importance of food-limitation with decreasing latitude and as a consequence lower biomass values. Furthermore, the general increase of maintenance metabolism with temperature reduces in tropical systems the size of flatfish at which oxygen limits further growth. This aspect is responsible for the general trend of a smaller flatfish size with decreasing latitude. Finally, implications for future flatfish research are discussed.