Effect of habitat shifts on feeding behaviour and growth of 0 year-group flounder Platichthys flesus (L.) transferred between macroalgae and bare sand habitats

In this study, short-term growth and feeding behaviour were compared among juvenile European flounder Platichthys flesus reared in enclosures in either their native habitat (bare sand or vegetation) or transferred to the opposite habitat. Growth was poorest in the vegetated habitat regardless of origin of the fish. The effect of the habitat shift differed between years. In 2000, the relatively small fish used grew fastest in their native habitat. In contrast, in 2001 when larger fish were used, growth was similar between native and introduced fish in the vegetated habitat, and introduced fish grew faster than native fish in the bare sand habitat. Diet composition and feeding intensity within a habitat were also similar among native and introduced fish in 2001, suggesting that the habitat switch had a minor influence on foraging efficiency. The different results obtained from the experiments in 2000 and 2001 suggest that fish size may determine the extent to which short-term habitat shifts influence feeding and growth in juvenile flounder, and, importantly, that the negative effects of habitat fragmentation are more severe for small compared to larger juvenile flounder.