SOCIAL INTERACTIONS AND THE DISTRIBUTION OF FOOD AMONG ONE-SEA-WINTERATLANTIC SALMON (SALMO-SALAR) IN A SEA-CAGE

In order to test whether the amount of food obtained by individual one -sea-winter Atlantic salmon was related to social status, the feeding interactions of 19 individually marked Atlantic salmon in a sea cage w ere monitored by underwater video (fish competed for single food pelle ts presented at regular intervals). Food was distributed unevenly amon g fish; no significant relationship was found between food intake and either weight or gender. More successful fish fed earlier in a feeding session than their companions, and smaller fish avoided competitors w hen approaching pellets. There was a positive relationship between foo d intake and frequency of being beaten to pellets, but no relationship between food intake and proportion of feeding attempts in which a fis h was beaten. This suggests that fish of a similar status were scrambl ing for food. Previous studies have shown a negative relationship betw een the coefficient of variation in daily food intake and total food i ntake, bur did not control for fish size. Here we found the same relat ionship after controlling for fish size, showing that more successful fish had less variation in their day today consumption than did less s uccessful conspecifics. These data suggest that, in order to prevent f ood monopolisation by few individuals, the food should be presented so that it is unpredictable in time and space.