PERSISTENT POLLUTANTS IN A SALMON POPULATION (SALMO-SALAR) OF THE SOUTHERN BALTIC-SEA

Persistent pollutants in an Atlantic salmon (Salmo salar) population s pawning in a river of southern Sweden were investigated. The populatio n was characterized by a high growth rate. Some males reached 20-30 kg after 3 to 4 years in the sea. The fat content of migrating salmon va ried by one order of magnitude and was the most significant correlate of pollutant concentrations. No relationships were recorded between fa t content and gender, age (weight, length), year at sea, or different measures of condition. The reasons for this may be the varied evolutio nary strategies for maximizing reproductive output; male salmon may en ter the spawning river as small grilse and spawn opportunely, or migra te at a larger size, when they can hold spawning territories in the ri ver. Females have a greater and more uniform size, and spend more ener gy on gonadal products. The varying fat content of individual fish may also be attributed to foraging in different areas of the Baltic and t hereby to migration distances as well as foraging strategies. When pol lutant levels were normalized for fat content, other factors such as a ge (weight, length) were shown to be important for uptake; older fish had higher levels of pollutants than younger ones.