PCB and p,p'-DDE in Lake Geneva brown trout (Salmo trutta L.), and their use as bioenergetic indicators.

Gross growth efficiency of Lake Geneva brown trout (Salmo trutta) was estimated by monitoring age-related PCB and p,p'-DDE accumulation, food contamination and annual growth.Estimation was carried out using 3-, 4-, and 5-yr old fish. Roach (Rutilus rutilus) were determined as the main component of trout diet. Estimated growth efficiency coefficients were 0.4 (3-4 yr old fish) and 0.17 (4-5 yr old fish). Nevertheless numerous parameters can affect the result; their respective influences are discussed.Related to fish age, PCB and p,p'-DDE concentrations increase if expressed on a wet weight basis, but not if expressed on a lipid weight basis.At the same age, organochlorine residue concentrations keep similar values for trout and roach in spite of different trophic levels. Growth must be considered as a more dilution factor of PCB and p,p'-DDE in trout compared with roach.