BASE-LINE STUDIES IN THE SLAVE RIVER, NWT, 1990-1994 .3. MFO ENZYME-ACTIVITY IN FISH

As part of the Slave River Environmental Quality Monitoring Program, a background data set of baseline concentrations was collected for vari ous environmental components including fish, water, bottom sediment, a nd suspended sediment. Fish collections included a series of hepatic M FO analyses on walleye, northern pike, lake whitefish, and burbot. The EROD and AHH activity and P450 levels of fish, as well as weight, len gth, age, condition factor, and liver and gonadal somatic indices are described. Levels of EROD and AHH activity were of an order of magnitu de expressed by the following relationship: walleye > northern pike > burbot > lake whitefish. Males consistently showed higher EROD, AHH ac tivity and cytochrome P450 content relative to females of the same spe cies even at control sites. Physical parameters varied very little wit hin sites and exhibited some differences with the reference sites. A g ood MFO data set was collected for walleye and northern pike, but limi ted conclusions were possible with the lake whitefish and burbot data due to the overlap of sampling with the spawning season. Hepatic MFO e nzyme activity indicated that some differences were evident in fish sa mpled from the Slave River relative to background/reference lakes; how ever, in many cases no differences were observed. Five years of bioche mical effects studies have determined that the Slave River had low lev els of induction suggesting a relatively pristine environment. This is further supported by the water, sediment, and body burden chemistry c omponents of the Slave River Environmental Quality Monitoring Program. (C) 1997 Elsevier Science B.V.