Baseline studies in the Slave River, NWT, 1990-1994. Part 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 various environmental components including fish, water, bottom sediment, and suspended sediment. Fish collections included a series of hepatic MFO analyses on walleye, northern pike, lake whitefish, and burbot. The EROD and AHH activity and P450 levels of fish, as well as weight, length, age, condition factor, and liver and gonadal somatic indices are described. Levels of EROD and AHH activity were of an order of magnitude expressed by the following relationship: walleye > northern pike > burbot > lake whitefish. Males consistently showed higher EROD, AHH activity and cytochrome P450 content relative to females of the same species even at control sites. Physical parameters varied very little within sites and exhibited some differences with the reference sites. A good MFO data set was collected for walleye and northern pike, but limited conclusions were possible with the lake whitefish and burbot data due to the overlap of sampling with the spawning season. Hepatic MFO enzyme activity indicated that some differences were evident in fish sampled from the Slave River relative to background/reference lakes; however, in many cases no differences were observed. Five years of biochemical effects studies have determined that the Slave River had low levels of induction suggesting a relatively pristine environment. This is further supported by the water, sediment, and body burden chemistry components of the Slave River Environmental Quality Monitoring Program.