Ec. Lamon et Ca. Stow, Sources of variability in microcontaminant data for Lake Michigan salmonids: Statistical models and implications for trend detection, CAN J FISH, 56, 1999, pp. 71-85
Citations number
28
Categorie Soggetti
Aquatic Sciences
Journal title
CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES
Variability in Lake Michigan salmonid microcontaminant data may arise from
differences in contaminant concentrations in the water column, fat content,
diet, age, location, and species-specific factors. Polychlorinated bipheny
l (PCB) concentrations for salmonids in Lake Michigan have been determined
for fish collected from a wide variety of locations and sizes for each of f
ive species. Lake managers and policy makers wishing to evaluate trends in
these concentration data must either remove this variability before trend a
ssessment or leave it and settle for less statistical power for identifying
the underlying time trend. Classification and regression trees (CART) have
proven to be a useful tool for identifying nonlinear patterns of variabili
ty in these data and portraying them graphically. We used CART to study pat
terns of variability in PCB concentrations in five species of Lake Michigan
salmonids, using data collected from 1972 to 1994 by both the Michigan and
Wisconsin Departments of Natural Resources. For most of the species studie
d here, length was the major source of variability, followed by location.