PARENT SESSION
MP2 - Aquatic Toxicology
Chair: Spehar, Bob1, 1 U.S. EPA, Duluth, MN
Co-chair: Henry, Mary2, 2 U.S. Fish and Wildlife Service, Arlington, VA
2:10 PM to 5:30 PM - Monday, 18 November 2002
Room Ballroom J
(263) Foraging Activity, Trophic Position, and PCB Concentrations in Rock Bass.
Paterson, Gord*,1, Drouillard, Ken1, Beth, Harold1, O'Rourke, Sarah1, Reaume, Dana1, Haffner, Douglas1, 1 University of Windsor, Windsor, Ontario, Canada
ABSTRACT- Many food web models have been developed to predict and demonstrate the biomagnification of persistent organic pollutants (POPs) with increasing trophic position in aquatic systems. This study focused on determining the characteristics at which the accumulation of POPs within a fish population departs from linearity and exhibits the logarithmic accumulation profile characteristic of biomagnification. Rock bass (Ambloplites rupetris) specimens ranging in mass from <1 - 250g were collected from the Detroit River during the fall of 2001 using a benthic trawl net. Samples were analysed for total polychlorinated biphenyl (PCB) concentrations, stable isotope (15N) ratios, foraging activity and age. Stable isotope and total PCB analyses were completed on whole body homogenates using mass spectrometry and gas chromatographic mass selective detection techniques, respectively. Foraging activity and age determination of specimens was completed via gut contents analysis and otolith evaluation of remaining specimens preserved in formalin. Total PCB concentrations ranged from 0.8 - 38.7 ug/g lipid and exhibited a log-linear trend across the size ranges of specimens collected. The accumulation of POPs demonstrated a departure from linearity coinciding with an increase in fish mass from approximately 30 - 200g and a general dietary shift from caddisflies and forage fish, including emerald shiners and round gobies, to large crayfish. The change in foraging activity occurred between the 2 and 3 year age classes and was also supported by the concomitant shift in trophic position as indicated by stable isotope ratios. These results demonstrate that fish size, measured as mass, trophic position and foraging activity and age, or possibly time to maturity, play significant roles in the onset of biomagnification in freshwater food webs.
Key words: Biomagnification, foraging, isotope, age