Present Status and Temporal Trends of Organochlorine Contaminants in Young-of-the-Year Spottail Shiner (Notropis hudsonius) from Lake Ontario

Contaminant residue data from Ontario nearshore collections of young-of-the-year spottail shiner (Notropis hudsonius) were used to assess present status and temporal trends of bioavailable organochlorine contaminants in Lake Ontario. PCB residues in spottail shiners were in excess of the International Joint Commission Aquatic Life Guideline at 11 of the 14 sites sampled in 1987; mirex residues exceeded the Guideline at 7 of the 14 sites sampled. PCB and total DDT residues in the recent shiner collections were significantly (p < 0.01) lower relative to residue levels in collections in the 1970's. However, residue declines have slowed during the 1980's. Thus, PCB residues in spottail shiners declined by 69% over a 5-yr interval (1975–80) whereas residues declined only by 17% at the same sites during the following 7-yr interval (1980–87). Residues of hexachlorobenzene, heptachlor, aldrin, total hexachlorocyclohexane, octachlorostyrene, total chlordane, and toxaphene were generally near their detection limits in all shiner collections. A Forage Fish Contaminant Index was established for the purpose of ranking the collection sites in relative order of contamination to assess the need for point-source investigations.