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The present study sought to determine whether environmentally realistic mixtures of agriculturally important pesticides are stressful to fish. Juvenile rainbow trout were exposed for 96 h to concentrations of a pesticide mixture found in a waterway that is the focus of salmon restoration efforts (Nicomekl River, BC, Canada). This mixture contained organochlorine, organophosphorus, phenylurea, and triazine classes of pesticides. Fish given a realistic mixture exposure (total concentration, 1.01 µg/L) had increased plasma cortisol concentration, packed red cell volume, hematocrit (Hct), as well as decreased white cell volume, leukocrit (Lct). Similar changes in Hct and Lct were apparent after exposure to a lower concentration (0.186 µg/L). Interestingly, no changes in plasma cortisol concentration, Hct, or Lct were noted after exposure to a higher concentration (13.9 µg/L). This suggests that the exposure likely impaired the mechanisms enabling the stress response. Across all exposures, plasma glucose concentration was related to plasma cortisol concentration, not to pesticide mixture concentration. This suggests that a secondary stress response may be more related to variability in individual primary stress response than to differences in pesticide exposure concentrations. In summary, the present study indicates that salmon living in agrichemical-contaminated waterways may be experiencing stress, and this may pose a threat to their survival., (Copyright © 2011 SETAC.)

Fish live in waters of contaminant flux. In three urban, fish-bearing waterways of British Columbia, Canada, we found the active ingredients of WeedEx, KillEx, and Roundup herbicide formulations (2,4-D, dicamba, glyphosate, and mecoprop) at low to high ng/L concentrations (0.26 to 309 ng/L) in routine conditions, i.e., no rain for at least one week. Following rain, these concentrations increased by an average of eightfold, suggesting runoff as a major route of herbicide introduction in these waterways. To determine whether fish might be able to limit point-source exposures through sensory-driven behaviors, we introduced pulses of representative herbicide mixtures to individual adult zebrafish (a model species) in flow-through tanks. Fish did the opposite of limit exposure; they chose to spend more time in pulses of herbicide mixtures representative of those that may occur with rain events. This attraction response was not altered by a previous 4-d exposure to lower concentrations of the mixtures, suggesting fish will not learn from previous exposures. However, previous exposures did alter an attraction response to an amino acid prevalent in food (L-alanine). The present study demonstrates that fish living within urban waterways may elect to place themselves in herbicide-contaminated environments and that these exposures may alter their behavioral responses to cues necessary for survival., (Copyright © 2011 SETAC.)

A nationwide study was conducted to examine concentrations of polybrominated diphenyl ethers (PBDEs) in top predatory fish, with a focus on lake trout (Salvelinus namaycush), across Canada, and to explore possible influences of food web processes. Concentrations of the three most abundant PBDE homolog groups (tetra-, penta-, and hexa-PBDEs) were, for the most part, higher in Great Lakes and Lake Champlain fish compared with fish from other systems. The Canadian Federal Environmental Quality Guideline for the penta-homolog was exceeded in 70% of the fish examined. However, virtually no guideline exceedances were found for other congeners. In general, PBDE-47 (a representative lower brominated congener) was significantly and positively correlated with fish length, weight, age, lipid content, and stable isotopes of nitrogen and carbon. Significant differences in the slopes of the PBDE-47/covariate relationships between sites prevented concentrations from being adjusted using an analysis of covariance (ANCOVA). However, plots showed that elevated concentrations of PBDE-47 in Great Lakes and Lake Champlain fish remained after accounting for the influence of covariates. In contrast, for PBDE-183 (a representative higher brominated congener), the relationships between fish concentrations and covariates were not consistent, which could be a result of biotransformation being more important in controlling its bioaccumulation. The data from the current study show an overall disconnect between fish PBDE concentrations and likely loadings, which may be caused by differences in food web processes between systems. Continued long-term fish contaminant monitoring is needed to evaluate potential risk to fish and their consumers. However, we also recommend sediment sampling and focused food web studies to provide information on PBDE inputs to the systems and mechanisms of biomagnification, respectively., (Copyright © 2011 SETAC.)