Tributyltin and the obesogen metabolic syndrome in a salmonid.

We conducted a dietary feeding study with juvenile chinook salmon (Oncorhynchus tshawytscha) to assess the potential for tributyltin (TBT) to elicit the obesogen response that has been described for mammals. The results show increases in whole-body lipid content, which is consistent with the obesogen response; however, we also observed associated parameters that were dissimilar. We found increases in body mass and alterations to several physiological parameters at doses between 0.4 and 3.5 ng/g fish/day (1.4-12 pmol/g fish/day) and reduced body mass at the highest dose after 55 days of exposure. Lipid related plasma parameters (plasma triacylglycerols, cholesterol, and lipase) exhibited monotonic increases over all doses while other values (glucose and insulin-like growth factor (IGF)) exhibited increases only for the low-dose treatments. The increases noted for several parameters in fish were opposite to those reported for the obesogen metabolic syndrome, which is characterized by a reduction in serum glucose, free fatty acids, and triglycerides. This is the first report of growth stimulation resulting from low-dose exposure to this pesticide, which is an unusual response for any animal exposed to an organic or organometallic xenobiotic. Because a number of environmental contaminants act as metabolic disruptors at very low doses, these results are noteworthy for a variety of species. Intuitively, enhanced growth and lipid storage may appear beneficial; however, for salmonids there are numerous potentially negative consequences for populations.

Bioaccumulation of polychlorinated biphenyls in juvenile chinook salmon (Oncorhynchus tshawytscha) outmigrating through a contaminated urban estuary: dynamics and application.

A field study was conducted to examine bioaccumulation of polychlorinated biphenyls (PCBs) for hatchery-raised and naturally reared (wild) ocean-type juvenile chinook salmon outmigrating through the Lower Duwamish Waterway (LDW), a contaminated urban estuary in Seattle, WA, USA. These results show differences in bioaccumulation of PCBs over time and space in this estuary, which may also occur for any contaminant that is distributed heterogeneously in this system. Highly mobile, outmigrating salmon accumulated approximately 3-5 times more PCBs on the east side of the LDW than fish on the west side, which is supported by an almost identical difference in mean sediment concentrations. The tPCB concentration data suggest that for most of the spring and early summer, juvenile chinook were likely segregated between the east and west side of the LDW, but may have crossed the channel later in the year as larger fish. Additionally, we used biota-sediment accumulation factors to assess the relative degree of bioaccumulation and explore these factors as potential metrics for predicting adverse sediment concentrations. These results highlight the importance of time and space in sampling design for a highly mobile species in a heterogeneous estuary.