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(T/FF220) Effects of dietary exposure of 4-nonylphenol on smoltification of juvenile coho salmon . Keen, Patricia 1, Higgs, David2, Hall, Ken 1, Ikonomou, Michael3, Clarke, Craig4, Brown, Scott5, 1 2 3 4 5 ABSTRACT- There is considerable concern that endocrine disrupting substances such as 4-nonylphenol (4-NP) in the freshwater environment may have adverse effects on the growth and survival of salmonids during and after their transfer to seawater. Other researchers have observed deleterious effects of waterborne 4-NP on the smoltification process of salmonids which were suspected to be caused by disruption of the endocrine system. To date, few experiments have examined effects of exposure of 4-NP to Pacific salmon species. Coho salmon (Oncorhynchus kisutch) were selected for this study. An experiment was conducted to examine the effects of dietary exposure of coho salmon to 4-NP during the parr-smolt transformation phase of their life cycle. Under laboratory conditions, juvenile coho salmon were fed by hand twice daily to satiation. The diets contained several concentrations of 4-NP varying between 0.002 mg/kg and 2000 mg/kg for a period of four weeks immediately prior to transfer to seawater. The growth of the fish was observed for two successive six week periods following seawater transfer. Concentrations of 4-NP in the livers, gall bladders, and flesh as well as those of vitellogenin and two thyroid hormones in blood plasma were followed in relation to diet treatment and sampling time. Dietary treatment did not appear to influence the growth and smoltification of coho salmon. Appreciable concentrations of 4-NP were present in the organs and the tissues after four week exposure of coho salmon to the highest dietary dose but 4-NP was effectively eliminated from the fish after seawater transfer. Key words: 4-nonylphenol, endocrine disruption, coho salmon, growth |
