title: 17-Beta estradiol and 4-nonylphenol delay smolt development and downstream migration in Atlantic salmon, Salmo salar.
abstract: The effect of 17-beta estradiol (E2) and 4-nonylphenol (4-NP) on smoltification and downstream migration of Atlantic salmon was studied in an integrated laboratory and field study. In a stock of hatchery-raised 1-year-old salmon, smoltification progressed from February until late May as judged by increased gill Na+, K+ -ATPase activity and 24 h sea water (SW)-tolerance. Starting late March, three groups of 150 fish were each given 6 serial injections over 20 days of 2 microg/g body weight E2, 120 microg/g 4-NP dissolved in peanut oil or peanut oil (4 microl/g) as control. After the last injection, all fish were individually tagged (Passive Integrated Transponder tags) and a non-lethal gill biopsy was taken. Two days later (8 April), 100 fish per group were transported to the field site and released into a small stream. Smolt migration was registered by measuring arrival time at a trap downstream of the release site. Serum vitellogenin levels increased several-fold in both male and female E2- and 4-NP-treated fish. Overall, E2- and 4-NP-treatment impaired smolting as judged by elevated condition factor, reduced gill Na+, K+ -ATPase activity and alpha-subunit Na+, K+ -ATPase mRNA level, reduced muscle water content and increased mortality following 24 h SW-challenge. After release, control fish initiated downstream migration immediately, with 50% of the total number of migrants appearing in the trap within 10 days. E2- and 4-NP-treated fish appeared in the trap with a delay in comparison to controls of 6 and 8 days, respectively. After the smolt run, no fish were registered by electro-fishing upstream of the trap. The total number of fish reaching the trap and thus post-release survival was in the order control (81%), E2 (53%), 4-NP (12%). Representatives from all treatment groups held under simulated natural conditions in the laboratory survived 100% through the migration period, suggesting that a combination of behavioural and in-stream factors (predation by herons) may contribute to the differential mortality. The study indicates that short-term exposure to natural and environmental estrogens may impair smolt development and survival and delay subsequent downstream migration in Atlantic salmon.
authors.affiliation: Institute of Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark. steffen@biology.sdu.dk
authors.forename: Steffen S
authors.initials: SS
authors.lastname: Madsen
authors.forename: Søren
authors.initials: S
authors.lastname: Skovbølling
authors.forename: Christian
authors.initials: C
authors.lastname: Nielsen
authors.forename: Bodil
authors.initials: B
authors.lastname: Korsgaard
mesh_terms: D000704:Analysis of Variance; D025041:Animal Migration / Q000187:drug effects*; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D001824:Body Constitution / Q000502:physiology; D004797:Enzyme-Linked Immunosorbent Assay; D004958:Estradiol / Q000494:pharmacology*; D008018:Life Cycle Stages / Q000187:drug effects*; D010636:Phenols / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism*; D045483:Rivers; D020317:Salmo salar / Q000254:growth & development*; D012623:Seawater; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014819:Vitellogenins / Q000097:blood
chemical_list: D010636:Phenols; D012333:RNA, Messenger; D014819:Vitellogenins; D004958:Estradiol; D000254:Sodium-Potassium-Exchanging ATPase; C041594:4-nonylphenol