Meeting Abstract

P1.113  Monday, Jan. 4  Smoltification and salinity tolerance of growth hormone transgenic coho salmon (Oncorhynchus kisutch) BYSTRIANSKY, J.S.*; CLARKE, C.; DEVLIN, R.H.; SCHULTE, P.M.; University of British Columbia; Pacific Biological Station, Nanaimo, B.C.; Department of Fisheries and Oceans Canada; University of British Columbia jbystria@zoology.ubc.ca

Transgenic coho salmon containing the growth hormone gene construct OnMTGH1 and non-transgenic coho salmon from the Chehalis river, British Columbia (progenitor strain of transgenic strain) were raised under a simulated natural photoperiod in freshwater and fed to satiation. Growth hormone transgenic salmon grew significantly faster and exhibited signs of smoltification one year prior to control salmon. Over a two year period individuals from each group were directly transferred to full strength seawater for 24 hours and plasma sodium concentration was determined. Transgenic salmon were significantly better than control salmon at regulating plasma sodium levels in their first year, coinciding with higher survival rates following seawater exposure. To assess whether the improved salinity tolerance of transgenic salmon was due to higher levels of growth hormone, or simply due to a larger body size a second experiment was conducted comparing sized matched growth hormone transgenic and control salmon. Size matching was accomplished through a ration restricted diet for transgenic fish which matched the appetite of control fish. A third experimental group consisting of transgenic salmon fed to satiation which were a year class younger (and therefore of similar size) was also included to differentiate any potential impact of ration restriction. Individuals from each group were exposed to seawater for up to 30 days and changes in plasma sodium, chloride, gill Na⁺K⁺-ATPase activity and isoform (mRNA) expression were monitored. In general, the three experimental groups showed a similar timeline for seawater acclimation suggesting that overall size is a larger determinant of seawater tolerance than growth hormone production.