Smolt development in growth hormone transgenic Atlantic salmon

Growth hormone transgenic Atlantic salmon (Salmo salar) produced using a ge ne construct comprised of an antifreeze protein (AFP) gene promoter from oc ean pout (Macrozoarces americanus) and the growth hormone (GH) gene from ch inook salmon (Oncorhynchus tshawytscha) were used for this study of smelt d evelopment. An F-2 generation of these transgenic salmon was initiated in N ovember 1995 using milt from a transgenic F-1 male and eggs from a normal f emale, hatching in January and first feeding in February 1996. With elevate d temperature (16 degrees C) initially and various combinations of temperat ure-photoperiod manipulation, the transgenic individuals approached smelt s ize (16 cm) in June; their normal siblings were < 10 cm. Most transgenic in dividuals survived > 96 h following direct transfer to 35 parts per thousan d seawater in June. Normal individuals survived less than 24 h. Transgenic individuals had high girl Na+-K+ ATPase activity levels and declining condi tion factor in late June, indicative of smelt status. Following transfer to seawater in early July, transgenic fish from the various temperature-photo period treatments grew rapidly, with few mortalities, until observations we re discontinued in October 1996. High temperature (16 degrees C) in one tre atment, which inhibits development or maintenance of elevated gill Na+-K+ A TPase activity in non-transgenic Atlantic salmon, resulted in only slightly lower gill ATPase levels in transgenic individuals. These survived and gre w well during 4 months in seawater. Similarly, constant light (LD:24) in an other treatment, which inhibits normal smelt development in non-transgenic salmon, did not prevent smelt development or adversely affect post-smelt su rvival and growth in seawater. It is concluded that transgenic salmon from all treatments completed smelting at age 6 months with satisfactory surviva l and growth in seawater. It appears that GH transgenic Atlantic salmon can be reared under temperature and photoperiod regimes which optimize growth, but which would inhibit normal smolt development and post-smelt performanc e of non-transgenic salmon. Crown Copyright (C) 1998 Published by Elsevier Science B.V.