Smolt development in growth hormone transgenic Atlantic salmon

Growth hormone transgenic Atlantic salmon (Salmo salar) produced using a gene construct comprised of an antifreeze protein (AFP) gene promoter from ocean pout (Macrozoarces americanus) and the growth hormone (GH) gene from chinook salmon (Oncorhynchus tshawytscha) were used for this study of smelt development. An F-2 generation of these transgenic salmon was initiated in November 1995 using milt from a transgenic F-1 male and eggs from a normal female, hatching in January and first feeding in February 1996. With elevated temperature (16 degrees C) initially and various combinations of temperature-photoperiod manipulation, the transgenic individuals approached smelt size (16 cm) in June; their normal siblings were < 10 cm. Most transgenic individuals survived > 96 h following direct transfer to 35 parts per thousand seawater in June. Normal individuals survived less than 24 h. Transgenic individuals had high girl Na+-K+ ATPase activity levels and declining condition factor in late June, indicative of smelt status. Following transfer to seawater in early July, transgenic fish from the various temperature-photoperiod treatments grew rapidly, with few mortalities, until observations were discontinued in October 1996. High temperature (16 degrees C) in one treatment, which inhibits development or maintenance of elevated gill Na+-K+ ATPase activity in non-transgenic Atlantic salmon, resulted in only slightly lower gill ATPase levels in transgenic individuals. These survived and grew well during 4 months in seawater. Similarly, constant light (LD:24) in another treatment, which inhibits normal smelt development in non-transgenic salmon, did not prevent smelt development or adversely affect post-smelt survival and growth in seawater. It is concluded that transgenic salmon from all treatments completed smelting at age 6 months with satisfactory survival 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 performance of non-transgenic salmon. Crown Copyright (C) 1998 Published by Elsevier Science B.V.