title: Early life-history consequences of growth-hormone transgenesis in rainbow trout reared in stream ecosystem mesocosms.
abstract: There is persistent commercial interest in the use of growth modified fishes for shortening production cycles and increasing overall food production, but there is concern over the potential impact that transgenic fishes might have if ever released into nature. To explore the ecological consequences of transgenic fish, we performed two experiments in which the early growth and survival of growth-hormone transgenic rainbow trout (Oncorhynchus mykiss) were assessed in naturalized stream mesocosms that either contained predators or were predator-free. We paid special attention to the survival bottleneck that occurs during the early life-history of salmonids, and conducted experiments at two age classes (first-feeding fry and 60 days post-first-feeding) that lie on either side of the bottleneck. In the late summer, the first-feeding transgenic trout could not match the growth potential of their wild-type siblings when reared in a hydrodynamically complex and oligotrophic environment, irrespective of predation pressure. Furthermore, overall survival of transgenic fry was lower than in wild-type (transgenic = 30% without predators, 8% with predators; wild-type = 81% without predators, 31% with predators). In the experiment with 60-day old fry, we explored the effects of the transgene in different genetic backgrounds (wild versus domesticated). We found no difference in overwinter survival but significantly higher growth by transgenic trout, irrespective of genetic background. We conclude that the high mortality of GH-transgenic trout during first-feeding reflects an inability to sustain the basic metabolic requirements necessary for life in complex, stream environments. However, when older, GH-transgenic fish display a competitive advantage over wild-type fry, and show greater growth and equal survival as wild-type. These results demonstrate how developmental age and time of year can influence the response of genotypes to environmental conditions. We therefore urge caution when extrapolating the results of GH-transgenesis risk assessment studies across multiple life-history or developmental stages.
authors: Fisheries & Oceans Canada, Centre for Aquaculture and Environmental Research, West Vancouver Laboratory, 4160 Marine Drive, West Vancouver, British Columbia, V7V 1N6, Canada; Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J1.
authors: Glenn T
authors: GT
authors: Crossin
authors: Fisheries & Oceans Canada, Centre for Aquaculture and Environmental Research, West Vancouver Laboratory, 4160 Marine Drive, West Vancouver, British Columbia, V7V 1N6, Canada; Uppsala University, Department of Ecology and Genetics/Animal Ecology, Norbyvägen 18 D, SE-752 36 Uppsala, Sweden.
authors: L Fredrik
authors: LF
authors: Sundström
authors: Fisheries & Oceans Canada, Centre for Aquaculture and Environmental Research, West Vancouver Laboratory, 4160 Marine Drive, West Vancouver, British Columbia, V7V 1N6, Canada.
authors: Wendy E
authors: WE
authors: Vandersteen
authors: Fisheries & Oceans Canada, Centre for Aquaculture and Environmental Research, West Vancouver Laboratory, 4160 Marine Drive, West Vancouver, British Columbia, V7V 1N6, Canada.
authors: Robert H
authors: RH
authors: Devlin
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified / Q000254:growth & development / Q000502:physiology; D017753:Ecosystem; D005260:Female; D018014:Gene Transfer Techniques; D005838:Genotype; D013006:Growth Hormone / Q000235:genetics* / Q000378:metabolism; D017686:Oncorhynchus mykiss / Q000254:growth & development / Q000502:physiology; D010063:Ovum / Q000254:growth & development / Q000378:metabolism; D011235:Predatory Behavior / Q000502:physiology
chemical_list: D013006:Growth Hormone