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Growth hormone (GH) transgenic fish have accelerated growth and could improve production efficiency in aquaculture. However, concern exists regarding potential environmental risks of GH transgenic fish should they escape rearing facilities. While environmental effects have been examined in some GH transgenic models, there is a lack of information on whether effects differ among different constructs or strains of transgenic fish. We compared growth and survival of wild-type coho salmon (Oncorhynchus kisutch) fry, a fast-growing GH transgenic strain containing a metallothionein promoter (TMT), and three lines/strains containing a reportedly weaker histone-3 promoter (TH3) in hatchery conditions and semi-natural stream tanks with varying levels of natural food and predators. Rank order of genotype size and survival differed with varying environmental conditions, both within and among experiments. Despite accelerated growth in hatchery conditions, TMT fry gained little or no growth enhancement in stream conditions, had enhanced survival when food was limiting, and inconsistent survival under other conditions. Rank growth was inconsistent in TH3 strains, with one strain having highest, and two strains having the lowest growth in stream conditions, although all TH3 strains had consistently poor survival. These studies demonstrate the importance of determining risk estimates for each unique transgenic model independent of other models. [ABSTRACT FROM AUTHOR]

Domesticated and growth hormone (GH) transgenic salmon provide an interesting model to compare effects of selected versus engineered phenotypic change on relative fitness in an ecological context. Phenotype in domestication is altered via polygenic selection of traits over multiple generations, whereas in transgenesis is altered by a single locus in one generation. These established and emerging technologies both result in elevated growth rates in culture, and are associated with similar secondary effects such as increased foraging, decreased predator avoidance, and similar endocrine and gene expression profiles. As such, there is concern regarding ecological consequences should fish that have been genetically altered escape to natural ecosystems. To determine if the type of genetic change influences fitness components associated with ecological success outside of the culture environments they were produced for, we examined growth and survival of domesticated, transgenic, and wild-type coho salmon fry under different environmental conditions. In simple conditions (i.e. culture) with unlimited food, transgenic fish had the greatest growth, while in naturalized stream tanks (limited natural food, with or without predators) domesticated fish had greatest growth and survival of the three fish groups. As such, the largest growth in culture conditions may not translate to the greatest ecological effects in natural conditions, and shifts in phenotype over multiple rather than one loci may result in greater success in a wider range of conditions. These differences may arise from very different historical opportunities of transgenic and domesticated strains to select for multiple growth pathways or counter-select against negative secondary changes arising from elevated capacity for growth, with domesticated fish potentially obtaining or retaining adaptive responses to multiple environmental conditions not yet acquired in recently generated transgenic strains. [ABSTRACT FROM AUTHOR]

Concerns with transgenic animals include the potential ecological risks associated with release or escape to the natural environment, and a critical requirement for assessment of ecological effects is the ability to distinguish transgenic animals from wild type. Here, we explore geometric morphometrics (GeoM) and human expertise to distinguish growth-hormone-transgenic coho salmon (Oncorhynchus kisutch) specimens from wild type. First, we simulated an escape of 3-month-old hatchery-reared wild-type and transgenic fish to an artificial stream, and recaptured them at the time of seaward migration at an age of 13 months. Second, we reared fish in the stream from first-feeding fry until an age of 13 months, thereby simulating fish arising from a successful spawn in the wild of an escaped hatcheryreared transgenic fish. All fish were then assessed from photographs by visual identification (VID) by local staff and by GeoM based on 13 morphological landmarks. A leave-one-out discriminant analysis of GeoM data had on average 86% (72-100% for individual groups) accuracy in assigning the correct genotypes, whereas the human experts were correct, on average, in only 49% of cases (range of 18-100% for individual fish groups). However, serious errors (i.e., classifying transgenic specimens as wild type) occurred for 7% (GeoM) and 67% (VID) of transgenic fish, and all of these incorrect assignments arose with fish reared in the stream from the first-feeding stage. The results show that we presently lack the skills of visually distinguishing transgenic coho salmon from wild type with a high level of accuracy, but that further development of GeoM methods could be useful in identifying second-generation fish from nature as a nonmolecular approach. [ABSTRACT FROM AUTHOR]

Genetically engineered fish containing growth hormone (GH) transgenes have been synthesized for more than 25 years, now with modifications made in multiple aquacultured species. Despite significant improvements in production characteristics being realized, these fish have not yet entered commercial production. The very strong enhancement of growth rates that can arise from GH transgenesis in fish has generated public and scientific concern regarding ecological and food safety. Little ecological risk is anticipated from engineered strains kept in fully contained facilities, so the concern is largely directed toward the reliability of containment measures and determining whether robust ecological data, pertinent to nature, can be generated within research facilities to minimize uncertainty and allow reliable risk-assessment predictions. This article summarizes the growth, life history, and behavioral changes observed in GH-transgenic fish and discusses the environmental and evolutionary factors affecting the adaptation, plasticity, and fitness of transgenic fish and their potential consequences on natural ecosystems. [ABSTRACT FROM AUTHOR]

In this study, individual growth patterns of wild-type and growth-enhanced coho salmon Oncorhynchus kisutch at 8, 12 and 16° C water temperature were followed. Despite large differences among individuals in growth rates, there was generally little variation in the shape of the growth curves among O. kisutch individuals of both genotypes and at all temperatures. Typically, individuals that were relatively large initially were also relatively large at the end of the growth period. The limitation in variation was more pronounced in the growth-enhanced O. kisutch than in the wild type, where the relative size of some individuals reared at 12 and 8° C changed by the end of the trial. As a warmer temperature seems to decrease the plasticity of growth trajectories in wild-type fish, it is possible that global warming will influence the ability of wild fish to adapt their growth to changing conditions. [ABSTRACT FROM AUTHOR]

Food consumption, number of movements and feeding hierarchy of juvenile transgenic common carp Cyprinus carpio and their size-matched non-transgenic conspecifics were measured under conditions of limited food supply. Transgenic fish exhibited 73·3% more movements as well as a higher feeding order, and consumed 1·86 times as many food pellets as their non-transgenic counterparts. After the 10 day experiment, transgenic C. carpio had still not realized their higher growth potential, which may be partly explained by the higher frequency of movements of transgenics and the ‘sneaky’ feeding strategy used by the non-transgenics. The results indicate that these transgenic fish possess an elevated ability to compete for limited food resources, which could be advantageous after an escape into the wild. It may be that other factors in the natural environment ( i.e. predation risk and food distribution), however, would offset this advantage. Thus, these results need to be assessed with caution. [ABSTRACT FROM AUTHOR]

Potential ecological consequences on the natural environment of fast-growing transgenic fish with elevated intrinsic growth rates is an important question should such fish be allowed in commercial production systems. One trait that will strongly affect the spatial extent of consequences is the propensity of transgenic fish to disperse. We addressed this question in three experiments using different measures of spatial dispersal where we compared very young genotypically wild coho salmon with transgenic conspecifics in terms of: (i) group cohesion, (ii) exploratory behavior, and (iii) up- and downstream movements. Transgenic fish were more loosely aggregated, more likely to explore, and less likely to swim upstream, but equally likely to disperse downstream compared with genetically wild fish. These results show that dispersal behavior has been affected by transgenesis and that transgenic fish therefore may venture into habitats previously not used by wild fish. Given the importance of dispersal in ecological risk-assessment of transgenic fish, continued work within this area is warranted and experimental habitats should mimic the potential receiving natural habitats to which transgenic fish are likely to escape or be released to. [ABSTRACT FROM AUTHOR]

We compared the performance of normal and growth hormone-transgenic coho salmon feeding on surface drifting edible and inedible novel prey items in various social environments. With an inherently higher appetite, we predicted that transgenic fish would be more willing to feed on novel prey, and that visual company with another fish would enhance this difference further. Transgenic and normal fish, of similar size and age, were equally willing to attack both the edible (live insects) and inedible (artificial angling lure flies) prey, but transgenic fish did so faster and were more likely to make repeated attacks. Transgenic fish managed to seize and consume the edible prey after fewer attacks than did normal fish. However, swallowing of prey took longer than for normal fish. More transgenic individuals interacted with the inedible prey compared with normal salmon, and initially, transgenic fish in visual company with another fish also interacted more with the prey than single transgenic or any constellation of normal focal fish. With repeated exposures, the number of individuals attacking and the number of interactions with the prey decreased. These responses were stronger in transgenic fish, partly explained by the initially low response in normal fish. The observed differences are most likely the consequences of elevated levels of growth hormone in transgenic fish generating enhanced feeding motivation and reinforcement capacity. In a natural environment, the performance of a growth hormone-transgenic fish may therefore depend on the relative abundance of profitable vs. unprofitable prey, as well as the presence of other transgenic individuals. [ABSTRACT FROM AUTHOR]

Abstract Growth hormone (GH) gene transgenesis has allowed the production of salmon with an inherently increased growth potential, on average two to threefold higher compared with daily specific growth rates observed in normal, non-transgenic fish. This difference quickly results in animals of very different sizes at age, and is associated with specific morphological effects and enhanced appetites in transgenic animals. However, less is known of the feeding and antipredator behaviour of GH-transgenic fish, information that can help with predictions of potential ecological consequences of release or escape of transgenic fish into the wild. In a series of experiments, transgenic (T) and normal (N) coho salmon of varying age and size (from 0.5 to 40 g, 3.5–21 mo) were studied singly, in pairs, and in groups during feeding and simulated predation threat. Vertical position generally did not differ between T and N fry, but at larger size (>4 g) T fish remained closer to the surface than N fish both during feeding and predatory attacks, probably as a consequence of inherent differences in feeding motivation and later reinforcement by associative learning. This difference in vertical position was not the result of competition as it remained even after either fish in the pair had been removed. In nature, where predators may attack from above (birds) or below (fish), this kind of behaviour may translate into higher risk of predation, which could increase mortality and lower the fitness of transgenic fish, unless their increased growth rate can compensate for the increased risk-taking. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the present study was to clarify the role of GH transgenesis and its production in social interactions in juvenile common carp Cyprinus carpio. With food pellets provided sequentially, the serum GH levels and behavioral effects were measured in 14 pairs of size-matched ‘all-fish’ GH-transgenic and non-transgenic common carp. In six consecutive observations during 3days, transgenic fish had a higher movement level as well as a higher social status, being 2.69 times as aggressive, two minutes before and after the 10-min feeding session compared to non-transgenic fish. Transgenic fish also were more than 1.74 times as likely to consume each pellet. During the 8-day experiment, transgenic fish had 4.09 times higher specific growth rate in body weight as well as 6.36 times higher serum GH level than the non-transgenic fish. These results show that GH transgenesis promotes over-expression of GH and alters behaviors in juvenile common carp, thereby increasing their ability to compete and gain food resources, presumably to meet a higher intrinsic growth rate, which gives direct evidence for the GH-induced elevation in feeding competitive ability of GH-transgenic common carp. Understanding these relationships would not only help evaluating potential ecological effects of the escaped/released transgenic fishes, but also help using potential aquaculture of this growth-enhanced strain. [Copyright &y& Elsevier]