Peter Dimoulas

Thesis Abstract:
If GH-transgenic coho salmon escaped into the natural environment would their performance during predator-prey encounters or spawning migrations be different from their wild conspecifics? We examined fast-start and sprinting performance to infer their prospective ability to evade predatory strikes and chasing predators, to chase prey, and to complete spawning migrations. Similarly, we addressed the effects of GH upregulation on muscle functioning. Fast-starts are rapid escape events, and are a summation of short-term behavior, white muscle intrinsic properties, musculoskeletal linking, and body shape. Sprinting additionally reveals the capacity of white muscle to support ATP turnover.
We sought length-matched cohorts, and we examined fast-starts among juveniles, and sprinting among juveniles and adults. We used 3 groups of Coho salmon: GH-transgenic fed to satiation (GHf), wild fed to satiation, and GH-transgenic par-fed according to the fed consumption of wild Coho salmon. For fast-start performance we simulated predatory strikes and quantified the mechanics and escape velocity via high-speed video. For sprinting performance between juveniles we measured: time to exhaustion, anaerobic substrate usage, velocity, and tail-beat frequency. For sprinting between adults, who had similar body lengths (though GHf were significantly longer than wild Coho), we quantified time to exhaustion and velocity.
During fast-starts we found similar mechanics and escape velocity between all groups. We conclude that juvenile GHf may have a similar ability to evade predatory strikes, and GH had no effect on the affectors of fast-starts (we additionally presented across-species comparisons of the effects of GH on muscle enzyme activity, fibre-types, and contractile properties). During sprinting between juveniles, we found similar velocity, tail-beat frequency, and substrate usage; however, GHf took significantly longer to exhaust. We concluded that juvenile GHf might have an enhanced ability to evade chasing predators and to chase prey, due to a higher capacity to support ATP turnover. Between adults, we found similar time to exhaustion, but GHf exhibited significantly lower velocities. While the scaling of velocity offered some insight, differences in body length complicated our analysis. Nevertheless, we suggest that adult GHf may have a reduced ability to evade chasing predators, to chase prey, and to complete spawning migrations.