As a continuation of the hatchery experiments, modifications to the SHReF have allowed for investigations into the effects of low oxygen on the incubation success of salmonids. This work has two main aims: Firstly, to determine the effects of different oxygen regimes during the incubation period on the survival of Atlantic salmon. Laboratory experiments exposing salmon embryos to a variety of oxygen regimes that mimic conditions present in the wild provide evidence of the effect of different hydrological processes upon the survival of Atlantic salmon in the earliest life-stages. This includes exposure to continuously depleted oxygen levels that may occur as a result of sedimentation and short spikes of severe oxygen depletion that are observed as a result of the upwelling of low dissolved oxygen groundwater. Key indicators of the effect of oxygen depletion on salmon embryos include pre-hatch mortality as well as a range of sublethal effects including altered time of hatch, reduced size at hatch, and increased susceptibility to predation.

The second part of the research focuses on demonstrating the adaptations that different populations of the same salmonid species may have developed in response to continuously depleted oxygen levels in their natural environment. This is achieved by exposing three different populations (chalk stream, Scottish highland stream, farmed) to the oxygen regimes outlined above and comparing their responses both in terms of mortality and sublethal effects. Furthermore, the morphology of the eggs from different populations is examined with a focus on size as well as differences in the structure of the egg chorion – the outermost surface of the egg that is known to be a barrier to oxygen diffusion.

People:

Dr Jack Bloomer

Prof. David Sear

Prof. Paul Kemp