The influence of hypoxia on the early life stages of rainbow trout (Oncorhynchus mykiss)

In fish embryos, hypoxia reduces growth, delays development and induces earlier hatching. My findings showed that early hatch in trout embryos exposed to hypoxic water did not accelerate growth, contrary to predictions. Studies on the oxygen concentration within the boundary layer next to the chorion or skin surface revealed that the dissolved oxygen (DO) concentrations in free-stream water, water flow rate, and developmental stage all impact the gradient and thickness of the oxygen boundary layer around embryos and larvae. The chorion was an additional barrier to oxygen diffusion. The number of body movements did not change when embryos were exposed to hypoxia, while larvae significantly decreased their number of movements when exposed to hypoxia. Taken together, this data shows that conditions similar to those observed in the wild influence the rate of oxygen supply to the embryo and, in turn, their growth and development.