The techniques of molecular biology offer a powerful means of investigating and controlling the genetic basis of mechanisms operating in living organisms. Genetic research on aquatic animals can reveal important information relating to growth, development, adaptation to the environment, and the transfer of novel genes. This volume presents some of the most exciting advances in this rapidly expanding area, and contains contributions on the evolution of adaptation to low temperature, adaptation to short-term fluctuations in temperature and salinity, gene expression during growth and development, myosin polymorphism and the generation of transgenic fish.