Skeletal muscle is one of the most plastic tissues in the body of fishes. Fishes can modify many of the structural and metabolic properties of their skeletal muscle in response to environmental, mechanical, and physiological stimuli. This chapter highlights the remarkable plasticity of fish skeletal muscle and discusses general patterns of muscle remodeling in response to stimuli such as exercise as well as alterations in environmental temperature or oxygen availability. This chapter also explores how changes in the skeletal muscle phenotype influence locomotor performance and therefore the ultimate survival and fitness of fishes.