Muscle fibre growth and quality in fish

Striated muscle in fish is in parity with skeletal muscle in higher vertebrates made up of three major compartments contractile proteins, lipids, and connective tissue, all affecting the product and food quality of the muscle as meat. The most striking difference between striated fish muscle and that found in higher vertebrates is the separation of fibre types in to discrete layers in fish, where the high glycolytic and anaerobic type (FastWhite fibres) dominates constituting 90-95% of all muscle in most fish species. Red muscle fibres are commonly confined to a narrow strip along the lateral line and constitute less then 10 % of the myotomal musculature. Intermediate or pink fibres are in accordance to their name not only intermediate in position between red and white muscle fibres but also in many other aspects. Salmonids seem not to have pink fibres. In contrast to other higher vertebrates in the majority of fish species growth continues through out life and the growth of muscle is the combined effect of formation of more muscle cells (fibres) and increase in size of already existing fibres. In spite of the apparent large connective tissue compartment of fish muscle, only 2-3 % of the protein is found here. All the above factors are believed to be in part under genetic control, but a gene x environment interaction seems to be evident. The current state of knowledge is reviewed here and the impact of muscle structure on quality is discussed.