Fish Swimming Movements: a Study of One Element of Behaviour

Abstract

Oscillatory swimming movements are the basic elements of fish behaviour. The prospect of an objective description of these elements in terms of contraction patterns of the lateral muscles is explored. During steady swimming, waves of curvature run down the fish body. These swimming movements are the result of muscle activities, the mechanical properties of the locomotory structures and reactive forces from the water. Dimensionless kinematic data of different species, swimming steadily and unrestricted in static water conditions are compared. The functional morphology of relevant structures of the gadoids saithe and cod is compared with that of mackerel. Swimming dynamic studies, based on kinematic data and on hydrodynamic theory, show that the relations between muscle contractions, bending moments and waves of curvature are different for saithe and eel. Muscle contraction patterns can only be used to describe swimming behaviour if the mechanical system in which the muscles operate and the interaction between fish and water is understood.