Fish are supposed to be able to adapt to various underwater environments.The mechanical properties of the body of a fish is of essential importance in order to explore the source of high efficiency during fish swimming.We investigate the viscoelastic properties of the fins,muscle and skin of Crucian carp(carassius auratus).A fractional Zener model is used to fit the relaxation force and the results show that the model can describe the relaxation process well.With a Fourier transform,we discuss the response functions of the fins,muscle and skin of Crucian carp under the external excitation of a harmonic force.Comparison of these results with the cruising frequency of Crucian carp shows that the dissipation due to internal viscoelasticity during cruising is small.
