To study the functioning of the jaw apparatus of fish was developed and tested kinematic scheme using crank mechanism. This model is a modified analogue of the previously used four-link hinge system. In this development, based on empirical studies, was taken into account the immobility of the pterygoid and Palatine bones, which in previous works were considered as moving elements. The application of the analytical approach allowed to determine the dependence of the angles and links of the mechanism, as well as the kinematic characteristics of the upper and lower jaw blocks. The morphometric data of the jaw apparatus of two closely related species of coastal Cottoidei, characterized by linear parameters of bones, were used for the implementation of kinematic analysis. As a result of the study, it was found that the increase in the length of the jaws affects the space-time kinematic characteristics, changing the amplitude and speed of movement. It is shown that the angle of rotation and the angular velocity of the maxillary block decreases with the transition of views to the power of large objects, since the extension of the mouth becomes less relevant and is compensated by an increase in its size. At the same time, this provides an increase in the angle of rotation of the mandibular block and, accordingly, the maximum height of the mouth opening. In General, the resulting kinematic scheme and analytical dependences can be used to calculate the range of possible options and the speed of movements in different species of fish with a similar type of jaw apparatus.