Fig. 4

Basic dependence structure of an HMM. The state at time t + 1 (S_t+1) is dependent on the observation at t + 1 (O_t+1) through the state distribution, and the state at the previous observation (S_t) through the transition matrix. The environment can act on the transition matrix and can thus affect the probabilities of a fish changing behaviour between detections. The Viterbi algorithm calculates the most probable state sequence for S_t:S_t+3 based on the observation sequence O_t:O_t+3 and the transition matrix [39]