Estimation of physical load of fish tightend by a nylon line using autoregressive analysis of heart rate variability

The heart beat variability has been known to show the activity of autonomic nerve system. In this study, we analized time series data of heart beat va riability to assess physical load of rainbow trout tightend by a nylon line , Based on the stochastic theory, an autoregressive model was applied to th e time series of heart beat valiability to express degree of physical load. Using some coefficients, a new parameter ARAV defined as the multiplicatio n of total time series variance and the ratio of residual term variance to autoregressive term variance was used. The results of experiments using 9 r ainbow trout showed the following tendency. In the hard tightened condition , the ARAV reduced to infinitesimal values and continued for a time. Subseq uently, the fish which indicated these ARAV values died within 24 h. But in the gentle load, the ARAV was constant or less variable in comparison with resting condition. It was assumed that the ARAV expressed the degree of ag onizing of the fish, and moreover gave the mortality or survival rate when injured and escaping from fishing gears.