CRITIQUE OF PROPORTIONAL HYPOTHESES AND METHODS FOR BACK-CALCULATION OF FISH GROWTH

Hypotheses which assume a contant proportional deviation of the indivi dual size of fish scales (S) or body (L) from mean size throughout lif e are biologically insignificant. Growth is considered and illustrated as a complex self-regulating process which continuously changes throu ghout ontogeny. Speed and form of changes of the growth of individual fish depend mainly on the initial size of the specimen and on the habi tat. Consider five main types of changes of the L-S regression lines f or individual fish with different initial sizes. They are basically di fferent from the current proportional model of individual growth. The regression lines for individual fish cannot and should not be used for back-calculating L from S either by proportional or by regression met hods, as individual L(S)/theoretical L(S) ratio, determined at the tim e of capture, are usually considerably different, compared to the prev ious years. For back-calculation of the average L values from average S values the use of separate equations for each age-group or for the w hole subpopulation are recommended.