[Properties of harmonically season-modified Bertalanffy function of growth in length]

For individuals submitted to a moderate seasonal influence upon length growth the Bertalanffy function can be modified to show suppressed or stagnating growth as was already demonstrated by the author for nyctiphanes couchii (euphausiids) off the coast of Britanny (Sagér 1983a). In this paper the properties of the revised structure of the formula are shown implying the growth function proper and the increase function. Moreover the influence of a shifting birth date upon the growth behaviour is followed up leading to a catching-up phenomenon or growth compensation within 12 months when all factors acting on length development remain strictly periodic. Graphs for the modified function and its increase values are added for a given example.