Recent time-geographic studies have focused upon an examination of the conceptual framework of Hagerstrand’s original model, while there has been little applied research except for its introduction to the techniques of urban planning. However, there remain some other fields where it can be applied, since time-geography is fundamentally designed as a common language for the expression of interactions not only between individuals and man-made objects but also between individuals and natural environmental elements. The present article aims to apply certain time-geography notions to observed human behavior under certain natural conditions, and thus to obtain a rational interpretation of individual behavior choices from a time-geographic point of view. As a case study, this article describes some fishermen's daily behavior in Hsingkang (新港), a fishing port in eastern Taiwan. Spatial-temporal paths of spear fishermen aiming to catch giant black marlin (Makaira malina) are described in Fig. 2-4. The paths of long-line fishermen aiming to catch dolphinfin (Coryphaena hippurus Linnaeus) are described in Fig. 7-8, and yellowfin tuna (Thunnus albacares) in Fig. 9-11. From a time-geographic view, these paths are interpreted as follows: Individual behavior is limited by a fisherman's physiology and by the physical capability of his tools. These two factors form a “prism”, which may be transformed by day-to-day weather conditions. Within this “prism” a fisherman's behavior, which aims at coupling with fish in space-time, is influenced by certain natural environmental conditions. There is a spatial condition characterized by the distribution of fishing spots, which is determined by submarine topography. The temporal conditions consist of seasonal and daily fluctuations of prey-food.