This study aims to examine the environmental adaptation of diving fishery groups with special attention to individual differences in fishing ground use.
In Wagu, a diving fishery is operated mainly around small islands and rocky reefs located about 2km offshore. Five types of abalone, a turban shell, a topshell and some other less-economically valued organisms are the target species. The divers (Ama) have three different types of operation: an individual operation (Hamako), an operation undertaken by by one diver and one operator who are primarily kin (Funedo), and an operation involving several divers and one boat operator (Kachido). Since the latter is becoming the predominant operational type, an analysis of Kachido's activity space is therefore crucial to an examination of the relationship between operation types and the fishing ground environment in Wagu.
The fishing grounds are divided into categories in relation to the abalone habitat. The largest is Iso, which consists of rocky bottom habitats identified by a specific name. In each Iso, there are small areas called Shima. These are dimensional but also topographical categories of the fishing ground. The selection of Shima is performed by individual Ama for all operational types, while that of Iso is performed differently. For Kachido, the boat operator recognizes available Iso for the day's operation in relation to the tidal current, water depth, and the Ama's diving ability.
In the practice of Kachido, the behavioral patterns of individual Ama are variable. Abalone collecting is most profitable, but the physical ability of older Ama to collect these shellfish is constrained. Instead, these Ama are able to collect turban shells and topshells in the course of searching for Shima, or when brought to shallower Iso by the boat operator. Ama with experience in recognizing Shima may collect more abalone than other Ama, however. It can be seen from these behaviors that fishing grounds recognized by the boat operator or Ama result in variability in shellfish collecting activities by individual Ama.
From the analysis, two significant characteristics of fishing ground use for Kachido operation are identified. The first is the recognition by the boat operator of the relationship between topography and tidal currents for the selection of Iso. The second is the use of different resources by Ama of variable age and experience that are adaptive to biophysical diversity within Iso.