Designing and Optimizing Commercial Red Sea Urchin Line Transect Diving Surveys by Set Theory Using Both Historical Survey Data and Observations from Fishers

People, especially fishers, are an integral part of understanding marine ecosystems and the causes and consequences of change. They develop precise knowledge of their resources, their environments, and their fishing practices. In this study, their knowledge was used to design a commercial sea urchin line transect diving survey along the Strait of Juan de Fuca in 2004. Following the first survey, which was conducted in 2001, the total harvest area of red sea urchin was divided into 73 uniform parts. Five experienced commercial fishers were interviewed and their information was filtered with the known 37 parts completed in 2001. They identified their respective fishing areas and provided spatial densities of red sea urchin over 18 to 32 parts (Some of their fishing areas overlapped). Their information was compared with pre-season line transect surveys conducted in 2001 and their accuracy varied from 44.44% to 100%.  Using set theory to combine and filter their information with a reliability measure, there was a 50.68% to 75.96% increase in red sea urchin spatial density information. Results from this study will help scientists and resource managers to design more efficient sampling protocols for long term monitoring, and significantly reduce the operating costs of field surveys.