Methodology of shellfish surveys based on a microcomputer geographic information system

Shellfish survey observations should be considered as spatially referenced, such that spatial mathematical models of stock density and sampling schemes are two major subjects of survey methodology. A mathematical method of spatial regression with supplementary variables is developed in order to integrate a few layers of spatial data. It allows incorporation of supplementary variables such as bathymetry, temperature, temperature gradient, current velocity, etc., into a model for survey data. The characteristic of spatial regression is the spatially indexed relationship among the variables. The approach permits a flexible sampling scheme. Spatial regression is a new powerful method for coupling layers of information in a geographic information system (GIS) for shellfishery applications. The microcomputer-based Spline Survey Designer Software System (SSDSS) was developed to implement this approach in an aquatic GIS. Employing SSDSS, rapid data analysis and mapping in real-time aboard a research vessel allows adaptive sampling during a survey as a means of improving the sampling scheme using currently available information. Two examples of surveys are given to emphasize characteristics of the methodology.