AkvaVis is a dynamic GIS tool for siting fish farms, and this report describes a prototype version for mussel farms. AkvaVis combines mappable characteristics such as depth, currents and distance from other objects, and it enables objects to communicate their properties to one another in order to determine the best locations for farms. AkvaVis also calculates the carrying capacity of individual sites by means of mathematical simulation models. The prototype has been developed for the Hardangerfjord, and the report provides a survey of the topography, hydrography and currents of this fjord. With the further development of the system in mind, it also provides an overview of the environmental requirements for new farmed species, as well as for salmon