AkvaVis - dynamic GIS-tool for siting of fish farms for new aquaculture species : environmental quality requirements for new aquaculture species and Atlantic salmon

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

BAKTRAK: Backtracking drifting objects using an iterative algorithm with a forward trajectory model

The task of determining the origin of a drifting object after it has been located is highly complex due to the uncertainties in drift properties and environmental forcing (wind, waves and surface currents). Usually the origin is inferred by running a trajectory model (stochastic or deterministic) in reverse. However, this approach has some severe drawbacks, most notably the fact that many drifting objects go through nonlinear state changes underway (e.g., evaporating oil or a capsizing lifeboat). This makes it difficult to naively construct a reverse-time trajectory model which realistically predicts the earliest possible time the object may have started drifting. We propose instead a different approach where the original (forward) trajectory model is kept unaltered while an iterative seeding and selection process allows us to retain only those particles that end up within a certain time-space radius of the observation. An iterative refinement process named BAKTRAK is employed where those trajectories that do not make it to the goal are rejected and new trajectories are spawned from successful trajectories. This allows the model to be run in the forward direction to determine the point of origin of a drifting object. The method is demonstrated using the Leeway stochastic trajectory model for drifting objects due to its relative simplicity and the practical importance of being able to identify the origin of drifting objects. However, the methodology is general and even more applicable to oil drift trajectories, drifting ships and hazardous material that exhibit non-linear state changes such as evaporation, chemical weathering, capsizing or swamping. The backtracking method is tested against the drift trajectory of a life raft and is shown to predict closely the initial release position of the raft and its subsequent trajectory.Comment: 28 pages, 8 figures, 2 table

AkvaVis - dynamisk GIS-verktøy for lokalisering av oppdrettsanlegg for nye oppdrettsarter : miljøkrav for nye oppdrettsarter og laks

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