Three comparable ecosystems
Three different ecosystems:
The Benguela Current   |  The Canaries Current  |  The Humboldt Current
Modelling, GIS, acoustic observation...

Modelling, GIS, acoustic observation... a panoply of tools and methods

Oceanographic research, especially in the realm of living marine resources, has long ignored or under-estimated the geographical or spatial component. And for several reasons: historically, the only possible observations of this vast study domain, largely hidden to the human eye, were made at a slow and costly rate using research vessels. In addition, representation and spatial analysis techniques were largely undeveloped. This situation has undergone spectacular changes over the last two decades with the following breakthroughs:
– Satellites now allow the quasi instantaneous observation of vast areas of the ocean surface. Resulting data includes surface temperature, indications of the richness in phytoplankton (through water colour), circulation (sea surface height through altimetry), and surface wind intensity (scatterometry).
– The contribution of commercial vessels through the taking of at-sea measurements (at the very least temperature and density profiles) has grown to the point that data bases encompass practically the entire planet, even if major navigation routes remain the most surveyed.
– Fixed anchors and drift gears (certain types ‘yo-yoing’ to sample the vertical plane) provide permanent data transmission to satellites, which transfer the data to research centres.
– Satellite technology has led commercial fishing vessels to be equipped with the Vessel Monitoring System (VMS). This enables the reconstitution of the vessel’s trajectory and hence its fishing zones.
– Certain animals also participate in this technique when they are tagged with telemetric satellite transmitters which provide data on their geographical position. Seabird data is transmitted at any time whereas data transmission on sea mammals is only possible when they come to the surface to breathe or when they are on shore in colonies (seals, otters). Using such data collected and retransmitted by satellite, scientists can follow animal displacements, discover their feeding areas, determine their diving depths, and quantify fisheries interactions. When boat position is also followed by satellite (VMS), fish and boat displacements can be observed in parallel.
– Modern research vessels are equipped with acoustic instruments which permit the sampling of large volumes of water, not only below the vessel (vertical beam) but around the vessel as well (lateral or omnidirectional sonar). Some of these instruments indicate seafloor topography, others fish distribution and recently that of zooplankton. Anchored and drifting buoys are now also similarly equipped.
– Progress in computer technology now permits three-dimensional modelling of the circulation and productivity of oceans. Some models are even capable of assimilating parts of the fore-mentioned data so as to improve their ability of quasi real-time prediction (operational oceanography). These models are tools for both simulation and experimentation in order to establish hydrodynamic equilibrium, explore possible fields and study climatic scenarios.
– Other types of models simulate passive and active displacements of organisms, sometimes coupling the physical models described above with biological models.
– Computer technology enables graphic and dynamic representations of data of diverse origins as well as their spatial analysis through the use of geographic information systems (GIS). In this way, it is possible to study the associations between different components of the ecosystem - physical factors, plankton, fish, birds, mammals and fishers - within a spatial context.