Silhouette video-based (SVP) three dimensional motion tracking and move path analysis allows detailed observations of the reactions of aquatic organisms to different environmental conditions. SVP is superior to standard cinematographic or video imaging techniques in various ways. First, it allows filming of events in a large depth of field (approximately 20 cm) with a relatively large field of view (15 cm). Second, magnification is independent of distance from the cameras and the resolution is very good; objects as small as 0.2 mm can be resolved. Third, image quality is unaffected by ambient light levels and the silhouette effect is attained without the use of intense light sources. As such, the behaviour of fish larvae and zooplankton can be observed under relatively natural conditions.
Schlieren video-based three dimensional analysis allows for more detailed/finer spatial scale observations than does SVP. Using 3 expanded and collimated HeNe lasers, we can observe the 3 dimensional coordinates of all particles larger than 3 um within a volume of 45 ml. Magnification is easily adjusted to provide a pixel resolution ranging from 1.5 um/pixel to 55 um/pixel. The light source and cameras are aligned to record from 3 perpendicular angles simultaneously. This redundancy ensures that the 3 dimensional location of any object ca not be shadowed by another object.
Analysis of the images obtained from these optical systems allows for detailed characterization of the reactions of aquatic organisms to different environmental conditions. These data provide information on the overall activity, swimming patterns, prey search behaviour, foraging and feeding rate, prey selectivity, attack success, etc. All of these variables are directly relevant, and of great importance, in developing appropriate rearing environments for intensive aquaculture and for parameterizing the predator-prey components of ecosystem models. Such observations can also be used to evaluate different combinations of rearing conditions and/or environmental conditions (e.g. in the context of global climate change).
For more information, see Browman, H.I., J.-F. St-Pierre, A.B. Skiftesvik & R.G. Racca. 2003. Behaviour of Atlantic cod (Gadus morhua) larvae: an attempt to link maternal condition with larval quality. pp: 71-95, In: H.I. Browman and A.B. Skiftesvik (Editors). The Big Fish Bang. Proceedings of the 26th Annual Larval Fish Conference.