Eonfusion: Providing insight into the behaviour and social life of Antarctic Krill
Antarctic krill are the keystone species in the Southern ocean ecosystem and the subject of the largest Southern Ocean fishery, taking some 125,000 tonnes annually. Management of this fishery relies on a thorough understanding of the biology and ecology of the species.
This includes information on distribution and abundance, recruitment, growth, and an understanding of their behaviour. Antarctic krill are obligate schoolers that exhibit complex social behaviour and are known to undertake vertical and horizontal migrations in the wild. Social behaviour within schools has important implications for all aspects of the biology of krill, and therefore behavioral studies are the key to a realistic understanding of krill biology. It is widely believed that schooling confers energetic as well as predator avoidance and other benefits to marine species, and as such, developing a quantitative understanding of schooling behaviour is key to calculating the contribution conferred by this behaviour.
Video imagery of moving krill was acquired using two digital video cameras located above the tank (Figure 1), providing stereo-coverage. The video streams were synchronised, so that locations of individual krill could be tracked from frame to frame and in space using standard stereo-photogrammetric techniques. This generates a large amount of data which is most easily interpreted with a visual representation through time.
Figure 1: Using Eonfusion, the raw position data (X, Y, Z) were used to derive metrics such as swimming speed, swimming direction, acceleration and nearest neighbour data. Visualized in 4D these were used to explore the behaviour of individuals over time, with respect to their location in the aggregation or school, and with respect to neighbouring individuals. CAD objects show the tank and video system configuration in context. The time window controls visibility of a sub-set of the time series-data within the scene. A second 'time line' was created within the scene with an attached probe, so that the video data could be explored frame by frame and linked to analyse the data. Exploration of combined track and video data provided the relative geometry and a visual assessment of the orientation of the krill. The 'waterfall' style plot in the foreground enabled exploration of swim speed correlation.
Eonfusion provides the capability to track, visualise and compare these complex and changing three-dimensional patterns, and to simultaneously view original video imagery, location, velocity and acceleration data. It also provides a capability to visualise the measurement errors associated with each of these derived metrics. From scrutinizing and integrating the raw data through to exploration and analysis, Eonfusion provides a unique set of capabilities for data exploration, tracking analysis, and the communication of methods and
results.
Figure 2: Krill connected to nearest neighbour (for distances <50mm), potentially complex relationships can be determined by tracking krill in three spatial dimensions through time.
Acknowledgements: For the provision of data and background Rob King1 So Kawaguchi1, Jon Osborn2, David Murphy3
1) Australian Antarctic Division;
2) University of Tasmania
3) Georgia Tech
