Visual Detection and Tracking Methods for E. superba (Antarctic Krill)

• Main Author: Yopak, Regina R.
• Format: Text
• Language: unknown
• Published: DigitalCommons@URI 2017
• Subjects: Antarctic; Antarctic Peninsula; Austral; Southern Ocean; Antarc*; Antarctic Krill
• Online Access: https://digitalcommons.uri.edu/theses/1045; https://doi.org/10.23860/thesis-yopak-regina-2017; https://digitalcommons.uri.edu/context/theses/article/2052/viewcontent/Yopak_uri_0186M_11694.pdf

Antarctic krill are a keystone species of the Southern Ocean. They have been well documented over large spatial scales but generally not quantfiably at the scale of single individuals in the open water column. It is important to study how individuals behave in their natural environment in order to further understand how they interact within dense krill aggregations. Using a pair of calibrated grayscale stereo cameras mounted on a towed instrument sled, krill were imaged in situ at 10Hz in the bays along the western Antarctic Peninsula during austral winter 2013. Krill were identified and tracked through the images using a newly developed identification and tracking method that collates krill motion properties such as distance traveled, velocity and track duration using image processing techniques. Stereo geometry was used to define the krill motion data in the camera coordinate system and define the overall imaging volume to be approximately 2:0m3. The tracking method performed successfully for 60 - 80% of tracks in a sample set of images. Difficulties in tracking krill successfully included excessive sled motion (heave), krill swarming (or schooling) behaviors and rapid changes in krill motion not accounted for by the tracking algorithm. An analysis of the krill velocities found that krill generally swam at less than 1m/s and increased to 2m/s while aggregating. This new imaging system successfully tracked and identified krill in the midwater column and can be used to generate large motion data sets to better inform Antarctic krill behavioral and circulation studies.