Integrating Sea Lion Tracking Data with Winter Prey Data Generated in Echoview
In 2003-2004, Dr. Mary-Anne Lea and Dr. Ben Wilson of the Behaviour@Sea team at the University of British Columbia in Vancouver collaborated with scientists at the Alaska Department of Fish and Game and NOAA's Auke Bay Laboratory to tag and track threatened juvenile Steller sea lions (Eumetopias jubatus). By documenting the near real time winter interactions between juvenile sea lions and fish in the Lynn Canal region of south east Alaska, their study aimed to determine which components of fish stocks were successfully and unsuccessfully caught by the young sea lions.
Figure 1: A group of Steller sea lions in Berner's Bay, Alaska (image courtesy of Mary-Anne Lea)
Individual juvenile sea lions were fitted with VHF transmitters and tracked from a research vessel during the winter of 2003. Concurrent vessel-based hydro-acoustic surveys of fish stocks provided data on general prey distribution and abundance in the areas used by the sea lions. Diving behavior was examined using time depth recorders. This multi-survey approach is rare in pinniped ecological research because it is expensive and labor intensive; however, it is one of the few ways to understand the fine-scale interactions between marine predators and their prey without the use of animal-borne cameras.
Figure 2: Using Eonfusion, sea lion tracking data seen as a yellow line is integrated with prey abundance data for various fish species generated using Echoview. Prey biomass variations and concentrations are indicated by color and halo size respectively. The predator and prey data are coincidently visualized with bathymetry and satellite imagery to create a unique multidimensional image of sea lion foraging behavior.
The Challenge
With such a unique field data set, the investigators require a software application which provides the ability to move through a multi-dimensional environment and visualize sea lion foraging behavior to infer how these predators are accessing their prey. The biggest challenge is the ability to quickly integrate and simultaneously visualize multiple diverse data sources.
"As we are working in a highly dynamic system consisting of large aggregations of schooling prey, strong weather systems and fjordic bathymetry, we need an approach and tools which enable us to visualize complex behavioral and environmental relationships in a single graphics environment. Eonfusion provides these capabilities." says Dr. Lea.
The Result
Using Eonfusion, a simple data flow was created which fused individual sea lion tracking data to the depth information from the time-depth recorders. Hydroacoustic prey data was processed using Echoview to classify fish stocks, and the output was incorporated into the data flow. Bathymetry and satellite imagery were then incorporated to create a multi-dimensional image of predator and prey habitat.
Figure 3: Hydroacoustic data was processed into curtains by Echoview and integrated with bathymetry and tracking data in Eonfusion.
"By using Eonfusion in conjunction with Echoview, we were able to observe the interplay between sea lions and fish schools more effectively. This was something that we could never do before." says Dr Lea.
One of the advantages of visualizing fish stocks simultaneously with sea lion movement was the ability to generate hypotheses about how sea lions were physically accessing their prey. By synchronizing fish stock depth data and seal dive data, Eonfusion cast new light on sea lion foraging behavior and how it related to the availability of fish stocks. The Eonfusion user interface enabled investigators to quickly zoom between a large and fine scale images and long and short time spans, without compromising image quality. The results were new insights and the extraction of maximum value from this unique field data set.
Acknowledgement
Myriax thanks Drs Mary-Anne Lea and Ben Wilson for their cooperation in the development of this case study. The juvenile Steller sea lion research was conducted under NOAA Permit No. 358-1564-06 (ADF&G) and was funded by NOAA and the Alaskan Fisheries Development Foundation through the North Pacific Marine Science Foundation to the North Pacific Universities Marine Mammal Research Consortium.
