Supplemental Experimental Procedures

Supplemental Experimental Procedures

The experiment was conducted in a large experimental tank (depth: 6 m; length: 10 m; width: 5 m; volume: 300 m3) located in the Hakodate Research Centre for Fisheries and Oceans (HRCFO), Japan. For the design of the experimental tank, see Puneeta et al. (2015). Maximum water turnover in the tank was kept at 15 m3 per hour in order to avoid the accumulation of debris on the floor of the tank. The photoperiod was kept constant at 11 h light from 07:00 h to 18:00 h. A small 80 W red light (Toshiba BRF) was used to prevent skin damage resulting from contact with the tank wall during the dark period.

Squids (n = 400), mantle length ranging from 9.5 – 16.6 cm and anchovy (n = 250), body length ranging from 7.5 to 13.6 cm, were collected from the coastal waters of southern Hokkaido, Japan, by set trap nets during July 2014. After collection squids were immediatley transported to HRFCO and healthy individuals were introduced to the large experimental tank. Anchovies were then released with an one day interval, and were fed with dried fish pellet feed twice a day.

The feeding and schooling behavior of squid were video-recorded by using fixed and handheld Sony HDR-CX590V handycam (Sony, Minato, Tokyo, Japan). All video footage was annotated, reviewed, and analyzed. Selected sequences from the 30 frames s-1 videos were captured with Adobe Premiere and exported as frames into ImageJ (http://imagej.nih.gov/ij/) to observe details of the behavior. All experiments were conducted according to the animal welfare guidelines of Hokkaido University, Japan.

References

Puneeta, P., Vijai, D., Yoo, H.-K., Matsui, H., and Sakurai, Y.(2015). Observations on the spawning behavior, egg masses and paralarval development of the ommastrephid squid Todarodes pacificus in a laboratory mesocosm. J. Exp. Biol. 218, 3825–3835.

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