Fig. 1

Overhead diagram of the experimental behavioural flume showing the five orientation parameters that were measured in this study over three successive positions in video recordings (t = −1, 0, and +1). The short dashed line represents the scampi’s projected path (if it had continued in a straight line), from which a turn angle value (TA) at point t = 0 is calculated. Heading angle (HA) is calculated from the difference of the bearing the scampi is travelling on and the bearing directly to the bait (short/long alternating dashed line). The long-dashed line represents a path that is straight upstream, from which a heading angle relative to upstream (HUp) is calculated