The effects of water flow velocity and odor release frequency on the odor-tracking behavior of swimming crabs ( Portunus trituberculatus)

Chemical-guided tracking is vital for critical activities such as foraging and mating in swimming crabs (Portunus trituberculatus), as it facilitates the detection and localization of odor sources. While water flow and odor release patterns are known to influence odor-tracking behavior, the specific mechanisms of their impact remain poorly understood. This study quantified the tracking behaviors of juvenile swimming crabs in response to varying water flow velocities (0.7 cm/s, 1.6 cm/s, and 2.5 cm/s) and odor release frequencies (0.5 Hz, 1.0 Hz, and 1.5 Hz). Results indicate that (1) at a flow velocity of 1.6 cm/s, crabs exhibited a higher proportion of tracking and success. Successful trackers at this flow velocity demonstrated better tracking performance, including higher netto-gross displacement ratios (NGDR), reduced gross displacements, shorter exit and track durations, and simpler tracking trajectories. (2) While odor release frequency did not significantly affect the proportion of tracking or success, the successful trackers at a higher frequency (1.5 Hz) had lower NGDR and higher gross displacements compared to those exposed to a lower frequency (0.5 Hz). (3) The successful trackers were not stastistically affected by the interaction between flow velocities and release frequencies. (4) In contrast to successful trackers, unsuccessful ones showed highly variable responses to flow velocity and odor release frequency, with generally inferior tracking performance. These findings provide valuable insights into the chemosensory ecology of swimming crabs, with implications for optimizing aquaculture management and formulated feeds production.