Olfactory search tracks in the Antarctic fish Trematomus bernacchii

Video observations were made of benthic fish approaching the source of an olfactory plume. Fish (identified as Trematomus bernacchii from their "saddleback" markings) all approached the source from downstream, with relatively straight approach tracks. When the plume was made visible it showed a distinct concentration of the stimulus at the point of release, and a plume which extended down-stream with a rapidly decreasing stimulus gradient. Computer simulations were made that could generate search strategies based on chemical gradient information, and current (rheosensory) information alone or in combination. Only the combination of chemosensory and rheosensory information provided an adequate match to the observed approach tracks.