Fig. 1. Experimental flume. (A) Top view diagram, to scale; with upstream targets (x denotes nozzle locations), downstream start box and dogfish swimming up one of the plumes (indicated by the dotted lines). (B) Photograph of upstream targets: two bricks and two nozzles dispensing odor or seawater. (C) Side view diagram of targets, to scale; arrows show relative flow velocity (flume center flow 3.5 cm s^–1); nozzle and weight hang down 15 cm upstream of brick (9x6 cm); turbulent odor dispersal sketched from dye trace.