Fig. 3. Relative attraction to experimental (pyrazine, black bars; herring, grey bars) and control slicks. Positive values (upward bars) indicate a positive attraction to pyrazine- or herring-scented slicks whereas negative values (downward bars) indicate a positive attraction to control (plain vegetable oil). So, for example, a value of +1 indicates that a species was only observed at an experimental slick and never at a control slick. An asterisk (*) indicates a significant attraction in the direction indicated (G-test for pooled data, P<0.05; Zar, 1996).