Table 1.

Statistical results of Rayleigh’s test applied to northern anchovy double swimming angles.

Corresponding figure	% polarization	ā (°)	SD	a (°)	R	z	u
2a	0	178	101	none	11.384	1.296	N/A
2b	19	210	78	218	23.156	5.362	3.229
2c	67	193	95	190	28.765	8.274	4.052
2d	98	185	105	180	28.956	8.384	4.086

Symbols are as follows: ā, mean double angle; SD, standard deviation; a, theoretical double angle; R, Rayleigh’s statistic; z, statistic for circular uniformity; u, statistic for distribution along a mean direction. The data represented by the mean double angle are uniformly distributed around the trigonometric circle if z ≤ z_0.05,100 = 2.988. The data are distributed along a specific mean direction (the angle a, corresponding to E_min) if u ≥ u_0.05,100 = 1.645. The panels on Fig. 2 corresponding to each statistic are indicated on the Table.