Fig. 8. Vortex filament model showing vortices near steadily swimming bluegill sunfish and brook trout. Numbers indicate vortex circulation (in mm² s^–1), to evaluate the relative vortex strengths, and the superscript letter identifies the source (see below). (A) 3D vortex structure for bluegill sunfish swimming at about 1.2 L s^–1. Gaps in the dorsal and anal fin vortices in the wake indicate regions where the vortices should link up to the caudal fin vortices, but for which there are too few data to identify the topology of the filament. (B) Experimentally observed vortices for the dorsal, anal and caudal fins of trout swimming at 0.5 L s^–1. Dotted lines in the caudal fin vortices indicate a region that might have a deformation, like in bluegill sunfish, but for which there are not appropriate data for any definitive conclusions. Sources of circulation data: ^a(Tytell, 2006); ^b(Drucker and Lauder, 2001) (estimated from published figures); ^c(Standen and Lauder, 2007); ^d(E.M.S. and G.V.L., unpublished data).