What the edges are. Cold edge: stated lower lethal (10 °C) — the source gives no method. Warm edge: upper lethal, laboratory, juveniles 72–130 mm (39.4 °C). These are not one consistent quantity across species. A measured avoidance temperature is where fish were seen leaving; a water-quality maximum is a regulatory ceiling written to prevent a kill, and it sits well above the point a day gets difficult.
Source. Zale, A.V. & S.G. Merrifield 1989, Species profiles (South Florida) — ladyfish and tarpon, U.S. Fish and Wildlife Service Biological Report 82(11.104). Read it.
Warmwater species swing their preference ten degrees or more between winter and summer in the same laboratory. One band per species is a summer simplification, and it is why the drawing shows a band rather than a line.