Naming. This record documents Landlocked salmon; the reviewed band was published under Atlantic salmon. Worth knowing before you lean on the numbers — the closer a name is to a regional one or a subspecies, the more the band is a reasonable neighbour rather than the same fish.
The record files this fish as “Landlocked salmon (wild)”. That condition is the agency’s and it outranks anything on this drawing.
What the middle band is. growth optimum on maximum rations, not a behavioural preferendum — and it falls as ration falls. A growth optimum is measured on juveniles fed all they can eat and a survey mode is where a net found the most of them; neither is the fish choosing, and both are worth less weight than a preferendum for deciding where to stand today.
What the edges are. Cold edge: lower incipient lethal, parr and smolts (0–2 °C). Warm edge: upper incipient lethal, parr and smolts (22–28 °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. Elliott, J.M. & J.A. Elliott 2010, Temperature requirements of Atlantic salmon, brown trout and Arctic charr, Journal of Fish Biology 77:1793–1817. 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.