And the list goes on and on. Before you throw this idea in the garbage or wonder whether the author has more than one head, bare with it for a moment.
Fish also have a preferred temperature.
A salmon prefers 53 degrees Fahrenheit. You go south to warm up. Water on the bottom of the lake is the heaviest at 39.2 degrees Fahrenheit. When your faced with a choice between 34 and 39 degrees the 39 IS Florida to a salmon. As river waters are much more shallow than their neighbouring lakes they warm up much faster in the spring.