Water temp. question?

[Hilltop123]

I'm reading a book on walleye, and the book states that spawing takes place when the water temp. is 40-52 degrees F..
Now is that surface temp?? If not what are they refering to?

[TheHunt]

I typically measure surface temperature for salmon and steelhead.

[Ripper]

Walleye usually spawn in shallow water so the temp would be surface to bottom I'd think. 1 to 5 feet or so.

[BLUEBULLS]

Walleye usually spawn in shallow water so the temp would be surface to bottom I'd think. 1 to 5 feet or so.

 

on the columbia between preist rapids and John day, 42-43 seems to be the magic numbers... surface temp.