I ripped this from thott but I can confirm his numbers from my own data tracked by fishing buddy ... Oh, all times are in server time.
"A little tip for all you aspiring anglers out there looking to hit it rich with Stonescales, their drop rate GREATLY varies depending on when you fish.
Rate greatly increases from 12AM to 12PM (approximately 15%-20% rate increase)
Rate greatly decreases from 12PM on, until midnight. (depending on the zone, it will be no more than a 1% to 2% drop rate)
In order, the best places to obtain Stonescales are:
1. Bay of Storms, Azshara
2. Steamwheedle Port, Tanaris
3. Revantusk Village, Hinterlands (Horde)
4. Feathermoon Outpost, Feralas (Alliance)
(This data is backed by 1000's of fish catches recorded by the Fishing Buddy addon, and is more or less correct.) "
"A little tip for all you aspiring anglers out there looking to hit it rich with Stonescales, their drop rate GREATLY varies depending on when you fish.
Rate greatly increases from 12AM to 12PM (approximately 15%-20% rate increase)
Rate greatly decreases from 12PM on, until midnight. (depending on the zone, it will be no more than a 1% to 2% drop rate)
In order, the best places to obtain Stonescales are:
1. Bay of Storms, Azshara
2. Steamwheedle Port, Tanaris
3. Revantusk Village, Hinterlands (Horde)
4. Feathermoon Outpost, Feralas (Alliance)
(This data is backed by 1000's of fish catches recorded by the Fishing Buddy addon, and is more or less correct.) "