Sturgeon general is an epic myth level 2 fish. It can be found in Krokotopia entrance hall in the sphinx in the right pond. It is also at a private fishing retreat which is currently on sale if you don't have it. In Krokotopia it will be the only myth fish if you use reveal. It will take several summon/refilling the pond unless you are very lucky.
Yes one of my wizards got it first time going for the Halloween fish then got the halloween fish next other wizards took very long time to get the myth one.