Now that you mentioned there are 3 types of muskie, its got to be a muskie. I do remember looking at a chart on that muskie charter i was on and its the only place i think i would of seen the different muskies. I don't know why i could not find them online though, i even typed in "spotted muskie"
Yes you are correct about the keeping size, it was even to small if it was a northern. Northerns have to be 24" and the muskies have to be 42" (
) and this was only 21". Even if it was keeping size, i usually throw pike back because i don't know how to get that 'Y' bone out of them...
I always remember the sizes of the fish we catch because we always throw a bet out for the biggest fish caught over 10". It makes for a real neat day on the water if you have a few friends all throwing in $5 or $10 bucks each!