Hey Eddy,
A lot of folks are confusing
mooring anchor line scope (long-term/overnight) with
fishing scope which is short-term with someone always on watch.
I've anchored in the Straits of Juan de Fuca in 200 feet of water with only 230-240 feet of line and held just fine.
I use a Rocna Fisherman 6kg
http://www.rocna.com/ with a boat-length of 3/8" galvenized Proof Coil chain.
The more rope the better to a point: you'll hold better, but your swing radius and accuracy of your fishing suffers.
Good luck!