I am pretty sure the iLvL cap on fished items is 10. However not everything below rank 10 can be fished. EX: Oil, Org. Rubber, Syrups, Juice, ect.
Most Liquids can not be fished.
However of the ones I have tested and the one most people will enjoy is that Dye can be fished with a Lux rod.
Scorpio 2
Felixoo7
http://wlodb.com/topics/2116 <-- Fishing!!!
http://wlodb.com/topics/2325 <-- Monsters!!
http://wlodb.com/topics/3690 <-- Economy!!!