You are correct, young fisher.  You will need a base skill of around 350 to cast with the items you have, and base skill of 375 to get a high success rate.  Get a +5 fishing skill enchant on your gloves, and invest some time flying from city to city in search of Fish Attractors.  Having a skill of 500-505 will give nearly 100% success rate in fishing in Skettis, as well as greatly increasing the odds that you will fish up Mr. Pinchy.

Happy fishing!