For the love of BlackBeard

First off...make sure you have 10 Grubs

Next, your ship is expendable. Power crash it into the Skull Fort island on a side where there are rock/hills.

Finally, fish off the edge of the rocks connected to the skull fort island.

Enjoy success!

You don't need to sit at an active fort to catch them. Skeletons ship captains aren't the brightest and you usually see a skeleton ship stuck on an island when out sailing. Just park near it and start fishing. I've been lucky and had one near a sea post and one near an inactive fort the last few days, which ment I could just get more bait from the barrel's every time they replenished.

This was my view for over an hour and could fish as many battlegill's as I wanted.

You can always sail past the fort and put the line out as you are passing - if you catch one then it will stay on the line as you sail into safety to reel it in. Turn around and repeat. Throw down a voyage to so you can rack up the miles as you do this strategy.

You could always use a rowboat. Invisible to the auto aiming cannons.