Why the Otranto Barrage remained porous

Why not rely on a mine barrage and sink any Austro-Hungarian minesweepers sent to clear it?

Minefields were already part of the barrage, but submarines could still slip through and most Austro-Hungarian convoys were not stopped.

The Otranto Barrage produced repeated convoy actions but did not reliably stop Austro-Hungarian traffic. Most of the convoys discussed still got through, exposing the difference between establishing a blockade line and making it impermeable. Some originated in Greece and other places outside the Adriatic, so each successful passage preserved an Austro-Hungarian supply route. Minefields formed part of the barrage, but submarines could still slip through the defensive line. The barrage remained a persistent patrol and interception problem rather than a sealed maritime wall.