Kendall,
I suspect you refer to the miles long hooked lines set near the surface in deep sea to catch large pelagic fishes-tunas, swordfish and such. Longlines set in coastal waters are much shorter,fished regularily, are more selective and normally are weighted to fish near the bottom (groundfish). Once the bait is gone, I suspect the hooks have little of the original fishing power. GPS makes them easier to locate in today's fishery.

As to gillnets, it also depends on the species sought. To minimize longterm impact biodegradable sections are becoming the norm in regulations.

The tremendous fishing power and seafloor habiat impacts of mobile operated trawls are when they are in operation. While some trawl sections are likely are lost at sea, I suspect lost trawls (otter and other) at sea are few.