Im a fly fisherman and tie my own flies,I havn't used live bait in over 40 years.the other side of the story are careless beer drinking fisherman who after the day is finished,just toss their leftover leeches,minnows and salamanders right in the lake without any thought at all,I've witnessed this before.this is a big problem getting invasive species,and this type of behavior is very hard to monitor and correct.if you want to catch more fish,,learn to use artificial lures.