A fishing question. What does this mean/?

check with your wildlife office. But that said, to me it sounds like they are talking about when the fish takes the bait and comes towards you. it is common to use a system which detects a bite when the fish takes the bait and heads away from the fisherman taking line. It is far less common to have a system that will detect a bite when the fish takes the bait and swims towards the fisherman resulting in slack line. This is more for fishing a bait on the bottom than anything else.