That's why all fishing lures have an effective speed range of operation. Many of us find a lure that will run hot in one direction, and then it runs cold, no new hits. The lure is no longer operating within its effective speed range. If just one lure is not operating at the proper speed, it can effect ones that are operating at their effective speed. Trollers should be aware, that not all water currents are over a large area and just on the surface.
Some water currents are small and narrow far below the boat.
For instance if your surface speed reads 2 mph and your lures are in a facing current of 1.5 mph. Your lure speed is only .5 mph. This wouldn't be an acceptable speed if you were running a lure that was designed to work in the 2-mph range. Different species of game fish prefer different temperature ranges. Your ability to find and monitor these zones is the key to consistent fishing success.