Like I said, it's a grass pickerel, not a chain pickerel. The chain pickerel has a light body with thin markings that look like interlocked links of a chain. The grass pickerel has thick dark markings like the fish in the photo.
Northern pike have a dark background with light spots in a more consistent pattern than pickerel have. Plus, there just aren't many northern pike in Tennessee. It's my understanding there are some in South Holston lake, but I think that's about it.