Sorry for questioning your handling of this beautiful pike. Once out of water fish are rather fragile ( they do not have the support of surrounding water) . They should be fully supported with both hands one under belly the other holding the tail....never place your hand in the gill area.
Hanging a fish (especially a large one) vertically ( even for a short time) will stretch back muscles and even separate vertebrae in the back bone plus damage gill arches and the connective tissue. The other mistake many anglers make is keeping fish out of water to long......a good idea is keeping the fish in the water while removing the hooks .....If a picture is taken a quick lift while supporting the fish fully....then back in the water.