I don't think it's puffer fish. First of all, is this fish a fine-scaled fish or a scaleless fish (I really can't tell). Generally, this fish will not be in the river, nor will it be in the river. It is certain that this fish is a marine fish. Yes, although it may not be a flat fish, it can be confirmed that it should be related to the flat fish. They may be two different species in the same strain, or they may be subspecies. You can look at the anatomical map and see if there are any weird body organs. If not, it should be no problem.