That mottled pattern is often seen on shore rocklings, sometimes it's a lot more vivid than that. It's not to do with being male or female just variations between individual fish. What is common throughout them all though is that when they have spots they are light coloured on a dark background whereas on a 3B they are always dark spots on a light background. Your fish is definately not a 3B so I would say it's either another shore rockling or it's a 5B if those lumps on the head are barbels rather than nostrils. As you are not sure about the barbels then I will go with shore rockling. Ok with you?