Great question — answering as the UphillTech team:
Is this House (1985)...? The film centers on Roger Cobb, a troubled author who moves into his late aunt Elizabeth Hooper's seemingly haunted house, and is forced to deal with supernatural phenomenon. All the while, he tries to solve the mystery of his son Jimmy's disappearance. It's a colour movie and more recent than you recall, but there's a scene about 42 minutes in where a swordfish on the wall of the titular house comes to life, and the protagonist decides to shoot it to kill it again. I could only find a very brief clip on YouTube, but the full scene is significantly longer than this.
Full answer by LogicDictates: https://movies.stackexchange.com/a/129797 (CC BY-SA 4.0).
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