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Which parts of a fish are removed during butchering?

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fish on a conveyor belt — fish processing Fish on a conveyor belt entering a processing plant, Newfoundland, Canada.

During the butchering process in fish processing, several nonedible portions are removed to prepare the raw material for final preservation or sale. These parts typically include:

Viscera (internal organs)
Head
Tail
Fins1

Depending on the specific butchering method, between 30 and 70 percent of the fish may be discarded as waste or repurposed for animal feed. The lower end of this range applies when fish are sold whole or canned, while the higher end occurs during filleting, where the skeleton is often discarded along with significant amounts of edible flesh. While bones are generally removed from tuna to facilitate processing, other species are frequently canned with their bones intact, as the thermal processing softens them and increases the calcium content of the final food product.13