From another article linked in the comments: > Compared to red meat and poultry, fish muscle is delicate. It needs all the structure it can get. So unlike red

From another article linked in the comments: > Compared to red meat and poultry, fish muscle is delicate. It needs all the structure it can get. So unlike red meat, where we like a little protein breakdown to enhance tenderness, anything that breaks down the structure of fish muscle is bad. Stress causes fish muscle tissue to break down.