@Hollow7F i think they aren´t made from waste, but can include parts of the fish normally not used for dishes where you use big parts of the meat. If its like Surimi as she states, its made from the whole fish without the head/fins and entrails. Though that might be different depending on the used fish, i.e. if its small enough, it can be completely minced and ground without having unpleasant bits left in the end product.