One would think that butchering fish would be similarly easy to butchering chicken. After all, it's easy to identify all of the parts. However, that is not true.
The list of difficulties is long, just like this salmon.
I think it has something to do with fish not being mammals, their structure is kind of alien. The scales, the slipperyness, the flaky flesh that tears easily.
The procedure is basically to cut into the head, take the two sides off the spine, then take the belly bones and fins and finally the skin off.
Then we had to pluck the pin bones out with pliers - they're small and embedded and remind me why I didn't like eating fish growing up - all the bones.
I've since grown into eating it - as least the boneless fileted versions of it, but the butchery's still hard.