He butchered the fish so quickly the he didn't have it properly weighed. I guarantee someone who is into fishing for the "sport" of it would have weighed that fish. It could have been a record catch.
Fish is best when butchered soon after death, it can decompose quickly, so I conclude he was planning to eat it. It's no different IMO then butchering a cow, Tuna, Goat, etc. My father-in-law hunts deer every winter and sends us venison steaks. Deer are beautiful creatures, but they sure make a lovely steak.
My point was really, theres no high ground to judge on unless you are a vegan and refuse animal protein.