This is honestly one of the first times I've been unable to distinguish a del from a sen, I feel kind of ashamed, lol. This fish has some mottling present on the pectoral fin, the finlets, and the gill plate, and I haven't ever seen quite that much on a sen. On the other hand, it's only got 9 finlets, which usually fits more into the sen range than that of dels. It also has a really strong contrast between the stomach and dorsal regions, which is something that seems to me to be more evident in dels than in sens. Based on everything I saw in both pictures, I'm leaning more towards del, but at this point anyone's guess is as good as mine. Could it be a possible hybrid? Anyone else have thoughts on a possible hybrid?
EDIT: Ah, Hao posted while I was posting mine. I post way too slowly, lol. Good to see someone else agrees.