Looked like the common carp we get in the uk. I saw a local somehow catching big ones with some strange bamboo hoop thing.
Maybe only traditional fishers who live around the lake are welcome to fish. That's the way at Lake Balanan.
I never did fish in Twin Lakes nor Balanan. Though Twin lakes is much closer to Dumaguete and thus to reach, the road conditions to get to Balanan is opposite. What I still do dislike is that entrance fee to Twin lakes is 2-system, a fee for pinoys and a different much higher fee for foreigners while more acceptable Balanan lake just charge a little entrance fee for their own surrounding population but the rest so pinoys and foreigners do pay the same. @least this was the situation the last time I go 2 Balanan lake somewhere middle of 2019. Don't know what's now.
please see andiflip response, much more colorful if a bit off putting. i read that carp is also called okoboji salmon, and talapia as st peters fish. should bring a lot more from the tourists.