It is a reason while I love Open Game Art more than itch when I need to find something under "free culture license" (mostly one of CC licenses)....
P.S Your sea creatures are very quality so I would recommend you to upload it on OGA too.... It is allowed there to write in the description links... Most of people who downloads it from OGA usually open itch page (that you can leave in the description on OGA). It can increase the count of views of your asset on itch