I just read Redmond O'Hanlon's book "Trawler". A good read and, yes, it is far from an in depth look at deep sea fishes but one point of emphasis that seems hard to dispute is that we still know very little about this environment and what lives in it. This paper only reinforces that.

While you're right about DC and EMF, there have been no actual site studies that I know that look at impacts of electrical fields on these environments.