I always thought that getting on the water at first light was a head maneuver as much as anything else-- it gives you time to sort out your strategy and while you're busting that move, if you're going to make a mistake or have some issues come up with the boat or the gear, having that extra part of the day allows you to get the crap out of the way and be properly loaded for bear when the bite does come on.
I'm a high-slack, low-slack kind of guy, but early AM always seems to fit right in between those two grooves, especially if one of the slacks is in the first few hours of daylight.
I agree with Sculpin--think deep April through June, but early AM, sometimes that 50/60 foot part of the column can light up. Not sure about ECVI, but that has been a productive part of the column for me in Bamfield late May/early June, then down to 150 once the light gets on the water.
I also noticed that some of the bigger fish I saw caught or heard about were hooked at 150+. I remember a guide getting a 40 lb early June fish at 250 feet. That was an eye-opener for me