While some are bigger than others, those fish are all slammers. There is no slow-mo on youtube (that I know of, at least) but if you manually move the little tab that scrolls along as clip goes on, you can get some good still views of those fish. While that still does no justice to how big those fish are it allows you to see it a little better than normal.
A lot of times when the Canadian fleet is catching fish this is what they are seeing- not only in PEI but in places like the Hell Hole. While its not always this ridiculous, you hear a lot of stories of fish up in chum like this. You also hear a lot of stories of fish being up like this in cuttings from groundfish boats. While we dont usually see this behavior in the Gulf of Maine, stuff like this can happen off the Cape at certain times of year. Why this only happens in some areas and at certain times of year is obviously impossible to say, but it could be that the fish are ravenous getting ready to migrate or something like that because a lot of times this happens late in the season. Whatever the reason, makes you a bit jealous to see videos like this because the fish are NUMB! Still great to watch though!
Not to discount anything Chris has stated in his above reply but I've caught literally hundreds upon hundreds of juvenile bft using this same technique. This is exactly how they act and you can hold the entire school of fish under the boat until the very last one has been caught. I believe if more fisherman understood this technique you would be able to hand feed giants pretty much anywhere!