It's a good question tomomothy. My understanding is that any manufacturer who is not in compliance with AAFCO standards is subject to stop sale actions. The question would be enforcement. As RD will tell you (and has in this thread), the "rules" are rather complicated. Not only do you have federal rules but individual states have their own.
But from the communications I've had with various domestic companies, their foods may contain whole fish (as an example, "Whole Salmon") but it's not listed on the ingredient label that way because it would "technically be out of compliance with AAFCO standards." Although some companies have held up the AAFCO regulation as a distraction. In other words, they reference the AAFCO regulation claiming they cannot label the product as "whole fish" without clarifying that they do in fact use whole fish. And then again, obviously, some companies are "technically out of compliance" by including an ingredient such as "Whole Salmon Meal" in their ingredient list. It's all very confusing but the AAFCO rules are clearly defined. For some reason, some companies must follow them, some companies don't, and some hide behind them.
I think the issue is even more pronounced for any foods imported from overseas as they are apparently held to a higher level of enforcement.
The "I read too much Tom Clancy" side of me suspects the rules are the way they are is because that's the way the big dogs in the industry want it. What prevents a company from utilizing a name such as "Grade A Fish Meal" (made up name) in their ingredient list is that the big dogs in the industry, who really do not want these types of labeling definition extensions because they use the worst quality ingredients, could call them out on it and be legally correct, potentially resulting in stop sale actions.
Keep in mind, these definitions are unique to the ingredient label and are not unique to fish foods. The same ingredient labeling rules apply to all animal feeds. And these rules are independent of marketing, product naming, and other descriptions that can be used on the product labels.
While this link does not deal specifically with fish food or ingredient labels, it gives you an idea of how detailed aspects of pet food labels are regulated (also provides some very good information when selecting dog or cat foods).
http://www.fda.gov/animalveterinary/resourcesforyou/ucm047113.htm
All of the ingredient definitions are in AAFCO Manual 51.14, which is only available to you if you pay $129 for it. So to directly answer your question about Krill and Algae, I don't know as I have not yet obtained a copy of the manual. I was able to get a scanned copy of the section that deals with fish meal.