This week, McDonald’s announced that it will start serving a lot more fast-food fish starting next month, in the form of “Fish McBites” that it hopes will boost sales.

The company also announced that all those bites, plus its Filet-O-Fish sandwiches, will be made from sustainable, wild-caught Alaska pollock, with the Marine Stewardship Council’s stamp of approval right there on the box.

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Marine Stewardship Council

The MSC “is proud to support McDonald’s and its commitment to sustainability.” The fast-food giant has been serving four kinds of MSC-labeled sustainable fish in European locations since October 2011.

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Is this the part where I’m supposed to say, “Yay McDonald’s”? Because yeah, that’s not happening.

Not all conservation groups can agree on what’s a sustainable fish and what’s not, and often what’s sustainable today is overfished tomorrow, especially when a company with an appetite as big as McDonald’s is involved.

Alaska pollock is not considered a “best choice” on the respected Seafood Watch list put out by the Monterey Bay Aquarium; rather, it’s lumped into the middle “good alternative” category. From Seafood Watch:

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Alaska Pollock populations are moderately healthy, but their numbers have been declining. Alaska Pollock are now at their lowest levels in over 20 years.

The fishery uses midwater trawling gear that’s designed to not impact the seafloor. However, these midwater nets contact the seafloor an estimated 44% of the time—resulting in severe damage to seafloor habitats of the Bering Sea.

Alaska pollock fishing operations also catch up large numbers of declining Chinook salmon, and might be hurting the endangered Steller sea lions and Northern fur seals that rely on the pollock for food.

Even presuming Alaska pollock is a “good alternative,” there’s still the matter of, you know, everything else McDonald’s does, from serving antibiotic-laden meats to leading the fast-food industrial complex. McDonald’s may be improving its treatment of fish, but it’s not improving its treatment of workers.