No, they did not. And the fish industry points out that their study has too few samples to be conclusive. I agree with you that it takes a lot of reading to sort out the real threats from the false fears !
One point of the study was to show how the EU decided the safe amount of mercury in tuna was different (higher) from all other fishes, for no reason other than because tuna contains more mercury. To me, unless there was a specific reason for which mercury in tuna would be absorbed differently, it just doesn't make sense. The safety threshold should be the same for all fishes. Unfortunately while national safety agencies mostly do a serious job, final decisions in the EU are very influenced by lobbies. It's a vicious circle that goes both ways because NGOs counter commercial and industrial lobbies by getting into lobbying themselves.
So do mine. We use apple seeds here to make jam, for pectine. Don't people do that in the US ?
We grow alfafa. I've never seen the chickens touch it or try to eat the seeds. Indeed when we cut it it's for the neighbours rabbits. Shadrach said the chickens in Spain were happy to dig in the alfafa left overs but I'm not sure they actually ate them.
Why not germinate seeds, or lentils ?
My chickens leave the barley out of the mix I buy them. I accidentally discovered it was quick to germinate, and then they will forage it either when it is like grass, or if I let it grow they love the seed on the plant. So now I use their left over to seed small parts of their yard I cover for two weeks, and then they eat it all in two days

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I had the same experience with chia seeds. They love the plant's leaves (it's more like a shrub really).
If you want to buy something that is ready to give out I would go for alfafa sprouts meant for humans.