Freshwater mussels are among the world's most endangered invertebrates. Their conservation involves welfare considerations for both the mussels themselves and the fish hosts they require.
Freshwater pearl mussel conservation welfare primarily involves the fish hosts rather than the mussels themselves. The mussel larvae (glochidia) that attach to salmon or trout gills to develop are not typically welfare-harmful to host fish at natural infestation levels. Captive breeding programs that handle host fish to expose them to glochidia require careful welfare management of the fish. The mussels themselves have such simple nervous systems that welfare considerations for them individually are minimal, but their conservation value is immense - as ecosystem engineers that filter river water, their recovery benefits entire river communities.