I found a paper from Nautilus (Apr. 1963, 76, 4) written by a friend of my
family, Don Erdman, "Records of Marine Mollusks Eaten By Bonefish in Puerto
Rican Waters."

Of course, bonefish is shallow water, and so is not germane to the original
question. But Erdman cites Clapp, W. F. (1912, Nautilus, 25: 104-106)
listing 68 species of mollusks from haddock.

And Clarke, A. H. (1955, Collecting Mollusks from Fish. "How to Collect
Shells" Publication of the American Malacological Union), is cited for his
recommendation of catching deep-water fish for the "interesting and rare
mollusk species" they might have in them.

Erdman, by the way, recorded 37 species of mollusks in the 56 bonefish taken
in the waters near La Parguera, Puerto Rico. The mollusks made up 56% of the
bonefish diet by volume (51% clams, 5% snails). He believed that many of the
micro gastropod species were not eaten live but ingested from sand inside
the sipunculid worms.

David Kirsh
Durham, NC