This article is about goldfish, not sharks, but it's the same urban legend:
Goldfish Only Grow to the Size of Their Enclosure
There is an element
of truth to this, but it is not as innocent as it sounds and is
related more to water quality than tank size. When properly cared for,
goldfish will not stop growing. Most fishes are in fact what are ...
I couldn't find any studies of aphrodisiac properties of the Geoduck clam.
Other clams have been investigated, for example, Aplysia dactylomela. In one experiment extract from clam is compared to negative control (vehicle) and positive control (Viagra). Authors showed that lipid extract from this clam does induce mounting behavior in mice above control. But ...