Experiments recently made at Tortugas show that fishes have the
faculty of remembering for at least twenty-four hours.
The fish studied at Tortugas are gray perch, whose favorite food
is the little silver sardine. The experimenters painted some of
the silver sardines light red; then they offered them to the
gray perch mixed with the unpainted sardines. The perch snatched
the silver sardines and ate them, then very deliberately and
cautiously they nibbled at the painted sardines. Finding that
the fish were the same whether red or silver, they devoured the
red fish.
Having given proof of their intelligence, they were permitted
to rest twenty-four hours. The experimenters offered them
silver sardines, sardines painted red, and sardines painted
blue. The perch quickly devoured the silver fish, then, without
an instant’s hesitation, they devoured the red fish. Finally,
gliding cautiously up to the blue fish, they took a bite and
darted away. As the taste was favorable they returned to the
blue fish, nibbled again, and devoured them.
The experimenters then tied sea-thistles to the blue sardines.
The perch nibbled, then, disagreeably surprized, darted away.
For twenty-four hours not a fish approached the painted blue
fishes. They remembered the sea-thistles. But their memory
is short; the day following again they snatched the blue
fish.--_Harper’s Weekly._
(2008)