From Nookipedia, the Animal Crossing wiki
The Barred Knifejaw (イシダイ, Ishidai) is a rare fish found in the ocean. This fish can be sold for 5,000 Bells at Tom Nook's store. It appears all day from March to November. A barred knifejaw has black and white stripes and, while in the water, has a shadow within the range of small and medium; the shadow resembles the squid, octopus, and the dab.
The City Folk fish encyclopedia description says the fish has seven white stripes. The information given from the fish encyclopedia gives an official color to the fish: black with white stripes. Along with the other ocean fish, the Barred Knifejaw appears in the back tank when it is donated to the Museum.
Donation to the museum
In Animal Crossing
Blathers will give this speech upon donation:
"Hoo! Indeed, WOO hoo! A barred knifejaw, I believe. Hoo! Hoo, I say! Just look at this magnificent creature! Truly, a king among edible aquatic beasts of the world! Tuna, scallops, oysters, lobsters, salmon, halibut, crabs, barnacles... Well, maybe not barnacles... One would have to be in dire straits indeed to consume a few of those jagged beasties!
"Now then, what say we set this chap up in his new home, eh wot?"
In Wild World
When the player donates this fish, Blathers will say this:
"<Player>, the very fact that you caught this tells me that you are quite a fisher! Oh, a recipe for Barred Knifejaw? I'd recommend putting it in a broth. Grilling makes the flesh rather tough, eh wot?"
In City Folk
When the player donates the barred knifejaw, Blathers will say this:
"Hootie hoo, look at you! You've hauled in a star catch this time! Indeed, simply marvelous work! The Barred Knifejaw is a clever fish that, it's said, requires some rather fancy fishing to catch. Their monotone color scheme certainly paints them as smart, sensible fish in my eyes, eh wot?"
In New Leaf
An information board in the aquarium will display this description of the barred knifejaw after donation:
"Barred knifejaws stand out thanks to the seven stripes adorning their white bodies. Their natural curiosity and strong pull make them a popular target of anglers, but they're no easy catch. They have strong teeth that allow them to make short work of sea creatures with tough shells. This means that both urchins and mollusks need to be careful, lest they become meals for these fish."
The striped beakfish, also known as the barred knifejaw, is a tropical fish, generally found in coral reefs and around Japan. It has been seen in Hawaii, but only once. It normally eats invertebrates.
Names in other languages