Don Ira Feinberg is the secondary antagonist of Shark Tale.
In Shark Tale
Don Feinberg first appeared as a singer at the restaurant inside Don Lino and his gang's Headquarters, while singing a song about Lino's deceased son Frankie. As he finished the song, Lino thanks him for his composition until another member, the hammerhead shark Giuseppe, comes and tells Lino that Lenny was missing.
Lino: I have to thank you for the song you sang for Frankie.
Don Ira: We all loved Frankie, of course; and now we have to be extra careful while traveling in the reefs, with a sharkslayer about.
Giuseppe: Signore, we're all very upset about what happened, but…Lenny's also missing.
Don Ira seemed to be another alpha of another gang of sharks that shared Lino's worries about Len's safety next to Lino's secretary Luca. He and Lino were very good friends, and it's possible that Feinberg also understands about the two young sharks.
Don Ira(after finishing his song): Frankie, we love you...
After that, the audience raised their cups to all honor the deceased one, and Lino thanks Ira for the song.
Also, not only friendly with Lino, Ira seemed to have a slightly self-confident side, as shown that he ignored the audience sharks' complaints of dissent when he asked whether he'll sing the Titanic theme song.
Don Ira(in a haughty way): Any requests? How about that Titanic song?
Audience sharks: Oh, please don't!!
Don Feinberg is a slender, old leopard shark.
Behind the scenes
Don Feinberg was portrayed by Peter Falk inside the film adaptation of Shark Tale.