The fishing shop in Alcudia - Totymar - does fishing excursions. The shop is in the port on the C. Teodor Canet next to the Tabacos and the large restaurant Bodega d'es Port. The guy is called Tolo. There is a website -
http://www.totymar.com - but frankly it's of little use. There may well be other operators based in the marina, but to be honest I've never noticed anything specific.