How did Louis Agassiz become interested in studying fish?

Louis Agassiz’s interest in ichthyology began in his youth, when he paid attention to the brook fish of western Switzerland. However, his permanent professional dedication to the field was sparked by his study of an extensive collection of Brazilian fishes, primarily from the Amazon River, which had been gathered by two naturalists in 1819 and 1820.

After one of the original collectors died in 1826, the collection was turned over to Agassiz to complete the classification. He published this work in 1829 as Selecta Genera et Species Piscium. Following this project, the study of fish became a prominent feature of his research, leading him to investigate both living species and the rich stores of fossil fishes found throughout Europe.1