The Justice Department has been conducting a criminal investigation of sports fishing expeditions in the Amazon that may have been used as covers for Americans to have sex with underage girls, according to newly filed court papers. The investigation and two related actions — a parallel criminal inquiry in Brazil and an unusual lawsuit filed in federal court in Georgia — could provide a rare look at the business operations of the multibillion-dollar international sex tour industry, which has increasingly focused on Brazil. “Brazil is taking over from Thailand as a premier sex tourism vacation” spot, said Kristen Berg, an official of Equality Now...