April 28 (SeeNews) - Croatia's blue-chip hotel owner and manager Valamar Riviera [ZSE:RIVP] said on Friday its adjusted EBITDA widened to a negative 19.1 million euro ($21 million) in the first quarter of 2023, from a negative 13 million euro in the same period of last year, following a significant increase in electricity costs and higher salaries of employees.