Its lakes and marshes support 45 freshwater fish species .
The Danube Delta is also the best preserved river Delta in Europe , a UNESCO World Heritage Site ( since 1991 ) and a Ramsar Site .
Danube Delta 's lakes and marshes support 45 freshwater fish species .
The Danube Delta is also the best preserved river Delta in Europe , a UNESCO World Heritage Site ( since 1991 ) and a Ramsar Site .