Complex sentence: In 1997--1998, over 1,200 gharials and over 75 nests were located in the National Chambal Sanctuary, but no surveys were carried out between 1999 and 2003.
Split into simpler sentences: In 1997--1998, over 1,200 gharials and over 75 nests were located in the National Chambal Sanctuary. But no surveys were carried out between 1999 and 2003.