Unionid mussels are native to the Hudson River in New York State. In the early 1990s, zebra mussels were introduced into the Hudson River. The table shows the number of unionid mussels and zebra mussels over the course of six years.
How did the population of unionid mussels change after zebra mussels were introduced?
Why did this change occur?
You didn't provide the table, but I expect the Unionid mussel numbers decreased as the invasive zebra mussels increased. Zebra mussels are taking space and nutrients and algae that the Unionids need to flourish. I think Zebra mussels even attach to unionids which kills them.