The dependant variable would be the salmon, because they depend on the water and pollution levels to give a result.
He would become shaky and his heart would begin to race/thump.
Reading through the entire investigation before beginning the procedure can help prevent accidents by giving you the knowledge of what to do beforehand and preparing you for what is to come.
Remember the cell theory by Virchow that states that all cells come from pre existing cells, if a single cell dies, it can be replaced unless it's a brain cell.
