A lake contains five different types of fish.
There are an estimated 350 Roach, 250 Bream, 200 Rudd, 150 Tench and 450 Carp.
John wishes to investigate the health of the fish in the lake.
He decides to take a sample of 120 fish.
Give a reason why stratified random sampling cannot be used.
Explain how a sample of size 120 could be taken to ensure that the estimated populations of each type of fish are fairly represented.
You should state the name of the sampling method used.