Background Paragraph: Fish mortality is a parameter used in fisheries population dynamics to account for the loss of fish in a fish stock through death. The mortality can be divided into two types:

Natural mortality: the removal of fish from the stock due to causes not associated with fishing. Such causes can include disease, competition, cannibalism, old age, predation, pollution or any other natural factor that causes the death of fish. In fisheries models natural mortality is denoted by (M).[1]
Fishing mortality: the removal of fish from the stock due to fishing activities using any fishing gear.[1] It is denoted by (F) in fisheries models. 
Story: Tony is about to go on two fishing trips in the up coming week. On Friday, he is going to Bear Lake, which is located near a factory that has been known to dump waste into the lake. On Saturday, he is going to Fox Lake, which is in a secluded valley.
Which day will Tony visit a lake that more likely has less fish? Which day will Tony visit a lake that more likely has more fish? Which lake most likely has a higher mortality rate for it's fish population? Which lake most likely has a lower mortality rate for it's fish population? Which lake probably has less fish in it? Which lake probably has more fish in it? Will Bear Lake have more or less fish than Fox Lake? Will Fox Lake have more or less fish than Bear Lake? Will fishing on Friday more or less likely be more fruitful than fishing on Saturday? Will fishing on Saturday more or less likely be more fruitful than fishing on Friday?