In the sentence from "The Boy Behind Braille" Discovering a system that worked was an uphill climb. How is the word uphill used?

Write a procedure to explain something you already know how to do

[he] let his gaze wander to the swirling water of the stream racing madly beneath his feet. a piece of dancing driftwood caught his attention and his eyes followed it down the current. how slowly it appeared to move! what a sluggish stream! what contrasting words are used to describe the stream in this passage?

How does the author introduces his idea of fish depletion in the first few pages of world without fish?