Animals marking their territory with urine is an example of

The answer is competition. It's competition because they are protecting their territory, so their way of protecting or fighting for their territory is to urinate on their territory. By a way of showing that they don't want nobody in their territory.

I’d have to say no because without oxygen in the water the fish would all be dead. so if you want to fish for dead fish, pick the ponds with the lowest oxygen concentrations.