 However, as these rivers have strong spring floods and high summer temperatures, neither bluegills nor trout fare as well there as they do elsewhere.Additional threats include habitat destruction by humans due to water pollution and overuse, and clearing of riparian for orchards.This is especially harmful, as it deprives the young fish (which are especially under pressure by the introduced species) of their shelter, and allows surface runoff carrying pesticides and fertilizers to pollute the rivers.