If you are referring to selection pressure, when the selection pressure decreases, there will be weaker forces of natural selection. The angler fishes without the favourable traits would not be that strongly selected against and vice versa. In some cases such as predation selection pressure, the population of angler fishes in the habitat may increase
So they respond by releasing hormones that stimulate the body to retain sodium and water. Blood vessels fill with additional fluid, and blood pressure goes up. The narrowing in one or both renal arteries is most often caused by atherosclerosis, or hardening of the arteries.
