Pink Salmon undergo physical changes when they enter their native river to spawn. When I took the shot, I saw the salmons in their normal state along with the ones going through the halocline which had already muted. It was a way of capturing there evolution instantly. The blurring of the water is caused when salt and fresh water mix as the salmons swim from one to the other. The blur adds to the drama of the event as the salmons will die soon after reproduction, the transformation being too harsh.