mallard preying on crayfish

american anas animal animals aphanomyces astaci astacus biological bird birds cambaridae clarkii control controlling courses crawfish crayfish crayfishes crushing damage devouring duck ducks ecological enemies epidemic european feeding fields fight freshwater fungus fungused help hunting impact infestation integrated invasion invasive juvenile life locations louisiana mallard mallards management natural pest plague platyrhynchos population populations predating preying problem problems procambarus red rice species swallowing swamp water wild wildlife