An improved portable trap was designed to capture migrating fishes in rivers prone to severe and rapid fluctuations in water level. The trap was constructed of metal and was assembled on site by three people in 2 h. Its unique design allowed for fast on-site modifications. The trap was tested in a portable weir in a small river in insular Newfoundland. It withstood flood conditions of a magnitude that caused washouts of previously used wooden traps. The overall performance of the metal trap was superior to that of conventional wooden traps. The cost of the metal trap in 1986 was around Can$5,000.