Polyvinyl chloride (PVC) directional flow tubes measuring 35 cm in length and 6.5 cm in diameter with a 15 cm centrally located vertical trap were placed in parallel and supplied with raw seawater to produce a directional flow. A float actuated valve in an upper reservoir provided equal water flow through the tubes at all times. Females were placed upstream and males downstream within their respective hosts. Male crabs exiting their hosts and attempting to proceed towards the female’s host fell into the vertical trap and were unable to exit. A common drain reservoir collected outflowing water.