In addition, field studies conducted by John Janssen indicate that mottled sculpins in the Grand Calumet River, southern Lake Michigan apparently suffered year class failure during 1994-1995 probably due to this mechanism. Round gobies are well adapted for transport in the ballast water of transoceanic ships and also freighters in the Great Lakes, which is probably how they got here in the first place and probably why they have been able to spread so far so fast. There are many incidences of freighter transport of other species of gobies into other water bodies across the world, so our experiences are not new. They may also have laid eggs on the undersides of ships or in suitable holes thereby allowing the eggs to be transported long distances before they hatched. The Family Gobiidae contains many species of cavefishes which are adapted for living in complete darkness.
Round gobies have a lateral line system which is very well adapted for feeding in the dark.
Studies performed by John Janssen on round goby have shown that round gobies can feed in complete darkness and can detect prey at a shorter distance than can mottled sculpin, giving them a competitive advantage in this area as well. These two creature features along with the round gobies' tolerance for degraded water quality has probably pre-adapted round gobies for transport in ships and their ballast water. Predators have shown an interest in round gobies in the St. Clair River, probably because they are so abundant in that system. There are two possibly damaging scenarios we are concerned about that may come to pass in the future. The first of these is food chain bioaccumulation of PCBs.