This little thing is called a Spiny Water flea. They’re native to Europe and Asia. This species was introduced to the Great Lakes by ballast water discharged from ships that had been in the ocean. They were discovered in Lake Ontario first and have since spread to the other Great Lakes.
As you can see from the fourth photo, courtesy of Oneida County Aquatic Invasive Species Program, this small aquatic water species can choke fish and puncture their guts. They feed off of local zooplankton and have a small amount of predators.
The first photo shows an accumulation of Spiny Water flea on a fishing line. This aquatic species can harm a fishing rod, causing those fishing to lose catches. The fact that there are a small amount of predators against the water flea means that they have the means to spread without a lot of resistance. This flea harms local fish biodiversity by harming the local species.
Management for this species is difficult due to the size of the species. The best way to manage the invasion, studies have found, is to prevent the transfer of any aquatic species. This includes drying boats, releasing water and cleaning fishing equipment. The species itself can be killed by being left to dry. The most effective management strategy is continued sampling of affected waters to continue biological monitoring.