Ship ballast is believed the most common pathway to the Great Lakes region for exotic species, but it's not the only one. Among others:
--Canals, channels and locks. Structures such as the Welland Canal, the St. Lawrence Seaway and the Soo Locks enable some critters to swim from one lake to another.
--Recreational boats. Tiny organisms encrust boat hulls and aquatic plant fragments get tangled on propellers and fishing gear.
--Fishing bait. Anglers sometimes transport nuisance species in bait containers, dumping what they don't use into the lakes.
--Intentional release. Government agencies and private individuals have planted fish in the lakes, hoping to establish viable populations.
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