Border officials at the Ambassador Bridge discovered and seized the first shipment of 2,600 pounds of live Asian carp Jan. 9, The Detroit News reported.
Inspectors discovered and seized 6,800 pounds of live carp Wednesday at the same border crossing.
Since 2005, transportation of live Asian carp has been banned to prevent the invasive species from establishing itself in Canada.
The carp are known to enter new areas, consume the food supply and force out native fish.
"The concern, of course, is that the carp will get entrenched here," said Jolanta Kowalski, a spokeswoman with the Ontario Ministry of Natural Resources. "And they've got a history that's not a good one in terms of what they do once they're established."