I wonder how sure they are that they closed the locks (for good) before the carp could get through. It looks like there was only another 12 miles of navigable river - so while a loss to shipping to the northern suburbs, it probably won’t have a huge impact on shipping.
Sounds like it is worth it if they can keep those nasty carp out of the hundreds of mile of river (and thousands of miles?) of tributaries to the north.
Someone will transport by design or accident to other lakes and rivers.