A study conducted by the Coast Guard Research and Development Center in coordination with the Environmental Protection Agency concluded that barge ballast tanks present a minimal risk for the incidental transport and introduction of Asian carp into the waters of the Great Lakes.
There has been concern that Asian carp eggs, larvae and fry contained in towboat and barge ballast tanks could be transported past electrical dispersal barriers operated by the Army Corps of Engineers and released into the Great Lakes, according to the Coast Guard News.
Specifically, the study investigated the possibility of early life stages of Asian carp entering barge ballast tanks through either cracks or holes in the hull and then surviving there, which could circumvent the existing electrical dispersal barriers in the Chicago Sanitary and Ship Canal that have helped prevent breeding population of the carp from establishing in the Great Lakes to date.
The study consisted of three parts:
· A hopper barge was modified by installing valves on 3-inch holes cut into the exterior of its four ballast tanks to simulate how larvae might enter a barge with a ruptured hull.
· Caged larvae were placed into the tank for set periods of time to investigate survival rates.
· The barge was de-ballasted through either 2- or 3-inch portable ballast pumps to determine whether larvae could survive the trauma of passing through a mechanical pump.
Results of the study indicated that although it may be possible for early life stages to be transported in a barge ballast tank for long periods, the probability that those life stages will survive passage through the pump when the tanks are de-ballasted is very low. The risk is further lowered because early life stages are present in the affected waterways only for a limited time each year.
A previous study evaluated barges and towboats on the Illinois River to determine the volume of water carried in ballast tanks. That study found that only 5 percent of the inspected tanks carried more than a couple of inches of water. Operators interviewed during that study indicated that barges were seldom ballasted except to clear low bridges and that tanks were inspected regularly.
The Great Lakes Restoration Initiative, in which the Coast Guard and EPA partner among 14 other agencies to rehabilitate the ecosystem’s health, provided funding for the study.
Asian carp are non-native, invasive fish that have been migrating up the Mississippi River and its tributaries since the mid-1990s.