January 29, 2010
This month brought more disturbing news about the distribution of Asian carp DNA upstream of the barrier and on the lakeside of the O'Brien Lock near Calumet Harbor. While the analyses and announcement of the results came this month, the samples themselves were taken some time ago. In the case of the Silver Carp DNA detections near Wilmette, the samples were taken in October.
eDNA Testing - A powerful tool
The environmental DNA sampling technique is a powerful detection tool, but due to the lag time between when the water samples are collected and completion of the analysis we cannot be certain the fish have remained in the same location for the intervening weeks or months. This and the fact that it is very difficult to capture fish like silver carp that are very capable of avoiding nets and that are present in low abundance with nets or electrofishing gear makes verification of the eDNA results difficult.
How did these fish get past the barrier?
It is highly unlikely that the Asian carp currently upstream of the electric barrier swam through the electric field. Even at one volt per inch, fish the size of the one captured during the rotenone application in December would not be able to swim through the barrier. At two volts per inch even small fish (4 inches) are stunned.
Chris Jerde at University of Notre Dame developed a model that illustrates the progression of Asian carp upstream in the Illinois and Des Plaines rivers.
Based on the model, bighead and silver carp were potentially at the barrier in low numbers as early as 2005. Looking back at the operating record of Barrier I over the last five years, we see the fish may have had several opportunities to swim through the barrier reach with little to no effect of the electric field.
September 19, 2005 – Lightning Strike
In September 2005 Barrier I was hit by lightning. It operated at less than full power for 56 hours.
September 2008 – Des Plaines River Floods
The eDNA results demonstrated the presence of Asian carp DNA in the Des Plaines River in 2009. If the fish were present as early as 2005 or 2006 they could have crossed the land bridge between the Des Plaines River and San-Ship Canal with flood waters in September, 2008.
October 2008 – Major Maintenance for Barrier I
In October 2008, Barrier I was shut down for 30 days to carry out a major maintenance operation. During the time the electrodes were replaced and the pulsers upgraded. Prior to the maintenance action the only attempt to detect Asian carp in the vicinity of the barrier was running electrofishing boats between the barrier and Lockport Lock. No fish were captured or observed, but the canal 25 feet or more in depth at that location and the effect of the electrofishing boat only extends about eight feet into the water. If Asian carp were present, they could easily have eluded the electrofishing boats and swam upstream unimpeded when the electric current was shut off.
The long-term solution
These events highlight the fallibility of a technological approach to prevent the spread of AIS. These approaches buy us time but are not the full solution to prevent the spread of organisms through the Chicago Area Waterways. We need to address this shortcoming through a parallel set of activities. We need to separate the Des Plaines River flood connection from the San-Ship Canal. The corps has been directed and funded to carry out this work in the current year. They will also address the connections with the I&M Canal. We need to augment the electric barrier with a second technological approach that uses bubbles, light and sound. The acoustic bubble barrier will add another filter to the barrier reach.
The second action that must occur is development of the ecological separation of Lake Michigan and the Des Plaines River. This is not an easy fix nor will it be cheap. The solution will have to address the storm and waste water discharges in the Chicago area, will need to address the transfer of passenger and recreational vessels between the Chicago River and Lake Michigan and will have to address the movement of commercial cargo between Lake Michigan and the Chicago Area Waterways.
This solution was identified in 2004 at the Aquatic Invasive Species Summit in Chicago but the only progress towards this solution was a study supported by the Alliance for the Great Lakes. It is time to separate the lake from the river. It is a challenge but it is not impossible. With the will, the authority and the funding it can happen.
December 8, 2009
Asian carp DNA found above the barrier
The announcement of the discovery of bighead and silver carp DNA above the electric barrier this week is of course disconcerting news. As we consider what this means we need to keep several points in mind.
Wasn’t the barrier supposed to be 100% effective?
One is that the barrier, though often touted as a 100 percent effective technology was never considered to be 100 percent effective when the Barrier Advisory Panel first recommended the approach. At the time (1997) an electric barrier was considered to be the best approach with the least number of drawbacks. The members of the Panel also recognized that no approach that relied on animal behavior or a technological approach, as opposed to a physical separation could be one hundred percent effective in stopping the movement of aquatic invasive species through the canal. Achieving 95 or 99 percent effectiveness was much better than nothing.
How could the fish get through the barrier?
Some people are wondering how the fish got through the barriers. The greatest likelihood is that they swam through when the barrier was not operating or got washed in from the Des Plaines River. Recent modeling on the rate of upstream spread of the Asian carp by the Lodge Lab at the University of Notre Dame suggests the fish could have been at the barrier site for about two years. If this is the case, the fish would have been present when Barrier I was shut down for maintenance in October of last year and could have simply swam upstream when the barrier was shut off. At that time, the only effort to remove carp from the area below the barrier was electrofishing. We know that when the abundance of these fish is low, electrofishing is not an effective way to collect these fish.
In September 2008, the Chicago region suffered a 50-year storm event that sent the waters of the Des Plaines River tumbling over the narrow strip of land between it and the Sanitary and Ship Canal at several locations above the barrier site. This fall Asian carp DNA was found in the Des Plaines. As mentioned above, if the fish were in the Des Plaines River for the last two years, they could have spread overland into the canal during this storm event.
Where else could the DNA come from?
It is most likely that a few silver and bighead carp are above the barrier but it is possible that the DNA could have come from a dead fish or scraps of an Asian carp dumped in the river. Asian carp are still sold in Asian food markets near Chicago, though they have to leave the store dead. Water in the void space of a barge has also been suggested as a source. While this is possible it is unlikely given that the samples were taken over about a week and the DNA in water degrades to an undetectable form in about 48 hours.
Was Barrier IIA turned on too late?
Barrier IIA was completed in May 2006. Due to safety concerns the barrier sat idle for nearly three years not operating full time until April 2009. Considering the modeling that suggests the fish could have been at the barrier site since 2007, it is possible that if Barrier IIA had been powered up and operated even at 1 volt per inch the upstream spread of these fish could have been slowed or prevented.
Still no bodies
Thus far despite significant sampling effort we still have only the DNA evidence as to the presence of these fish above and below the barrier in the Lockport Pool. This suggests the abundance is very low and again indicates we’ve not reached the end of the Great Lakes ecosystem.
Where was the DNA found?
The samples that tested positive for silver and bighead carp DNA were collected between September 23 and October 1. They were only recently analyzed. The samples that tested positive were collected at the junction of the Cal-Sag Channel and San-Ship Canal about 9 miles above the barrier and at a point about a mile below O’Brien Lock which is about 30 miles above the barrier. The O’Brien Lock is about 12 miles from Lake Michigan.
How about closing the locks?
While closing the locks could impede movement of the fish towards the lake it would also close navigation access between the lake and the canal. This may be under consideration as a short term option but is not likely to be implemented for the long term. We must keep in mind too that the fish have been there for at least six weeks and could already have passed through the lock with barges or other boats. Also the Chicago River, North Shore Channel and CalumetRiver are not the only access routes to the lake from the current known location of the fish. The GrandCalumetRiver and Little Calumet River form a confluence with the CalumetRiver below the O’Brien Lock and connect with Lake Michigan in Indiana. There are no control structures on these rivers to stop the lakeward movement of the fish. Waterway Illustration
What about capturing or poisoning the fish upstream?
Asian carp are very good at avoiding nets and seem to be able to elude electrofishing boats particularly when the fish are not abundant. Poisoning the fish is being considered below the barrier in conjunction with the maintenance of Barrier IIA. Fish in that six mile reach are contained by the Lockport Lock on the lower end of the treatment zone and the barrier on the upper end. The fish above the barrier are not contained, nor do we really have a good idea of their current location. It will cost about $1 million for the fish kill operation in the six mile reach below the barrier; about 25% of that cost is for the chemical. We don’t have a chemical that only kills Asian carp so all fish in the canal would be affected. There are numerous slips and tributaries along the Cal-Sag that also would be affected or would form refuges for the carp. Poisoning out the 79 miles of canal that lies upstream of the barrier is not really a feasible option.
Does this spell doom for the Great Lakes?
It has been a mistake to convey the impression that if these fish get into the Great Lakes disaster would ensue. Certainly, if the fish become established in the lakes and are present in large numbers the ecological effect could be devastating. On the other hand, if a few fish get into the lakes, as have been present in Lake Erie, and are not able to become established this is a population level we can and will need to live with.
Should the barriers keep operating?
Even though a few fish have made their way upstream continued operation of the barriers will prevent thousands more from gaining access to the upper portion of the canal and entering Lake Michigan. Separating the Des Plaines River flood flows from the San-ShipCanal is also a critical step in preventing the upstream spread of Asian carp. By keeping the number of Asian carp low that gain access to the Great Lakes we reduce the chance that they may find one another and suitable spawning habitat in tributaries.
There are only 22 tributaries to the Great Lakes on the U.S. side that offer suitable spawning habitat for Asian carp. The carps require about 63 miles of open flowing channel for the eggs to hatch and the young to develop. The young must then be able to find quiet back water areas to being to feed. The Illinois River is the perfect habitat for these fish. These Great Lakes tributaries may provide the open channel but may not all have the suitable backwater areas for the young carp to thrive. Like most other fish, Asian carp have external fertilization; the females do not carry fertilized eggs, she must find a male who will fertilize her eggs when she sheds them into the river. So when these fish make their way into Lake Michigan, they must find an adequate tributary, both males and females must be present in adequate numbers to ensure fertilization of the eggs. The tributary must have suitable spawning habitat as well as habitat for the young.
Separation, the long-term solution
The presence of Asian carp, or at least their DNA, above the barrier underscores the need for a long term, permanent separation of the Great Lakes and MississippiRiver basins in order to effectively stop the interbasin spread of aquatic nuisance species. The electric barrier or acoustic bubble barriers or any other option that relies on technology and a behavioral response from the target organism for effectiveness has the potential to fail. We can begin with Chicago and the Sanitary and Ship Canal but in order to protect the Great Lakes and other external drainage basins, we must redouble our efforts to identify and implement an ecological or hydrologic separation of the Great Lakes and other formerly separate drainage basins that are currently connected by man-made canals.