Lord knows the recent fisheries management work at Wehrspann Reservoir in west Omaha has been THE topic of discussion this week. I want to add this update. . . .
Our field biologists that did the treatment went back today to see how things looked. As you can imagine they discovered hundreds of thousands of dead shad. How many? I cannot tell you an exact number or even an estimate. But, there are photos floating around the internet and here is one of a wind-blown cove on the south side of the reservoir:
I will tell you this: When we did the exact same treatment at Pawnee reservoir three years ago, we had some graduate students from the University of Nebraska–Lincoln estimate both the numbers of white perch and gizzard shad pre- and post-treatment. There were no white perch in Wehrspann, the target there was gizzard shad. At Pawnee the research concluded that the low-dose rotenone treatment there got pretty much all of the gizzard shad, somewhere around 650,000 shad. I am betting the numbers of gizzard shad in Wehrspann would have been similar to Pawnee if not higher, and if you calculate the shad kill there on a per-acre basis and apply that to the smaller Wehrspann Reservoir, I am betting at least a quarter of a million dead shad at Wehrspann would be a minimum ball-park estimate. You absolutely can question my numbers, no estimates of the number of dead shad at Wehrspann have been made, but that is the best guess I can come up with.
In addition our field biologists walked the shorelines of the entire perimeter of Wehrspann from the walk/bike bridge on down to the dam and they counted the numbers of other fish they saw dead. Here is what they found: 51 dead walleyes, almost half less than 16 inches long, but some as large as 26 inches; 61 dead channel catfish, 70% less than 16 inches, but 16% 20-25 inches long; 52 dead blue catfish with 40+% being 28-35-inch fish. They also found more dead common carp than they expected, 284 of those with almost all of them being 20-30-inch fish.
Now, I am NOT saying that they accounted for every non-target fish that died after the low-dose rotenone treatment and I wish that such a treatment could have been done without mortality of any sport fish. What I am saying is that there is some perspective, and it illustrates how the Wehrspann fishery was dominated by gizzard shad.
I am going to address one other criticism that has been repeated in the past couple days, that being that we did not let anyone know about this ahead of time. That is true, and there are a couple of reasons for that. First, we did not want our field crews to have to try to get this work done on a cold, miserable day while spending any more time than necessary on the water. If folks would have known about it ahead of time, we would have had to take time to answer questions and work with and around those who would have showed up to see what was happening. Not that that is not part of our jobs, it is, and we appreciate that folks are very interested in our resources and what we are doing. Just is sometimes it is easier to get in and “Get-R-Done” and then answer questions. Secondly, and you can call us pointy-headed fish biologist paranoid if you wish, but Wehrspann was one of the last waters in the Omaha area to have an abundance of gizzard shad. We wanted to get in and eliminate as many of those shad from Wehrspann as possible without someone knowing ahead of time and trying to save some shad and illegally transfer them to another nearby body of water. As I said, you can call us paranoid if you wish, but I know of illegal shad collections at Wehrspann, and subsequent transfers that have been bragged about. Yes, law enforcement cases were made on that, but we did not want to encourage any more of that activity.
As I said before, we are confident that this fisheries management activity will make fishing better at Wehrspann. We have had very positive results on other waters where it has been done (e.g. Louisville Pit #2, Pawnee Reservoir), and we expect a great future for the Wehrspann fishery.