Gizzard Shad
From: "Flammang, Mark" <[email protected]>
Date: November 25, 2019 at 1:22:09 PM CST
Cheryl:
As you might imagine, I have spent a great deal of time heading off mistaken perceptions, innuendo, half truths, and flat out lies about the treatment at Sugema over the last few weeks. The bottom line is, the treatment proceeded as planned and everything we know up to this point is as expected. If you don't mind, instead of rewriting a lengthy email, I'll attach the text of yet another one I sent last week. Please let me know if you have questions beyond what is provided here.
Mark
Pasted response below:
I am going to address your specific questions, but as you may guess, I have addressed these and many other questions in various formats in the last few weeks. I am also attaching a rather lengthy response to another email that I believe will give you some additional information regarding the need to remove the gizzard shad.
Secondly, thank you for posing your questions in a polite manner. I find that through this I have had some very good discussions with folks who just want answers and are able to ask reasonable and well conceived questions. Those are theo folks I can talk to all day. As you may guess, there are folks who are not so easy to communicate with.
I've been doing this now for about 30 years. The research that has gone into Iowa's gizzard shad management is more than 11 years in the making. This was a plan of attack that was desperately needed. As you point out, bucket biology has affected us as anglers for a very long time, and as you are aware, it's not just shad. This project has lead to real solutions to gizzard shad and yellow bass introductions and other states are even using our work to move forward with similar programs, Nebraska, Kansas, and Kentucky to name just a few. The project we took on had two phases, a field phase where we performed this same kind of treatment on 19 lakes. The other phase involved a 2 year study in hatchery ponds to answer questions just like you posed, what percentage of game fish are impacted by these treatments.
Before I move on, there is one thing worth stating. It's a simple disclosure, but one I think people don't think of, or never consider. I am a fisheries biologist. However, I'm an angler, and a very avid one at that. The IDNR doesn't take steps to alter fish communities unless there are very good reasons to do so. We don't look at a problem and poke it with a stick. We have a plan, we research the plan, and we implement that plan. We treated shad back about a decade ago in Sugema. They were reintroduced again, illegally. They were gone, they returned. We have documented this. Sugema was treated at 5 parts per billion the first time around. It worked that time in Sugema, but in other lakes in the 19 lake study, treatments that were performed at less than 8 parts per billion were successful only about 50% of the time when it came to removing shad. Further, our hatchery pond study told us we could eliminate shad at 8 parts per billion with a MAXIMUM loss to largemouth bass of about 15%, Bluegills up to 20%,and crappie up to about 7%, while we expect total removal of all gizzard shad. The loss of game fish is disturbing when you see the fish along the shore, but from a population level, the impact is relatively small or even undetectable. I can go on about this for hours. The thing is, the total ecological underpinnings of this situation don't lend themselves well to text messages, emails, or even phone calls. It's a very complex situation, but I hope some of what I have said thus far has made sense.
In regard to "waiting a few years", I'll approach it as I did with another crappie angler I know from the area. I asked him, based on the idea that crappie loss will be relatively light from a population level, what is the benefit to waiting? There really isn't one. Meanwhile, largemouth bass recruitment continues to decline, bluegill quality remains very poor, we're still not able to manage for walleye or musky, water quality continues to suffer, and for much of the year angler attention continues to dwindle. Again, I appreciate your comments and I don't dismiss them at all. I'm just trying to express that this type of project is a big undertaking and unfortunately, there is always the potential for second guessing.
As I recall, you also asked about ponds in the watershed that may have gizzard shad. This is a valid concern. Specifically, there are 3 ponds that legitimately could have held shad that were in close enough proximity to the lake to deliver shad back to Sugema. We treated all three of these as well, prior to Sugema's treatment. We found shad in two of them. We knew they were in both by the way. Tug Fork West and a large wetland northwest of there also had them. Interestingly, we literally saw buffalo and shad moving up form Lake Sugema into the wetland last spring following a heavy rain event.
Steve, I hope I have addressed your concerns. I'm also attaching the email I spoke of earlier that will provide some additional background. Please come back in the spring. I do believe there will be fish to catch.
Mark
PREVIOUS EMAIL RESPONSE FOR YOUR REVIEW
I appreciate the opportunity to fill you in on our removal of gizzard shad from Lake Sugema. You may get a little more information than you requested, but I’m trying to be thorough with folks. As you suggested, there is a lot of rumor regarding this project and to be honest, it’s hard to head all of that off. This type of work doesn’t lend itself easily to Facebook posts, text messages, or short emails. I’ll do my best to explain the issue, how we arrived at the solution, and what you can expect for the future out of Lake Sugema.
In Iowa there is a history of illegal introductions of fish in a number of systems across the state. In this case, we are dealing with gizzard shad. While gizzard shad do have their place in some of our larger systems, they are not a good addition to most of our lakes across the state. In regard to how we know they were illegally introduced, there is no other method that realistically can result in this type of fish movement. Gizzard shad are a relatively fragile species and take some care to move. A few years ago we were battling this same issue at Lake Wapello near Drakesville, Iowa. At that time, an individual was questioned after taking credit for moving the shad to that system, not once, but twice. Unfortunately, nothing stuck in that case; however, it demonstrated that the issue was real.
Shad are a problem for two ecological reasons. First they have a very negative impact on the food web of our lakes and secondly, they negatively impact water quality. First, shad eat zooplankton, and lots of it. This plankton is the food for all very young fish, regardless of species. Without plankton we find that recruitment of fish (which means the number of fish that are hatched and survive each year) declines dramatically. That means that gamefish density (bass, bluegill, crappie, etc.) declines. There are some reasons why this is a bigger problem at the northern limit of the gizzard shad range (like Iowa), but the bottom line is, they reduce gamefish density. Even more importantly, they change the way that food moves through the ecosystem. There is a disconnect in the delivery of energy (which really means food here) from the bottom of the food chain (plants, phytoplankton, algae, etc.) to the top of the food chain (predators like largemouth bass) and everywhere in between (panfish like bluegill and crappie). Like I said, this is a difficult topic to explain via email or text message. I actually have a second job as a college instructor in Environmental Science and we can spend weeks discussing this sort of thing.
At any rate, there is less food available for many species at all life stages. Bluegill are the first species to show negative effects from gizzard shad introduction. However we eventually see signs up and down the food chain. Largemouth bass that are in the lake when the shad take off may actually show a slight increase in growth rates, which looks good to anglers at first. But what ends up happening is that bass recruitment goes down. This means we have fewer bass entering the population each year. So, we end up with a fairly high percentage of larger fish, but fewer fish overall. Because bass are the top level predator, this can have additional negative impacts on other fish like crappie and bluegill. Crappie are also negatively impacted eventually. The thing about crappie is, they are slower to show the negative effects. Crappie, unlike bluegill and redear sunfish, usually don’t produce a year class every year. In fact, if crappie are successful in pulling off a year class every 3 to 5 years, we are doing well. That’s why crappie fishing cycles. It goes through boom and bust years on most lakes, not just in Iowa. Eventually crappie numbers also will decline. As it happens, we just happen to be at a peak in crappie year class strength right now at Sugema, meaning we had great fishing this fall. For reasons I will continue to explain, there is no reason to assume that won’t happen again this winter or next spring.
Now, to explain the water quality angle. Gizzard shad eat zooplankton. These are microscopic animals that eat phytoplankton (plant plankton). When the shad eat this plankton they are not only starving the young fish that hatch each spring, they also allow phytoplankton blooms to go unchecked. This has a tendency to turn lakes more green than they normal, in other words, they reduce visibility. In addition, shad also eat detritus. This just means they eat dead leaves and plant material off of the bottom of the lake. This dead organic matter is the remnants of living plants that are decomposing on the bottom. When the shad eat this material they remove the nutrients (primarily nitrogen and phosphorus) in these dead leaves from the bottom of the lake where it is pretty much out of circulation. They resuspend it back up into the water column. Essentially they fertilize the water which then leads to even more phytoplankton growth, making the lake even greener and decreasing water clarity even more. This also can lead to a greater likelihood of summer kill.
I realize I just spent a great deal of time explaining what the problem is, but it’s important to get that information out there. The solution then comes in one of two paths. Traditional fish management would result in the DNR and the local community watching the quality of their fishery decline for a period of years. Eventually the entire fishery would decline dramatically. We have already noted large declines in bluegill and readear sunfish and big reductions in largemouth bass density at Sugema. Eventually, after years of declining angling opportunity, fewer angler visits, and declining economic return for the local community, a drastic solution would have to be sought. This normally involved the removal of the entire fish community. In other words, all fish would have to be removed and the lake would have to be restocked. This is an expensive path, not just for the costs associated with manpower and chemical costs to remove the fish, but even more importantly, the costs to the local economy brought about by the loss of angling and the time it will take the lake to recover after restocking. About 12 years ago the Iowa DNR began an intensive research study to evaluate a method to remove gizzard shad with minimal impacts to the gamefish population. This involved the use of rotenone, a natural botanical pesticide that is used to remove fish. The difference being, we apply at a rate that is less than 5% of what is normally used to kill all fish in the lake. We can do this because gizzard shad are more vulnerable to rotenone that most gamefish. As a part of this study that lasted more than 7 years, we treated approximately 20 lakes and did extensive testing in small ponds at the Rathbun Fish Hatchery. We were able to determine ideal treatment concentrations for the removal of gizzard shad while attempting to limit the impacts on gamefish. This type of treatment has gained popularity throughout the Midwest. Kentucky and Kansas, for instance, have aggressive programs modeled after ours with the same goal, to remove gizzard shad with minimal impacts to gamefish.
Throughout I have stated “minimal impacts”. What this means to us is that changes in the gamefish population will not result in large declines in gamefish abundance and angling quality. By treating just the shad, we can have relatively little impact and no long term issues with most species of gamefish in these systems. We know through our studies that some gamefish will die during these treatments. There is no way to completely mix all water in a 600 acre lake at one single moment. There will be an area of higher rotenone concentration as we apply. However, what I can tell you is that these gamefish losses are not sufficient to overly harm a population. I understand as an angler myself; it’s hard to see gamefish die with the shad. However, everything about this project parallels what we have seen at other successful projects from the past. When we come back next spring to survey the Lake Sugema fishery, we will find that the gamefish populations will remain relatively intact. We typically are unable to measure a decline in largemouth abundance or size quality. The same will hold true for crappie. Bluegill quality is already very poor at Sugema, and with the removal of shad, we expect bluegill quality to greatly improve next year alone. In short, everything is still here in Lake Sugema. Angling quality will remain good going into next spring and we will see improvements on multiple fronts as 2020 progresses.
I realize this is a long story, I hope you have made it this far. To answer your question about the lake level, the gate was closed on the day of the application. The lake was actually down 23 inches at that time and is continuing to refill now. When it fills is dependent on precipitation so it could be next spring before it fills, that will depend on Mother Nature.
I hope this information has been somewhat helpful and please feel free to share it with others you know who may be interested. Thank you and please let me know if you have additional questions.
Mark
Date: November 25, 2019 at 1:22:09 PM CST
Cheryl:
As you might imagine, I have spent a great deal of time heading off mistaken perceptions, innuendo, half truths, and flat out lies about the treatment at Sugema over the last few weeks. The bottom line is, the treatment proceeded as planned and everything we know up to this point is as expected. If you don't mind, instead of rewriting a lengthy email, I'll attach the text of yet another one I sent last week. Please let me know if you have questions beyond what is provided here.
Mark
Pasted response below:
I am going to address your specific questions, but as you may guess, I have addressed these and many other questions in various formats in the last few weeks. I am also attaching a rather lengthy response to another email that I believe will give you some additional information regarding the need to remove the gizzard shad.
Secondly, thank you for posing your questions in a polite manner. I find that through this I have had some very good discussions with folks who just want answers and are able to ask reasonable and well conceived questions. Those are theo folks I can talk to all day. As you may guess, there are folks who are not so easy to communicate with.
I've been doing this now for about 30 years. The research that has gone into Iowa's gizzard shad management is more than 11 years in the making. This was a plan of attack that was desperately needed. As you point out, bucket biology has affected us as anglers for a very long time, and as you are aware, it's not just shad. This project has lead to real solutions to gizzard shad and yellow bass introductions and other states are even using our work to move forward with similar programs, Nebraska, Kansas, and Kentucky to name just a few. The project we took on had two phases, a field phase where we performed this same kind of treatment on 19 lakes. The other phase involved a 2 year study in hatchery ponds to answer questions just like you posed, what percentage of game fish are impacted by these treatments.
Before I move on, there is one thing worth stating. It's a simple disclosure, but one I think people don't think of, or never consider. I am a fisheries biologist. However, I'm an angler, and a very avid one at that. The IDNR doesn't take steps to alter fish communities unless there are very good reasons to do so. We don't look at a problem and poke it with a stick. We have a plan, we research the plan, and we implement that plan. We treated shad back about a decade ago in Sugema. They were reintroduced again, illegally. They were gone, they returned. We have documented this. Sugema was treated at 5 parts per billion the first time around. It worked that time in Sugema, but in other lakes in the 19 lake study, treatments that were performed at less than 8 parts per billion were successful only about 50% of the time when it came to removing shad. Further, our hatchery pond study told us we could eliminate shad at 8 parts per billion with a MAXIMUM loss to largemouth bass of about 15%, Bluegills up to 20%,and crappie up to about 7%, while we expect total removal of all gizzard shad. The loss of game fish is disturbing when you see the fish along the shore, but from a population level, the impact is relatively small or even undetectable. I can go on about this for hours. The thing is, the total ecological underpinnings of this situation don't lend themselves well to text messages, emails, or even phone calls. It's a very complex situation, but I hope some of what I have said thus far has made sense.
In regard to "waiting a few years", I'll approach it as I did with another crappie angler I know from the area. I asked him, based on the idea that crappie loss will be relatively light from a population level, what is the benefit to waiting? There really isn't one. Meanwhile, largemouth bass recruitment continues to decline, bluegill quality remains very poor, we're still not able to manage for walleye or musky, water quality continues to suffer, and for much of the year angler attention continues to dwindle. Again, I appreciate your comments and I don't dismiss them at all. I'm just trying to express that this type of project is a big undertaking and unfortunately, there is always the potential for second guessing.
As I recall, you also asked about ponds in the watershed that may have gizzard shad. This is a valid concern. Specifically, there are 3 ponds that legitimately could have held shad that were in close enough proximity to the lake to deliver shad back to Sugema. We treated all three of these as well, prior to Sugema's treatment. We found shad in two of them. We knew they were in both by the way. Tug Fork West and a large wetland northwest of there also had them. Interestingly, we literally saw buffalo and shad moving up form Lake Sugema into the wetland last spring following a heavy rain event.
Steve, I hope I have addressed your concerns. I'm also attaching the email I spoke of earlier that will provide some additional background. Please come back in the spring. I do believe there will be fish to catch.
Mark
PREVIOUS EMAIL RESPONSE FOR YOUR REVIEW
I appreciate the opportunity to fill you in on our removal of gizzard shad from Lake Sugema. You may get a little more information than you requested, but I’m trying to be thorough with folks. As you suggested, there is a lot of rumor regarding this project and to be honest, it’s hard to head all of that off. This type of work doesn’t lend itself easily to Facebook posts, text messages, or short emails. I’ll do my best to explain the issue, how we arrived at the solution, and what you can expect for the future out of Lake Sugema.
In Iowa there is a history of illegal introductions of fish in a number of systems across the state. In this case, we are dealing with gizzard shad. While gizzard shad do have their place in some of our larger systems, they are not a good addition to most of our lakes across the state. In regard to how we know they were illegally introduced, there is no other method that realistically can result in this type of fish movement. Gizzard shad are a relatively fragile species and take some care to move. A few years ago we were battling this same issue at Lake Wapello near Drakesville, Iowa. At that time, an individual was questioned after taking credit for moving the shad to that system, not once, but twice. Unfortunately, nothing stuck in that case; however, it demonstrated that the issue was real.
Shad are a problem for two ecological reasons. First they have a very negative impact on the food web of our lakes and secondly, they negatively impact water quality. First, shad eat zooplankton, and lots of it. This plankton is the food for all very young fish, regardless of species. Without plankton we find that recruitment of fish (which means the number of fish that are hatched and survive each year) declines dramatically. That means that gamefish density (bass, bluegill, crappie, etc.) declines. There are some reasons why this is a bigger problem at the northern limit of the gizzard shad range (like Iowa), but the bottom line is, they reduce gamefish density. Even more importantly, they change the way that food moves through the ecosystem. There is a disconnect in the delivery of energy (which really means food here) from the bottom of the food chain (plants, phytoplankton, algae, etc.) to the top of the food chain (predators like largemouth bass) and everywhere in between (panfish like bluegill and crappie). Like I said, this is a difficult topic to explain via email or text message. I actually have a second job as a college instructor in Environmental Science and we can spend weeks discussing this sort of thing.
At any rate, there is less food available for many species at all life stages. Bluegill are the first species to show negative effects from gizzard shad introduction. However we eventually see signs up and down the food chain. Largemouth bass that are in the lake when the shad take off may actually show a slight increase in growth rates, which looks good to anglers at first. But what ends up happening is that bass recruitment goes down. This means we have fewer bass entering the population each year. So, we end up with a fairly high percentage of larger fish, but fewer fish overall. Because bass are the top level predator, this can have additional negative impacts on other fish like crappie and bluegill. Crappie are also negatively impacted eventually. The thing about crappie is, they are slower to show the negative effects. Crappie, unlike bluegill and redear sunfish, usually don’t produce a year class every year. In fact, if crappie are successful in pulling off a year class every 3 to 5 years, we are doing well. That’s why crappie fishing cycles. It goes through boom and bust years on most lakes, not just in Iowa. Eventually crappie numbers also will decline. As it happens, we just happen to be at a peak in crappie year class strength right now at Sugema, meaning we had great fishing this fall. For reasons I will continue to explain, there is no reason to assume that won’t happen again this winter or next spring.
Now, to explain the water quality angle. Gizzard shad eat zooplankton. These are microscopic animals that eat phytoplankton (plant plankton). When the shad eat this plankton they are not only starving the young fish that hatch each spring, they also allow phytoplankton blooms to go unchecked. This has a tendency to turn lakes more green than they normal, in other words, they reduce visibility. In addition, shad also eat detritus. This just means they eat dead leaves and plant material off of the bottom of the lake. This dead organic matter is the remnants of living plants that are decomposing on the bottom. When the shad eat this material they remove the nutrients (primarily nitrogen and phosphorus) in these dead leaves from the bottom of the lake where it is pretty much out of circulation. They resuspend it back up into the water column. Essentially they fertilize the water which then leads to even more phytoplankton growth, making the lake even greener and decreasing water clarity even more. This also can lead to a greater likelihood of summer kill.
I realize I just spent a great deal of time explaining what the problem is, but it’s important to get that information out there. The solution then comes in one of two paths. Traditional fish management would result in the DNR and the local community watching the quality of their fishery decline for a period of years. Eventually the entire fishery would decline dramatically. We have already noted large declines in bluegill and readear sunfish and big reductions in largemouth bass density at Sugema. Eventually, after years of declining angling opportunity, fewer angler visits, and declining economic return for the local community, a drastic solution would have to be sought. This normally involved the removal of the entire fish community. In other words, all fish would have to be removed and the lake would have to be restocked. This is an expensive path, not just for the costs associated with manpower and chemical costs to remove the fish, but even more importantly, the costs to the local economy brought about by the loss of angling and the time it will take the lake to recover after restocking. About 12 years ago the Iowa DNR began an intensive research study to evaluate a method to remove gizzard shad with minimal impacts to the gamefish population. This involved the use of rotenone, a natural botanical pesticide that is used to remove fish. The difference being, we apply at a rate that is less than 5% of what is normally used to kill all fish in the lake. We can do this because gizzard shad are more vulnerable to rotenone that most gamefish. As a part of this study that lasted more than 7 years, we treated approximately 20 lakes and did extensive testing in small ponds at the Rathbun Fish Hatchery. We were able to determine ideal treatment concentrations for the removal of gizzard shad while attempting to limit the impacts on gamefish. This type of treatment has gained popularity throughout the Midwest. Kentucky and Kansas, for instance, have aggressive programs modeled after ours with the same goal, to remove gizzard shad with minimal impacts to gamefish.
Throughout I have stated “minimal impacts”. What this means to us is that changes in the gamefish population will not result in large declines in gamefish abundance and angling quality. By treating just the shad, we can have relatively little impact and no long term issues with most species of gamefish in these systems. We know through our studies that some gamefish will die during these treatments. There is no way to completely mix all water in a 600 acre lake at one single moment. There will be an area of higher rotenone concentration as we apply. However, what I can tell you is that these gamefish losses are not sufficient to overly harm a population. I understand as an angler myself; it’s hard to see gamefish die with the shad. However, everything about this project parallels what we have seen at other successful projects from the past. When we come back next spring to survey the Lake Sugema fishery, we will find that the gamefish populations will remain relatively intact. We typically are unable to measure a decline in largemouth abundance or size quality. The same will hold true for crappie. Bluegill quality is already very poor at Sugema, and with the removal of shad, we expect bluegill quality to greatly improve next year alone. In short, everything is still here in Lake Sugema. Angling quality will remain good going into next spring and we will see improvements on multiple fronts as 2020 progresses.
I realize this is a long story, I hope you have made it this far. To answer your question about the lake level, the gate was closed on the day of the application. The lake was actually down 23 inches at that time and is continuing to refill now. When it fills is dependent on precipitation so it could be next spring before it fills, that will depend on Mother Nature.
I hope this information has been somewhat helpful and please feel free to share it with others you know who may be interested. Thank you and please let me know if you have additional questions.
Mark
