Curriculum designed by: Colleen Masterson Biologist & Education Director Inland Seas Education Association

Transcription

1 GREAT LAKES INVADERS ~ LAKE TROUT AND SEA LAMPREY CASE STUDY ~ TEACHER EDITION Curriculum designed by: Colleen Masterson Biologist & Education Director Tom Wessels Science Coordinator Traverse Bay Area Intermediate School District

2 GREAT LAKES INVADERS ~ Lake Trout & Sea Lamprey Case Study ~ Teacher Edition This Great Lakes Invaders curriculum unit has been designed as a tool for educators to guide their students through an exploration of the nature of the invasive species problem. The unit is comprised of five main lessons, focused on a case study of the relationships between the native lake trout (Salvelinus namaycush) and the invasive sea lamprey (Petromyzon marinus). Through this case study, students will be exposed to authentic data from Great Lakes scientists and be urged to make their own predictions and conclusions regarding trends in the data. The Great Lakes Invaders curriculum unit will guide your students through a process of discovery based on the ecological, economical and ethical questions surrounding the introduction and spread of invasive species in the Great Lakes. Lesson 1: The Fishin is Lousy!. 1 Lesson 2: Let s Learn About Lake Trout 4 Lesson 3: The Sea Lamprey Connection. 8 Lesson 4: Learning More About the Sea Lamprey. 13 Lesson 5: The Lampreys Are Here. Now What? 19 Michigan Curriculum Framework Science Content and Social Science Content Benchmarks Addressed by the Great Lakes Invaders Curriculum Sea Lamprey Fact Sheets, Great Lakes Fishery Commission. 32 We are interested in your feedback on this Great Lakes Invaders curriculum unit. Please phone, write or Christine Diana, Chief Scientist & Education Director at Inland Seas Education Association with any comments, questions or concerns regarding this curriculum unit, or with suggestions for the development of future Great Lakes Invaders curriculum units. Colleen Masterson Biologist/Education Director P.O. Box 218, Suttons Bay, MI (231) phone (231) fax CMasterson@GreatLakesEducation.org

3 Great Lakes Invaders Lesson 1: The Fishin is Lousy! Teachers Edition One of the most important ways we use the natural resources in our Great Lakes is by fishing. Some of us fish for recreation (sport fishing), while others make their living by catching and selling fish for food (commercial fishing). Throughout the history of the Great Lakes, one of the most important kinds of commercial fish has been the lake trout, Salvelinus namaycush. For years, lake trout were a dependable source of food in the Great Lakes. But, several decades ago, something happened to change all that. The data table below was compiled by the Great Lakes Fishery Commission and shows the amount of lake trout that were commercially caught from 1940 through Table 1. Commercial production of lake trout, Salvelinus namaycush, in thousands of pounds, in Lake Michigan. (Data taken from Great Lakes Fishery Commission) Year 1000 Pounds Caught

4 Questions: 1. What has happened to the amount of lake trout caught in Lake Michigan from ? The amount declined dramatically. 2. Sometimes, we can see changes and trends better when we make a graph of the data. Make a graph that shows the amount of lake trout caught in Lake Michigan from The year should go on the bottom (horizontal) or x axis, and the amount caught should go on the vertical or y axis. Commercial production of lake trout, Salvelinus namaycush, in thousands of pounds, in Lake Michigan catch (thousands of pounds) year 3. Why do you think there were fewer lake trout being caught from ? See if you can give at least three different hypotheses. Some possible answers may include: a. Disease b. Pollution c. They migrated to another location d. Loss of habitat e. Overfishing f. They ran out of food g. A similar fish was competing with them for food or habitat g. Predator 2

5 4. Choose one of your hypotheses from Question 3. How could you find out if it were correct? Is there an experiment you could do? What other information would you need? Write a plan below to test one of your hypotheses. Be prepared to share your ideas with the rest of the class. There are many possible answers. Students should first identify the kinds of information they will need. They should also compare data from before and after the lake trout decline. They may want to consult with experts from other locations. For example, if we thought a disease was killing the lake trout, we would first want to know which diseases lake trout were susceptible to. Then we may want to sample some of the fish that were caught and examine their bodies and tissues for signs of the disease. We may also want to check with people from other states and countries to see if lake trout were getting a disease there too. 5. In order for us to try to solve the mystery of why the lake trout were disappearing, we need to know more about them. For example, we don t know yet what lake trout eat. What else do you think would be important to learn about lake trout? What do they eat? What types of predators eat them? How do they reproduce? What habitat do they need? What kinds of diseases do they get? What kinds of fish compete with them for habitat and food? Do they migrate from one place to another? What is the fishing pressure like? Has it changed? Is the water in Lake Michigan becoming more polluted? 3

6 Great Lakes Invaders Lesson 2: Let s Learn About Lake Trout Teachers Edition Before we can figure out why the amount of lake trout in Lake Michigan declined between 1940 and 1960, we probably need to learn a lot more about them. At the end of the first lesson, you came up with several things about lake trout that you would like to know. In this lesson, we ll use those questions to help us learn more about lake trout. Here are a few informative websites you can use to learn more about lake trout: Department of Fisheries and Oceans Canada Alaska Department of Fish and Game British Columbia Ministry of Fisheries NOTE: These websites were chosen to provide a good background in lake trout life history without talking about the sea lamprey, which we want students to consider later. Since most Great Lakes websites do mention sea lamprey as the main cause of the decline in lake trout populations, you may want to restrict the students surfing to the websites above. As you surf through these four websites, try to answer as many of your questions from Lesson 1 as you can. In the process, make sure you find out about what lake trout eat, what kinds of habitat they need, what their life cycle is like, and how people fish for them. On a separate sheet of paper, write a 2-3 paragraph report about what you have found. Be prepared to share your information with the rest of the class. Depending on the size of your class, and the amount of time you have available, you may want to structure this lesson in one of several ways: Have students work individually, or in small groups of 2-3 students (this is probably preferable); Have all the students (or all the groups) look at all four websites; 4

7 Have each group investigate a different website; Have each group investigate a different aspect of lake trout (e.g. one group research food while another looks at reproduction, habitat, disease, etc.) It is important, if you re having different groups look at different aspects of lake trout life history, that the groups have the opportunity to share their findings with each other. This way, all students will have a good background to be able to continue with subsequent lessons. Here s a possible rubric you could use to evaluate their presentations: Criteria Apprentice Basic Meets Exceeds Completeness 1-2 basic 1-2 facts 3-4 relevant 3-4 relevant of Research facts w/ facts w/ facts, conconclusion conclusion clusions, & references Effectively unclear clearly clearly clearly Communicated presentation communicated communicated communicated w/ visual w/ multiple aid (e.g. poster) visual aids & handouts Ability to unable to answers answers answers Answer answer some most questions & Questions questions questions questions elaborates Questions: 1. Some of the internet information you studied came from other states or Canadian provinces. How might things be different for lake trout in those locations when compared to Lake Michigan lake trout? In some of these locations, food sources may be different (for example, lake trout in Alaska feed on grayling, which we don t have here in Michigan). Other factors such as habitat and climate may vary as well. 2. Two of the important food fish for lake trout in Lake Michigan are ciscoes (also known as lake herring), and rainbow smelt. If the numbers of lake trout in Lake Michigan decreased between 1940 and 1960 as you observed in Lesson 1, what do you think happened to the catch of ciscoes and smelt during that time? Explain why. 5

8 Some students may think that whatever was causing the decline in lake trout (e.g. pollution, habitat loss or disease) could also cause the populations of ciscoes and smelt to go down, which is a valid prediction. However, most students will likely conclude that since the lake trout population (the predator ) has gone down, the numbers of ciscoes and smelt (the prey ) will increase. 3. Below is a table showing the catch of lake trout, cisco and smelt from Do these data agree with your expectations from question 2? If not, can you describe a reason why? As you can see from these data, as the lake trout population decreased, the numbers (or at least the catch) of ciscoes and smelt increased. It s not important that students had the correct answer in question #2, but rather that, after considering the data, they can recognize the predator-prey relationship that exists and the population dynamics that result from it. Table 2. Commercial production of lake trout, ciscoes, and smelt, in thousands of pounds, in Lake Michigan. (Data taken from Great Lakes Fishery Commission) Year Lake Trout Ciscoes Rainbow Smelt

9 4. Make a graph showing the amount of lake trout, cisco, and smelt caught in Lake Michigan from Your graph should have 3 lines, one connecting the data points for each species of fish. Be sure to label each of these lines, and the x and y axis. Commercial production of Lake Trout, Ciscoes and Smelt in Lake Michigan from catch (thousands of pounds) lake t rout cisco smelt year 5. Conclusion: In general, what have you learned about the relationship between the populations of predators (like lake trout) and prey (like cisco and smelt)? In other words, as the number of lake trout decreased, what happened to the number of cisco and smelt? If, in the future, the number of lake trout increases, what would you expect to happen to the populations of cisco and smelt? In general, as the number of predators decreases, the number of prey increases, and vice versa. If the lake trout numbers were to rebound, we d expect the numbers of cisco and smelt to decline. 7

10 Great Lakes Invaders Lesson 3: The Sea Lamprey Connection Teachers Edition In Lessons 1 and 2, we studied lake trout populations in Lake Michigan. But, what about lake trout populations in the other Great Lakes? Since Lake Erie is not well suited to lake trout, there has never been an appreciable catch of lake trout there. In fact, other than 3000 lbs caught in 1980, Lake Erie shows no data for U.S. lake trout catch. For reasons we ll discuss later, we re not going to look at Lake Ontario yet either. We do have fishing data from Lake Huron and Lake Superior, though. Take a look at the following data table. Table 3. U.S. commercial production of lake trout, Salvelinus namaycush, in thousands of pounds, in Lakes Michigan, Huron, and Superior. (Data from Great Lakes Fishery Commission) Year Lake Michigan Lake Huron Lake Superior ? ? ? ? ? ? ? ? ? ? ? 120 8

11 Questions: 1. In Lesson 1, we looked at the decline in lake trout in Lake Michigan. From the data in Table 3, is Lake Michigan the only Great Lake that experienced a decline in lake trout populations between 1940 and 1960? No the data shows a similar decline in Lakes Huron and Superior. 2. Think back to Lesson 1. During which years did the lake trout population seem to decrease the most in Lake Michigan? From the mid-1940 s through How does this compare with the other Great Lakes? Did the lake trout population seem to go down around the same time in the other Great Lakes? If not, in which lake did we observe the lake trout decline first? Where was it last observed? In Lake Huron, the decline in lake trout occurred slightly earlier, through the 40 s. In Lake Superior, the decline occurred much later, dropping most dramatically in the late 50 s and early 60 s. During the time the lake trout populations were declining in the Great Lakes, many commercial fishermen noticed round scars on the sides of the lake trout and whitefish they did catch. Occasionally, a lake trout would be brought to the surface with a long, eel-like creature attached to it. These creatures were sea lampreys, aquatic vertebrates that are native to the Atlantic Ocean, but can live in both salt and fresh water. 9

12 Sea lampreys are primitive fish that have no jaws. Instead, they have a suction cup mouth filled with sharp teeth. They attach to fish, drill a hole in their skin and feed on their blood, usually killing the fish. Sea Lamprey mouth Sea lampreys were first noticed and described in the Great Lakes by naturalist Charles Fothergill, who observed them in a tributary of Lake Ontario in Sea lampreys are native to the Atlantic Ocean and can reach Lake Ontario through the St. Lawrence Seaway. However, they could not enter the other Great Lakes because of the Niagara Falls. Once the Welland Canal was built in 1829, and especially after it was enlarged in 1919, the sea lamprey had a much easier time moving up into the other Great Lakes. It is thought that the lampreys swam up through the lakes, although there is some evidence they may have attached themselves to the bottom of ships and travelled that way, too. Sea lampreys were later observed in Lake Erie in 1921, in Lake St. Clair in 1934, in Lake Michigan in 1936, in Lake Huron in 1937, and in Lake Superior in Use the map of the Great Lakes below to label the years in which sea lamprey were first discovered in each lake (including Lake St. Clair.) Draw arrows on the map that show the movement of sea lampreys through the Great Lakes system (from the earliest to the most recent year of discovery). How does this compare with the trend for the decline in lake trout (see Question #3)? Sea lamprey seem to be moving in an upstream direction from the St. Lawrence Seaway through the upper Great Lakes. It is interesting that lampreys were observed in Lake Michigan a year before they were seen in Lake Huron. This doesn t seem to make sense because they would have to go through Lake Huron to get to Lake Michigan. However, it s entirely possible that lampreys were present in each lake for a time before they were first sighted. The one-year difference between Lakes Michigan and Huron is probably not significant, although your students may initially think it s important. 10

13 Let s assume that the sea lamprey were causing the numbers of lake trout to decrease in the Great Lakes. From the data for Lakes Michigan, Huron and Superior, about how many years passed between the time sea lampreys first appeared in a lake and the resulting decline in lake trout populations? Why do you think there was such a delay? There seems to be a year time lag between the lampreys first sighting and the dramatic decline in lake trout numbers. Your students may come up with several reasons for the delay. Whenever an exotic species invades a new area, it may take several years for it to become established (if it ever does). In the next lesson, we ll learn about the lamprey s life cycle, in which they may spend up to 10 years in a sedentary larval stage and become parasitic only after they reach adulthood. 6. In order to fully understand how sea lampreys have affected the lake trout in the Great Lakes, we need to learn more about them. Remember that at the end of Lesson 1, we thought of several things we wanted to learn about lake trout. Now, let s do the same thing for sea lampreys. What do you think would be important to learn about sea lampreys? 11

14 Your students should brainstorm about some of the life history characteristics that would be important for them to learn about the sea lamprey. Many of these may be similar to the characteristics that they identified for lake trout at the end of Lesson 1. Most prominent will likely be exactly how the sea lampreys prey on lake trout. 12

15 Great Lakes Invaders Lesson 4: Learning More About the Sea Lamprey Teachers Edition At the end of Lesson 3, we tried to think of several questions we had about the sea lamprey. In this lesson, we ll try to answer those questions. As we did in Lesson 2, we ll use a few informative websites to help us learn more. Here are a few: Fish of the Great Lakes. Wisconsin Sea Grant Basic summary of sea lamprey characteristics, life history & control rch_invasive_fish USGS Great Lakes Science Center. Life of a sea lamprey, effects & control measures Sea Lamprey: the battle continues Thorough review of sea lamprey life history & control As you investigate these websites, try to answer as many of your questions from the end of Lesson 3 as you can. As you do, be sure to answer the following questions. 1. Where and when do sea lampreys usually lay their eggs? Sea lampreys usually lay their eggs in nests that they build in the tributaries of the Great Lakes in the spring/summer. Although migration to these tributaries lasts from April through July, the peak spawning occurs in June and July. Males initiate nesting in gravel beds. Females anchor themselves using their oral disc to a stone near the nest and the male wraps his body around the female, to enable the genital pores to be in close contact. The eggs from the female are fertilized externally (in the water) by the sperm of the male. Spawning occurs every 5-10 minutes and then the adults resume nest building. The spawning female on average produces 60,000 eggs, of which 13

16 approximately 14% are likely to be deposited into the nest. Once eggs have been deposited, they have a 90% chance of survival. 2. Describe the sea lampreys nest. The sea lampreys nest is built as a horseshoe-shaped ridge built in clean gravel with flowing water. Once the eggs are laid, they fall through the crevices of the nest and remain safe below the rocks. 3. What happens to the adult sea lampreys after their eggs are laid and fertilized? Both male and female sea lampreys die within days of laying their eggs. 4. After the eggs hatch, the young sea lampreys are called larvae, or ammocoetes. How big are the larvae? Where to they live? What do they eat? How long do they stay in this larval stage? Within days of hatching from the egg stage, tiny larvae drift downstream to areas with slower currents and sand/silt bottoms. Here they burrow in the stream bottoms and filter microorganisms from the water for food. The ammocoetes remain in this sedentary stage for 3-17 years (average 3-6 years). The ammocoetes reach a size of up to 120mm (4.7 inches) before metamorphosis. 5. What happens to the sea lamprey after it completes the larval life stage (ammocoetes)? Where do the adult sea lampreys live? What do they eat? How long do they spend in the adult stage? The ammocoete undergoes metamorphosis after completing its sedentary larval stage. The lampreys experience external changes, such as the development of functional eyes and a sucking oral disc lined with teeth. This is the beginning of the parasitic adult stage. The adults leave the streams and enter the Great Lakes. During this adult stage, the sea lampreys feed by attaching themselves to host fish with their oral discs and sucking blood and body fluids from the fish. The parasitic adult phase lasts from months. 14

17 6. Complete the figure on the next page that shows the four stages in the life cycle of the sea lamprey. For each stage, be sure to include the following: a. A picture (try to include the size or length); b. The habitat it needs; c. The food it eats; d. How much time it spends in that stage. 15

18 SPAWNING ADULT size: cm habitat: migrates upstream to spawn in gravel bed food: no feeding length of stage: less than 1 year PARASITIC ADULT size: rapid growth, cm habitat: open Great Lakes waters food: host fish such as lake trout, salmon, whitefish length of stage: mo. size: less than 6 mm habitat: gravel nest in stream with flowing water food: no feeding length of stage: 13 days EGG size: mm habitat: burrow in sandy or silty area of stream, low flow food: microorganisms from water length of stage: 3-17 years AMMOCOETE LARVA 16

19 7. About how long does the entire life cycle of a sea lamprey last? On average, the entire life cycle of a sea lamprey lasts 5-8 years, although it may be over 18 years. 8. Once we learned that the sea lamprey were killing many of the lake trout in the Great Lakes, we decided to try very hard to reduce the lamprey population. But first, we had to get an idea of just how many sea lamprey there were in the Great Lakes. Do you think it would be possible, or practical, to count all of the sea lampreys in the Great Lakes? Why? Here, your students will likely conclude that it is not practical to count all of the sea lampreys in the Great Lakes because of the difficulty in finding/catching them. 9. If you were going to try to estimate the number of sea lampreys in the Great Lakes, how would you do it? What would you look for? When would you look? Where would you look? What tools would you need? What groups of people could you ask to help? This question is designed to get students thinking about sampling methods for catching and/or counting sea lampreys. Should we count larvae, parasitic adults or spawning adults? Should we try to count them in the open lake, or when they are concentrated in a stream? These ideas will be explored further in the next lesson. Some tools that we may use would include nets, electroshocking, traps, decoys, etc. People to ask for help may include professors, government biologists, tribal biologists, commercial and sport fishermen, etc. 10. Finally, how do you think we could best reduce the numbers of sea lamprey in the Great Lakes? When would be the best time to try? Which stage in the sea lamprey s life cycle would be the most vulnerable? In the next lesson, we ll learn more about how scientists have tried to control the sea lamprey. Here your students may come up with a variety of control techniques, again based on dealing with sea lampreys in any of the 4 life stages they described above. A likely example would be catching adults in a net or trap and killing them. However, they will want to think about when the sea lamprey may be most vulnerable perhaps when they are in their sedentary larval stage in streams or when they are migrating into or out of the streams. In these cases, there are many lampreys concentrated together in one spot, in comparison with their expanded dispersal in the open lake as parasitic adults. Your students 17

20 may also come up with ideas on why one stage would be better to reduce than others for example, it may be best to kill the young eggs or larvae BEFORE they can become parasitic adults. On the other hand, it may be best to kill the adults before they are able to reproduce. The parasitic adult phase is the one that causes the most problems for Great Lakes fisheries, but exactly how to go about reducing these numbers may be a direct or indirect task. 18

21 Great Lakes Invaders Lesson 5: The Lampreys Are Here. Now What? Teachers Edition Lesson 4 could probably best be summed up by the phrase know your enemy. We learned about the various stages of the sea lamprey s life cycle, including the egg, larva, the parasitic phase adults and the spawning phase adults. We found that it is probably not practical to count every single sea lamprey in the Great Lakes. Instead, we have to use other methods of estimating, or assessing their populations. In this final lesson, we ll learn more about how we as scientists can try to assess the numbers of sea lamprey in the Great Lakes. We ll also learn how we re trying to control their numbers, and counteract the damage they ve caused to our Great Lakes fishery. NOTE: This lesson can be divided into 5 main parts: (1) assessment (2) control - TFM (3) control barriers (4) control sterile male release technique (5) synthesis. We recommend that the final synthesis portion of the lesson be completed by each student in the class. However, because of the large amount of material covered in this lesson, you may wish to split your class into small groups to explore the control methods. You may want to have 3 groups, in which case each group would explore one control method and share that information with the class through a presentation (in this scenario, all students/groups would explore the assessment and synthesis portion of the lesson). Alternatively, you may wish to have 4 groups, in which case one group will explore the assessment methods and the other 3 will explore the 3 control methods. All information would again be shared with the class so that all students have the background necessary to complete the synthesis section of the lesson. To learn more about how we control the sea lamprey, we will read several of the Fact Sheets from the Great Lakes Fishery Commission. Take a look at FACT SHEET 7: Sea Lamprey Assessment. 1. How do scientists try to count sea lamprey larvae? Scientists use a backpack electro-fisher to assess larval sea lampreys in shallow waters. This equipment delivers electricity to the stream water and stimulates the larvae out of their burrows. Where the larvae live in deep, hardto-reach waters, biologists stimulate larvae to the surface with a deep-water electro-fisher or with a granular formulation of the lampricide Bayer

22 2. How do they count parasitic-phase adults? Charter boats and commercial fishermen provide state, federal, tribal and provincial agencies with data on the occurrence of parasitic-phase sea lampreys in the open waters of the Great Lakes. These may be sightings of parasiticphase sea lampreys themselves, or evidence of the lampreys in the form of scars on host fish. 3. How do they count spawning adults? Scientists monitor adult sea lamprey spawning migrations in spring and early summer to estimate the number of spawning sea lampreys in selected Great Lakes streams. To monitor spawning sea lamprey migrations, mechanical traps are used to catch the sea lampreys and to measure their abundance from year to year. 4. What kinds of information are recorded during these assessments? Length, weight, age, sex, distribution. 5. How is this information used? The information is used to estimate how well larval sea lamprey populations grow and survive in each stream or offshore area, to better understand and predict the extent of damage to the fish communities caused by parasitic-phase sea lampreys, and to understand population characteristics of larval, parasitic-phase and spawning-phase sea lampreys. This information can then be used to help design and improve the methods for sea lamprey control. 6. Of the three assessment methods described larval assessment, parasitic-phase assessment, and spawning-phase assessment which of these do you think provides the most accurate data? Why do you think so? Students will most likely pick either the larval assessment or the spawninga phase assessment as the source of the most accurate data. In both of these cases, the sea lampreys are concentrated in a smaller geographical area, and more thorough assessment can be completed. The parasitic-phase assessment depends on the types of fish caught by charterboats and commercial fishermen, as well as their willingness to share such data with scientists. 20

23 Students may pick any of the 3 assessment methods, as long as they support their choice. 7. Suppose you are a scientist trying to assess parasitic adult sea lampreys. To do this, you will need the help of local commercial and sport fishermen. These people fish every day, and probably see more evidence of lamprey than you. Do you think it would be difficult to get these people to help you? What would you tell them in order to get their help? What kinds of information would you ask them to record for you? Students may or may not think that it will be difficult to get local fishermen to help them in their sea lamprey assessment. With a thorough explanation of the sea lamprey issue, many fishermen are naturally willing to help provide scientists with the data they need to better manage the sea lampreys. The sea lampreys prey on fish that are very important to the fishermen, so by helping scientists assess and reduce the number of sea lampreys, they are also helping their own livelihood. The fishermen would record sightings of sea lampreys themselves, and sightings of sea lamprey scars on host fish. Supporting data would include the time and location of the sighting, the length/age/weight of the lamprey, the number and severity of scars on host fish, etc. At the end of lesson 4, we tried to think of as many ways to control the numbers of sea lamprey as we could. Now, let s look at three main ways sea lampreys are currently being controlled in the Great Lakes. These methods are: chemical control with a lampricide called TFM, the sterile-male technique, and lamprey barriers. Note: If you are going to split your students into groups to explore the control methods, you should do so here. The first group will explore Fact Sheet 4 (TFM and Sea Lamprey Control), the second group will explore Fact Sheet 5 (Sea Lamprey Barriers) and the third group will explore Fact Sheet 6 (Sterile Male Release Technique). Read through FACT SHEET 4: TFM and Sea Lamprey Control. 8. What is the most vulnerable stage of the sea lamprey s life cycle? Sea lampreys are most vulnerable to chemical control during their larval stage. 9. What is TFM? How many chemical compounds were tested before TFM was discovered? 21

24 TFM is 3-trifluoromethyl-4-nitrophenol, which is remarkably effective in controlling sea lampreys without significantly impacting other species. Scientists tested almost 6,000 compounds before TFM was discovered. 10. Give at least three reasons why TFM is such an effective way of controlling sea lampreys. 11. TFM is selective for sea lampreys - at treatment levels, it is non-toxic to other fishes. Because treatments are carried out on an average 4-year rotation, populations of shorter-lived invertebrates, which may be affected, can recover between treatments. It targets the larval stage, and is used in streams when larvae are concentrated. It breaks down in a matter of days, and therefore does not bioaccumulate in the aquatic environment. Are all of the streams leading into the Great Lakes treated every year with TFM? Why or why not? About 250 Great Lakes tributaries are treated at regular intervals with the lampricide. Tributary streams to the Great Lakes where larval sea lampreys are found are treated at three to ten year intervals, depending on the abundance, rate of growth, and age of the populations. Larval sea lampreys are usually not found throughout an entire stream, so lampricide treatments target only infested areas within a stream. Not all streams leading into the Great Lakes are treated every year with TFM, because not all streams have sea lampreys in them, it would be very expensive to treat each stream each year, an d a gap of several years allows invertebrate populations that may have been affected by the lampricide to recover. Perhaps most important, however, is the life cycle of the sea lampreys themselves. Because of the length of time that the ammocoetes remain in the streams, it is possible to treat the stream every few years. For example, if the stream was treated every 3 years, larvae that are any age from less than a year up to 3 years would be affected by the treatment. There is no need, therefore, to treat every year (since the ammocoetes will be there for at least 3 years). 12. How effective has TFM been in controlling sea lampreys? Remarkably effective sea lamprey populations in the Great Lakes have been successfully reduced by 90%, due to the use of TFM. However, now that they are here, we are unlikely to be able to completely wipe them out (based on previous pest management efforts). 22

25 Read FACT SHEET 5: Sea Lamprey Barriers. 13. What is a sea lamprey barrier? 14. Sea lamprey barriers are constructed on streams in strategic locations throughout the Great Lakes basin to prevent sea lampreys from spawning, and thus, to effectively reduce the number of streams that produce sea lampreys. Give at least three advantages or benefits of using sea lamprey barriers when compared to the use of TFM. The benefits of barriers include savings in lampricide costs, decreased application costs and more efficient sea lamprey control. Trapping facilities associated with barriers allow removal of sea lampreys from the spawning population, provide assessment information and provide male sea lampreys for the sterile-male-release technique. 15. Draw a picture of, and briefly describe the four main types of barriers used by the Great Lakes Fishery Commission: Refer to the pictures on Fact Sheet 5 for student drawings of sea lamprey barriers. a. Low Head Barriers The low-head barrier is the most common type of barrier used on the Great lakes to prevent sea lamprey spawning. This relatively simple barrier creates a two to four foot drop that stops sea lampreys from proceeding further upstream. A lip is often used to keep sea lampreys from using their suction cup mouth to climb over the barrier. b. Adjustable-crest Barriers Adjustable-crest barriers draw upon the best aspects of the low-head barrier design and add improvements that make the barrier less intrusive, enhance passage of fish and still prevent sea lamprey passage. These barriers have air bladders that inflate an adjustable barrier crest. This crest is raised only during the sea lamprey spawning runs; it remains lowered on the river bottom during all other times of the year, permitting free passage of all species of fish. 23

26 The air bladder is controlled by a computer which automatically adjusts that barrier height based on specific water levels, thus minimizing the alteration of the river s natural flow. c. Velocity Barriers Sea lampreys are poorer swimmers than most fish. They tire easily and need to attach to solid surfaces in order to rest. Velocity barriers exploit this poor swimming ability by creating areas of very fast moving water with surfaces to which sea lampreys cannot attach. The result is a fish pass through which fish can swim, but through which sea lampreys cannot. These experimental structures have been effective in passing a variety of jumping and non- jumping fish species. d. Electrical Barriers Some of the first barriers used to control sea lampreys used alternating current (AC) electric power, but the barriers at the time were ineffective because they were often flooded and were plagued by power outages. Today, sea lamprey control agents are experimenting with entirely new electrical barrier designs that use direct current (DC) electric power to deter sea lampreys without risk to other fish or animals. These barriers are built into the stream bed and, in contrast to the low-head dams, do not block the flow of a stream at all. Electrical barriers are used only during the sea lamprey spawning runs and, where required, can utilize improved fishways to enhance passage of fish. Read FACT SHEET 6: Sterile Male Release Technique. Keep in mind as you read this sheet that a sterile male is one that does not produce viable sperm cells, even though he may go through the spawning process. Therefore, any eggs produced by the females he mates with will not hatch and produce larvae. 16. How are the male sea lampreys caught? The sea lampreys are caught in lamprey traps that have been placed in strategic locations on Great Lakes tributaries. 17. Once they are caught, how are they sterilized? The sea lampreys receive a carefully measured dose of bisazir, a sterilant. They are then marked with a fin clip and are kept for 48 hours, which allows 24

27 the bisazir to completely clear from their system. The sterilized male sea lampreys are then released. 18. According to the fact sheet, about 25,000 male sea lampreys are caught each year in traps. If you had the choice between destroying these lampreys, or sterilizing and then releasing them, which would you choose? Give a reason to support your answer. As mentioned in the fact sheet, many people wonder why we sterilize some sea lampreys and release them back into the Great Lakes, rather than just destroying them. First of all, it is important to remember that all of the males collected for this procedure are spawning males so they are past their parasitic phase and will no longer prey on Great Lakes fish. Scientists believe that releasing sterilized male sea lampreys back into the Great Lakes may actually reduce the number of sea lampreys produced in Great Lakes tributaries. The sterilized males may out-compete the normal males to mate with females, producing nests of infertile eggs. Without the sterilized male sea lampreys competing during the spawning run, all spawning would be done by normal males. Note: This is where the synthesis portion of the lesson begins. If you have had your students working in groups to explore the control methods, this is where you will want each group to share their findings with the entire class. Have each student or group of students complete the rest of this lesson in order to bring all of the previously-introduced concepts together and conclude the overall Great Lakes Invaders unit. We ve studied three main methods of controlling sea lamprey numbers in the Great Lakes. Let s see how they all work together. 19. If you were managing the Great Lakes fishery, which method of sea lamprey control would you devote the most time and money to lampricides, sterile males, or barriers? Students may choose any of the three control methods for their greatest allocation of time and money, as long as they support their position with information gathered in the previous sections of this lesson. For example, students may select the use of lampricides, because of the great success rate of this control method. However, other students may select the use of barriers because it is a single investment rather than spending resources (monetary and manpower) to continue lampricide control measures. Students may come up with other reasons for choosing a particular method for example students may not like the idea of the sea lamprey barriers because they may interfere 25

28 with recreational boating or canoeing in the area. Some thought should be given to the use of several of the control measures together. 20. Do you think it will ever be possible to eliminate all the sea lampreys in the Great Lakes? Why or why not? Theoretically, with enough money and manpower it seems as though we mght be able to eliminate all of the sea lampreys in the Great Lakes. However, this is very unlikely. There will always be some small proportion of sea lampreys that escape barriers, spawn in unusual areas, or are resistant to lampricides. Just think of our track record for wiping out other pests (examples range from crabgrass to human diseases) control measures must continue. 21. According to the Great Lakes Fishery Commission, the annual cost of sea lamprey control is nearly $9 million. Do you think this is a worthwhile investment? Why or why not? Make a pie graph, showing how you would allocate this $9 million to (a) lampricide, (b) lamprey barriers and (c) the sterile male release technique. This question will allow students to think about the economic impacts of invasive species like sea lampreys and consider how big of an investment they would be willing to make for sea lamprey control. How much is the fishery of the Great Lakes worth in a monetary sense, an ecological sense and a cultural sense? How much money should we spend on repairing the damage done by invasive species? A few numbers you may want to use with your students in an economic discussion: 1999 commercial dockside value of catch (not including processing, etc.): $9.5 million, $7.7 million of which is whitefish (also negatively affected by sea lamprey); estimated economic impact of recreational fishing in 1996 was $2.85 billion. These numbers give us an idea of the relative importance to the economy of commercial and recreational fishing. The actual breakdown of the nearly $9 million for lamprey control, according to the Great Lakes Commission is as follows: ( a) $6.7 for TFM; (b) $1.5 for barriers, and; (c) $485,000 for the sterile male release technique (see pie graph below). Compare this breakdown with that of your students. 26

29 Sterile males $485,000 Barriers $1.5 million Lampricide $6.7 million Even though these methods of controlling sea lampreys have been quite successful, over the years, the numbers of lake trout had become very low. We had hoped that, once the sea lamprey were under control, the remaining lake trout would begin to naturally reproduce, and their numbers would increase to their previous levels. But, this didn t happen. So, to help increase the numbers of lake trout, we began raising young lake trout in hatcheries, and then releasing them into the Great Lakes. Again, we had hoped these lake trout would begin reproducing on their own. But, for some reason, this has not hap pened yet. For example, although we stock large numbers of lake trout in Lake Michigan, there are currently thought to be no naturally reproducing lake trout there Looking back on the situation, which do you think would have easier (and cheaper), preventing the sea lamprey from getting into the Great Lakes, or trying to control them once they arrived? An ounce of prevention is worth a pound of cure. Do you think we knew 100 years ago, the kind of damage sea lampreys could cause to our Great Lakes fishery? How might things have been different if we had known? We certainly did not know the kind of damage that sea lampreys could cause to our Great Lakes fishery. Students may begin to think of the unforeseen consequences of modifying our environment in many ways (in this case through canal-building). What would we have done differently if we had known the damage that the sea lampreys would cause, though? Would we not 27

30 have built the canals in the first place? Could we really give up the tremendous amount of commerce that depends on the shipping routes the canals provided? 24. Why is it important for scientists to study other invasive species? Why is it important for us to try and prevent the introduction and spread of new invasive species? After completing these 5 lessons, the students should have some well-thought responses for this question. We need to study invasive species to determine the possible extent of their effects on the natural ecosystem and to understand their life history well enough to develop effective control programs. After understanding this lake trout sea lamprey story, it should be clear to the students that it is MUCH easier nowadays to prevent the introduction and spread of new invasive species than to actually try to control or eliminate them once they have arrived in our Great Lakes. 25. FINAL PROJECT: Let s suppose that the government has recently proposed that the state of Michigan add $1 to the price of every fishing license sold. The generated income from this price increase would be used for sea lamprey control. Many fishermen are upset about this new price increase. In your groups, create a second radio or television commercial to convince the fishermen in the State of Michigan that their money is going to be well spent. Each group will perform their commercial in front of the entire class. Remember you have to be convincing! This final project will give students a chance to summarize all they have learned in the 5 lessons of the Great Lakes Invaders unit into a clear, concise second commercial designed to reach the fishermen of the State of Michigan. Students should use some of the major concepts that they have explored throughout the lessons and present their argument in a clear, organized and creative manner. You may want the class as a whole to choose the most convincing commercial after each group has performed, as a fun conclusion to the unit. 28

31 MICHIGAN CURRICULUM FRAMEWORK SCIENCE CONTENT AND SOCIAL SCIENCE CONTENT BENCHMARKS The Great Lakes Invaders curriculum addresses the following Michigan Curriculum Framework Science Content and Social Science Content Benchmarks for students at the elementary, middle and high school levels: I. ELEMENTARY SCHOOL Science Benchmarks Generate questions about the world based on observation Develop solutions to problems through reasoning, observation, and investigations. Develop strategies and skills for information gathering and problem solving. Construct charts and graphs and prepare summaries of observations. Develop an awareness of the need for evidence in making decisions scientifically. Show how science concepts can be illustrated through creative expression such as language arts and fine arts. Develop an awareness of and sensitivity to the natural world. Describe life cycles of familiar organisms. Compare and contrast food, energy, and environmental needs of selected organisms. Explain how physical and behavioral characteristics of animals help them to survive in their environments. Identify familiar organisms as part of a food chain or food web and describe their feeding relationships within the web. Describe positive and negative effects of humans on the environment. Social Studies Benchmarks Describe how people use the environment to meet human needs and wants. Describe the ways in which their environment has been changed by people, and the ways their lives are affected by the environment. Suggest ways the people can help improve their environment. Explain basic ecosystem concepts and processes. Describe the location, use, and importance of different kinds of resources and explain how they are created and the consequences of their use. Describe the Great Lakes ecosystem, and explain physical and human processes that act upon them. Locate information using people, books, audio/video recordings, photos, simple maps, graphs and tables. Organize social science information to make maps, graphs and tables. 29

32 II. MIDDLE SCHOOL Science Benchmarks Generate scientific questions about the world based on observation. Design and conduct scientific investigations. Use sources of information in support of scientific investigations. Evaluate the strengths and weaknesses of claims, arguments, or data. Describe limitations in personal knowledge. Show how common themes of science, mathematics and technology apply in real-world contexts. Develop an awareness of and sensitivity to the natural world. Describe common patterns of relationships among populations. Predict the effects of changes in one population in a food web on other populations. Describe the likely succession of a given ecosystem over time. Explain how humans use and benefit from plant and animal materials. Describe ways in which humans alter the environment. Describe how surface water in Michigan reaches the ocean and returns. Social Studies Benchmarks Locate, describe, and compare the ecosystems, resources and human environment interactions of major world regions. Explain the importance of different kinds of ecosystems to people. Explain how humans modify the environment and describe some of the possible consequences of those modifications. Describe the consequences of human/environment interactions in several different types of environments. Describe how social and scientific changes in regions may have global consequences. Use traditional and electronic means to organize social science information and to make maps, graphs, and tables. Interpret social science information about he natural environment and cultures of countries from a variety of primary and secondary sources. III. HIGH SCHOOL Science Benchmarks Ask questions that can be investigated empirically. Design and conduct scientific investigations. Gather and synthesize information from books and other sources of information. Discuss topics in groups by making clear presentations, restating or summarizing what others have said, asking for clarification or elaboration, taking alternative perspectives, and defending a position. Describe some general limitations of scientific knowledge. Show how common themes of science, mathematics, and technology apply in real-world contexts. Explain the social and economic advantages and risks of new technology. Develop an awareness of and sensitivity to the natural world. 30