Lake Istokpoga Chapter 2 1-28-19

Background and history of Lake Istokpoga habitat management

Aristotle (384—322 B.C.E.): “There is no time apart from change”

Geologic History of Florida leading to Geology of Highlands/Polk County surrounding Lake Istokpopga:

Geologists estimate the age of the Earth at more than 4.5 billion years. The Florida plateau, which is the platform upon which Florida is perched, was formed about 530 million years ago by a combination of volcanic activity and marine sedimentation during the early Ordovician Period. When the Florida plateau was part of the supercontinent, Florida was sandwiched between what were to become North and South America and Africa. Movement of the tectonic plates that compose the Earth’s crust eventually caused split into Laurasia (North America, Europe, and portions of Asia) and Gondwana (South America, Africa, India, Australia, and Antarctica). When North America split from Laurasia and drifted northwesterly, it dragged the Florida plateau with it.

During the glacial periods (110,000 to 15,000 years ago) sea levels fluctuated hundreds of feet having a profound effect on formation of Florida’s geology and resulting ecology. The changing sea levels influenced the formation of bedrock, soils, and surface topography. These geological factors influence the formation of lakes and the fertility of the soils within the lakes watersheds. Many lakes in Highlands County including Lake Istokpoga are nutrient rich, located in the Kissimmee/Okeechobee Lowland where the geology is dominated by undifferentiated sand, shell, clay, marl, and peat of the Holocene (Griffith et al 1997).

Settlement History of Florida leading to the creation of Highlands County Florida:

• 1565 The Spanish founded St. Augustine, the first permanent white settlement in what is now the United States. Pensacola was founded by the Spanish in 1698, but there was little significant European settlement in Florida until the late eighteenth century. • 1763: At the close of the Seven Years' War (French and Indian War), Britain gained control of Florida. Settlers from Europe and the American colonies to the north began to move into the area. The provinces of East Florida and West Florida were formed. • 1783: Most of the British settlers left when Spain regained the Florida’s. • 1812: The United States annexed portions of West Florida to Louisiana and the Mississippi Territory. • 1812, 1816 and 1817: Seminole Indian Wars (Osceola; Seminole Chief 1804-1838) • 1819: Spain ceded the remainder of West Florida and all of East Florida to the United States for $5,000,000. Official United States occupation took place in 1821. • 30 March 1822: Florida Territory organized. • 18 September 1822: Treaty of Fort Moultrie between the United States and the Seminole Indians. • 1835-1842: The Second Seminole War was caused by reaction to the Treat of Payne's Landing (1832) and the attempts by the U.S. to remove them from Florida. The Seminole's, led by Chief Osceola, Wild Cat, Alligator and Aripeka, conducted a guerrilla war. Over 1,500 U.S. troops lost their lives. • 1842: At the close of the Seminole War, most of the Indians were removed west to present-day Oklahoma, but a few hundred escaped into the swamps. • 3 March 1845: Florida became a state. • 1861: Florida seceded from the Union. It was readmitted in 1868.

• 1870-1900 The post-Civil War boom brought many settlers to Florida, as developers from the north built railroads and resorts. • 1911: The Hollywood Indian Reservation was established for the Seminole Indians. • 1921-1925 The last 13 of the state's 67 counties were organized as the Florida land boom attracted new settlers from the north. • 1921--Highlands County was created 23 April 1921 from DeSoto County.

Starting around 1910, Lake Istokpoga’s first settlers began to lay down their roots along the marshy Northeast shore of the lake. While many towns in Florida were started by skilled real estate developers with capitalistic dreams of striking it rich, the first towns started around Lake Istokpoga were not. The first town of Lorida was comprised of cowboy homesteaders seeking the country life, building their own version of Eden on the edge of the Everglades. After the first settlers arrived came the ultimate need to adjust the land and water to make life easier and populations within the whole county began to grow. According to the US Decennial Census the population of Highlands County has increased from approximately 9,200 in 1930 to an estimated 100,100 in 1916 (Table 1).

Year Population 1930 9,192 1940 9,246 1950 13,636 1960 21,338 1970 29,507 1980 47,526 1990 68,432 2000 87,366 2010 98,786 Est. 2016 100,917

Table 1. Population statistics for Highlands County, FL from the US Decennial Census.

Lake Istokpoga Location, Physical Description, Rainfall, Water Level/Hydrology and Land Use

This brief description of Lake Istokpoga is not meant to be all inclusive but enough information to give the reader background for evaluating an aquatic plant management plan being developed for Lake Istokpoga. A more complete description Lake Istokpoga’s surroundings can be found in in a report entitled “Minimum Flows and Levels for Lake Istokpoga” developed by the South Florida Water Management District (Zahina et al. 2005). The report can be downloaded using the following web site link: https://www.researchgate.net/publication/305316159_Minimum_Flows_and_Levels_for_Lake_Istokpoga.

The Lake Istokpoga basin is located northwest of Lake Okeechobee in central Florida and is within the Kissimmee Basin Planning Area (SFWMD 2000) (Figure 1). The Lake Istokpoga basin drains an area of approximately 920 mi2 (Milleson 1978) within Highlands and Polk counties. Approximately two-thirds of the basin is within the Southwest Florida Water Management District (SWFWMD), while the remaining portion of the basin and all of the lake itself are within the SFWMD. Lake Istokpoga resides within the Kissimmee/Okeechobee Lowland Region, and the Lake Wales Ridge borders it to the west (White 1970).

Figure 1. Major Landscape Features in the Lake Istokpoga Vicinity, from SFWMD 2000.

Lake Istokpoga is Florida’s fifth-largest lake, at approximately 27,000 acres; the lake is shallow, with an average depth of roughly 4 feet (McDiffett 1981). Direct rainfall combined with tributary inflows from Josephine and Arbuckle creeks input to Lake Istokpoga and waters are directed either to the Kissimmee River or Lake Okeechobee through a system of canals and water control structures. The S-68 and the G- 85 provide control of Istokpoga’s water levels (Figure 1). The S-68, which was constructed in 1962 and became operational that same year, is a gated water control structure that discharges outflows into the C- 41A Canal to the south. Water is generally routed to the Kissimmee River and/or Lake Okeechobee (Figure 1). Historically, Istokpoga Creek, paralleling today’s Istokpoga Canal, provided the only means for channelized outflow from the lake, and significant quantities of overland (sheet) surface water once flowed toward the Kissimmee River and Indian Prairie during times of high water levels.

Lake Istokpoga is a unique regional resource in several ways. It is an important source of water supply for agricultural lands located southeast of the lake (Indian Prairie). The scenic beauty of the lake has encouraged the establishment of waterfront residences along the northern and eastern shores. The lake is recognized as one of the top fishing lakes in the state of Florida, and several annual bass fishing tournaments are held there, providing significant benefit to the local economy. Waterfowl hunting is a popular sport on the lake and its fringing marshes. Remnant cypress swamps are found along the western half of the lake, providing important habitat for wildlife. Bird watching is also a significant activity.

Rainfall on a lakes watershed is the primary factor determining water levels in most lakes. Rainfall at Avon Park near Lake Istokpoga averages approximately 50 inches a year and ranges from less than 30 inches/year to over 80 inches/year. This rainfall variation caused Lake Istokpoga to fluctuate almost 7.5 feet prior to man’s attempt to stabilize the water levels.

The US Geologic Society has maintained a continuous record of Lake Istokpoga’s water level since 1936 (Figure 2). Prior to any water level manipulations (1936 to 1962) the water level in lake Istokpoga fluctuated approximately 7.5 ft from 35.4 ft Mean Sea Level (MSL) to 42.9 ft MSL (South Florida Water Management District 2005; Report on Minimum Flows and Levels). In 1948 the G-85 water control structure was constructed on the Istokpoga canal maintaining higher water during drought situations. By 1962, the flood control canal was completed allowing water to flow southeast to Lake Okeechobee and the Army Corps of Engineers completed the S-68 water control structure on Istokpoga. After these water level manipulations and until 1989, Lake Istokpoga’s water level never exceeds 40 ft. MSL and only occasionally dropped below 37 ft. MSL (approximately 3.9 ft. fluctuation). After 1989, the US Army Corps of Engineers revised the water level schedule in response to stakeholder’s complaints about access during drought situations and the new schedule allowed the lake fluctuated only about 2.7 ft. The extreme lows shown in 1962 and 2001(Figure 2) were actually managed drawdowns, the first to install the S-68 structure and the second to scrape and remove accumulated muck in the littoral zone.

Figure 2. Monthly mean water level for Lake Istokpoga from 1936 to 2016.

Water level fluctuations and stabilization within lakes can have a large impact on the ecology of Florida lakes (Hoyer et al 2005, Florida LAKEWATCH 2017). Many mechanisms are affected by water level fluctuations. For example, when water levels decrease due to drought situations nutrients in some lakes

4 can increase while decreasing in others. Nutrients can increase due to increased sediment resuspension and in some lakes can decrease because more light can penetrate to the bottom increasing the abundance of aquatic macrophytes, which decrease open water nutrients (Hoyer et al. 2005). On the other extreme, stabilizing water levels in lake systems can cause the development of large littoral zone of aquatic vegetation, which can both trap and create organic matter dramatically increasing the buildup shoreline muck (Florida LAKEWATCH 2017). Lakes that fluctuate naturally tend to move organic matter out of a lake during extremely high-water levels and oxidize organic matter at extreme low water levels both mechanisms tending to maintain cleaner shorelines. Lakes with stabilized water levels tend to accumulate organic matter in the littoral zone allowing emergent vegetation like cattail and pickerel weed to grow well because aquatic plants tend to get most of their nutrients from the sediments and these nutrients are more available in organic sediment than mineral sediments. Thus, the more organic sediments, the more aquatic plants, which create and trap more organic matter expanding the littoral zone and creating more muck dominated shorelines.

This water level stabilization was most probably responsible for the accumulation of muck that caused the Florida Fish and Wildlife Conservation Commission to draw Lake Istokpoga down in 2001, scraping and removing muck from about 1,300 acres of the littoral zone. For example, Figure 3 shows the buildup of muck and emergent vegetation at the mouth of Arbuckle Creek draining into lake Istokpoga from 1958 to 2017. The consecutive (1944 to 2001) aerial photographs of Lake Istokpoga in Appendix I also clearly show the extensive expansion of littoral zone after water level stabilization occurred in 1962. The 1944 picture shows the clearly defined shoreline and littoral zone while the picture in 1999 shows the large expansion of whole lake’s littoral zone and especially the expansion around the islands in the south part of the lake.

Arbuckle Creek Lake Istokpoga 1958 and 2017

Figure 3. Aerial photographs take in 1958 and 2017 of the mouth of Arbuckle Creek which drains into Lake Istokpoga.

Similar aerial photographs and rapid expansion of littoral muck accumulation after water level stabilization can be found for Lake Tohopekaliga (Hoyer et al. 2008). This accumulation of muck caused 5 a similar whole lake muck removal projects for Lake Tohopekaliga. Recently, Hoyer et al.( 2017) estimated the muck accumulation rates for lake Tohopekaliga approximately 50 years prior to the muck removal program in 2004 and again 10 years after muck removal and found a significant decrease in sediment accumulation rates from 1.00 cm/year to 0.22 cm/year. One reason for the decrease in sedimentation rate during recent decades was attributed to the maintenance control of water hyacinths. In tanks studies water hyacinths left uncontrolled produce three times as much organic matter as water hyacinths managed at less than 25% coverage in the tank (Joyce 1992). It was not until the late 1980’s that the State of Florida aggressively managed water hyacinths (Figure 4) and until then large mats of unchecked water hyacinths were producing incredible amounts of organic matter on most of the big lakes in Florida.

Figure 4. Estimates of water hyacinth abundance over time using statewide data from Florida’s Bureau of Aquatic plant Management surveys.

A similar problem existed in lake Istokpoga prior to the 1980’s. Water hyacinths have been abundant on lake Istokpoga since they arrive in the state as the pictures in Figure 5 show. Florida’s Aquatic Plant Control Program was developed with Department of Natural Resources (DNR) in the mid-1980’s and the DNR worked with Highlands County to take over as the water hyacinth control program contractor in the mid-1980s from the South Florida Water Management District. The District managed hyacinth out of the Okeechobee Office, but could not get to Lake Istokpoga as often as needed for maintenance control, thus abundant water hyacinths were on Istokpoga for almost 80 years contributing to the acceleration of organic build up.

Figure 5. Pictures of abundant water hyacinths in Lake Istokpoga on Arbuckle Creek in 1918 and Istokpoga Canal 1920.

The existing land use in the Kissimmee Basin Planning Area is generally more urban in the north than in the south. Continued urbanization is anticipated in the north, while in the south, agriculture land use in Highlands, Glades and Okeechobee counties is projected to increase through 2020 (SFWMD 2000a). This projection reflects the general migration of the citrus industry to more southerly locations following the severe freezes of the 1980s. Land use within Highlands County and the Lake Istokpoga watershed is 7 predominantly agricultural. The main agricultural types are pasture lands (including rangeland, which typically is not irrigated), citrus, cropland (including row crops and some sugarcane production), and ornamental landscape plants (“other”). Sugarcane is also a growing form of agriculture in Highlands County and production is expected to increase to 15,300 acres by 2020. Recent research examining the impacts different land uses can have on water quality of Florida lakes indicates that lakes with larger amounts of agriculture tend to have higher nutrient concentrations (Xiong and Hoyer 2018). These elevated nutrient concentrations can also increase algal abundances which can also contribute to increases organic sedimentation.

With increases in agricultural practices and the continued use of herbicides some individuals are concerned about accumulations of pollutants in the sediments that may be causing environmental impacts. Addressing these concerns, Florida Department of Environmental Protection routinely samples sediments from Florida’s public lakes and analyzes them for some pesticides, nutrients, metals, organics and other compounds. Istokpoga is one of the lakes that has been sampled in nine different years between 2007 and 2017. Comparing the average sediment chemistry found in lake Istokpoga to the average sediment chemistry from 72 other Florida lakes shows that for every parameter Istokpoga sediment chemistry is less than the mean for all other lakes. These data suggest that the sediment chemistry in Lake Istokpoga is not elevated in the 21 parameter listed in Table 2.

Lake Istokpoga Florida Lakes Parameter Units Samples Mean Number Mean Min Max 2,4-D Sediments ug/kg 2 22.4 23 34.2 4.3 180.0 Aluminum Sediments mg/Kg 37 8690.3 72 22056.5 740.0 90600.0 Arsenic Sediments mg/Kg 37 2.4 72 5.3 0.4 23.8 Cadmium Sediments mg/Kg 37 0.2 72 0.6 0.1 2.4 Carbon, Total Sediments % C 37 16.5 72 15.5 0.3 50.0 Chromium Sediments mg/Kg 37 12.2 72 30.6 6.2 99.9 Copper Sediments mg/Kg 37 7.2 72 21.4 0.6 162.0 DDD (p,p') Sediments ug/Kg 24 1.6 48 5.6 0.0 67.0 DDE (p,p') Sediments ug/Kg 24 2.1 48 11.2 0.0 200.0 DDT (p-p') Sediments ug/Kg 24 2.3 48 7.0 0.1 67.0 Dieldrin Sediments ug/Kg 24 0.8 48 2.2 0.2 9.1 Inorganic Carbon, Sediments % C 37 0.1 72 0.2 0.1 3.2 Iron Sediments mg/Kg 37 6477.4 72 10438.0 279.0 48503.3 Lead Sediments mg/Kg 37 9.7 72 38.6 0.9 273.0 Mercury Sediments mg/Kg 37 0.1 72 0.1 0.0 0.5 Methymercury Sediments mg/Kg 10 0.0 54 0.0 0.0 0.0 Nickel Sediments mg/Kg 37 5.0 72 10.5 0.8 26.3 Organic Carbon, Sediments % C 37 16.5 72 15.4 0.2 50.0 Phosphorus, Total (as P) mg/Kg 37 638.3 72 1139.6 38.7 8962.5 Sediments Total Kjeldahl Nitrogen, Total mg/Kg 37 10133.5 72 12524.1 330.0 53000.0 (as N) Zinc Sediments mg/Kg 37 18.6 72 64.6 5.1 641.0

Table 1. Comparison of Lake Istokpoga Sediment samples to sediments samples from 72 Florida lakes. Not all parameters were measured on all Florida lakes. Data are from Florida Department of Environmental Protection.

Lake Istokpopga Water Chemistry:

Florida LAKEWATCH is a volunteer water quality monitoring program that has been monitoring Lake Istokpoga since 1996. LAKEWATCH has been sampling northern (Istokpoga North 1, 2, and 3) and southern (Istokpoga 1, 2 and 3) parts of the lake (Figure 6) and they monitor total phosphorus, total nitrogen, chlorophyll, color, specific conductance, and water clarity measured with the Secchi Disk. Appendix I is a summary report provided by LAKEWATCH showing the means and ranges of water quality data for Istokpoga North and Istokpoga and how it relates to the Florida Department of Environmental Protections (FDEP) numeric nutrient concentrations. The reports also present an analysis determining if there are any trend in the data and the time series are plotted in Figures 7 through 11.

Figure 6. Location of the Florida LAKEWATCH water quality monitoring stations.

Lake Istokpoga is classified as a colored lake because the average color for the lake exceeds 40 Pt-Co units (Figure 6), which means the water is darker than the general color of ice tea. The long-term mean chlorophylls for Istokpoga (43 µg/L) and Istokpoga North (41 µg/L) exceeded FDEP’s chlorophyll standard of 20 µg/L set for colored lakes. Average total phosphorus and total nitrogen concentrations for Istokpoga (TP = 57 µg/L and TN = 1399 µg/L) and Istokpoga North (TP = 67 µg/L and TN = 1353 µg/L) also both exceeded the FDEP’s minimum calculated numeric interpretation of 50µg/L total phosphorus and 1,270 µg/L total nitrogen. While these values suggest that the lake is impaired for nutrients the local geology must be considered.

Bachmann et al. (2012) recognized the influence of geology on the productivity of Florida lakes and used data from over 1,100 Florida lakes to partition Florida into six total phosphorus (TP) zones and five total nitrogen (TN) zones (phosphorus and nitrogen a two nutrient determining lake productivity) (Appendix II). Lake Istokpoga falls within TP Zone 5 and TN Zone 5 suggesting that Lake Istokpoga is naturally nutrient rich based on the geology in which the lake lies. Ninety percent of all lakes within TP Zone 5 and 9

TN Zone 5 have nutrient concentration less than 252 µg/L (TP) and 2,701 µg/L (TN). Thus, the LAKEWATCH water chemistry values suggest Lake Istokpoga has nutrient and chlorophyll values that are normal for the region. However, these nutrient concentration could be elevated above background due to the large percentage of agricultural land uses within the lakes watershed.

Figure 7. Average annual water color measure by Florida LAKEWATCH for Lake Istokpoga station located in south and north areas of the lake plotted by year of sampling. The blue line is for data from Istokpoga North stations and the red line is for Istokpoga stations.

Figure 8. Average annual total phosphorus concentrations measure by Florida LAKEWATCH for Lake Istokpoga station located in south and north areas of the lake plotted by year of sampling. The blue line is for data from Istokpoga North stations and the red line is for Istokpoga stations.

Figure 9. Average annual total nitrogen concentration measure by Florida LAKEWATCH for Lake Istokpoga station located in south and north areas of the lake plotted by year of sampling. The blue line is for data from Istokpoga North stations and the red line is for Istokpoga stations.

Figure 10. Average annual chlorophyll concentrations measure by Florida LAKEWATCH for Lake Istokpoga station located in south and north areas of the lake plotted by year of sampling. The blue line is for data from Istokpoga North stations and the red line is for Istokpoga stations.

Figure 11. Average annual Secchi depth (water clarity) measure by Florida LAKEWATCH for Lake Istokpoga station located in south and north areas of the lake plotted by year of sampling. The blue line is for data from Istokpoga North stations and the red line is for Istokpoga stations.

Figures 7-11 show apparent trends in water chemistry data from 1996 to 2017, with nutrients and chlorophyll increasing and water clarity decreasing. Appendix II confirms that LAKEWATCH trend analyses shows significant increases in total nitrogen, chlorophyll and significant decreases in water clarity. Indeed, summer average total phosphorus and total nitrogen concentrations measured in 1980 (Canfield 1981; TP = 45 µg/L and TN 995 µg/L) are somewhat less than the LAKEWATCH long-term average total phosphorus and total nitrogen concentrations for Istokpoga (TP = 57 µg/L and TN = 1399 µg/L) and Istokpoga North (TP = 67 µg/L and TN = 1353 µg/L). However, some of the trends can be explained with the large changes in the abundance of hydrilla in Lake Istokpoga over time and we do not have data for aquatic plant abundance in 1980 when Canfield (1981) sampled Lake Istokpoga. As aquatic plants fill a water column with biomass multiple mechanisms tend to clear water by decreasing open water algae (estimated with chlorophyll) and nutrient concentrations (Hoyer et al 2005). Algae attached to aquatic plants (periphyton) compete with open water algae for nutrient, plant decrease waves and thus wind resuspension of nutrients and by decreasing turbulence in the water column algae and other suspended particle are allowed to settle out of the water column clearing the water. For example, the average water clarity for LAKWATCH stations Istokpoga 1, 2 and 3 directly follows the abundance of hydrilla (the dominant submersed aquatic plant) over time (Figure 12). When hydrilla is abundant water clarity is high and when hydrilla decreases so does water clarity. This may explain the common statement

14 that Lake Istokpoga used to have clear water and you could see the bottom ,which was the case when hydrilla cover most of the lake.

Figure 12. Relation between Secchi depth (ft) and coverage of hydrilla (acre) over time in Lake Istokpoga.

Lake Istokpoga Aquatic Plants:

Aquatic plant management is an important aspect of lake management. As with other lake management issues, controversies come with the territory. Thus, a well evaluated and carefully designed management plan must be developed for each water body. With reasonable care in the decision making process, aquatic plants can be managed successfully without destroying the desirable attributes of lakes that attract us to these water bodies.

Much aquatic plant research has been stimulated by the need to control nuisance aquatic plant species such as hydrilla (Hydrilla verticillata), water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes), which are plants common to Lake Istokpoga. Understanding aquatic plant biology is important to the immediate problems of managing aquatic plants and aquatic ecosystems, and it makes the development of new management techniques, the application of present techniques, and the assessment of environmental impacts more efficient. Interest in restoring and restructuring macrophyte communities and an appreciation for the littoral zone (the littoral zone is that portion of a water body extending from the shoreline lake ward to the greatest depth occupied by rooted plants) are growing. There is also a need to make management results more predictable, especially when considered in a long-term ecosystem context.

The development of effective and environmentally acceptable aquatic plant management programs also requires some knowledge of lake limnology. Limnology is the scientific study of the physical, chemical, geological, and biological factors that affect aquatic productivity and water chemistry in freshwater ecosystems-lakes, reservoirs, rivers, and streams. Many limnological processes affect the species, distribution, and/or abundance of aquatic plants that will be present in a water body. Making things more complicated, aquatic plants can also impact limnological processes like nutrient, chemical and temperature regimes and other biota in a lake or reservoir, especially in the littoral zone. A single written document cannot review all the aquatic plant biology, limnology and management techniques that might be relevant to the management of aquatic plants in Lake Istokpoga. However, Florida LAKEWATCH’S Information Circular #111 entitled “A beginners guide to water management-Aquatic Plants in Florida” is a good place to get the basics (http://lakewatch.ifas.ufl.edu/pubs/circulars/Circular111_FA16300_pdfta- 10-22-14.pdf).

Starting in 1982 the Bureau of aquatic plant management was housed in the Florida Department of Natural Resources, then the Florida Department of Environmental Protection and Finally Florida Fish and Wildlife Conservation Commission. Throughout that time Regional Biologists have been monitoring aquatic plant coverage in Florida’s public water bodies, primarily to keep track of invasive plant types. Thus, there is a good time line for the abundance (acres) of major problem aquatic plants (Water lettuce, water hyacinth and hydrilla) in Lake Istokpoga (Figures 13-15). In addition to the three major problems species, many littoral invasive plants also require significant management efforts (e.g., cattail, pickerel weed and water primrose).

Figure 10. Abundance (acres covered) of water lettuce in Lake Istokpoga from 1982 to 2017.

Figure 14. Abundance (acres covered) of hydrilla in Lake Istokpoga from 1982 to 2017.

Figure 15. Abundance (acres covered) of water hyacinth in Lake Istokpoga from 1982 to 2017.

It is easy to see that in the 1980’s floating plants like water hyacinth and water lettuce were the major aquatic plant problems in Lake Istokpoga with coverages up to 800 acres for hyacinth and 60 acres for water lettuce (Figure 13 and 14). The management of water hyacinth in Istokpoga and other lakes around the state with an approach called “maintenance control” has been quite successful in keeping water hyacinths at a low level (Figure 4 and 14). Florida Statute 369.22 defines maintenance control as “a maintenance program is a method for the control of non-indigenous aquatic plants in which control techniques are utilized in a coordinated manner on a continuous basis in order to maintain the plant population at the lowest feasible level as determined by the department.” It is important to note that this management strategy requires many repeated treatments on a regular basis using little herbicide instead of allowing problem plants to cover large areas and having to spay large amounts of herbicide to achieve control. This is important because allowing one hyacinth plant to grow will yield about one acre of hyacinth by the end of a growing season (Florida LAKEWATCH Information Circular #111). As pointed out earlier allowing water hyacinth to reach high level dramatically increases the production of organic matter increasing lake succession and decreasing the life of a lake.

Hydrilla was first observed in Lake Istokpoga in 1979 and by 1988 it had expanded to approximately 14,000 acres (Figure 15). The first herbicide treatment using Fluridone began in 1987 and continued multiple times until it was discovered that hydrilla had developed a resistance to fluridone and unique bacteria in the lake were actually able to digest fluridone. In 1992, after a largescale fluridone treatment, over 125,000 grass carp were stocked in the lake in an attempt to control the expanding problem. Even with continued herbicide treatments and a carp stocking, hydrilla expanded coverage to just under 25,000 acres by 1996 and Lake Istokpoga was reportedly accessible only with air boats. However, with continued maintenance control of hydrilla using herbicides other than fluridone, hydrilla coverage has fluctuated around 5,000 acres.

Statewide, the management objectives for hydrilla was a point of disagreement and contention between many different user groups and managers of the State’s freshwater lakes and rivers. Prior to July 1, 2008 the invasive plant management program was under the direction of the Department of Environmental Protection (DEP) and the DEP rule was to manage nonindigenous aquatic plants in a coordinated manner on a continuous basis in order to maintain the target plant population at the lowest feasible level as determined by DEP. The Legislature moved the invasive plant management program from DEP to the Fish and Wildlife Conservation Commission (FWC) in July of 2008. With that change FWC developed a hydrilla management policy and this new policy is one of the reasons why we are in the process of developing a Lake Istokpoga aquatic plant management plan with input from all stakeholder groups.

FWC’s current position on the management of hydrilla is a follows:

• It is the position of the Florida Fish and Wildlife Conservation Commission (FWC) that native aquatic plant communities provide ecological functions that support diverse native fish and wildlife communities in Florida waterbodies. FWC considers hydrilla to be an invasive, non- native aquatic plant that can, at high densities, adversely impact native plant abundance, sportfish growth, recreational use, flood control, and dissolved oxygen. Once established, hydrilla has proven difficult if not impossible to eradicate with current technology and is expensive to manage. Therefore, FWC opposes the deliberate introduction of hydrilla into waterbodies where it is not currently present. FWC prefers to manage for native aquatic plants, but recognizes that in waterbodies where native submersed aquatic plants are absent or limited, hydrilla at low to moderate densities can be beneficial to fish and wildlife. FWC will manage hydrilla on a waterbody by waterbody basis using a risk-based approach to determine the level of management. 18

• In waterbodies where hydrilla is well established, it will be managed at levels that are commensurate with the primary uses and functions of the waterbody and fish and wildlife. FWC will determine the level of hydrilla management on each public waterbody using a risk-based analysis that considers human safety issues, economic concerns, budgetary constraints, fish and wildlife values, and recreational use, with input from resource management partners and local stakeholders. Factors such as available control technology (e.g. herbicides), current waterbody condition, and activities occurring within the watershed will also influence the timing and level of hydrilla management.

The three major aquatic plants mentioned above and the tussock forming primrose willow family of plants are the current focus of aquatic plant management activities in Lake Istokpoga. However, in all the plant surveys conducted since 1982 over 100 species of aquatic plant have been identified in the lake. Each one of these species has varying benefits to fish and wildlife as well as potential to impact the uses of the lake. To understand these littoral plants FWC has been monitoring them with aerial photography since 2005 (Mallison 2018).

The results of this monitoring shows on Lake Istokpoga during 2005-2015 revealed 31 classes (groups of aquatic plant that generally occur together) that exceeded 25 acres of dominant coverage in at least one mapping year (Table 2, Figure 16). Other than open water, the most abundant class was freshwater marsh in all years. The next-most abundant class was cattail in 2005 and 2012, SAV in 2007 and 2009, and spatterdock in 2015. Between 2007 (baseline map) and 2015 (most-recent map), lake-wide coverage declined by more than 100 acres for four classes (SAV, freshwater marsh, cattail, and water primrose/knotweed-cupscale). During this period, lake-wide coverage increased by more than 100 acres for eight standard classes (marsh with shrubs & brush, cattail-pads, lotus, pickerelweed/arrowhead-pads, cattail-pickerelweed/arrowhead, bulrush-pads, pickerelweed/arrowhead-water primrose/knotweed, and water lily) and two new classes (mixed pads and dead vegetation). The mixed pads class was added in 2012 in response to an observed increase in mixtures of spatterdock, water lily, and/or lotus as these classes expanded. The dead vegetation class was added in 2015 to document effects of herbicide treatments that had recently been applied (treatment of the western marsh). Fluctuations of greater than 100 acres between years were also observed for open water, spatterdock, and pickerelweed/arrowhead. From these data it is easy to see that even when not considering the major problem plants in lake Istokpoga, there is abundant aquatic littoral vegetation for some fish and wildlife habitat.

The monitoring of littoral vegetation (Mallison 2018; years 2005 to 2015) also showed that without counting submersed vegetation (primarily hydrilla), emergent vegetation averaged over 17% coverage of Lake Istokpoga, ranging annually from 15.9% to 19.6 %. Additionally, wetland woody class averaged an additional 3.7% coverage of wetland ranging annually from 2.8% to 4.7%. This is important because a goal of many fisheries managers is to maintain a minimum of 15% coverage of a lake to maintain a healthy fishery (Canfield and Hoyer 1992; Bergstrom et al. 1996; Kirk and Henderson 2006).

Figure 15. Littoral vegetation maps of Lake Istokpoga from 2015.

2007 to 2015 change Class *2005 2007 2009 2012 2015 acres percent Open water 23,467 21,143 21,411 20,962 21,047 -96 0% Freshwater marsh 1,014 1,546 952 1,016 947 -599 -39% Spatterdock 659 727 904 708 822 95 13% Marsh with shrubs & brush 116 304 483 504 782 478 157% Forested wetlands 460 456 448 474 505 49 11% Cattail-pads 73 90 274 290 456 366 409% Lotus n/a 199 163 666 443 244 122% SAV 11 1,473 930 363 417 -1,056 -72% Cattail 972 767 716 731 340 -427 -56% Mixed pads n/a n/a n/a 144 333 n/a - Pickerelweed/arrowhead-pads 108 77 120 122 276 199 257% Bulrush 229 281 253 254 229 -51 -18% Cattail-pickerelweed/arrowhead 58 70 276 479 183 114 163% Bulrush-pads 32 17 47 53 178 161 977% Pickerelweed/arrowhead-water primrose/knotweed 3 18 3 68 165 147 808% Dead vegetation n/a n/a n/a n/a 157 n/a - Water lily n/a 13 17 188 152 139 1074% Upland 142 140 136 136 140 -1 0% Water primrose/knotweed-pads 0 47 91 111 117 70 147% Pickerelweed/arrowhead 111 116 182 239 96 -20 -17% Water primrose/knotweed 80 131 107 85 46 -85 -65% Willow 0 32 56 90 20 -12 -36% Pickerelweed/arrowhead-torpedograss 31 27 97 103 18 -9 -33% Cattail-bulrush 11 5 15 28 16 11 231% Maidencane/Egyptian paspalidium 36 24 27 19 16 -9 -35% Torpedograss 56 49 68 36 13 -36 -73% Pickerelweed/arrowhead-bulrush 54 24 36 41 10 -14 -57% Water primrose/knotweed-cupscale 22 110 107 34 8 -102 -93% Cupscale 110 24 10 5 3 -21 -87% Spikerush 4 26 11 4 1 -25 -97% Spikerush-pickerelweed/arrowhead 89 32 35 12 0 -32 -99% Other emergent plants 44 18 9 15 18 0 2%

Table 2. Area (acres) that was dominated by plant classes on Lake Istokpoga, based on littoral vegetation mapping in 2005-2015. Change in acres and percent were based on differences observed between 2007 and 2015 (*2005 was research and development and did not follow standardized sampling protocols). Other emergent plants = combined coverage of all uncommon plant classes (<25 acres coverage in each year). n/a = class was not in the classification system that year and therefore was not mapped.

Lake Istokpoga Fish populations:

In the late 1980’s Canfield and Hoyer (1992) examined the relations among water chemistry, aquatic plant abundance/communities and fish abundance/communities. At the time, hydrilla was dominating many lakes in Florida and management agencies wanted to know at what level aquatic plants needed to be 21 managed. The objective of the research was to determine what level of aquatic vegetation was needed to have a natural population of fishes. The overall finding of this research was that if lakes had less than 15% or more than 85% coverage of aquatic vegetation there was a probability of having depressed fish populations. Thus, some moderate level of vegetation is optimal for normal populations of fish and has also been found ideal for may sportfish. The research also showed that each fish species has an individual life history that is impacted by the surrounding habitats. For example, gizzard shad and threadfin shad are found in greater abundances when a lake has little submersed vegetation and is nutrient rich (Hoyer and Canfield 1994), most likely because abundant aquatic vegetation interferes with shad feeding characteristics. Many smaller fish species (e.g., bluespotted sunfish, golden topminnow, spotted sunfish) are more abundant in lakes with abundant aquatic vegetation, probably because they are protected from predation in abundant vegetation. Thus when managing aquatic plants the total abundance of fish generally stays the same but the relative abundance of individual fish species changes depending on the life history of that species.

There is a tremendous amount of fisheries data that have been collected on Lake Istokpoga over the last 20 years. Fisheries independent data (electrofishing catch per unit effort) examining the whole fish community has been collected in 15 different years from 1999 to 2017. Fisheries dependent (creel data interviewing anglers) have also been collected consistently since 2006.

Fisheries Independent Data

In the 15 years of electrofishing, 35 native freshwater, 2 marine and six exotic species of fish were collected (Table 3). Hoyer et al. (2011) examined long-term electrofishing data for 30 Florida lakes and found that after 8 years of data collection no additional species of fish were added to the cumulative list of species for individual lakes suggesting that the 15 years of data for Lake Istokpoga yields a complete list of species present to that sampling gear. Examining all available fisheries data for the Southeastern United States Swift et al (1985) report the presence of 46 fish species present in the Kissimmee River Drainage suggesting the possibility of having other rare species present in lake Istokpoga.

Common Name Status Common Name Status Black Crappie Native Lined Topminnow Native Bluefin Killifish Native Longnose Gar Native Bluegill Native Pugnose Minnow Native Bluespotted Sunfish Native Redbreast Sunfish Native Bowfin Native Redear Sunfish Native Brook Silverside Native Sailfin Molly Native Brown Bullhead Native Seminole Killifish Native Brown Darter Native Spotted Sunfish Native Chain Pickerel Native Swamp Darter Native Channel Catfish Native Taillight Shiner Native Coastal Shiner Native Threadfin Shad Native Dollar Sunfish Native Warmouth Native Eastern Mosquitofish Native White Catfish Native Flagfish Native Yellow Bullhead Native Florida Gar Native Atlantic Needlefish Marine Gizzard Shad Native Sailfin Catfish Marine Golden Shiner Native Blue Tilapia Exotic Golden Topminnow Native Brown Hoplo Exotic Inland Silverside Native Nile Tilapia Exotic

Lake Chubsucker Native Oscar Exotic Largemouth Bass Native Vermiculated Sailfin Catfish Exotic Least Killifish Native Walking Catfish Exotic

Table 3. List of fish species collected with electrofishing in Lake Istokpoga between 1999 and 2017. Exotic fish and marine fish names are underlined.

Hoyer and Canfield (1994) published statewide average electrofishing CPUE values from data collected on 60 Florida lakes ranging in nutrient concentrations and abundance of aquatic macrophytes. Largemouth bass and bluegill CPUE data collected for the last 15 years on Lake Istokpoga are generally above the statewide averages published by Hoyer et al. (1994) while black crappie and redear sunfish are generally below the statewide averages (Figure 16). Over the 15 year period the estimated CPUE these four sportfish fluctuated considerably from a low of 70% of the long-term mean for black crappie to a high of 138% of the long-term mean for largemouth bass. As with all fish populations, these fluctuations are caused by variations in annual reproductive success and survival (natural and angling) of each population, which is due to annual changes in many environmental pressures over time (temperature, water quality, water level, habitat availability etc.).

18 16 14 12 10 Black Crappie 8 6 CPUE (no/hr) 4 2 0 2000 2005 2010 2015 SurveyYear

1000 Bluegill 800

600

400 CPUE (no/hr) 200

0 2000 2005 2010 2015 SurveyYear

450 400 350 Largemouth Bass 300 250 200 150 CPUE (no/hr) 100 50 0 2000 2005 2010 2015 SurveyYear

90 80 70 Redear Sunﬁsh 60 50 40 30 CPUE (no/hr) 20 10 0 2000 2005 2010 2015 SurveyYear

Figure 16. Electrofishing catch per unit effort data (no/hour) collected for major sportfish (black crappie, bluegill, largemouth bass and redear sunfish) from 1998 to 2017 on Lake Istokpoga compared to statewide averages calculated from data collected on 60 Florida lakes (black dashed line, Hoyer and Canfield 1994).

Fisheries Dependent Data

Florid Fish and Wildlife Conservation Commission staff routinely conduct creel surveys on many of the major fishing lakes in Florida, including Lake Istokpoga. Similar creel method were used on nine major Florida fishing lakes over the same time period (2006-2017) for two of Florida’s major sportfish, largemouth bass and black crappie. Comparing all of the data shows that long-term fishing effort for largemouth bass in Istokpoga (3.2 angler hours/100 d/ha) exceeded the mean of all lakes combined (2.5 angler hours/100 d/ha) and averaged higher than five of the other eight lakes (Figure 17). Largemouth bass success for Lake Istokpoga averaged 0.58 fish/hr exceeding the average for five other lakes (Figure 18). Fishing effort for black crappie in Lake Istokpoga averaged 1.9 (angler hours/100 d/ha) exceeding only three of the other major fishing lakes (Figure 19). However, one of those lakes the Istokpoga exceeded with similar water level stabilization and hydrilla issues was Lake Tohopekaliga. Long-term average black crappie success rates (fish/hr) in lake Istokpoga was 1.5 fish/hr exceeding four other lakes in the data set (Figure 20).

Comparing Lake Istokpoga creel data for largemouth bass and black crappie to other Florida lakes shows that Istokpoga is about average for the these nine important Florida fishing lakes when considering fishing effort and success. One interesting observation when comparing data among lakes is that the variability in fishing effort and success is generally smaller in Lake Istokpoga than the other Florida lakes (Figure 17- 20). Even though Istokpoga’s variability among lakes is small, there are annual fluctuations in fishing

24 effort and success for both largemouth bass and black crappie (figure 21 and 22). 6

ort (angler hr/100 d/ha) 2 ﬀ

LMB e 1

0 n ﬃ Gri Harris George Orange Istokpoga Lochloosa Kissimmee Okeechobee Tohopekaliga Lake Figure 17. Box plot showing largemouth bass fishing effort summary statistics for nine lakes each with 11 years of creel data. Line in the middle of the box is the median, edges of the box are the 25% and 75% of the data distribution and the outside bars are the minimum and maximum data. The line across the plot is the grand mean of all data.

1.5

0.5 LMB Catch success (ﬁsh/hr)

0 n ﬃ Gri Harris George Orange Istokpoga Lochloosa Kissimmee Okeechobee Tohopekaliga Lake Figure 18. Box plot showing largemouth bass fishing success summary statistics for nine lakes each with 11 years of creel data. Line in the middle of the box is the median, edges of the box are the 25% and 75% of the data distribution and the outside bars are the minimum and maximum data. The line across the plot is the grand mean of all data.

10 ort (angler hr/100 d/ha) ﬀ 5 BLCR e 0 n ﬃ Gri Harris George Orange Istokpoga Lochloosa Kissimmee Okeechobee Tohopekaliga Lake

Figure 19. Box plot showing black crappie fishing effort summary statistics for nine lakes each with 11 years of creel data. Line in the middle of the box is the median, edges of the box are the 25% and 75% of the data distribution and the outside bars are the minimum and maximum data. The line across the plot is the grand mean of all data.

2.5

1.5

0.5 BLCR Harvest success (ﬁsh/hr) 0 n ﬃ Gri Harris George Orange Istokpoga Lochloosa Kissimmee Okeechobee Tohopekaliga Lake Figure 20. Box plot showing black crappie fishing success summary statistics for nine lakes each with 11 years of creel data. Line in the middle of the box is the median, edges of the box are the 25% and 75% of the data distribution and the outside bars are the minimum and maximum data. The line across the plot is the grand mean of all data.

4 0.8

3.5 0.7

0.6 3

0.5 ort (angler hr/100 d/ha) ﬀ 2.5 LMB Catch success (ﬁsh/hr)

LMB e 0.4

2 0.3 2006-2007 2007-2008 2008-2009 2009-2010 2010-2011 2011-2012 2012-2013 2013-2014 2014-2015 2015-2016 2016-2017 Year Left Scale: LMB eﬀort (angler hr/100 d/ha)

LMB Catch success (ﬁsh/hr) Right Scale: Figure 21. Overlay plot showing annual largemouth bass fishing effort (red line with circle points) and success (blue line with plus sign for points) for Lake Istokpoga with 11 years of creel data.

2.5

2 1.5 ort (angler hr/100 d/ha) ﬀ 1.5 1 BLCR Harvest success (ﬁsh/hr) BLCR e

0.5 1 2006-2007 2007-2008 2008-2009 2009-2010 2010-2011 2011-2012 2012-2013 2013-2014 2014-2015 2015-2016 2016-2017 Year Left Scale: BLCR eﬀort (angler hr/100 d/ha)

Right Scale: BLCR Harvest success (ﬁsh/hr)

Figure 22. Overlay plot showing annual black crappie fishing effort (red line with circle points) and success (blue line with plus sign for points) for Lake Istokpoga with 11 years of creel data.

The largemouth bass and black crappie populations in Lake Istokpoga are healthy but having stability (a constant number in the population) is rarely the case in nature. Rather, populations are typically cyclical, fluctuating naturally based on a variety of factors including spawning success, natural mortality and fishing mortality, as well as habitat, prey availability and other factors. These fluctuations in addition economic considerations, weather conditions (e.g., hurricanes), lake access to fishing (e.g., hydrilla coverage) and other factors can cause fluctuations in fishing effort and success over time.

Most aquatic habitat in Florida lakes is in the form of aquatic plants, which have the potential to impact both fish populations characteristics and actual angling activities/success. Aquatic plants influence some sportfish fish populations by increasing abundance of small prey like macroinvertebrates and by providing refuge for young-of-year (YOY) fish from larger predators allowing them reach adulthood (Savino and Stein 1982, Canfield and Hoyer 1992, Sammons and Maceina 2005). However, high abundance of aquatic vegetation (>50% coverage of the lake surface area) also can restrict angler access (Colle et al. 1987), and reduce fish feeding success and thus growth (Bettolie et al. 1992). Intermediate levels of aquatic vegetation (Canfield and Hoyer 1992, report between 15% and 85% coverage and Sammons and Maceina 2005, report between 20% and 50% coverage) has been found to provide a good trade-off between prey production and predator efficiencies, leading to good growth, condition and abundance of sportfish such as largemouth bass. Intermediate levels of vegetations also provide the best angling opportunities (Wilde 1992).

Maintaining a moderate abundance of aquatic plants is needed for fish populations and angling. However, managing aquatic vegetation at a moderate level is a difficult task when exotic invasive plants like water lettuce, water hyacinth and hydrilla are involved. The growth potential of these plants is large requiring a constant management approach. There are many tools in the aquatic plant management box to use to reach management goals including but not limited to multiple herbicides, mechanical harvesting, water level manipulation and scraping, biological control (Insects, pathogens, grass carp) and others. Each tool has an associated cost and effectiveness that must be considered when developing a management plan. Defining a target level of aquatic plant abundance is also a difficult decision because multiple uses are optimized at different levels of aquatic plant management. Istokpoga is primarily a fishing lake so a moderate level is best for the use and the target windows for good fish populations and angling are relatively large (Canfield and Hoyer 1992, report between 15% and 85% coverage and Sammons and Maceina 2005, report between 20% and 50% coverage).

Aquatic Birds and Wildlife

Conventional wisdom suggests that the base fertility of a lake (trophic status) is a primary driver for the abundance of aquatic organisms, including but not limited to zooplankton abundance (Canfield and Watkins 1984), fish populations (Bachmann et al. 1996), bird abundance (Hoyer, and Canfield 1994), and even populations of top predators like the alligator (Evert 1999). All these results support the predictions of Fretwell (1987), who suggested that as nutrient levels increase among systems, the abundance of organisms, including top predators, would also increase. As with fish populations mentioned above aquatic bird populations, research shows that each aquatic bird species has an individual life history that is also impacted by the surrounding habitats. For example, anhingas and double-crested cormorants are found in greater abundances when a lake has little submersed vegetation and is nutrient rich (Hoyer and Canfield 1994b), most likely because abundant submersed aquatic vegetation interferes with both bird species feeding characteristics. Many duck species (e.g., ring-necked duck) are more abundant in lakes with abundant aquatic vegetation, probably because they use abundance submersed vegetation as an actual food source. Thus, after significantly changes in aquatic macrophytes the total abundance of fish and/or aquatic birds generally stays the same but the relative abundance of individual fish species changes depending on the life history of that individual species.

The following are three summaries from local experts, showing the current status of Osprey, Snail Kite and wading bird populations in Lake Istokpoga:

Osprey Michael McMillian Environmental Specialist, Highland County

I have tracked nesting Ospreys on Lake Istokpoga from 1989 to present. In 1910 DJ Nicholson rowed his boat around the shoreline of Istokpoga including it’s two interior islands and noted 75 Osprey nests. Remember that this is pre-settlement with no people, no surrounding agriculture and no water control structure. In 1973, Dr. Jim Layne duplicated Nicholson’s survey and noted 9 nests of which only 6 were active. All Osprey nests were located on one of the two interior islands. During Nicholson’s trip there was no marsh on the Lake Istokpoga. There most likely was a very narrow littoral zone. During Dr. Layne’s survey a marsh would have just started forming because of the installation of the S68 water control structure in the late 60’s. In 1989, when I began there were 55 Osprey nests and in 1990 there were 60. Beginning in 1991 I began tracking reproductive success and in 1995 I included all nests associated with Istokpoga which included nests located on various structures off the lake (i.e. telephone poles, communication towers, etc).

By 1993/1994 the number of Osprey nests on the lake equaled the number located by Nicholson in 1910. I thought the number might level off but was wrong. The number continued to increase and in 2005 surpassed 300 nests for the first time. The number now appears to fluctuate around 300 nests, lower in some years and higher in others. From 2016 to present the number has exceeded 300 with 313 in 2018. With the possible exception of Blue Cypress Lake near Vero, this is the largest concentration of nesting Osprey in the world especially when you consider the area of Lake Istokpoga (just over 28,000 acres). I have seen this claim made for the Chesapeake Bay region however the area is immense.

Snail Kite Tyler Beck Snail Kite Conservation Coordinator Species Conservation and Planning Section Division of Habitat and Species Conservation Florida Fish and Wildlife Conservation Commission

The Snail Kite (Rostrahamus sociabilis) is an endangered raptor that inhabits shallow lakes and marshes of Florida and feeds almost exclusively on aquatic snails in the genus Pomacea. While the Florida apple snail (Pomacea paludosa) historically was the primary food of Snail Kites in Florida, in recent years, the invasive exotic apple snail (Pomacea maculata) make up a substantial portion of their diet. Snail Kite nesting is monitored by a research group with the University of Florida.

The first Snail Kite nesting in recent history (since at least 1987) on Lake Istokpoga was reported in 2005. Four nests were found that year and all were successful. There weren’t any nests found the following year but at least a handful of nests (1-4) have been found on the lake each year since then. Nesting began on west shoreline (2005 and 2007) then expanded to the islands in 2008 and north and northeast shores in 2009. The invasive apple snail was first detected in Lake Istokpoga in 2011 and at least 12 nests have been found on the lake every year afterwards. The highest Snail Kite nesting effort to date came in 2016 with 60 active nests, 25 of which were successful.

Lake Istokpoga Snail Kite nesting 70

0 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

Active Nests Successful Nests

Wading Birds Mark I. Cook and Mac Kobza South Florida Wading Bird report South Florida Water Management District

Page 38 of the wading bird report contains the following table and the text noting that Bumblebee rookery is the largest in the region. It has been the largest in the region for a long time and is one of the larger in Florida period. Istokpoga has rather steep edges so usually doesn’t furnish much foraging habitat, but the water surrounding the island makes it protected and an ideal nesting spot. The table shows a steady increase in wading bird nests since 2010 illustrating a healthy wading bird population on Lake Istokpoga.

Lake Istokpoga Time Line Summary:

This is a brief history of some of the important ecological components of Lake Istokpoga including geologic history, human population growth/settlement, water quality, water level fluctuations, and aquatic plant abundances and management. The short and well thought out mission statement of the Florida Fish and Wildlife Conservation Commission is to “Managing fish and wildlife resources for their long-term well-being and the benefit of people.” This history shows that Lake Istokpoga has been and will continue to be in a state of change requiring consistent management activities to provide ecosystem services for both fish/wildlife and the benefit of people.

To maintain a natural abundance of all fish and wildlife species will require maintaining multiple types of natural habitats in abundances that are dictated by the surrounding abiotic conditions. Water level stabilization for Lake Istokpoga has made this a difficult task. Eliminating large water level fluctuations tended to make it favorable for extensive monocultures of individual aquatic plant species (e.g., pickerel weed, cattail) decreasing space for other unique habitats that are favorable for individual species of fish and/or wildlife. FWC has done excellent job identifying and monitoring individual habitat types in Lake Istokpoga and classifying those habitats quality for different fish and wildlife species (See Table 1 in: Mallison C. 2018. Lake Istokpoga Habitat Evaluation – 2015. Final Report). Using these littoral habitat classifications and the regular aquatic vegetation mapping from aerial photography and sonar equipment to better monitor submersed aquatic vegetation can inform management agencies when planning aquatic plant management activities.

Literature Cited:

Bachmann R. W., B. L. Jones, Donald D. Fox, M. V. Hoyer, L. A. Bull, and D. E. Canfield, Jr. 1996. Relations between trophic state indicators and fish in Florida (U.S.A.) lakes. Canadian Journal of Fisheries and Aquatic Sciences 53: 842-855.

Bachmann, R. W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for Florida lakes. Lake Reserv Manage. 28:84-92.

Bergstrom J. C., R. J. Teasley, H. K. Coordell, R. Souter, B. B. K. English. 1996. Effects of reservoir aquatic plant management on recreational expenditures and regional economic activity. J. Applied Econ. 28:409-422.

Bettoli, P. W., M. J. Maceina, R. L. Nobel, R. K. Betsill. 1992. Picivory in largemouth bass as a function of aquatic vegetation abundance. North American Journal of Fisheries Management. 12:509-516.

Canfield D. E. Jr., 1981. Chemical and trophic state characteristics of Florida lakes in relation to regional geology. Final Report. Cooperative Fish and Wildlife Research Unit, University of Florida, Gainesville FL.

Canfield, D. E., Jr., and M. V. Hoyer. 1992. Relations between aquatic macrophytes and the limnology and fisheries of Florida lakes. Final Report. Bureau of Aquatic Plant Management, Florida Department of Natural Resources, Tallahassee, Florida.

Canfield DE Jr, Watkins CE II. 1984. Relationships between zooplankton abundance and chlorophyll a concentrations in Florida Lakes. J Freshw Ecol. 2:335–344.

Colle, D. E., J. V. Shireman, W. T. Haller, J. C. Joyce, D. E. Canfield, Jr. 1987. Influence of hydrilla on harvestable sportfish populations, angler use, and angler expenditures at Orange Lake, Florida. North American Journal of Fisheries Management 7:410-417.

Griffith GE, Canfield DE Jr., Horsburgh CA, Omernik JM. 1997. Lake Regions of Florida. Corvallis (OR): US Environmental Protection Agency; National Health and Environmental Effects Research Laboratory; EPA/R-97/127; [cited 5 July 2010] Available from http://www.epa.gov/wed/pages/ ecoregions/fl eco.htm.

Evert JD. 1999. Relationships of alligator (Alligator mississippiensis) population density to environmental factors in Florida Lakes [master’s thesis]. [Gainesville (FL)]: University of Florida.

Florida LAKEWATCH. 2017. A beginners guide to water management-Muck: Causers and Corrective Actions. Information Circular #112. Program of Fisheries and Aquatic Sciences, School of Forest Resources and Conservation, University of Florida/Institute of Food and Agricultural Sciences. Library, University of Florida. Gainesville, Florida.

Florida LAKEWATCH. 2007. A beginners guide to water management-Aquatic Plants in Florida. Information Circular #111. Department of Fisheries and Aquatic Sciences, University of Florida/Institute of Food and Agricultural Sciences. Library, University of Florida. Gainesville, Florida.

Fretwell SD. 1987. Food chain dynamics: the central theory of 25ecology? Oikos. 50:291–301.

Henderson, J. E., J. P. Kirk, S. D. Lamprecht, E. Hayes. 2003. Economic impacts of aquatic vegetation to angling in two South Carolina reservoirs. J. Aquat. Plant Manage. 41:53-56.

Hoyer, M. V., and D. E. Canfield Jr. 1994. Handbook of common freshwater fish in Florida lakes. SP 160. University of Florida/Institute of Food and Agricultural Sciences. Gainesville, Florida.

Hoyer, M. V., and D. E. Canfield Jr. 1994b. Bird abundance and species richness on Florida lakes: Influence of lake trophic status, morphology, and aquatic macrophytes. Hydrobiologia 297/280: 107-119.

Hoyer, M. V., C. A. Horsburgh, D. E. Canfield, Jr., and R. W. Bachmann. 2005. Lake level and trophic state variables among a population of shallow Florida lakes and within individual lakes. Canadian Journal of Fisheries and Aquatic Sciences. 62: 1-10.

Hoyer, M. V., R. W. Bachmann and D. E. Canfield Jr. 2008. Lake management (muck removal) and hurricane impacts to the trophic state of Lake Tohopekaliga, Florida. Lake and Reservoir Management 24: 57-68.

Hoyer, M. V., J. P. Bennett and D. E. Canfield, Jr. 2011. Monitoring freshwater fish in Florida lakes using electrofishing: Lessons learned. Lake and Reservoir Management. 27:1-14.

Joyce, J. C. 1992. Benefits of maintenance control of water hyacinth. Aquatics.

Mallison C. 2018. Littoral vegetation trend analysis for Lake Istokpoga (2005-2015). Annual Report. Florida Fish & Wildlife Conservation Commission, Lakeland, FL.

McDiffett, W. F. 1981. Limnological Characteristics of Eutrophic Lake Istokpoga, Florida. Florida Scientist, 44(3): 172–81. 32

Milleson, J.F. 1978. Limnological Investigations of Seven Lakes in the Lake Istokpoga Drainage Basin. Technical Publication 78–1. Resources Planning Department, SFWMD, West Palm Beach, FL.

Sammons, S. M., M. J. Maceina. 2005. Effects of aquathol K treatments on activity patterns of largemouth bass in two coves of Lake Seminole, Georgia. J. Aquat. Plant Manage. 43:17-24.

Savino JF, Stein RA. 1982. Predator-prey interactions between largemouth bass and bluegills as influenced by simulated, submerged vegetation. T Am Fish Soc.111;255– 266.

South Florida Water Management District. 2000a. Kissimmee Basin Water Supply Plan. Water Supply Department, SFWMD, West Palm Beach, FL. Available from http://www.sfwmd.gov/org/wsd/wsp/kisswsp.htm.

Swift CS, Gilbert CR, Borton SA, Burgess GH, Yerger RW. 1985. Zoogeography of the freshwater fishes of the southeastern United States: Savannah River to Lake Pontchartrain. Hocutt CH,Wiley EO, editors. The zoogrography of North American freshwater fishes. New York (NY): John Wiley & Sons.

White, W.A. 1970. The Geomorphology of Florida. Florida Department of Natural Resources. Tallahassee, FL, p. 164.

Wilde, G. E., R. K. Riechers, J. Johnson. 1992. Angler attitudes toward control of freshwater vegetation. J. Aquat. Plant Manage.. 30:77-79.

Xiong C., and M. V. Hoyer. 2018. Influence of land use and rainfall variability on nutrient concentrations in Florida lakes. Lake and Reservoir Management. In Review.

Zahina, John, Huffman, April, McCarthy, Cath, Petti, Tara, Swift, David, Van Arman, Joel. 2005. Minimum Flows and Levels for Lake Istokpoga. DO - 10.13140/RG.2.1.1411.9920

Appendix I. Aerial photographs of Lake Istokpoga taken between 1944 and 2001.

Appendix II. LAKEWATCH Report for Istokpoga in Highlands County Using Data Downloaded 10/17/2016

Introduction for Lakes In this report, we present summary data collected on individual systems that have been part of the LAKEWATCH program. This summary is from the whole period of record for individual systems. The first part of this summary will allow a comparison of the long-term mean nutrient concentrations with the nutrient zone concentrations published by LAKEWATCH staff (Bachmann et al. 2012; http://lakewatch.ifas.ufl.edu/publications.shtml). The second part of the summary will allow the comparison of data with Florida Department of Environmental Protections Numeric Nutrient Criteria. Finally, this report examines data for any long-term trends that may be occurring in individual systems but only for systems with five or more years of data. Base File Data: Definitions The long-term data summary will include the following parameters listed with a definition after each one: • County: Name of county in which the lake resides. • Name: Lake name that LAKEWATCH uses for the system. • Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system. • Water Body Type: Four different types of systems; lakes, estuaries, streams and springs. • Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available. • Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a lake that LAKEWATCH uses for estimating plant abundances. • Period of Record (year): Years a lake has been in the LAKEWATCH program. • TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012). • Long-Term TP and TN Mean Concentration (µg/L: min and max): Average of all annual means (µg/L) listed with minimum and maximum annual means. • Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be classified into three group based on color and alkalinity or specific conductance; colored (color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less the or equal to 100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C). • Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average concentration and the classification system from; Forsberg, C and S. R. Ryding. 1980. Eutrophication parameters and trophic state indices in 30 Swedish waste receiving lakes. Arch. Hydrobiol. 89:189-207).

CITIZEN'SCIENCE'SINCE'1986'

Appendix II. LAKEWATCH Report for Istokpoga in Highlands County Using Data Downloaded 10/17/2016

Base File Data and Nutrient Zone Comparisons for Lakes

County Highlands Name Istokpoga Latitude 27.3428 Longitude -81.3073 Water Body Type Lake Surface Area (ha and acre) 12188 ha or 30116.54 acre Mean Depth (m and ft) 1.4 m or 4.6 ft Period of Record (year) 1996 to 2016 Lake Classification Colored Lake Lake Trophic Status (CHL) Hypereutrophic TP Zone TP5 Long-Term TP Mean Concentration (µg/L, minimum 56 (34 to 74) and maximum) TN Zone TN5 Long-Term TN Mean Concentration (µg/L, minimum 1382 (983 to 1634) and maximum)

Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the upper 90% of lakes within each zone (Bachmann et al. 2012c).

Appendix II. LAKEWATCH Report for Istokpoga in Highlands County Using Data Downloaded 10/17/2016

FDEP Nutrient Criteria Lakes For lakes, the applicable numeric interpretations of the narrative nutrient criterion in paragraph 62- 302.530(47)(b), F.A.C., for chlorophyll a are shown in the table below. The applicable interpretations for TN and TP will vary on an annual basis, depending on the availability of chlorophyll a data and the concentrations of nutrients and chlorophyll a in the lake, as described below. The applicable numeric interpretations for TN, TP, and chlorophyll a shall not be exceeded more than once in any consecutive three-year period. If there are sufficient data to calculate the annual geometric mean chlorophyll a and the mean does not exceed the chlorophyll a value for the lake type in the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual geometric means of lake TN and TP samples, subject to the minimum and maximum limits in the table below. However, for lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit shall be the 490 µg/L TP streams threshold for the region; or if there are insufficient data to calculate the annual geometric mean chlorophyll a for a given year or the annual geometric mean chlorophyll a exceeds the values in the table below for the lake type, then the applicable numeric interpretations for TN and TP shall be the minimum values in the table below.

Long-Term Data Summary Lakes: Definitions

The following long-term data are the primary trophic state parameters collected by LAKEWATCH volunteers and classification variables color and specific conductance (LAKEWATCH recently began analyzing samples quarterly for color and specific conductance): • Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae in Florida’s fresh and saltwater environments. • Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting when nitrogen to phosphorus ratios are generally less than 10. • Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative abundances of open water algal population. • Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity (how far one can see into the water) and are listed with English and metric units. • Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after particles have been filter out. • Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity and can be used to estimate the amount of dissolve materials in water.

Appendix II. LAKEWATCH Report for Istokpoga in Highlands County Using Data Downloaded 10/17/2016

Parameter Minimum and Maximum Mean of Annual Means Annual Means (Sampling years) Total Phosphorus (µg/L) 34 - 74 56 (19) Total Nitrogen (µg/L) 983 - 1634 1382 (19) Chlorophyll- uncorrected (µg/L) 22.7 - 62.4 41.9 (19) Secchi (ft) 1.8 - 4.4 2.5 (19) Secchi (m) 0.6 - 1.3 0.8 (19) Color (Pt-Co Units) 36 - 110 77 (14) Specific Conductance (µS/cm@25 C) 102 - 193 153 (8) Lake Classification Colored Lake

FDEP Numeric Nutrient Criteria Long Term Geometric Annual Minimum calculated Maximum calculated numeric Mean Lake Color and Geometric numeric interpretation interpretation Long-Term Geometric Mean Annual Annual Annual Annual Mean Color, Alkalinity and Chlorophyll- Geometric Geometric Geometric Geometric Specific Conductance corrected Mean Total Mean Total Mean Total Mean Total Phosphorus Nitrogen Phosphorus Nitrogen > 40 Platinum Cobalt Units 20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L Colored Lakes ≤ 40 Platinum Cobalt Units and > 20 mg/L CaCO3 20 µg/L 30 µg/L 1050 µg/L 90 µg/L 1910 µg/L or >100 µS/cm@25 C Clear Hard Water Lakes ≤ 40 Platinum Cobalt Units and ≤ 20 mg/L CaCO3 6 µg/L 10 µg/L 51 µg/L 30 µg/L 930 µg/L or < 100 µS/cm@25 C Clear Soft Water Lakes 1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit shall be the 490 µg/L TP streams threshold for the region. For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity data are available, long-term geometric mean specific conductance values shall be used, with a value of <100 µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data are available.

Appendix II. LAKEWATCH Report for Istokpoga in Highlands County Using Data Downloaded 10/17/2016

Trend Analyses Lakes

The following data are for linear regression statistics derived by plotting annual average total phosphorus, total nitrogen, chlorophyll, and Secchi data by year of data collection. Linear regression analysis is a common statistical approach used to determine if significant trends are occurring over time. These analyses define statistics based on the best fit line drawn through the data after plotting them with year on the horizontal line (x-axis) and the data value on the vertical line (y-axis). Figure 2 shows example plots with linear regression statistic of lakes that show significant total phosphorus increases, decreases and no change over time. The statistics that are listed include the following:

• Number of years (n): This is simply the number of years of data that were used to calculate annual means. • Intercept (a): This is the value on the y-axis that the fitted line would cross if the x-axis where zero. • Slope (b): This is the rate at which the fitted line increases (positive number) or decreases (negative number). • Coefficient of determination (R2): This value is an indication of how much variance above and below the fitted line there is in the data. This value ranges from 0 to 1. A high value means a tight fit and a low value means a loose fit. • Probability of Significance (p): For most statistical analyses a p-value of less than 0.05 means the statistic is significant and analyses with p-values greater than 0.05 are not significant.

Statistic Total Total Nitrogen Chlorophyll Secchi Phosphorus Number of Years (n) 19 19 19 19 Intercept (a) -896 -34821 -2023 133 Slope (b) 0.47 18.05 1.03 -0.06 Coefficient of 0.08 0.46 0.36 0.39 Determination (R2) Probability of 0.24 0.00 0.01 0.00 Significance (p) Potential Trend No Trend Increasing Increasing Decreasing

Appendix II. LAKEWATCH Report for Istokpoga North in Highlands County Using Data Downloaded 10/17/2016

CITIZEN'SCIENCE'SINCE'1986'

Appendix II. LAKEWATCH Report for Istokpoga North in Highlands County Using Data Downloaded 10/17/2016

Base File Data and Nutrient Zone Comparisons for Lakes

County Highlands Name Istokpoga North Latitude 27.401 Longitude -81.3332 Water Body Type Lake Surface Area (ha and acre) 12188 ha or 30116.54 acre Mean Depth (m and ft) m or ft Period of Record (year) 1996 to 2016 Lake Classification Colored Lake Lake Trophic Status (CHL) Hypereutrophic TP Zone TP5 Long-Term TP Mean Concentration (µg/L, minimum 67 (53 to 91) and maximum) TN Zone TN5 Long-Term TN Mean Concentration (µg/L, minimum 1347 (973 to 1614) and maximum)

Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the upper 90% of lakes within each zone (Bachmann et al. 2012c).

Appendix II. LAKEWATCH Report for Istokpoga North in Highlands County Using Data Downloaded 10/17/2016

Long-Term Data Summary Lakes: Definitions

Appendix II. LAKEWATCH Report for Istokpoga North in Highlands County Using Data Downloaded 10/17/2016

Parameter Minimum and Maximum Mean of Annual Means Annual Means (Sampling years) Total Phosphorus (µg/L) 53 - 91 67 (21) Total Nitrogen (µg/L) 973 - 1614 1347 (21) Chlorophyll- uncorrected (µg/L) 11.2 - 52.4 41.1 (21) Secchi (ft) 1.5 - 3.1 2.0 (21) Secchi (m) 0.4 - 0.9 0.6 (21) Color (Pt-Co Units) 46 - 165 94 (15) Specific Conductance (µS/cm@25 C) 109 - 197 162 (9) Lake Classification Colored Lake

Appendix II. LAKEWATCH Report for Istokpoga North in Highlands County Using Data Downloaded 10/17/2016

Trend Analyses Lakes

Statistic Total Total Nitrogen Chlorophyll Secchi Phosphorus Number of Years (n) 21 21 21 21 Intercept (a) 1010 -28285 -1101 42 Slope (b) -0.47 14.77 0.57 -0.02 Coefficient of 0.08 0.35 0.13 0.06 Determination (R2) Probability of 0.22 0.00 0.11 0.28 Significance (p) Potential Trend No Trend Increasing No Trend No Trend