Progress 10/01/08 to 09/30/09
Outputs
OUTPUTS: We have continued to implement a long-term effort initiated in 1998 to restore native prey and sport fish communities in lakes of the Adirondack region of New York by removing dominant populations of a non-native piscivore (smallmouth bass) that had been introduced to these lakes 50 years earlier. An intense level of removal of smallmouth bass was expected to reduce competition and predation from this species, thereby improving conditions for the growth and survival of the native apex predator (lake trout) and increasing the abundance of native littoral fishes. Intense harvests are common in freshwater and marine ecosystems throughout the world, and the consequent changes in population and ecosystem dynamics influence the ability to achieve intended management goals. One specific realm of management applications in which piscivore removals have been regularly implemented are those targeting undesirable and abundant, non-native piscivores. Results from this study are providing unique insights in understanding fish population and ecosystem responses to intense over-harvest, whether for commercial or sport purposes, or harvest intended to control undesirable organisms. These results are also providing an opportunity to understand the extent to which ecosystems can be restored by removing dominant, non-native organisms. PARTICIPANTS: Individuals who worked on this project included Clifford Kraft, Principal Investigator (project design and implementation), Daniel Josephson, Research Associate (project design and implementation), Justin Chiotti, Research Aid IV (project design and implementation), Kurt Jirka, Research Support Specialist, (project design and implementation). Partner organizations included the Adirondack League Club and New York State Department of Environmental Conservation (NYSDEC). TARGET AUDIENCES: Angler (e.g. Trout Unlimited) and conservation (e.g. Nature Conservancy) organizations, plus state (NYSDEC), private landowners, and local bodies of government (e.g. Town of Webb, Herkimer County) responsible for managing Adirondack lake fisheries. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The ecosystem response to this experiment has been substantial, as evidenced by: 1) changes in the trophic position and fundamental energy source of the native apex predator (lake trout), 2) an increase in growth and mercury bioaccumulation in the apex predator, 3) increased abundance of seven species of native littoral fish, and 4) an increase in growth and abundance of one state-endangered species and the recent appearance of a native cyprinid fish species that hadn't been observed for over 40 years. Every aspect of this long-term project has been conducted to date (and will continue to be conducted) in association and close collaboration with managers from fisheries management agencies, private landowners, and NGOs. This project will address numerous tangible management goals that will help guide: 1) the conservation of aquatic resources and rare species, 2) the management of angling fisheries for recreation and human health (e.g. reducing mercury contamination), 3) control of undesirable non-native species, and 4) the restoration of ecosystems that have been degraded by anthropogenic impacts.
Publications
- Zipkin, E.F., C.E. Kraft, E.G. Cooch and P.J. Sullivan. 2009. When can efforts to control nuisance and invasive species backfire Ecological Applications 19:1585-1595.
- Zipkin, E.F., P.J. Sullivan, E.G. Cooch, C.E. Kraft, B.J. Shuter and B.C. Weidel. 2008. Overcompensatory response of a smallmouth bass population to harvest: release from competition Canadian Journal of Fisheries and Aquatic Sciences 65:2279-2292.
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Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: During the past year we concluded an eight-year study of brook trout in an unstratified Adirondack Lake in which we found that an aggregate measure of chronically stressful summer water temperatures strongly influenced brook trout population level characteristics. Previous studies had concluded that brook trout are negatively affected by water temperatures over 20 degrees C, therefore we used the cumulative degree-days that bottom water temperature exceeded 20 degrees C (DD>20) as an index of chronic thermal stress. Across years with similar brook trout densities, hotter summer water temperatures resulted in decreased brook trout growth. However, we also observed positive growth in a year with warm water temperatures and relatively low fish density, which suggests that decreased density can mediate the negative impacts of warm water temperatures. Maximum stomach fullness of brook trout in this study was negatively related to water temperature. The number of brook trout spawning sites (known as "redds") were negatively correlated with DD>20 and were less dependent on female brook trout density. Periods of chronically stressful summer water temperatures resulted in extensive mortality of age two and older fish at 156 DD>20 and fish age one and older at 210 DD>20. In contrast, extensive mortality was not evident in any year classes when DD>20 was less than 115. PARTICIPANTS: Clifford Kraft (Associate Professor, Cornell University) directed project efforts. Jason Robinson (Ph.D Student, Cornell University, Field of Natural Resources) and Dan Josephson (Research Associate, Cornell University, Little Moose Field Station) were the primary individuals responsible for field data collection and data analysis, as well as all aspects of project implementation. Additional project support was provided by Kurt Jirka (Research Support Specialist, Cornell University) and Justin Chiotti (Research Assistant, Cornell University). TARGET AUDIENCES: Project results have been regularly reported in oral presentations and written summaries to a wide variety of private cooperators in the Adirondack region of New York, including members of the Adirondack League Club, Rock Lake Club, Wilmurt Lake Club, Mohawk Valley Chapter of Trout Unlimited and staff from the New York State Department of Environmental Conservation (including Steve Hurst, Jim Daley, Bill Schoch, Frank Flack, Chris VanMaaren, Leo Demong, and Rich Preall). PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Results from our long-term (e.g. eight year) study demonstrate that population studies of fish populations in lake ecosystems at the margin of the thermal range of a particular fish species can provide important insights into changes that will occur if temperatures increase in response to anthropogenic impacts. We concluded that brook trout in Adirondack lakes have, to date, been able to thrive during a decade in which summer temperatures have been relatively warm (by comparison with the past 100 years). We also concluded that increasing the population density of brook trout by stocking fish into a particular lake may exacerbate the negative impacts of warm summer conditions on this coldwater fish species -- and perhaps other trout and salmon that require cold water conditions to survive throughout the year. Results from this effort have provided the basis for a new effort to evaluate the impact of changing climate conditions upon brook trout in a variety of Adirondack lake types.
Publications
- Josephson, D.C., J.M. Robinson, B.C. Weidel and C.E. Kraft. 2008. Long-term retention and visibility of visible implant elastomer tags in brook trout. North American Journal of Fisheries Management 28:1758-1761.
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Progress 10/01/06 to 09/30/07
Outputs
OUTPUTS: In order to understand the potential impact of climate change on coldwater fisheries, we are identifying water temperature metrics that influence brook trout growth, reproduction and survival in Adirondack lakes. For the past eight years (2000 to 2007) we have surveyed a shallow lake (Rock Lake, Herkimer County) with no known thermal refuge for adult fish during a period of variable summer thermal conditions. Annual water temperature, gill net, trap net, angling, and redd survey data were collected. These data have provided us with the ability to identify cumulative annual degree-days exceeding 20 degrees C as the measure of annual thermal stress that had the most influence on annual brook trout reproduction and mortality. A threshold of 155 degree-days had a negative influence on reproductive activity and successfully predicted mortality events in two of eight study years. Additionally, growth was negatively impacted by severe summer temperature conditions. Ongoing work
will establish more precise degree day thresholds at which substantial mortality occurs and reproduction is negatively impacted that will be useful for managing wild brook trout populations in thermally marginal lake systems. This study has highlighted the importance of temperature monitoring in thermally stressed aquatic ecosystems and considering degree-days, in addition to temperature thresholds, when making fishery management decisions.
PARTICIPANTS: Individuals who worked on this project included Clifford Kraft, Principal Investigator (project design and implementation), Jason Robinson, Graduate Student (project design and implementation), Peter Stevens, Graduate Student (project design and implementation), Daniel Josephson, Research Associate (project design and implementation). Partner organizations included the Adirondack Lake Survey Corporation, New York State Department of Environmental Conservation (NYSDEC), Adirondack League Club, Rock Lake Club, Wilmurt Lake Club and Bay Pond Park. Collaborators and contacts included Barry Baldigo, Watersheds Research Section, US Geological Survey, Troy, NY; Rich Preall, Bureau of Fisheries, NYSDEC (Ray Brook); Chris VanMarren, Bureau of Fisheries, NYSDEC (Watertown); Jim Daley, Bureau of Fisheries, NYSDEC (Albany).
TARGET AUDIENCES: Angler (e.g. Trout Unlimited) and conservation (e.g. Nature Conservancy) organizations, plus state (NYSDEC), private landowners, and local bodies of government (e.g. Town of Webb, Herkimer County) responsible for managing Adirondack lake fisheries.
Impacts
Based on these project results, we have identified information required to understand the ability of brook trout to survive in Adirondack lakes: (1) Summer water temperature (cumulative degree days exceeding 20 degrees C, which is the stressful temperature limit for brook trout), (2) groundwater hydrology (cold groundwater inputs to study lake shorelines), (3) brook trout population abundance & reproduction, and (4) adult brook trout body condition. We are attempting to more broadly implement data collection efforts in Adirondack lakes - in collaboration with other agencies and stakeholders - to understand the impact of changing climate conditions on brook trout populations.
Publications
- No publications reported this period
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Progress 01/01/06 to 12/31/06
Outputs
I. Round whitefish (Prosopium cylindraceum), also called frostfish, are a salmonid species that was once found in more than 80 Adirondack lakes. During 2006, we completed work evaluating the status and recovery of round whitefish in New York. An observed decline in round whitefish populations led to their listing as a New York State endangered species in 1983 and prompted the New York State Department of Environmental Conservation to begin a recovery program. As of 1979 round whitefish were found in fewer than 15 New York lakes and by 2000 there were only four known remaining self-sustaining populations. Round whitefish are an important component of lake food webs, consuming both zooplankton and benthic invertebrates. In turn, round whitefish are prey for larger sport fish such as lake trout. Based on our research efforts, we have concluded that: (1) many extirpated populations resulted from failed introductions during the 1800s, (2) that the decline in round
whitefish was caused by a combination of lake acidification, non-native species, and failed introductions, (3) non-native smallmouth bass reduce round whitefish recruitment and round whitefish growth is limited by intraspecific competition, and (4) several methods for capturing round whitefish in Adirondack lakes have been identified. II. In recent years we have also expanded our coldwater fisheries research efforts to evaluate the extent of mercury contamination in fish from Adirondack waters. Cornell researchers collected specimens of lake trout, brook trout, landlocked salmon, and smallmouth bass for mercury analysis in 2006, and results from these tests indicated that smallmouth bass and lake trout regularly exceeded recommended fish consumption advisory levels. We are continuing to conduct additional studies to determine the impact of lake chemistry and food web interactions on mercury levels in fish from Adirondack lakes. III. Suitable temperatures and dissolved oxygen are
required for the survival and growth of brook trout. The summers of 2005 and 2006 were unusually hot and provided an opportunity to evaluate the influence of warm summer water temperatures on brook trout populations in Adirondack lakes. Conditions in six stratified lakes (Canachagala Lake, Chambers Lake, East Lake, Fourth Bisby Lake, Green Lake, and Wilmurt Lake) and six unstratified lakes (Combs Lake, Lower Sylvan Pond, Mountain Pond, Panther Lake, Rock Lake, and Wheeler Pond) were evaluated. These lakes ranged in size from 6 to 200 acres, with maximum depths of 8 to 44 feet, and pH levels ranging from 5.8 to 7.0. Two contrasting patterns were evident by late summer in water temperature and dissolved oxygen surveys in stratified lakes: one in which dissolved oxygen was depleted below 5 ppm up to the thermocline depth, and one in which no dissolved oxygen depletion was evident. The primary difference between brook trout in stratified and unstratified lakes was that larger brook trout
were observed in stratified lakes. Based on our observations during these two summers, warm water temperatures primarily influenced brook trout growth, but did not influence overall abundance.
Impacts
Several species of coldwater salmonid fishes are native to the Adirondack Mountain Region of New York State. Although almost all coldwater Adirondack lakes historically supported wild, self-sustaining populations of these fishes, recent surveys indicate that only a small proportion of these waters still support thriving populations. Furthermore, mercury contamination of several of these species now present a human health concern, and warmer temperature conditions and changes in seasonal precipitation also present new challenges to native fisheries. We are maintaining ongoing studies of factors influencing the survival, growth and reproduction of brook trout, lake trout and round whitefish in Adirondack waters, with a special focus on anthropogenic factors that influence the ability to maintain and restore self-sustaining populations of these native species. Based on this research, we are implementing management practices to restore and sustain populations of these
fishes that will support angling fisheries.
Publications
- Lepak, J.M., C.E. Kraft, and B.C. Weidel. 2006. Rapid food web recovery in response to removal of an introduced apex predator. Canadian Journal of Fisheries and Aquatic Sciences 63:569-575.
- Warren, D.R., S.D. Sebestyen, D.C. Josephson, J.M. Lepak, C.E. Kraft. 2005. Acidic groundwater discharge and in situ egg survival in lake spawning brook trout (Salvelinus fontinalis) redds. Transactions of the American Fisheries Society 134:1193-1201.
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Progress 01/01/05 to 12/31/05
Outputs
Previous fishery management and research efforts have identified several impediments to brook trout recruitment that continue to affect Adirondack waters, including acid deposition, absence of groundwater, competition and predation from introduced fish species, loss of spawning and nursery habitats, out-migration of mature fish, and behavior of stocked strains. For many waters, brook trout recruitment has been reduced due to a combination of these factors. For example, self-sustaining brook trout populations have been documented post-treatment in only 2 of more than 30 acidic western Adirondack lakes in which pH has been neutralized (limed) in the past 25 years. In addition, the chemical removal of competing/predating fish species (reclamation) has led to the development of self-sustaining brook trout populations in only two of ten western Adirondack waters reclaimed during the same time frame. Unfortunately, the factors required to establish self-sustaining brook
trout populations remain incompletely understood, though it is now apparent that groundwater availability and quality are key requirements. Brook trout reproduction in Adirondack streams and lakes relies on the presence of spawning habitat where upwelling groundwater is present. Sizeable tributaries are absent from many small lakes typical of the Adirondack mountains of New York, and in these cases, brook trout reproduction relies solely on areas of discharging groundwater along the lake shoreline. While groundwater is usually well buffered relative to lake ecosystems, we have documented acidic groundwater discharging into brook trout redds in a small lake in the western Adirondacks with poor wild brook trout reproduction (Warren et al. 2005). We are continuing to explore the prevalence of this phenomenon in Adirondack aquatic ecosystems, including an evaluation of watershed conditions that may promote the development of acid groundwater. In order to predict locations of sufficient
groundwater discharge for brook trout reproduction and summer thermal refuge, we have also implemented procedures used by hydrologists to predict locations that are likely to concentrate water (procedures described in the hydrology and soil conservation literature). A computationally simple topographic index (TI) was applied by Canadian researchers to identify nearshore groundwater discharge locations in several Algonquin Park lakes. They determined that this approach could successfully eliminate between 58 and 81% of lake shoreline as potential brook trout habitat. We have successfully implemented this predictive modeling approach for identifying brook trout habitat in Adirondack lakes, and have initiated field verification of the presence and use of groundwater by brook trout at these locations.
Impacts
Brook trout are endemic to the Adirondack Mountain Region of New York State. Although almost all coldwater Adirondack lakes historically supported wild, self-sustaining brook trout populations, recent surveys indicate that only a small proportion still support wild brook trout. Brook trout reproduction in Adirondack streams and lakes relies on the presence of spawning habitat where upwelling groundwater is present. We are developing landscape models to predict locations of sufficient groundwater discharge for brook trout reproduction and summer thermal refuge in Adirondack waters. These models will be used to identify lakes within which self-sustaining populations of brook trout can be restored.
Publications
- Warren, D.R., S.D. Sebestyen, D.C. Josephson, J.M. Lepak, C.E. Kraft. 2005. Acidic groundwater discharge and in situ egg survival in lake spawning brook trout (Salvelinus fontinalis) redds. Transactions of the American Fisheries Society 134:1193-1201.
- Smith, T.A. and C.E. Kraft. 2005. Stream fish assemblages in relation to landscape position and local habitat variables. Transactions of the American Fisheries Society 134:430-440.
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Progress 01/01/04 to 12/31/04
Outputs
Temperature plays an important role in the survival of brook trout, therefore we are identifying periods during which water temperatures in Adirondack lakes are stressful or lethal to brook trout. One long-term study lake, Rock Lake, is both uniformly shallow (maximum depth 20 feet) and has a large surface area (190 acres), therefore wind-generated currents regularly mix the water column throughout the summer. For the past four years (2000 to 2003), automated temperature loggers have been placed on an anchored buoy line in Rock Lake at three depths (0.5 m, 3.0 m, and 6.0 m) from May through October. Based on the daily maximum bottom water temperature recorded within Rock Lake from mid-June through the end of August over a four-year period, the frequency and duration of stressful conditions has varied dramatically from year to year. In 2000, maximum bottom water temperatures did not exceed 72 degrees F and conditions were only moderately stressful for brook trout
throughout the summer. Conversely, maximum bottom water temperatures exceeded 68 degrees F for long periods during 2001 and 2002. In both of these years, bottom water temperatures were lethal to brook trout (exceeding 77 degrees F) for a similar amount of time: nine days in 2001 and seven days in 2002. The summer of 2003 showed a swing back to cooler summer conditions, with bottom water temperatures never exceeding 75 degrees F; however, an extended period of stressful water temperatures (68 to 75 degrees F) occurred from mid-July through mid-August. We evaluated the cumulative number of days during which temperatures ranged from 68 to 79 degrees F to identify the frequency of chronic (i.e., stressful) and acute (i.e., lethal) thermal conditions during the four-year period. Based on these results, the most stressful and/or lethal thermal conditions for brook trout occurred in 2002, with 2001, 2003, and 2000 following in descending order of stressfulness. During 2001 and 2002, a large
number of days exceeded both stressful temperatures (75 days in 2001; 83 days in 2002) and lethal temperatures (7 days in 2001; 4 days in 2002). Lethal temperatures were never recorded during either 2000 or 2003; however, stressful water temperatures were more frequently observed in 2003 by comparison with 2000. We have used fall trap net catches to provide a measure of relative abundance that may be related to three potential temperature metrics, including (1) acute exposure to lethal temperatures greater than 77 degrees F, (2) chronic exposure to stressful temperatures greater than 68 degrees F, and (3) cumulative exposure to stressful temperatures greater than 68 degrees F. Our results to date suggest that stressful water temperatures have the greatest potential for explaining observed fall trap net catches of adult brook trout.
Impacts
Native strain selection and enhancement of lake tributary habitats can be implemented in northern lakes to restore and sustain native fish populations, particularly salmonid fisheries. Removal of non-native predators from Adirondack lakes is also a practical tool that can also be applied to restore native fish communities and productive salmon and trout fisheries in northern lakes.
Publications
- No publications reported this period
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Progress 01/01/03 to 12/31/03
Outputs
The recovery and presence of a heritage strain of brook trout within Honnedaga Lake (Adirondack Region, New York) was initially recognized during fall 2000, following 30 years of their absence from the lake due to reductions in lake water pH. This study was subsequently implemented to evaluate remaining impediments to sustaining this brook trout population, as well as to identify management practices that will help develop and sustain an angling fishery within this lake. To date, this project has involved: (1) Seasonal water quality surveys in the lake and its tributaries (beginning May 2002); (2) Fall assessments of brook trout spawning (beginning fall, 2001); and (3) Egg collections and stocking of Honnedaga brook trout fingerlings (fall 2002 & 2003); The project goal is to ensure the continuing recovery of the Honnedaga Lake brook trout fishery. The recovery of the Honnedaga Lake brook trout population is dependent on: (1) the continued improvement of lake water
chemistry, and (2) successful natural reproduction. Water quality surveys conducted within Honnedaga Lake during the past two years indicate that pH conditions remain marginal for brook trout survival and growth, though water quality in two lake tributaries is clearly sufficient for this purpose. We will continue to evaluate water quality and tributary habitat conditions, and their possible influence upon changes in brook trout growth and abundance observed during the course of this study. Based upon our recent two-year effort to enhance Honnedaga brook trout abundance via supplemental stocking, we will also evaluate the success of this effort through surveys conducted during upcoming years as these fish mature and grow.
Impacts
Native strain selection and enhancement of lake tributary habitats can be implemented in northern lakes to restore and sustain native fish populations, particularly salmonid fisheries. Removal of non-native predators from Adirondack lakes is also a practical tool that can also be applied to restore native fish communities and productive salmon and trout fisheries in northern lakes.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
For 40 years, angler harvest has been reported from a dozen oligotrophic Adirondack lakes (New York, USA) as part of a cooperative fishery research and management effort involving Cornell University scientists and private landowners. The relative abundance of fall-spawning salmonine fishes has also been estimated periodically in these lakes. Management of these coldwater fisheries has changed over the past forty years, reflecting the dynamics of environmental factors affecting fish communities and attitudes of anglers. Based on angler records and fall assessments, we have observed contrasting long-term trends in lake trout (Salvelinus namaycush) abundance in two lakes, likely reflecting historical differences in management practices, harvest, and environmental factors. In lakes dominated by brook char (Salvelinus fontinalis), we have observed substantial improvements in angler CPE and average weight of angler caught fish since 1958. In all fisheries, we have observed
both a decline in annual angler effort and a voluntary increase in the relative proportion of released fish in the reported catch. From 1970 through 1985, 15-35 percent of the catch was released by anglers; since 1991, over 60 percent of the catch has been released by anglers. Changed angling practices, in conjunction with research-based management of these lakes, have resulted in the development and maintenance of productive angling fisheries. This outcome has been achieved despite continued anthropogenic challenges to the quality of Adirondack ecosystems. In the spring of 2000 through the fall of 2001, a total of 19,529 smallmouth bass were removed from an Adirondack lake, predominately by boat electrofishing. Pre-removal population estimates indicate that at least 90 percent of the adult smallmouth bass population has been removed. Abundance indices (CPUE) of native littoral prey fish and crayfish species have increased following the reduction of the smallmouth bass population.
Predation risk has significantly declined for native littoral prey fishes. Growth and condition of the remaining smallmouth bass have improved, likely a result of lowered intraspecific competition. We expect improved growth and increased abundance of native char and prey species due to reduced predation and interspecific competition by smallmouth bass.
Impacts
Native strain selection, blocking of lake tributary outlets, and habitat enhancement can be implemented in northern lakes to restore and sustain native fish populations, particularly salmonid fisheries. Removal of non-native smallmouth bass from Adirondack lakes is a practical tool that can also be applied to restore native fish communities and productive salmon and trout fisheries in northern lakes.
Publications
- Schneider, R.L., E.L. Mills, and D.C. Josephson. 2002. Aquatic-terrestrial linkages and implications for landscape management. Pages 241-262. In: Integrating landscape ecology into natural resource management (Editors J. Lui and W.W. Taylor). Cambridge University Press, Cambridge, UK.
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