Progress 10/01/01 to 09/30/06
Outputs
Activities on this project has centered on work in the Adirondacks, Oneida Lake, and the Great Lakes. Our primary tool for investigations of spatial patterns has been hydroacoustics. We have developed standard operating procedure of hydroacoustic surveys in the Great Lakes including investigations of the target strengths and its variability for important Great Lakes species like alewife and rainbow smelt. We have also developed a method for quantitative assessments of mysids using acoustics. We continued to incorporate experiments, field observations and models to predict the effect of changing environment on the spatial distribution of mysid shrimp, their predators (alewife) and their prey (zooplankton). Mysid behavior in artificial temperature and light gradients were consistent with field observations and allowed us to refine models of their distributions. Mysids are important predators on zooplankton in the Great Lakes and the spatial distributions of both mysids
and fish are dramatically affected by both temperature and light. Measurements of carbon and nitrogen stable isotope ratios in organisms have helped to identify and quantify energy sources and the relative trophic position of fishes in lake food webs. This approach can also be used to identify changes in the spatial pattern of habitat use in aquatic systems with distinct isotope signatures in key habitats. Shifting carbon sources and food web structure of an Adirondack lake trout population was assessed using measurements of the naturally occurring stable isotope ratios. Smallmouth bass abundance has declined precipitously in one lake due to a removal effort. Prior to the bass removal, lake trout in Little Moose Lake were largely restricted to the pelagic zone and relied on zooplankton as a food source. Following the bass removal, lake trout were expected to be able to more fully utilize the littoral zone and take advantage of increased numbers of near-shore native prey fishes
resulting from diminished smallmouth bass predation. As predicted, higher C-13 measurements indicate that lake trout assimilated more carbon from the littoral zone after bass removal. Lake trout also exhibited elevated N-15 measurements and increasing numbers of prey-fish in their diets following bass removal. Much of the current research on harvest and its subsequent effects on population dynamics focus on maximizing yield. However, harvest (or the permanent removal of individuals) can also be an effective method to control over-abundant species where the goal may not be to maximize yield. During 2005 and 2006, we worked on a nonlinear population model with stage and spatial structure to examine the possibility of control through harvest in populations with a known spatial structure and in cases where there the spatial structure has uncertainty. We apply this model to lake trout and white sucker populations in Adirondack lakes. The State of Lake Ontario, edited by M. Munawar was
published in 2003 with contributions from the PIs to three chapters. These works are important milestones in our understanding of the Lake Ontario ecosystem.
Impacts
Development of standard operating procedures for hydroacoustics will increase the availability of the technique for fisheries managers across the Great Lakes basin as well as in inland lakes. The negative impacts of non-native fishes in Adirondack lake systems can be reversed by removing dominant non-native predators that restrict native apex predators from being able to take advantage of food-rich lake habitats. This approach can lead to the restoration of native northern lake fish communities. Understanding the interactions between mysids, their predators and prey will allow for predictions of the effects of ecosystem change, such as increased water clarity and decreased nutrient loading, on important food web linkages in the Great Lakes. Investigations of spatial patterns in zooplankton and lower trophic levels have revealed large differences between the effects of exotics like zebra mussels and the predatory zooplankton Cercopagis pengoi in the nearshore and
offshore of the Great Lakes.
Publications
- Lepak, J.M., Kraft, C.E. and Weidel, B.C. 2006. Rapid food web recovery in response to removal of an introduced apex predator. Canadian Journal of Fisheries and Aquatic Sciences. 63:569-575.
- Parker Stetter, S. L., L. G. Rudstam, J. L. Stritzel Thomson, and D. L. Parrish. 2006. Hydroacoustic separation of rainbow smelt (Osmerus mordax) age groups in Lake Champlain. Fish. Res. 82:176-185.
- Smith, N. G., P. J. Sullivan, and L. G. Rudstam. 2006. Using otolith microstructure to determine natal origin of Lake Ontario Chinook salmon. Transactions of the American Fisheries Society 135:908-914.
- Warner, D. M., L. G. Rudstam, H. Benoit, E. L. Mills, and O. E. Johannsson. 2006. Changes in the nearshore zooplankton abundance patterns in Lake Ontario following establishment of the exotic predator Cercopagis pengoi. Journal of Great Lakes Research 32:531-542.
- Irwin, B. J. 2006. Evaluating effects of ecological change on important sport fishes in Oneida Lake, New York. Ph.D. Cornell University, Ithaca. Boscarino, B. 2006. An analysis of the environmental factors affecting the migration patterns and vertical distribution of Mysis relicta. Masters. Cornell University, Ithaca. Fitzgerald, D. G., B. Zhu, S. B. Hoskins, D. E. Haddad, K. N. Green, L. G. Rudstam, and E. L. Mills. 2006. Quantifying fish habitat in freshwater ecosystems with aerial photograph interpretation. Fisheries 31(2):61-73.
- Gal, G., L. G. Rudstam, E. L. Mills, J. R. Lantry, O. E. Johannsson, and C. H. Greene. 2006. Mysid and fish zooplanktivory in Lake Ontario: quantification of direct and indirect effects. Canadian Journal of Fisheries and Aquatic Sciences 63:2734-2747.
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Progress 01/01/05 to 12/31/05
Outputs
Activities on this project in 2005 have centered on spatial distributions of fish and invertebrates in Lakes Ontario and Champlain, the development of models of harvested population in a spatial context, and preparation of a manuscript Lepak, J.M., C.E. Kraft and B.C. Weidel. Rapid food web recovery in response to removal of an introduced apex predator that is now in press in the Canadian Journal of Fisheries and Aquatic Sciences.. We continued to incorporate experiments, field observations and models to predict the effect of changing environment on the spatial distribution of mysid shrimp, their predators (alewife) and their prey (zooplankton). Experiments were conducted in temperature control rooms in a new experimental facility at the Cornell Biological Field Station. Mysid behavior in artificial light gradients supported previous field observation of avoidance of light levels of 0.001 lux. A model of mysid vertical distribution was updated with these recent
experimental results. Understanding the extent of the diel migration on these freshwater shrimp and the interactions between predators and prey are critical for our understanding of their role in the food web and the effect of ecosystem changes on this important Great Lakes zooplanktivore. Much of the current research on harvest and its subsequent effects on population dynamics focus on maximizing yield. However, harvest (or the permanent removal of individuals) can also be an effective method to control over-abundant species where the goal may not be to maximize yield. In the case where the population is structured in some way (i.e. age, size, stage, or space), population control through harvest can be considerably more complicated. During 2005, we started to build a nonlinear population model with stage and spatial structure to examine the possibility of control through harvest in populations with a known spatial structure and in cases where there the spatial structure has
uncertainty. During 2006 we will apply this model to a freshwater fish population known to exhibit size and spatial structure. Other great lakes work involving spatial analysis with contribution from this project was also completed in 2005. One Ph.D. student (Sandra Parker Stetter) completed her degree in 2005 and has submitted two manuscripts on the analysis of spatial patterns in fish populations based on her thesis. We continue work on development of standard operating procedures for the use of hydroacoustics in great lakes systems.
Impacts
Development of standard operating procedures for hydroacoustics will increase the availability of the technique for fisheries managers across the Great Lakes basin as well as in inland lakes. Understanding the interactions between mysids, their predators and prey will allow for predictions of the effects of ecosystem change, such as increased water clarity and decreased nutrient loading, on important food web linkages in the Great Lakes. Native fish communities in Adirondack lakes can recover if an exotic top predator is removed and the methods developed for predator removal has potential as a management tool.
Publications
- Lepak, J. 2004. Stable isotope measurements as indicators of diet shifts in lake trout (Salvelinus namaycush) populations in northern lake ecosystems. M.Sc. Cornell University, Ithaca.
- Parker Stetter, S. L. 2005. Hydroacoustic evaluation of rainbow smelt Osmerus mordax abundance, spatial distribution, and cannibalism in Lake Champlain. Ph.D. Cornell University, Ithaca.
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Progress 01/01/04 to 12/31/04
Outputs
Activities on this project in 2004 have centered on spatial distributions of fish and invertebrates in Lakes Ontario and Champlain. Mysis relicta, an abundant freshwater shrimp in the Great Lakes, was the focus of research activities in Lake Ontario in 2004. We used a combination of experiments, field observations and models to predict the effect of changing environment on the spatial distribution of this shrimp, their predators (alewife) and their prey (zooplankton). Experiments were conducted in temperature control rooms in a new experimental facility at the Cornell Biological Field Station. Artificial temperature gradients show that the shrimp select temperatures in the 6 to 8oC, and rarely venture into temperatures over 16oC. The animals react to both predator smell and presence of zooplankton prey, and these factors modify their distribution in temperature gradients. Observations in the field confirmed the importance of the temperature and light gradients in
determining the distributions of mysids as well as their prey and predators. A model of their vertical distribution was published in 2004. Understanding the extent of the diel migration on these freshwater shrimp and the interactions between predators and prey are critical for our understanding of their role in the food web and the effect of ecosystem changes on this important Great Lakes zooplanktivore. The State of Lake Ontario, edited by M. Munawar, was published late in 2003 with contribution from this research group to three chapters. Research on Lake Champlain continued with the main focus on developing techniques for acoustic assessment of the important forage fish, the rainbow smelt. We determined the target strengths to be expected from different age groups, developed the algorithms to separate young-of-year and adults using acoustic data. We also compared geostatistical and standard methods for analyzing and understanding spatial distributions. These findings will be
included in the standard operating procedure for acoustics in the Great Lakes.
Impacts
Development of standard operating procedures for hydroacoustics will increase the availability of the technique for fisheries managers across the Great Lakes basin as well as in inland lakes. Understanding the interactions between mysids, their predators and prey will allow for predictions of the effects of ecosystem change, such as increased water clarity and decreased nutrient loading, on important food web linkages in the Great Lakes. The publication of the State of Lake Ontario is an important milestone for our understanding of this great lake.
Publications
- Johannsson, O.E., L.G. Rudstam, G. Gal, and E.L. Mills. 2003. Mysis relicta in Lake Ontario: Population dynamics, trophic linkages, and future questions. In: Munawar, M. (ed.) State of Lake Ontario (SOLO)Past, Present, and Future. Ecovision World Monograph Series.
- Mills, E.L. 2003. Preface. In: Munawar, M. (ed.) State of Lake Ontario (SOLO)Past, Present, and Future. Ecovision World Monograph Series.
- Gal, G., L. G. Rudstam and O. E. Johannsson. 2004. Predicting Mysis relicta vertical distribution in Lake Ontario. Arch. Hydrobiologie 159:1-23
- Negley, T.L., E.L. Mills, B. Baldwin, R. OGorman, and R.W. Owens. 2003. The ecology and impact of the invasion of Lake Ontario by the zebra mussel (Dreissena polymorpha) and quagga mussel (D. bugensis). In: Munawar, M. (ed.) State of Lake Ontario (SOLO)Past, Present, and Future. Ecovision World Monograph Series.
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Progress 01/01/03 to 12/31/03
Outputs
Activities on this project has centered on work in the Adirondacks and the Great Lakes. Spatial patterns of fish in the Great Lakes and Lake Champlain are investigated with hydroacoustics. Currently, the investigators are developing a standard operating procedure of working with acoustics in the Great Lakes, and one paper that will be part of the knowledge base for developing these standardizations were published in 2003. Measurements of stable isotopes of carbon and nitrogen from a native apex predator, lake trout (Salvelinus namaycush), were used to evaluate spatial differences in lake food webs prior to and following the large-scale removal of non-native smallmouth bass from an Adirondack lake. The removal was initiated in May 2000 (30,000 bass removed, equivalent to 90 percent+ of the adult population), resulting in increased prey fish abundance. Prior to the bass removal, lake trout in Little Moose Lake relied primarily on benthic chironomids as a food source.
Following removal, changes were observed in lake trout delta13-C values (-25.9 percent o to -24.9 percent o) and trophic position (3.5 to 3.9), commensurate with observed increases in littoral prey fish abundance and their occurrence in lake trout diets. The quick shift of principal energy sources and trophic position of lake trout indicate a change in the spatial dependence and availability of food resources for apex predators in this lake, following removal of a dominant, non-native predator.
Impacts
Development of standard operating procedures for hydroacoustics will increase the availability of the technique for fisheries managers across the Great Lakes basin as well as in inland lakes. The negative impacts of non-native fishes in Adirondack lake systems can be reversed by removing dominant non-native predators that restrict native apex predators from being able to take advantage of food-rich lake habitats. This approach can lead to the
Publications
- Rudstam, L. G., S. L. Parker, D. W. Einhouse, L. D. Witzel, D. M. Warner, J. L. Stritzel, D. L. Parrish, and P. J. Sullivan. 2003. Application of in situ target strength estimations in lakes - examples from rainbow smelt surveys in Lakes Erie and Champlain. ICES J. Mar. Sci. 60:500-507.
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Progress 01/01/02 to 12/31/02
Outputs
Activities on this project has centered on work in the Adirondacks and the Great Lakes. Spatial patterns of fish in the Great Lakes are investigated with hydroacoustics. Currently, the investigators are developing a standard operating procedure of working with acoustics in the Great Lakes, and two papers that will be part of the knowledge base for developing these standardizations were published in 2002. Measurements of carbon and nitrogen stable isotope ratios in organisms have helped to identify and quantify energy sources and the relative trophic position of fishes in lake food webs. This approach can also be used to identify changes in the spatial pattern of habitat use in aquatic systems with distinct isotope signatures in key habitats. Shifting carbon sources and food web structure of an Adirondack lake trout (Salvelinus namaycush) population was assessed using measurements of the naturally occurring stable isotope ratios 13C/12C and 15N/14N. Smallmouth bass
(Micropterus dolomieu) abundance has declined precipitously in Little Moose Lake, a 271 hectare oligotrophic lake in the Adirondack mountains (New York, U.S.A.) due to a removal effort initiated in May 2000. Prior to the bass removal, lake trout in Little Moose Lake were largely restricted to the pelagic zone and relied on zooplankton as a food source. Following the bass removal, lake trout were expected to be able to more fully utilize the littoral zone and take advantage of increased numbers of near-shore native prey fishes resulting from diminished smallmouth bass predation. The 13C/12C and 15N/14N ratios from lake trout tissue samples, as well as lake trout diet and condition, were examined prior to and following removal of smallmouth bass to identify the impact of smallmouth bass upon trophic position and ultimate carbon sources of lake trout. As predicted, higher deltaC13 measurements indicate that lake trout assimilated more carbon from the littoral zone after bass removal.
Lake trout also exhibited elevated deltaN15 measurements and increasing numbers of prey-fish in their diets following bass removal.
Impacts
Development of standard operating procedures for hydroacoustics will increase the availability of the technique for fisheries managers across the Great Lakes basin as well as in inland lakes. The negative impacts of non-native fishes in Adirondack lake systems can be reversed by removing aggressive predators that restrict native fishes from occupying food-rich lake habitats. This approach can lead to the restoration of native northern lake fish communities.
Publications
- Warner, D. M., L. G. Rudstam, and R. A. Klumb. 2002. In situ target strength of alewives in freshwater. Trans. Am. Fish .Soc. 131:212-223.
- Rudstam, L. G., A. J. VanDeValk and M. D. Scheuerell. 2002. Comparison of acoustic and standard estimates of larval fish abundance in Oneida Lake, New York. Fish. Res. 57: 145-154.
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