Brook Trout Conservation and Management in a Changing Climate:
A long-term effort being conducted by current personnel - Dan Josephson, Justin Chiotti & Kurt Jirka - with ongoing assistance from former graduate students Jason Robinson and Brian Weidel
Increasing evidence of changes in climate conditions, along with a series of unusually warm summers since 1998, has prompted us
to monitor summer water temperatures and oxygen levels for the past eight years in a number of thermally stratified and unstratified Adirondack lakes in conjunction with ongoing evaluations
of brook trout populations. Based on eight years of data collection in one unstratified lake, we have identified a metric - the cumulative degree days of bottom water temperatures above 20°C - useful for predicting
summer brook trout survival. In this lake, total mortality of all age 1+ and 2+ fish occurred during two years in which 156 and 210 cumulative degree-days of bottom water above 20°C were observed. The cumulative degree day
metric also accounted for 85% of the variation in fall spawning activity (i.e. redd construction) by brook trout in this lake, and this negative relationship (i.e. warmer summer resulted in less spawning) was not influenced by the
abundance of mature females. In six study years during which the cumulative degree-days above 20°C was 115 or less, summer survival of brook trout was not influenced by temperature conditions. During the course of this work we also found evidence
that increased population abundance from supplemental fish stocking in a lake with a naturally reproducing population increased the negative impact of high temperatures on brook trout growth, suggesting that thermally stressful systems that are
supported by stocking could benefit from reduced stocking densities - hence we are continuing to evaluate the impact of stocking on brook trout growth, survival and abundance.
We are now building upon our previous work in Adirondack lakes to identify changing climate conditions that are now showing signs of detrimental impacts upon brook trout survival, reproduction and growth. We are pursuing a comprehensive data collection effort in six Adirondack lakes that represent a range of representative lake conditions in this region. By pursuing a thorough evaluation of lake conditions and key brook trout population characteristics in a broad range of lakes, we will develop a broad understanding of the biological response of this valuable and popular sport fish to a changing climate regime. Specifically, we will we are conducting seasonal evaluations of the following during each of the next four years (work began in 2008): (1) Water temperature, (2) groundwater hydrology (e.g. cold groundwater inputs to study lake shorelines), (3) brook trout population abundance, growth & reproduction, (4) brook trout diets, and (5) brook trout body condition.
The Environmental and Ecological Importance of Thiaminase in Aquatic Food Webs (Collaborators: Dale Honeyfield, USGS Northern Appalachian Research Lab; Esther Angert, Dept. of Microbiology, Cornell)
Environmental factors responsible for a large-scale and ongoing mortality of salmonine fishes from thiamin deficiency - regularly observed in the Laurentian Great Lakes and Baltic Sea for the past 40 years
- present a large unsolved mystery. Recent studies have demonstrated that the thiamin deficiency observed in predatory salmonine fishes is caused by the presence of a thiaminase, an enzyme that degrades available thiamin. Yet the source
and conditions responsible for increased thiaminase levels in fish, and subsequent fish mortality, remain poorly characterized. Although the primary hypotheses invoked to explain the presence of thiaminases within predatory fish have
focused on food web pathways leading to the accumulation of thiaminase within these fish, my collaborators and I are pursuing other perspectives to advance an understanding of this important problem in fisheries and aquatic ecosystem
management.
In my earlier work on this subject, conducted in collaboration with former graduate student Jesse Lepak and USGS Researcher Dale Honeyfield, we conducted laboratory experiments to evaluate the effect of two stressors on thiaminase activity in alewife, a species that consistently has high thiaminase levels. More recently, my collaborators and I have been pursuing leads provided by recent discoveries in the realm of molecular biology and structural chemistry that provide insights potentially useful to identifying the role of thiaminase in an ecological context, particularly with regard to environmental conditions likely to produce high thiaminase levels in fishes. We are pursuing experiments with cultured organisms in an attempt to manipulate conditions believed responsible for inducing the production or accumulation of thiaminase in aquatic organisms and aquatic food webs.
Fish Community and Population Response to Removal of Naturalized Smallmouth Bass in an Oligotrophic
Adirondack Lake
A long-term effort being conducted by current personnel - Justin Chiotti, Kurt Jirka & Dan Josephson - with ongoing assistance from
former graduate students Brian Weidel, Jason Robinson, Elise Zipkin and Jesse Lepak At the start of the new millenium (i.e. 2000) - following two years of pre-removal surveys - we initiated the removal of all smallmouth bass captured during Spring and Fall boat electrofishing surveys in the study lake; a similar removal effort was initiated in a smaller (100 ha) nearby lake in 2003.
In the larger lake the relative abundance of six native littoral species increased (4-90 times pre-removal abundance) in response to smallmouth bass removal, and decreases in relative predation risk during the experiment reflected the reduction in littoral predators.
A similar response was observed in the smaller lake, which is inhabited by fewer littoral species of fish. The population response of smallmouth bass to the intense harvest effort indicated that the population was resilient to removal, producing strong year classes throughout the experiment. Mechanical removal was successful at decreasing bass abundance and increasing native fish abundance, but has to date required ongoing annual harvest
to maintain the fish community benefits of reduced abundance of large (i.e. > 150 mm) smallmouth bass. Our results provide experimental evidence regarding the need to prevent littoral predator introductions in Adirondack waters and offer support for nonnative control wherever native fish species conservation is a management priority. As we continued to observe large annual recruitment of smallmouth bass following years of an intense bass removal effort, graduate student Elise Zipkin developed a density dependent, stage structured model to examine conditions under which population control through harvest could result
in the increase of a targeted species. Parameter values were derived from a 54-year dataset collected from another north temperate lake (Lake Opeongo, Ontario, Canada) smallmouth bass population. Sensitivity analyses identified the demographic conditions that could lead to increased abundance in response to harvest.
Of particular relevance to our intense removal effort, an increase in population abundance with harvest was most likely to occur when either: (1) per capita recruitment at low levels of spawner abundance was large, juvenile survivorship was high, and maturation of age-4 and older juveniles was moderately high, or (2) per capita recruitment at low levels
of spawner abundance was slightly lower, yet the maturation rate of age-3 juveniles and adult survivorship were high. Our modeling results together with empirical evidence from Little Moose Lake further demonstrate the importance of understanding population overcompensation as a substantial factor to consider in efforts to regulate population abundance through harvest.
Zipkin's work led to a broader analysis - across taxonomic groups - of population control control efforts where harvest has been employed to reduce the abundance of nuisance and invasive species.
These results identify key issues that have been seldom recognized by managers that are potentially generic across a variety of taxa. We are continuing to use these model results
to evaluate ways to further decrease smallmouth bass population abundance in our study lake, as well as understand ongoing population dynamics observed during the last decade. For further information: 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. [Link to Full article] Weidel, B.C., D.C. Josephson and C.E. Kraft. 2007. Littoral fish community response to smallmouth bass removal from an Adirondack lake. Transactions of the American Fisheries Society 136:778-789. [Link to Full article]
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. [Link to Full article]
Zipkin, E.F., C.E. Kraft, E.G. Cooch and P.J. Sullivan. 2009. When can nuisance and invasive species control efforts backfire? Ecological Applications. Ecological Applications 19:1585–1595. [Link to Full article]
Effects of Old-growth Riparian Forests on Adirondack Stream Systems (Collaborators: William
Keeton, University of Vermont; Former Graduate Student: Dana Warren) Forested streams within the northeastern U.S. typically provide a source of cold, clean
water, but many other aspects of the forested landscape also contribute
to abundant fish populations. Wood in lakes and streams provides important
fish habitat, yet human impacts on streamside forests throughout the northeastern
U.S. have changed the role that wood formerly provided in aquatic systems.
This research effort is focused on evaluating the structural attributes
of scarce old-growth riparian forests within the Adirondack region to
assess linkages between forest structure and in-stream habitat structure
and associated biological processes. For further information: Keeton, W.S., C.E. Kraft and D.R. Warren. 2007. Structure and dynamics of old-growth riparian forests and effects on low order Adirondack stream habitats. Ecological Applications 17:852-868. [Link to Full article]
Warren, D.R. and C.E. Kraft. 2008. Dynamics of large wood in an eastern U.S. mountain stream. Forest Ecology and Management. 256:808-814. Warren, D.R., W.S. Keeton, and C.E. Kraft. 2008. A comparison of line-intercept and census techniques for assessing large wood volume in streams. Hydrobiologia 598:123-130. For images of accumulations of wood within streams in old-growth Adirondack forests, click here. Implementing a Topographic Index Approach to Identify Locations of Groundwater Input Along Adirondack Lake Shorelines (Graduate Student: Peter Stevens) Brook trout (Salvelinus fontinalis) are dependent on locations of groundwater upwelling for spawning, nursery habitat and thermal refugia for both young-of-year (YOY) and adult fish. Landscape-scale anthropogenic disturbances, such as logging and road construction, have the potential to influence brook trout habitat by altering these groundwater regimes. Despite the importance of groundwater discharge zones to brook trout, few attempts have been made to empirically model or predict groundwater discharge into lakes. This collaborative project, initiated in summer 2006, is developing a modeling approach that can be used to identify areas of groundwater discharge in Adirondack lakes that provide refuge and spawning habitat for brook trout. During the course of this project, a water flow modeling procedure will be tested and evaluated in a variety of Adirondack lakes. This model will be implemented within a Geographic Information System (GIS) framework using readily available information. Fish surveys conducted in the nearshore zone of three study lakes during summer 2006 indicated that recently hatched brook trout were using cooler nearshore habitat locations that corresponded to model predictions.
This research project was funded by the New York Department of Environmental Conservation.
Restoration of Round Whitefish in Adirondack lakes (Former Post-Doctoral Associate:
Geoff Steinhart) The round whitefish (Prosopium cylindraceum),
once widespread in northern New York, has experienced a reduction
in distribution during the twentieth century. Also known as the "frostfish,"
this fish is characteristic of cold, oligotrophic northern lakes. Formerly known to be resident in more than 80 Adirondack lakes, 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. Little Moose Lake -- adjacent to the Little Moose Field Station -- contains one of the largest
thriving populations of round whitefish remaining in New York State. The round whitefish
was first classified as an endangered species by the New York State Department
of Environmental Conservation (DEC) in 1983 and was later ranked as a
priority species for restoration. Unfortunately, the causes for the decline
of round whitefish within their historic range were poorly understood. From 2004 through 2006, we evaluated the status and recovery of round whitefish in New York, as well as the seasonal distribution, growth and overall ecological role of these fish in lake food webs (i.e. as both predators and prey). Round whitefish consume both zooplankton and benthic invertebrates and, in turn, are prey for native lake trout and non-native smallmouth bass. Based on our research efforts, we have concluded that: (1) many extirpated round whitefish populations resulted from failed human efforts to expand the distribution of these fish during the 1800s, (2) that the decline in round whitefish was caused by a combination of low pH, interactions with non-native species, and failed introductions, (3) non-native smallmouth bass reduced round whitefish recruitment, (4) round whitefish growth is limited by intraspecific competition, and (5) we successfully developed several new methods for capturing round whitefish without extensive mortality in north temperate lakes. This study was funded by the New York State Department
of Environmental Conservation and the U.S. Fish and Wildlife Service. Project post-doctoral associate, Geoff Steinhart, is now on the faculty at Lake Superior State University where he plans to continue work on this species. Wood Dynamics Along the Terrestrial-aquatic Boundary in Northeastern Forests: The 1998 Ice Storm (Former Post-Doctoral Associate: Andrew A. Millward) The 1998 ice storm was a large-extent ecological disturbance that severely
affected eastern Adirondack forests. Ice damage produced widespread breakage
of limbs and trunks in susceptible trees. Although ice storms are regularly
occurring disturbances within northeastern North American forests, the
magnitude and extent of the 1998 storm exceeded "typical" ice
storms observed within the past 100 years. While plot and stand-scale
ecological impacts of ice storms have received attention insofar as tree
species vulnerability, stand age susceptibility, and microhabitat alterations,
larger-extent damage patterns have not been previously evaluated. To do
this, we employed the normalized difference vegetation index (NDVI) to
assess forest vigor and canopy density in atmospherically corrected Landsat
Thematic Mapper (TM) satellite images collected prior to and following
the 1998 ice storm. We compared forest condition prior to the ice storm
(1990 NDVI data) with forest condition observed in the post-storm image
(1998 NDVI data). Forest damage was separated from natural
variations in canopy reflectance by employing a generalized linear model
that incorporated in situ measurements. Our unpublished analysis indicates that greater forest canopy damage occurred along streams and lakes than locations inland from riparian or lake shorelines.
This project was funded by the Fulbright Fellowship Program and Hydro-One. Project post-doctoral associate, Andrew Millward, is now on the faculty at Ryerson University A previous publication from this work is: Millward, A. A. and C. E. Kraft. 2004. Physical influences of landscape on a large-extent ecological disturbance: the
northeastern North American ice storm of 1998. Landscape Ecology 19:99-111.[Link to Full article]
Declines
in native fish populations have been associated with the establishment
of introduced smallmouth bass (Micropterus dolomieu) populations
in the northeastern U.S. Introductions of non-native smallmouth bass have
limited the abundance and diversity of native soft-rayed fishes, altered
the trophic status of lake trout, and reduced brook trout biomass in Adirondack
lakes and other northern waters. This study has demonstrated the potential
for reversing the impact of a widely introduced, non-native fish predator
in a large (271 hectare) Adirondack lake. 
This
study is a collaborative effort between members of the Kraft lab group
and a team led by William Keeton, Associate Professor of Forest Ecology and Sustainable Forestry at the Rubenstein School of Environment and Natural Resources, University of Vermont. From 2002 through 2006, we surveyed old-growth, mature, and young, mixed
northern hardwood-conifer forests and associated streams within the
Adirondacks. We identified structural attributes of old-growth hardwood-conifer riparian forests in the Adirondack Mountains of New York that influenced in-stream wood recruitment and dynamics along 1st and 2nd order streams. Sites were classified as mature forest (6 sites), mature with remnant old-growth trees (3 sites), and old-growth (10 sites). Forest structure was characterized over stream channels and at varying distances from each stream bank. Large logs, debris dams and pools were surveyed; a line-intercept method was used to measure wood volume in streams and on the riparian forest floor. In-stream wood volumes were significantly greater at old-growth sites (200 m3/ha) compared to mature sites (34 m3/ha) and were strongly influenced by the basal area of adjacent forests. In-stream large-log densities correlated strongly with debris-dam densities. AIC models that included large-log density, debris-dam density, boulder density, and bankfull width provided the most support for predicting pool density. A greater proportion of wood-formed pools was found at old-growth sites by comparison with mature sites that were dominated by boulder-formed pools. Our results show that old-growth riparian forests provide in-stream habitat features that have not been widely recognized in eastern North America, representing another potential benefit of riparian forest management upon in-stream processes.
