Current and Recent Research Projects
Co-investigator: Bill Ardren, USFWS
Graduate student: Bret Ladago
Lake trout populations disappeared in the Great Lakes by 1960, due to the effects of overfishing and predation by exotic sea lamprey. Evidence of natural reproduction by stocked fish has been limited and is largely restricted to shallow, nearshore reefs, where littoral and exotic predators are highly abundant. In Lake Champlain, lake trout spawn at several sites lakewide, with extremely high egg and fry densities at three sites. However, annual assessments of adult lake trout collect only a low percentage of unclipped fish. My research focuses on the factors that affect lake trout survival between emergence from spawning reefs and the end of their first year of life.The invasion of alewife in 2003 poses a new threat to salmonids in Lake Champlain: alewife contain thiaminase, an enzyme that breaks down thiamine in their predators, lake trout and Atlantic salmon. When these species spawn, their eggs have insufficient thiamine, and the hatched fry exhibit behavioral and physical abnormalities known as Thiamine Deficiency Complex. We have been tracking the changes in egg thiamine levels since 2004; the current project will examine differences in severity of TDC in hatchery-reared and wild fry and impacts on foraging and predator evasion by fry.
The videos linked below were taken with a home-built ROV on a spawning 'reef' (actually a breakwall) in Lake Champlain. We hypothesize that the reef is particularly attractive to lake trout due to its proximity to a hatchery effluent stream, 0.5 km away.
Pre-spawning lake trout video Oct. 23
Pre-spawning lake trout with lamprey
Clustered lake trout
Swarming lake trout, late afternoon Nov. 6
Swarming lake trout, early evening Nov. 6
Co-investigators: Aude Lochet, post-doctoral associate, UVM; Stuart Ludsin, Ohio State University; Brian Fryer, University of Windsor
Funding agency: Great Lakes Fishery Commission
Sea lamprey is an nuisance species in the Great Lakes and Lake Champlain that is responsible for the decline of valuable commercial and recreational fisheries. Larval lamprey spend 4-6 years buried in stream sediments, but after metamorphosis they migrate to a lake and spend 12-18 months as parasites of teleost fishes, primarily lake trout and Atlantic salmon. Sea lamprey populations are controlled by barriers that block their access to spawning streams, and by treating streams and deltas with lampricides on a four-year cycle to kill resident larvae. Streams are prioritized for treatment based on larval densities; however, larval density may not be a good predictor of survival to the parasitic stage. A method is needed to identify the stream origins of parasitic sea lamprey in order to optimize choice of streams to treat with lampricides. Our research is focused on using the microchemistry of the statolith, or ear bone, of sea lamprey to identify their natal stream. The statolith acquires chemical elements in stream water during larval growth which can be detected using ICPMS (inductively-coupled plasma mass spectrophotometry). We have determined that we can identify the natal stream of larvae with a success rate up to 77%; however, analysis of tagged, known-origin parasites and spawners did not correctly identify their natal stream. Further analysis indicates that the statolith does not appear to be inert, as has previously been assumed for lamprey and teleosts; the chemical composition of statoliths alters during metamorphosis. Our current objective is to determine whether the chemistry of post-metamorphic sea lamprey can be used to identify the stream origin of parasites and spawners.
In the 1950s, over 80 acres of shoreline and submerged habitat near Alpena, MI, were degraded by inputs of lime kiln dust from a nearby industry. Valuable fish habitat, particularly spawning reef substrate, was lost due to covering and filling of interstitial space within the natural reef. This loss may be contributing to the lack of substantial progress toward restoration of self-sustaining lake trout populations. To remediate this damage, we constructed 27 artificial reefs in Thunder Bay in 2010 and 2011. The reef design allows testing of factors (reef orientation, height, and size) that attract spawning lake trout and lake whitefish and maximizes egg and fry survival. The reefs will also provide valuable foraging areas for walleye and basses.
|Habitat fragmentation in Lake
Co-investigators: William Kilpatrick, UVM
Funding: State Wildlife Incentive Grant, VT
Since the early 1800s, Lake Champlain has been progressively fragmented by causeways that create virtually isolated bays (Inland Sea, Mallet’s Bay, Carry Bay, the Gut, northern section of the Northwest Arm). The effect of these divisions on fish movement is largely unstudied. The combination of physical isolation or reduced connectivity between bays has resulted changes in water movement and nutrient retention, and may have created population sub-structuring of species such as smelt and lake whitefish. For example, although lake whitefish larvae are widespread and abundant in the Main Lake, extensive sampling in the Inland Sea in 2007-2009 yielded only one individual; no larvae were found in Mississquoi Bay, which once supported a thriving commercial fishery. The focus of this study is to examine genetic differentiation among whitefish populations in the isolated basins of Lake Champlain, and estimate the amount of exchange between basins.
|The Champlain Canal as an exotic
Funding agency: NOAA
Currently, 49 non-indigenous species are established or present in Lake Champlain. Of those species for which the vector of introduction is known, 40% likely entered the lake via the Champlain Canal which links the lake to the Hudson River, Mohawk River, and Great Lakes drainages. There is substantial probability of additional invasions, both from the Great Lakes, where over 180 exotic species are established, and the Hudson River with 91 exotic species. Most other pathways of invasion, including deliberate stocking, bait bucket introductions, and horticulture escapes, have been at least partially addressed by changes in management priorities or new legislation. The threat of unauthorized stocking of fish, and transport of exotics on boat trailers, is being addressed by increased public education and surveillance by stewards at public boat ramps. The canals remain a major and uncontrolled vector for invasive species introductions into Lake Champlain. The goal of this project is to determine the taxon-specific risk posed by the Champlain Canal for transmitting new exotic species into Lake Champlain. Specifically, the objectives are to broadly characterize the species community resident in a section of the canal (taxonomic diversity and species abundance), and identify taxa that are likely to use the canal as a vector in the future. Sampling included gillnetting, benthic grabs, handing sampling, boat electroshocking, and collecting organisms stranded in locks drained for annual maintenance. To date we have found 25 plant species, 21 molluscs, 40 fish, and 3 crayfish species, plus unidentified sponges. Twenty-one species are exotic either to the Hudson River, Lake Champlain, or both watersheds. Over half of the fish species in the canal are reproducing within the canal.
Graduate student: Seth Herbst (MS 2011)
Lake whitefish is one of the most important commercially fished species in the Great Lakes and, historically, in Lake Champlain. Populations of lake whitefish have recently declined in abundance and condition in the Great Lakes, in part due to the loss of one of their most important prey items, the burrowing amphipod Diporeia. Lake whitefish is rare in Lake Champlain, and commercial fishing has been limited to Missisquoi Bay for over 80 years. The goal of this project was to study the current status of lake whitefish in Lake Champlain (age structure, sex ratio, abundance on spawning grounds, diet) and compare these data with historic records in an effort to document changes in the population. Of particular concern was the possible effect of the introduction of zebra mussels, which have negatively affected whitefish in the Great Lakes. We compared Lake Champlain lake whitefish diet, condition, and energy density following the dreissenid mussel invasion to values for lake whitefish from Lakes Michigan, Huron, Erie, and Ontario. Lake whitefish larvae and adults were collected using ichthyoplankton nets, gillnets and bottom trawls, and their diet was quantified seasonally. Larval lake whitefish were found at sites throughout the Main Lake and larval densities were among the highest recorded for the species. Population characteristics in the Main Lake are characteristic of an unexploited population; however, evidence of spawning is absent, or rare, in portions of their historic range where habitat has been altered. In contrast to some of the Great Lakes, Lake Champlain lake whitefish did not show a dietary shift towards dreissenid mussels, but instead fed primarily on fish eggs in spring, Mysis diluviana in summer, and gastropods and sphaeriids in fall and winter. Lake Champlain lake whitefish condition and energy density were high compared to post-dreissenid lake whitefish from Lakes Michigan, Huron, and Ontario which consumed dreissenids, and similar to lake whitefish from Lake Erie which did not. Comparisons to populations in Great Lakes indicate that Lake Champlain lake whitefish diet and condition has not been not negatively affected by the dreissenid mussel invasion.
Last modified November 09 2012 08:56 AM