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As of 2004, this project is no longer current. Please see the Research Programs page for a list of current research projects.
Mechanisms Affecting Recruitment of Yellow Perch in Lake Michigan
GLERL Principle Investigator: Doran Mason
Collaborators:
John M. Dettmers (Illinois Natural
History Survey)
David J. Jude (University of Michigan)
R. Scott McNaught (Central Michigan University)
John Janssen (WATER Institute, Milwaukee).
Sponsor: Great Lakes Fishery Trust
Rationale: Yellow perch Perca flavescens
is the most important nearshore sport fish in Lake Michigan, comprising
nearly 85% of all recreationally caught fish and forming the basis of
a multi-million dollar fishery. Furthermore, yellow perch is 
an important ecological
link between the nearshore and pelagic food webs. Despite its economic
and ecological importance, the yellow perch population has declined drastically
during the last decade because of extremely poor recruitment. As a result,
the current annual harvest of yellow perch is significantly less than
the minimum annual harvest targeted by the Lake Michigan Fish Community
Objectives and the present harvest rate is not likely to increase in the
near future. Lakewide monitoring of yellow perch has revealed that few
young-of-year (YOY) yellow perch have been collected since 1989. However,
larval yellow perch densities showed no appreciable decline until 1994,
suggesting that recruitment failure occurred during the larval stage.
In fact, year-class strength is often determined during the larval stage,
although many possible mechanisms operate to influence year-class strength.
It is the focus of this proposal to explore which mechanisms currently
determine recruitment of yellow perch in Lake Michigan.
Hypotheses: We hypothesize that at least three mechanisms may structure the survival of larval yellow perch. Food resources (i.e., zooplankton) frequently limit growth and/or survival of larval fishes, and there are indications that nearshore zooplankton resources have declined during the last decade. Predation on larval yellow perch by adult alewife Alosa pseudoharengus does occur. This impact has not been quantified in a regional or lakewide context, but yellow perch recruitment is negatively related to adult alewife abundance. Finally, abiotic factors associated with upwelling events may interact with resource availability and predation to influence survival of yellow perch.
This project was completed in 2003. Currently there is no active research on this project
Hydroacoustics proved to be highly efficient at detecting larval yellow perch with swim bladders, but field density estimates were extremely sensitive to water surface conditions. The spatial and temporal overlap of larval yellow perch and potential predator distributions varied greatly among years, with highest predation likely occurring in offshore waters in 2000. This study provides insight into new methods for sampling larval yellow perch, and shows that predation on larval yellow perch may be a factor influencing yellow perch year-class strength.
2003 Plans
Field work. We will estimate regional density of larval yellow perch by relying on monitoring by the Yellow Perch Task Group (YPTG). This monitoring is one way in which GLFT funds will be matched by contributions from our own and other institutions. In combination with these larval estimates, we will quantify the abundance (using hydroacoustics) and diet (using gill nets or trawls) of alewife as they move nearshore to spawn. This information will then be combined with larval yellow perch density to quantify the potential impact of alewife predation based on our estimates of regional larval abundance. In addition, we will coordinate sampling for larval fishes and zooplankton on each side of the southern half of the lake to coincide with upwelling events. By simultaneously collecting comparable data on each side of the lake during upwelling, we can begin to evaluate the role of abiotic forces in driving the spatial distribution of larvae and their food resources. Finally, with help from YPTG members, we will collect YOY yellow perch for otolith and isotope analyses (see below).
Laboratory work. We will conduct experiments to explore 1) the interactive effect of temperature and food availability on yellow perch growth and survival, 2) temperature and time of day as cues for the timing of yellow perch emergence, and 3) competitive interactions among larval yellow perch and other planktivores (e.g., alewife). This experimental work will allow us to rigorously explore the varied conditions fish larvae might experience in the lake and quantify their response to these manipulations. By controlling these experiments in the laboratory, we will explore in much more detail and with much more certainty the importance of mechanisms that might take decades of field data to interpret. We also will examine otoliths and the stable isotope ratios of otoliths and muscle tissue from larval and YOY yellow perch from current sampling (broad regional data is available from 1998; we expect similar data during the next three years with YPTG cooperation) and historical collections dating from 1986 (Jude and Dettmers) to determine the temperature, growth, and integrated feeding profiles of surviving yellow perch. This information will allow us to pinpoint the conditions that fostered yellow perch survival.
2002 Plans
Emphasis will be placed on repeating the TS-experiments performed in 2001 and final processing and analysis of the field data. Predation models will be developed using the density and spatial distribution data from the hydroacoustics to estimate mortality rates in regions of alewife and larval yellow perch overlap to determine the potential for alewife to limit yellow perch recruitment in Lake Michigan.
Accomplishments to date
Field Sampling
Hydroacoustics data have been collected off Waukegan in
Lake Michigan from Late-May to Mid-July for 2000 and 2001. A Biosonics
129kHz DT6000 digital split-beam transducer was used for all field collection.
Use of the down-looking transducer configuration collected information
on alewife spatial distribution and abundance. Since larval yellow perch
are found near the surface, a side-looking transducer configuration was
employed to quantify larval yellow perch density and spatial distribution.
Bottom trawls for the collection of adult fish and neuston net tows for
larval fish were performed to identify acoustic targets.
Analysis of hydroacoustics was performed using EchoView v2.20 software (SonarData Pty Ltd., Hobart, Australia). Established equations predict the acoustic target strength of alewife (of lengths observed in 2001 trawl collections) to be approximately between -40dB and -50dB. Analysis of down-looking hydroacoustics data shows high concentrations of similar size targets in and above the thermocline from late-June through mid-July along the offshore transect.
Preliminary analysis of side-looking hydroacoustics detected targets of the size expected for larval yellow perch. Hydroacoustics estimates of larval yellow perch compared favorably to estimates of larval densities from neuston net samples, but only when sea state was calm. When waves and corresponding turbulence were present, near surface estimates of larval abundance using hydroacoustics quickly diverged from neuston net estimates.
Laboratory Work
Laboratory work was conducted in July 2001 to further assess the ability
of hydroacoustics 
to detect larval
yellow perch. A small fiberglass fish run (approximately 0.75m x 0.75m
x 2m) was cleaned and filled with filtered Lake Michigan water. Water
temperatures in the tank were approximately equal to those observed on
the lake during field data collection, and filtering the water eliminated
the risk of acoustic signal contamination that could result from debris
in the tank. The Biosonics 129kHz transducer was set on its side at one
end of the fish run, and aimed so the acoustic cone would run the length
of the tank. Fine adjustments of the transducer (e.g. raising. lowering,
tilting, and rotating) minimized noise from acoustic side-lobes. Larval
yellow perch with and without swim bladders were used. Fish without swim
bladders ranged from 6-11mm, and fish with swim bladders were 10-17mm.
Individual fish were released in the tank at a distance >1.5m from
the transducer face, and hydroacoustics data were collected as the fish
swam or sank through the acoustic beam. This allowed for target strength
estimation of larval yellow perch at different stages of development.
We also used a Biosonics 418kHz DE6000 split-beam transducer. This allowed
for the comparison of yellow perch target strength between frequencies,
as well as assess the potential for using a 418kHz transducer for data
collection in the field.
The 129kHz hydroacoustics system was able to detect all larval yellow perch which had inflated airbladders, but could not detect fish without an inflated airbladder. Target strengths measurements of airbladder fish were comparable to predictions calculated using established size to target strength relationships. The 418kHz hydroacoustics system was able to detect fish with and without inflated airbladders. The ability of the 418kHz to detect smaller fish, and fish without inflated airbladders, may be useful during future field sampling seasons if such equipment becomes available. The results of the 129kHz target strength estimations will assist with analysis of side-looking hydroacoustics data collected on Lake Michigan from 2000-2001, as well as offer insight into potential improvements of the side-looking technique for future field sampling.
Products
Publications
Balge, Matthew. 2003. Spatio-Temporal Dynamics of Yellow Perch- Implications for Yellow Perch Recruitment Alewife Interactions in Lake Michigan. Master of Science Thesis. Michigan State University.
Reports
Dettmers, J.M,, A.S. McNaught, D.M. Mason, D.J. Jude, and J. Janssen. Mechanisms Affecting Recruitment of Yellow Perch in Lake Michigan. Biannual Report to the Great Lakes Fishery Trust. January 2003. 12pp.
Presentations
Balge, Matthew P., Doran M. Mason, John M. Dettmers and Bernard Pientka. 2002. Evidence for spatio-temporal overlap of larval yellow perch and their potential predators in southwestern Lake Michigan. Midwest American Fisheries Society Meeting Bettendorf, Iowa. December 2002
Last updated: 2004-06-29 ahc