**ABSTRACT NOT FOR CITATION WITHOUT AUTHOR PERMISSION. The title, authors, and abstract for this completion report are provided below. For a copy of the full completion report, or with questions, please contact the GLFC via email at stp@glfc.org or via telephone at 734-662-3209.**
Compilation
and Analysis of Lake Erie Spatial Fisheries Data: A Proposal to Develop
Inter-Agency Geo-Referenced Database of Fishery and Tagging Data to permit
Spatial Analysis of Walleye and Yellow Perch Data
1 University
of Michigan
School of Natural Resources and
Environment
Institute for Fisheries Research
218 Museum Annex Bldg
1109 N. University Ave
Ann Arbor, MI. 48109-1084
May 2006
ABSTRACT:
Walleye and yellow perch support important
recreational and commercial fisheries in Lake Erie, and historically have been
managed as one unit stock. Although
spatial data on fishing activity (effort & harvest) and fish behavior
(tagging) have been collected by each agency on their Lake Erie fisheries for
many years, no comprehensive analysis or summary of spatial and geographical
stock distribution exists for Lake Erie walleye and yellow perch. The objectives of this study were to 1)
assemble spatial data on fishing effort and harvest, tag recaptures, survey
data and pertinent habitat data into a central, shared, spatial database that
supports queries and statistical analyses; 2) Analyze the data and map patterns
of fishing and fish density distributions; 3) Combine walleye catch rate data
with tag recapture data to determine monthly stock-specific exploitation rates
within 10-minute grids by angler and/or commercial fisheries; 4) make
recommendations for improving data collection; 5) relate habitat information to
fish distribution, relative abundance and movement. We assembled spatial data on fishing effort
and harvest, walleye tag recaptures, agency survey data and pertinent habitat
data into a central ACCESS database and ArcGIS framework that supports queries,
statistical analysis, and mapping.
Analyses of tag recapture data and modeling of walleye growth suggested
multiple walleye stocks exist that differ in growth and migration
patterns. Walleye tag return data
indicated that in summer, western basin (WB) walleyes migrated to the central
(CB) and eastern basins (EB) of Lake Erie and north to Lake St. Clair and
southern Lake Huron, while fish in the CB and EB basins of Lake Erie and in
Lake St. Clair were primarily resident. Temporal changes in sport and
commercial catch per unit effort (CPUE) for walleyes confirmed movements
suggested by tag return data. CPUE was highest in the WB in spring to early
summer, and then shifted to the CB in late summer and fall. Mean length of
recaptured walleyes, regardless of origin, was greater in the CB and EB of Lake
Erie than in the WB of Lake Erie or Lake St. Clair. The migratory WB walleyes
were larger and contained a higher proportion of females than resident WB
walleyes. The six largest WB stocks that expressed variable migratory behaviors
and population parameters could be assigned into three super groups: a group
with largest mean length at tagging, a group with very low percentages of
females and small mean length at tagging, and a group with low percentages of
resident fish and high percentages of females. Summer temperatures in the WB
often exceeded the optimal temperature (20-23C) for growth of large
walleye, and the migration of walleyes to the east might have been a
size-dependent response to warm summer temperatures that raised metabolic
costs. Cooler temperatures and attraction to soft-rayed forage fishes likely
contributed to an energetically favorable foraging habitat in the CB and EB
that attracted large walleyes. We tested this hypothesis by comparing walleye
movement patterns to habitat quality as indexed by a spatially-explicit growth
rate potential (GRP) model. The GRP
model was configured using forage fish gillnet CPUE and water surface
temperature data derived from AVHRR satellite imagery. Walleye GRP patterns were compared with
Ontario MNR experimental gillnet survey data that indexed relative abundance,
and with the observed walleye movement, growth, and life history patterns. Results demonstrated that growth rates of
young (<age 3 yrs) walleye were highest in the WB,
but growth rates of older walleye were higher in the CB and EB. Bioenergetic growth
rate potential (GRP) of age-2 walleye was highest in the WB, where age-2
walleye densities were highest.
Predicted GRP of older walleye did not vary among basins, in contrast to
growth and migration patterns.
Consequently, older Lake Erie walleyes may not select habitat to optimize
growth, but to lower metabolic costs.
Walleye in the WB and CB were distributed in water columns of high GRP,
whereas in the EB walleye favored areas with warm temperatures over areas of
high GRP. In contrast to walleye,
temporal and spatial variability in yellow perch density and catch rate
patterns did not indicate stock movement among basins. Surveys indicated age-0 and older perch were
found in high concentrations throughout Lake Erie, with highest densities in
WB, followed by CB and EB. Ontario fall
gillnet surveys CPUE (#/net) and sport angler CPUE data (# fish/hr) also indicated relative abundance of older perch was
higher in WB and CB compared to EB.
However, biomass CPUE of commercial gillnet fishers indicated highest
catch rates were made in CB, followed by WB and EB. Seasonal trends in commercial gillnet and
sport CPUE data suggested highest catches were made in spring and fall. Neither sport nor commercial CPUE trends
indicated yellow perch movement across basins.
Our analysis of yellow perch spatial and seasonal CPUE trends are
supported by earlier tagging studies of yellow perch in western and central
Lake Erie indicating yellow perch move less 30 miles (48 km) over a
season. Analysis of yellow perch habitat
preference, as indicated by high densities, suggest that in WB perch were found
over shallow depths <15m, with predominantly low gradient mud bottoms of
high Hexagenia spp
density. In CB, perch were predominantly
found over low gradient mud bottoms in depths 13-33m. In EB, highest perch densities were found
over mud and sand-gravel substrates of intermediate gradient at depths from 20
to 40m.