This article is based on a recent paper, Spawning site fidelity and apparent annual
survival of walleye (Sander vitreus) differ between a Lake Huron and Lake Erie tributary,
in Ecology of Freshwater Fish, The paper is available here.
Imagine you are a fish in a Great Lake preparing to spawn. Where would you go? How
would you find a mate? If it's your first time spawning in one of these vast lakes,
then you might have to pick a spot and hope for the best, or use some other clue
to find a spawning location. But if it's your second time and you already know the
first place you spawned was a good one, wouldn't you go back to the same place again?
New research funded by the Great Lakes Fishery Commission suggests walleye do just
For fish, the habit of returning to the same place year-after-year to spawn is called
"spawning site fidelity". Spawning site fidelity can be a consequence of learning
by fish, or the result of imprinting while young on natal, or birth, locations (called
natal homing). Either way, returning to previous spawning areas is advantageous
because fish experience less risk when they spawn; that is, a fish can safely assume
if mates were present last year, mates will likely be present again in future years.
Likewise, habitat suitable for spawning one year is likely to be suitable in subsequent
In the past, scientists studying walleye spawning site fidelity in the Great Lakes
had to infer fish behavior after-the-fact based on data obtained from marking a
fish with an external tag, such as a jaw tags, and recapturing the fish months or
years later. Although this method was useful for telling scientists when a fish
was present at a particular location, the method only provided a snapshot of where
the fish had traveled. Scientists did not know when the fish arrived, how long the
fish stayed, how many times the fish visited, and where the fish went in between
visits to the specific locale.
A research team led by Dr. Todd Hayden and collaborators at Michigan State University,
the U.S. Geological Survey, Michigan Department of Natural Resources, Carleton University,
and the Great Lakes Fishery Commission, began tagging walleye with acoustic telemetry
tags to fill in those knowledge gaps. Acoustic telemetry allows scientists to track
movements of fish in great detail. If older methods like jaw tags provide data akin
to photographs, then acoustic telemetry is like a video, providing a detailed history
of movements and behaviors through space and time.
Acoustic telemetry works like electronic toll collection systems such as I-Pass
or E-ZPass: an internally-tagged fish swims through a network of receivers, like
a car passing through a toll-booth. The acoustic tag inside the fish continuously
"pings" a unique ID number, which receivers-essentially underwater computers-detect
and record, along with the date and time for every tagged fish that swims nearby.
By stationing receivers in a wide variety of locations (known migration corridors,
presumed spawning locations, and other places where scientists expect fish to be),
and later retrieving the receivers to download the data collected, scientists can
determine the exact movements of a particular fish.
For the walleye study, Dr. Hayden and collaborators wanted to confirm previous observations
of walleye spawning site fidelity with greater certainty than older tagging methods
allowed. Additionally, the research team investigated whether spawning site fidelity
differed between walleye aggregations in two spawning areas: the Tittabawassee River
(a tributary to Saginaw Bay in Lake Huron) and the Maumee River (a tributary to
the western basin of Lake Erie). The researchers chose these sites because of the
large number of walleye spawning at each site: the Tittabawassee River supports
the largest known spawning aggregation of walleye in Lake Huron, estimated at almost
200,000 fish, and the Maumee River supports a walleye population of approximately
During 2011 and 2012, the research team implanted acoustic telemetry tags in almost
500 walleye, then followed their movements through the 2014 spawning season. More
than 300 receivers were used to track the fish, including multiple receivers in
both rivers, near the river mouths, across key migration corridors, and along the
shorelines of Lake Huron and Lake Erie. In total, 311,180 detections from tagged
walleye were recorded on the receiver network. When the research team compiled the
detections to create movement paths for the walleye, the results were remarkable.
Walleye in the Tittabawassee River showed strong spawning site fidelity, with a
95% return rate to the river. Walleye in Lake Erie showed less spawning site fidelity,
although 70% were still faithful to the Maumee River.
"Greater fidelity of walleye tagged in the Tittabawassee River than in the Maumee
may be due to the close proximity of the Maumee River to other spawning sites in
Lake Erie," Dr. Hayden explained. "Multiple spawning sites in close proximity to
the Maumee River may increase the likelihood that some individuals will stray, choosing
a different spawning location from previous years."
In contrast, the Tittabawassee River supports the largest known spawning aggregation
in all of Lake Huron. Walleye that previously spawned in the Tittabawassee River
may return to the river in subsequent years because the probability of encountering
other spawning aggregations in Saginaw Bay or Lake Huron is low. Alternatively,
high spawning site fidelity for these fish may be due to natal homing, although
the potential for homing has not been studied in Lake Huron walleye.
Another notable outcome of this work was documenting lengthy migrations of walleye
in Lake Huron. Many walleye undertook annual migrations of almost 500 miles round-trip,
moving from spawning areas in the Tittabawassee River to feeding grounds in northern
Lake Huron. Although these long migrations had been suggested previously based on
jaw tag studies, the research team was able to confirm in detail the timing and
popular migration pathways of walleye migration in Lake Huron.
Understanding spawning site fidelity has important implications for management of
walleye in the Great Lakes. When spawning site fidelity is low or moderate for a
fish species in a given lake, those fish can be managed as a single population-essentially,
all of the fish in the lake can be considered to be part of a single group. However,
as spawning site fidelity increases, management actions need to increasingly focus
on individual populations within lakes. In other words, fish spawning in different
locations should be considered different groups, and may need to be managed using
different strategies tailored to each group. A good example of this approach is
Pacific salmon management on the west coast of North America. Salmon have high spawning
site fidelity to individual rivers which flow into the Pacific Ocean. Consequently,
in some areas, salmon in different rivers are managed as separate populations, with
river-specific harvest rates, seasons, and gear types allowed.
"Based on these findings, the current paradigm of managing the western Lake Erie
walleye stock as a single population may be justified given that approximately 30%
of walleye we tagged did not return to the Maumee River but likely spawned at different
locations in Lake Erie or did not spawn every year," explained Dr. Hayden. "Conversely,
due to the high spawning site fidelity of walleye to the Tittabawassee River, managers
may need to consider treating that river as its own unique population to conserve
adaptations of those walleye to the area."
"Walleye support the second largest fishery in the Great Lakes, and the single most
valuable fishery in Lake Erie," said Commissioner Jim McKane, chair of the Great
Lakes Fishery Commission. "Studies which inform management practices, such as the
one conducted by Dr. Hayden and colleagues, are essential to maintaining productive
fisheries and protecting our valuable natural resources in the Great Lakes."