Cisco update.
Posted: July 7th, 2025, 2:00 pm
Progress of the Cisco Program in Lake Huron (Dr. Dave Fielder, Fisheries Research Biologist and Modeler; and
Dr. Jose Bonilla-Gomez, USFWS Lake Huron Native Species Program Coordinator).
Dave and Jose presented a comprehensive update on the ongoing efforts to reestablish cisco
populations in Lake Huron, a key native pelagic prey species that historically supported robust food
web dynamics and commercial fisheries throughout the Great Lakes.
Background and Justification
Cisco once supported commercial harvests of over 4 million pounds annually in Lake Huron alone but
collapsed in the mid-20th century due to overfishing, habitat degradation, and competition from
invasive species like rainbow smelt and alewife.
Recognizing cisco's ecological value, reintroduction efforts were formally initiated in 2003 as part of a
broader objective to restore native prey fish and enhance food web stability for predators like lake
trout, Chinook salmon, and walleye. The effort also aligns with Great Lakes Fishery Commission
(GLFC) fish community objectives.
Hatchery Production and Stocking Strategy
The U.S. Fish and Wildlife Service assumed primary responsibility for hatchery propagation, given the
scale of the project and limited capacity within Michigan DNR's hatchery system.
• Production Site: Jordan River National Fish Hatchery (USFWS)
• Annual Target: ~1 million fingerlings
• Marking: All stocked fingerlings are treated with oxytetracycline (OTC) to allow for future
identification.
• Stocking Focus: Northern Lake Huron, including areas adjacent to Saginaw Bay and Thunder
Bay.
Dr. Bonilla-Gómez noted that gametes are collected from remnant populations in northern Lake Huron
to maintain genetic integrity and ensure adaptability to current lake conditions.
Monitoring and Evaluation
Stocking success is being evaluated through multiple methods:
1. Spawning Assessment:
o In both 2022 and 2023, adult cisco were observed in Saginaw Bay exhibiting
reproductive behavior, indicating possible spawning.
o To date, over 60 OTC-marked adults have been recaptured in Saginaw Bay, providing
evidence of survival and return to natal areas.
2. Acoustic Telemetry with Predation Tags:
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o USFWS and DNR have partnered on tagging studies using advanced telemetry tags that
register predation events.
o Results show high initial predation rates, which were not unexpected for a reintroduction
scenario. Despite early losses, dispersal patterns among surviving fish were consistent
with expectations.
3. Recruitment and Natural Reproduction:
o Evidence of natural recruitment remains limited, but the presence of mature, marked
f
ish and repeat spawners is encouraging.
o Dave emphasized that successful reintroduction will likely require sustained stocking
over multiple year classes.
Strain Suitability and Habitat Use
In response to a question from Frank, Dave explained that the current source stock is genetically
similar to historic Lake Huron populations. However, early telemetry and netting surveys suggest some
of the stocked fish may be using nearshore and littoral zones, diverging from traditional pelagic
behavior.
This may reflect plasticity in habitat use or adaptive responses to modern lake conditions shaped by
dreissenid mussels, round gobies, and altered thermal profiles.
Jose confirmed that ongoing research is evaluating habitat use and potential strain-specific behavior
to refine future stocking efforts.
Health and Hatchery Concerns
Steve Shafto asked about disease or health issues at the hatchery. Jose noted that while occasional
health issues occur—as is typical in hatchery environments—the USGS Fish Health Center has been
proactive in monitoring and treating outbreaks. Overall fish health has been good, with no significant
concerns that would jeopardize stocking operations.
Long-Term Outlook and Funding
The program is currently funded through federal sources, primarily the Great Lakes Restoration
Initiative, through FY2025. Both speakers expressed concern about potential funding shortfalls beyond
that time and stressed the importance of federal support to maintain momentum.
Tom Andris asked whether the program was originally intended as a 10-year effort and whether it
should continue. Dave responded that sustained stocking over multiple generations is necessary, and
periodic strong year classes (even every 5 years) may be sufficient for reestablishment.
He emphasized that the current effort is both an ecological restoration and an evaluation study.
Stocking is not an end goal, but a tool to determine whether naturalized cisco populations can take
hold in modern Lake Huron.
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Dr. Jose Bonilla-Gomez, USFWS Lake Huron Native Species Program Coordinator).
Dave and Jose presented a comprehensive update on the ongoing efforts to reestablish cisco
populations in Lake Huron, a key native pelagic prey species that historically supported robust food
web dynamics and commercial fisheries throughout the Great Lakes.
Background and Justification
Cisco once supported commercial harvests of over 4 million pounds annually in Lake Huron alone but
collapsed in the mid-20th century due to overfishing, habitat degradation, and competition from
invasive species like rainbow smelt and alewife.
Recognizing cisco's ecological value, reintroduction efforts were formally initiated in 2003 as part of a
broader objective to restore native prey fish and enhance food web stability for predators like lake
trout, Chinook salmon, and walleye. The effort also aligns with Great Lakes Fishery Commission
(GLFC) fish community objectives.
Hatchery Production and Stocking Strategy
The U.S. Fish and Wildlife Service assumed primary responsibility for hatchery propagation, given the
scale of the project and limited capacity within Michigan DNR's hatchery system.
• Production Site: Jordan River National Fish Hatchery (USFWS)
• Annual Target: ~1 million fingerlings
• Marking: All stocked fingerlings are treated with oxytetracycline (OTC) to allow for future
identification.
• Stocking Focus: Northern Lake Huron, including areas adjacent to Saginaw Bay and Thunder
Bay.
Dr. Bonilla-Gómez noted that gametes are collected from remnant populations in northern Lake Huron
to maintain genetic integrity and ensure adaptability to current lake conditions.
Monitoring and Evaluation
Stocking success is being evaluated through multiple methods:
1. Spawning Assessment:
o In both 2022 and 2023, adult cisco were observed in Saginaw Bay exhibiting
reproductive behavior, indicating possible spawning.
o To date, over 60 OTC-marked adults have been recaptured in Saginaw Bay, providing
evidence of survival and return to natal areas.
2. Acoustic Telemetry with Predation Tags:
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o USFWS and DNR have partnered on tagging studies using advanced telemetry tags that
register predation events.
o Results show high initial predation rates, which were not unexpected for a reintroduction
scenario. Despite early losses, dispersal patterns among surviving fish were consistent
with expectations.
3. Recruitment and Natural Reproduction:
o Evidence of natural recruitment remains limited, but the presence of mature, marked
f
ish and repeat spawners is encouraging.
o Dave emphasized that successful reintroduction will likely require sustained stocking
over multiple year classes.
Strain Suitability and Habitat Use
In response to a question from Frank, Dave explained that the current source stock is genetically
similar to historic Lake Huron populations. However, early telemetry and netting surveys suggest some
of the stocked fish may be using nearshore and littoral zones, diverging from traditional pelagic
behavior.
This may reflect plasticity in habitat use or adaptive responses to modern lake conditions shaped by
dreissenid mussels, round gobies, and altered thermal profiles.
Jose confirmed that ongoing research is evaluating habitat use and potential strain-specific behavior
to refine future stocking efforts.
Health and Hatchery Concerns
Steve Shafto asked about disease or health issues at the hatchery. Jose noted that while occasional
health issues occur—as is typical in hatchery environments—the USGS Fish Health Center has been
proactive in monitoring and treating outbreaks. Overall fish health has been good, with no significant
concerns that would jeopardize stocking operations.
Long-Term Outlook and Funding
The program is currently funded through federal sources, primarily the Great Lakes Restoration
Initiative, through FY2025. Both speakers expressed concern about potential funding shortfalls beyond
that time and stressed the importance of federal support to maintain momentum.
Tom Andris asked whether the program was originally intended as a 10-year effort and whether it
should continue. Dave responded that sustained stocking over multiple generations is necessary, and
periodic strong year classes (even every 5 years) may be sufficient for reestablishment.
He emphasized that the current effort is both an ecological restoration and an evaluation study.
Stocking is not an end goal, but a tool to determine whether naturalized cisco populations can take
hold in modern Lake Huron.
Page 13 of 17