Sea Lamprey Abundances Below Target In Lakes Michigan And Ontario And Are Decreasing
In Lakes Superior, Huron, And Erie
Ann Arbor, Michigan, November 12, 2019 - The Great Lakes Fishery Commission today
reported that populations of the invasive, parasitic sea lamprey remain at near-historic
lows, below targets, in Lakes Michigan and Ontario, and above target, but holding
steady, in Lakes Huron, Superior and Erie. Sea lamprey populations in Lake Huron
are close to target levels and have been holding steady for the past five years.
Abundances in Lakes Superior and Erie remain above target but have also decreased
significantly since the near-record highs observed in 2017. Sea lampreys are the
worst of the alien species to invade the Great Lakes. Before control, sea lampreys
destroyed many times the human fish catch. Today, sea lamprey control is the foundation
of the $7 billion Great Lakes fishery.
The Commission and its partners are encouraged by the overall decrease in abundance
of sea lampreys throughout the Great Lakes basin during 2019, but caution that environmental
conditions, such as a prolonged spring and high precipitation events, contributed
to the decrease.
Sea lampreys are native to the Atlantic Ocean but have been an unwelcome nemesis
in the Great Lakes since they invaded through man-made shipping canals in the early
20th century. By 1939, sea lampreys were ravishing the system and laying waste to
millions of fish. They do little good for the Great Lakes ecosystem as they prey
on important species and have no natural predators. Sea lampreys feed on the blood
and body fluids of fish by attaching to them with a tooth-filled, suction cup mouth
and file a hole through the fish's scales and skin with a razor-sharp tongue. The
average sea lamprey will kill up to 40 pounds (18 kg) of fish during its parasitic
stage. Sea lampreys prefer trout, salmon, whitefish, and sturgeon, but they also
attack smaller fish like walleye and perch.
Sea lampreys successfully reproduce in more than 500 Great Lakes tributaries and
thus, the battle to keep their populations in check must remain steadfast. Thanks
to more than six decades of successful sea lamprey control, the Great Lakes fishery
is worth $7 billion annually to the people of Canada and the United States today.
Before control, sea lampreys killed an estimated 103 million pounds (47 million
kilograms) of fish per year. Today, because of ongoing control, sea lampreys kill
less than 10 million pounds (4.5 million kilograms) of fish per year. Sea lampreys
are a coiled menace; they are extremely hardy and relentless, and history has shown
that if control efforts are ceased, or even relaxed for a short period of time,
their populations will rebound and the fishery will suffer.
The Great Lakes Fishery Commission was established by the Governments of Canada
and the United States in 1955 as a response to the catastrophic damage wrought by
the sea lamprey invasion. The 1954 Convention on Great Lakes Fisheries charges the
Commission with sea lamprey control and research, fisheries research and fisheries
management coordination. Sea lamprey control and research is conducted in partnership
with Fisheries and Oceans Canada, the US Fish and Wildlife Service, and the US Geological
Survey. Sea lamprey control consists of several techniques including lampricides,
barriers, and traps. The Commission also is evaluating the use of chemosensory cues
as a means to influence migratory and spawning behaviors. For more information,
"Keeping sea lamprey populations in check is absolutely critical if we want a fishery
in the Great Lakes," said Jim McKane, chair of the Great Lakes Fishery Commission.
"Each year, we must wage the battle anew. We cannot rest on our laurels or rely
on our past success. Sea lampreys are here to stay. Fortunately, we can control
their populations such that the damage they inflict on the fishery is a fraction
of what it once was."
McKane added: "It is estimated that only one in seven fish will survive a sea lamprey
attack. Sea lamprey abundance targets are our benchmarks for a healthy fishery—targets
for each lake were determined based on the average number of sea lampreys across
a five-year period when wounding rates were deemed acceptable. We continually strive
to reach and maintain a level of sea lamprey suppression that allows for the establishment
of a fishery that supports the millions of people that live, work, and recreate
in the Great Lakes."
"The Great Lakes sea lamprey control program is the most successful aquatic vertebrate
pest control program administered at an ecosystem scale in the world," said Doug
Stang, the Commission's vice-chair. "Its effectiveness is built upon partnerships
with both federal governments, the U.S. states the province of Ontario, tribes,
and the Commission. The fishery makes these lakes great, and without sea lamprey
control, there would be no fishery."
The latest sea lamprey status, by lake, is as follows:
- LAKE ONTARIO: Treatment effort on Lake Ontario has remained steadily consistent
for the past three decades. As a result, lamprey numbers have remained steadily
at or near target and at historic lows.
- LAKE MICHIGAN: Lake Michigan has received a considerable amount of targeted
treatment effort since 2012, including biennial treatment of the major lamprey-producing
Manistique River; this effort is evident in the continuation of historically low
abundances of sea lampreys. Lake Michigan likely benefits from treatments in the
northern portion of Lake Huron, such as the St. Marys River.
- LAKE HURON: For nearly a decade, heightened and targeted treatment strategies,
including two large-scale treatments of the St. Marys River, have been employed
in Lake Huron. While sea lamprey abundances are slightly above target, they are
still near historic low and are holding steady. Two tributaries to northern Lake
Huron, the Mississagi and Garden Rivers, have been a focus of the control program.
The Mississagi was treated in 2019 in partnership with the Mississauga First Nation
and the Garden River will be treated in 2020, as part of an ongoing alliance with
the Garden River First Nation. We expect the benefits of these treatments to be
seen in the 2021 population numbers.
- LAKE SUPERIOR: Lake Superior received a targeted treatment effort in both
2016 and 2019. The effects of the 2016 targeted treatment were not evident in the
2019 sea lamprey abundances and the impact of the 2019 targeted treatment will likely
not be seen until 2021. While sea lamprey populations are above target, they are
holding steady. Contrary to the high populations, lake trout wounding rates are
near target and decreasing, though there are pockets of higher wounding rates throughout
the lake. Environmental factors, including a prolonged spring and high precipitation
events, have long been hypothesized as being influential on sea lamprey catchability
and natural mortality; this hypothesis was corroborated this year in that trap catches
were low. In 2017 and 2018, the population estimate from the Brule River was greater
than 40% of the total catch, but this trend did not hold in 2019.
- LAKE ERIE: Challenging trapping conditions and poor catch rates in 2019 likely
influenced the abundance estimate, which is above target but holding steady. Near
record walleye year classes may be increasing, thereby creating predatory pressure
on recently metamorphosed juvenile sea lamprey, especially from the Huron-Erie corridor.