Types of GEM
Category 1b GeM Project Example: Estimating distribution
Using environmental DNA to detect the expansion of Asian carp
into the Great Lakes.
Invasive species threaten the integrity of terrestrial and freshwater
systems around the world. For example, the sea lamprey (Petromyzon
marinus) invaded in the Great Lakes of the United States from
the Atlantic Ocean via canals constructed in the 1820s. The Great
Lakes support a $7 billion fishing industry, however, the lamprey
has had a dramatic impact: lake trout catch in Lake Huron fell
from 7.5 million kg in 1937 to virtually nothing in 1947. In Lake
Michigan, the catch fell from 12.1 million kg in 1946 to 885 kg
in 1953 (Mills
et al. 1993). To address the lamprey threat, U.S. and Canadian
control program has successfully reduced sea lamprey populations
by 90% at an average cost of $16 million annually (MN
|Asian carp can grow to 100 pounds and eat 40% of their body
weight daily. Such intake rates can devastate plankton-based
An ongoing threat to the Great Lakes are Asian carp. Seven species
of Asian carp have been introduced to the United States: feral
bighead, grass, and silver carps have all established reproducing
populations in several major rivers of the United States.
Asian carp produce massive numbers of eggs, potentially 1,000,000
over the lifetime of a single female. They also show tolerance
to a broad range of climatic conditions, and are very mobile,
being able to evade barriers. Given these factors for a fish that
can grow to 100 pounds and eats 40% of its body weight daily,
Asian carp are likely to cause ecological and economic effects
where-ever populations become established (Kolar
et al. 2007).
|eDNA monitoring results for Asian carp invading
Lake Michigan as of April, 2010.
In November 2009, the Army
Corps of Engineers reported the first evidence of Asian carp
in Lake Michigan. Genetic material from the carp was identified
in water samples beyond the barriers designed to stop carp from
reaching the lake.
This new approach, referred to as environmental DNA (eDNA), may
detect the presence of invasive species such as Asian carp much
earlier than direct observation.
All species release DNA into the environment via, for example,
mucous, feces, and urine. Although DNA degrades in the environment,
this is not an instantaneous process. As such, DNA can be held
in suspension and transported in water currents. Target species
can therefore be identified by filtering water samples then extracting
and amplifying short fragments of DNA.
In response to the detection of Asian carp in eDNA, federal officials
proposed a $78.5 million dollar effort to keep Asian carp out
of the Great Lakes early in 2010. Experts believe that control
of this species will be impossible once they establish a population.
Therefore, as with any exotic species, the sooner managers can
address the invasion, the more likely they are to be successful.
|Image of a gel showing detection of Asian carp in the waters
near Lake Michigan.
Advanced surveillance methods such as eDNA will allow greater
geographic coverage and allow early detection of species that
occur low densities, potentially before traditional methods could.
Limitations exist: these methods do not allow the size or sex
of individuals to be differentiated, nor is detection an index
to abundance. Samples can be collected anywhere, including locations
previously inaccessible to traditional methods such as electrofishing.
eDNA is a powerful new approach that may give greater advanced
notice to implement management programs.