Genetic Monitoring for Managers


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 DNR 2010).

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Asian carp can grow to 100 pounds and eat 40% of their body weight daily. Such intake rates can devastate plankton-based food webs.

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).

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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.

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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.