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US Fish & Wildlife Service FieldNotes

Night Moves: A Quick Look into Alpena's Ichthyoplankton Sampling for Early Detection of Aquatic Invasive Species 

Region 3, July 23, 2013
A sample collected from Sandusky Bay, OH during an Alpena FWCO Ichthyoplankton sampling cruise.
A sample collected from Sandusky Bay, OH during an Alpena FWCO Ichthyoplankton sampling cruise. - Photo Credit: n/a
The use of light traps was a major component for the Alpena FWCO Ichthyoplankton sampling. They effectively sampled shallow areas where the bongo net was unable to be used.
The use of light traps was a major component for the Alpena FWCO Ichthyoplankton sampling. They effectively sampled shallow areas where the bongo net was unable to be used. - Photo Credit: n/a

U.S. Fish & Wildlife Service fish biologists, Stephen Hensler and Eric Stadig, from the Alpena Fish & Wildlife Conservation Office (Waterford Substation) completed another larval fish sampling cruise. Armed with bongo nets and light traps aboard the R/V Kraken, the biologists searched for non-native species on Maumee and Sandusky bays. Larval fish sampling concluded on both bays after sampling in May, June, and July. This unique nighttime effort represents one of four portions of the Service’s large scale early detection monitoring program using traditional and non-traditional gear types within the Great Lakes.

 

Ichthyoplankton (a.k.a larval fishes) are planktonic, meaning they cannot swim effectively against currents under their own power. Early stage larvae swim poorly and are impacted by hydrodynamic condition such as seiches. Lake Erie is particularly prone to seiches because of its east-west orientation and shallow depths. Lastly, larval fish are heavily influenced by light conditions, such as exhibiting diel vertical migration being drawn to the surface by the moonlight. This behavior allows the larval fish to feed at the surface when their predators cannot see them as easily. This does, however, make them more susceptible to traditional sampling gear (such as bongo nets) during nighttime sampling.

The Alpena FWCO crew is seeing their larval fish sampling pay off with numerous samples filled with larval fishes. These samples will be analyzed with collaboration with U.S. Environmental Protection Agency (USEPA) offices in Duluth, Minnesota and Cincinnati, Ohio using both traditional taxonomic identification and genetic barcoding. Genetic barcoding is a particularly useful for early detection of aquatic invasive species, as results are automatically cross-checked against a global database of genetic codes for various types of species. The concept could provide an adaptation to fisheries monitoring plans worldwide.

Contact Info: Eric Stadig, 248-891-1298, Eric_Stadig@fws.gov