First field day completed, without a hitch!
That title was for my mom. In reality, there were a few hiccups - dried up streams, backwards batteries, missed alarms, sunset, etc... BUT we made it through.
A little background
Today I began field work for my master's thesis in Environmental Science and Policy at George Mason University. My research will focus on fish passage use at road crossings, in northern Virginia portions of Potomac River tributaries. In particular, I hope to determine if two anadromous fish species and two invasive species are present at each crossing, as well as if they are able to cross from one side of the passage to the other. An anadromous fish is one that spends its adult life in the ocean, in this case the Atlantic, but performs migrations into freshwater tributaries to spawn. An invasive species is an organism that inhabits an area outside of its historic range, and typically outcompetes local organisms for resources. The two species of anadromous fish I am interested in are Alewife (Alosa pseudoharengus) and Blueback Herring (Alosa aestivalis), both of which are collectively named river herring and are managed together due to their similar physical appearance. Intense habitat degradation resulted in the need for formal protection of these two species, and as such, the Potomac River populations are currently under a moratorium (i.e., cannot be fished) [1]. The two invasive fish species I am interested in are Blue Catfish (Ictalurus furcatus) and Northern Snakehead (Channa argus), both organisms that have the potential to negatively impact the persistence of river herring if present in overlapping stream reaches.
In order to answer these questions, I am collecting 1 liter water samples, as well as water quality measurements (e.g., temperature, turbidity, dissolved oxygen, pH, and streamflow), above and below road crossings from streams that meet the following criteria, as indicated in the Freshwater Network Chesapeake Region's Fish Passage Prioritization project tool: 1) are within the potential current range of Alewife and Blueback herring (i.e., areas just outside of the known current range with no definitive barrier to movement, but lack supporting data) and 2) have a road crossing intersecting the stream (i.e., the stream passes under a bridge or through a culvert).
You may wonder, why water samples?
When organisms are present in an environment, they constantly shed DNA through saliva, reproductive fluids, skin, and more. This DNA resides in the surrounding environment (e.g., water or soil) for a short period of time once leaving the organism, and can be used to identify which species are, or were, once present. This type of sample is called environmental DNA, or eDNA, and relative to traditional biological monitoring approaches (e.g., 24-hour block nets) is a non-invasive, time and cost effective method.
So you collected water... now what?
Once water samples were collected, we brought them back to the lab to filter using hand pump filtration set ups. Each water sample was passed through a 1 micron pore size, 47 mm diameter filter paper. Then, the filter paper was placed in a tube and frozen in a -80 degree Celsius freezer. At the end of this field season, all frozen filters will be transported (in a cooler) to the University of Maryland Center for Environmental Science's Horn Point Laboratory (Led by PI, Louis Plough) in Cambridge, MD, where all DNA will be extracted from the filter paper and amplified using quantitative PCR (qPCR) protocol. The qPCR will only indicate whether or not any river herring DNA were present in each sample. In order to determine which species specifically (i.e., Alewife, Blueback herring, or both) were present, the samples that indicated river herring "hits" will then be sent to another lab for Sanger Sequencing. The presence of Blue Catfish and Northern Snakehead will be determined by a third party lab using high through-put metabarcoding.
There are many more field and lab days ahead, but we are off to a promising start and I am excited for what the remainder of this season will bring!
Reference
[1] ASMFC. 2009. Amendment 2 to the interstate fishery management plan for shad and river herring (river herring management). Atlantic States Marine Fisheries Commission, Washington, D.C. Available from http://www.asmfc.org/uploads/file/amendment2_RiverHerring.pdf [accessed January 2013].