SAV Survey

Submerged Aquatic Vegetation (SAV) Survey, Neabsco Creek, Woodbridge, VA


Jim and I performed an SAV survey of the fresh-tidal headwaters of Neabsco Creek this morning.  We launched out of Smallwood State Park in Charles County, Maryland at 4:30 AM and were on-site in Woodbridge by 5:00 AM.


It was important for us to be on-site at the peak of high tide.  The tidal range on the Potomac is a bout 3-feet between high and low tide, and we were worried that portions of our study area might be inaccessible exposed tidal flats if our timing was off.


With newly flown, close-up aerial photography, we were able to survey most all of the study area, less a portion blocked by a large sycamore that fell over (recent beaver activity) an open water portion of one of the three dendrite stream stems.  Our mapping included multiple spot checks for depth (bathymetry).


We GPS field-located all of our findings, which we will later plot onto CAD mapping.  Several open water streams splay out onto a broad wetland delta.  From open water of the channels, the first zone of vegetation is usually SAV, then backed by a secondary zone of spatterdock, mixed with pockets of pickerelweed.  This zone transitions into high marsh, dominated by wild rice, smartweed and mixed obligate forbs.

In the winter time much of this bay will be expressed as shallow open water, as the vegetation dies back.


We mapped hydrilla (Hydrilla verticillata) with regularity, mixed with small amounts of coontail (Ceratophyllum demersum).  Hydrilla occupied about 80-percent of the margins of the open water creeks.


The streams began to further braid and became ill-defined as we worked to the backs of the study area.  Spatterdock was the dominant, mixed with pockets of hydrilla.  I was surprised at the number of large crayfish I observed in the clear waters of the SAV.


We completed our work by 10:00 AM and the tide was moving out fast, draining the Neabsco out into the Potomac (the effects of the 6-hour range for the twice-a-day high/low tide cycle).  By 10:00 AM the SAV flats were compressed and impassable, loaded with opportunistic egret and heron.


Leaving out from the Neabsco train trestle, we observed an extensive bed of wild celery (Vallisneria americana) mixed with spiny naiad (Najas minor) all along the frontage of the rock outcroppings of Leesylvania State Park and Freestone Point.


We motored across the Potomac and back to the Mattawoman, stopping for a little bit of after hours fishing.  At the mouth of the Mattawoman, along the walls of the Indian Head Naval Facility (Main Side), I was able to bag a largemouth bass from along the edge of the grass line.


Moving further upstream along the north bank and around the ordinance burn point, I landed a redfish (Sciaenops ocellatus)!  I felt like I was in the mangrove marshes of Florida.  What a special catch!  Redfish occur in the Gulf of Mexico, from Texas, around Florida and up along the Atlantic coast to Virginia.  They are certainly uncommon/infrequent in Maryland and listed as rare in New Jersey, with Virginia representing the northernmost extent of its natural range.


The Latin word ocellatus means oscillated or “spotted,” as identifiable spot or spots occur on or near the tail.  The spot is a “false-eye” leading predators to strike at the tail, allowing the redfish a better opportunity to elude being eaten.  Redfish also have chameleon qualities, with body pigmentation that can change from deep bronze to bright silver, depending upon environ.


They are absolutely delicious to eat, but I released this one.  I’ve always considered the redfish an indicator species of relatively good habitat.  The timely link below suggests the fish made a push into Maryland waters due to the lack of rainfall and higher salinity of the Chesapeake Bay.  I did see lots of crab pots on the Potomac.

Check out the following article from today’s (9/12/12) WTOP News web site, entitled Unusual Fish Lurks Near the I-95 Woodrow Wilson Bridge,

A beautiful morning!