Aerial and Field SAV Observations

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Mattawoman Creek SAV, 9-17-11

September 21st, 2011 by Peter Bergstrom · No Comments

I surveyed about 2.5 miles of tidal Mattawoman Creek by kayak on 9-17-11, starting at the kayak launch at the end of Mattingly Road and paddling upstream, not quite reaching the bridge across the creek. The trip included high tide so it was only near the end of the trip that SAV was visible at the surface, but I found some almost everywhere I raked in the shallows.

Almost all of the SAV I found was hydrilla (Hv), with milfoil (Ms) and coontail (Cd) mixed with it in a few locations, and spiny naiad (Nm) mixed with it once. In the shallows, almost all of the SAV was mixed with either emergent or floating aquatic vegetation (EAV and FAV), although at the few places where I checked, Hv extended deeper than the EAV/FAV. See the map of the survey with species found labeled.

An interesting thing about the hydrilla beds on this creek is that they have a light signature in aerial photos, as opposed to the more usual dark signature that I’ve seen in photos of other areas. I found some of the densest beds next to a string of dredge islands, from waypoints 432 to 433 on my survey map. Dave Wilcox sent me the section of the 2011 SAV survey photo that shows those islands with the approximate bed outline drawn, which agrees well with what I saw. I saw additional Hv at waypoints 416 & 417 on the other side of the islands, but where SAV is mixed with a lot of EAV/FAV it is hard to identify it in aerial photos, so the aerial survey underestimates the amount of SAV where it is mixed with EAV/FAV.

The SAV I found here was almost exactly the same species that I found on the tidal fresh Patuxent on 6-25-11; see my report here. The main difference was that the SAV was much more abundant and widely distributed on Mattawoman Creek than on the Patuxent. Also, the Hv on Mattawoman Creek (see photo) had smaller leaves and more closely spaced whorls than what I saw on the Patuxent in June.

Another difference was that we saw a lot more birds on Mattawoman Creek than on the Patuxent, probably because it had more fish. On Mattawoman we had one or more great egrets and/or great blue herons in view most of the time, and saw many gulls, terns, and kingfishers, as well as four bald eagles being mobbed by crows and several osprey, all piscivorous birds. The greater number of people fishing that we saw on Mattawoman Creek was also a clue to the fish populations. Most were catching catfish but you can also catch snakeheads there (see link to USDA page about them).

Tags: SAV Observations · SAV Restoration · Water Quality

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