Chad Boyce Fisheries Biologist

Va. Dept. of Game and Inland Fisheries

3909 Airline Blvd. Chesapeake, VA 23321

(757)-465-6812

History and Importance of Submerged Aquatic Vegetation

(SAV) in Back Bay, VA

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Before we get started...Let’s acknowledge a few points! 1. Local history and culture is strongly opinionated when it comes to

everything pertaining to Back Bay! 2. Back Bay has an extremely dynamic history!

3. When it comes to improving Back Bay - especially regarding SAV in

the bay - my (VDGIF’s) goal is the same as yours!

4. INCREASE SAV COVERAGE THROUGHOUT THE BAY!!

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Notes on Measuring Salinity

Older reports show salinity as “% Sea Strength (SS)”, modern data reported as “parts per thousand (ppt)”

% Sea Strength – Convert to ppt Example = 5% SS (0.05 X 34 = 1.7 ppt 5% SS = 1.7 ppt 10% SS = 3.4 ppt (.10 x 34 = 3.4) 15% SS = 5.1 ppt (.15 X 34 = 5.1) Freshwater – 0 ppt Oceanwater – 34 ppt Current Back Bay average – 1- 2 ppt

The Past…

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Average Salinity in Back Bay 1925-2007 data source, Va Dept. of Environmental Quality

1933 storm

1935 storm

Ash Wed storm

Saltwater pumping

Saltwater pumping

drought

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Early Accounts of Back Bay Water Quality and SAV Forrest (1853) – “ …was very remarkable for extensive fishing operations and apparently greatest around the inlet.” Regarding the closing of Currituck inlet…”with the freshening of the sound, the saltwater fish disappeared and freshwater fish took their place.” Weiland (1897) – Regarding the closing of Currituck Inlet, “…Further there were such changes in vegetation as brought countless thousands of ducks of species that had been only occasional before. The salt water fishes were driven out and fresh water fishes took their place.” O’Connor (1929) – When referring to the condition of the bay’s grasses, “…has been a steady, progressive diminution in the number of ducks in Back Bay since about 1920…compares with the decrease of duck food.”

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Bourn (1932) - “Water is extremely turbid and …turbidity of the waters of Back Bay and Currituck Sound has probably been a chief factor responsible for the destruction of the submerged seed plants.” Coast Guardsman (1939) – “I have seen the grass in the middle of Back Bay so thick that the yellow shanks walked on it the same as if they were on land.” Bourn (1944) “While traveling from Refuge HQ to Ragged Island in 1944, considerable difficulty was had in clearing the boat propeller from sago pondweed…” Chamberlain (1948) – “…waters are very turbid and turbidity was primary factor limiting aquatic growth.”

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Unique History of Diverse Habitat and Fisheries Salinity Influenced Through Ocean Inlets 1500’s -1820’s

Open ocean inlets, Marine and brackish fishes (presupposed, i.e. sparse data), little SAV data ~1829 – Closing of New Currituck Inlet, almost immediate freshening of bay occurred, shift from marine to brackish SAV and fishes, improved SAV growths 1840-1900’s (“before 1924”– Frequent ocean overwash, SAV moderate (personal accounts), good numbers of fish and waterfowl,

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1920-30’s –Relatively Low SAV abundance, fish and waterfowl decrease, salinity <2 ppt, some overwash after 1933 storm. 1950 -1962- except during 1950-1952, Good SAV growths, Freshwater gamefish dominated, good waterfowl numbers, salinity <2 ppt 1962 -Ash Wednesday Storm, massive ocean overwash, initial SAV decrease, but resurgence in following years, avg. max salinity near breaches was 26 ppt with bay-wide average of 6 ppt, then back to <2 ppt until saltwater pumping initiated in 1965 .

June 1929 October 1946

October 1947

1956

June 1929

Maps of Historical Distribution of SAV (Sincock et. al. 1964)

1964- 1968- Post 1962 storm overwash - Explosion of SAV, pumping of seawater - (theorized ocean overwash rejuvenated SAV growth-ducks) 1968-1978 – Highest historical growths of SAV, initial saltwater pumping in 1965

Eurasian Watermilfoil (exotic plant first documented in 1966). *Important to note when referring to historical SAV in the bay, milfoil is an exotic, not documented in the bay before 1966 All other references to SAV prior to 1966 did not include milfoil

1979-1987 Nationally-ranked trophy bass fishery, even though SAV is steadily decreasing. Bass fishery collapsed in 1980’s. Saltwater pumping continued until 1987

When it comes to Salinity and SAV Abundance…1 + 1 ≠ 2

Timeline Post-1933 but Pre-1962 – low salinities (<2 ppt), SAV varied but remained moderate to low 1965-1987- Saltwater pumping initiated 1966 – Milfoil enters the bay, saltwater pumping continues 1968-1978- Milfoil explodes in growth, but salinity higher 1978- Milfoil begins to die-off, saltwater pumping continues 1987 – Saltwater pumping ceases, salinity is high but SAV abundance at lowest point in 30 years.

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Additional Notes on Introduction and Establishment of Eurasian Watermilfoil 1. First documented in 1966 2. Seeds could have over washed during 1962 storm or

saltwater pumping 3. Beginning of bass fishing boom, fragments on boat/trailer 4. Not uncommon behavior of exotic species upon establishment

- Documented presence, explosion in growth and distribution

- Rapid colonization by fragmentation and seed dispersal - Growth explosion followed by gradual or rapid period of

reduction of distribution (disease, nutrient limiting?)

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1987- late 1990’s Bass Fishery collapse, overharvest, lack of recruitment, poor water quality, low SAV Written off as “a big mud hole”, bass and waterfowl near non-existent Classic “Catch 22” - high turbidity and no SAV, No SAV because of high turbidity, look at exotics = even looked at hydrilla.

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Largemouth Bass Citations from Back Bay, Virginia 1965 - 2016

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% SAV Coverage vs Largemouth Bass Citations from 1965 - 1990

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Anecdotal Notes on SAV / Flooding Anonymous letter in Sincock report (~1920) “…people in this area have always been bothered occasionally by high water—even twenty-five (1899) to fifty years ago(1874)—but the water did not do so much damage because the waters did not stay as high as long.” Many Back Bay “old timers” refer to the periods of high SAV and bay water not fluctuating as much during wind events. Points to SAV density affecting water flow by creating friction. Likely that higher densities of SAV retards water flow and reduces amplitude and duration of water flooding events. More SAV means less wave action - Less waves mean less marsh island erosion. Loss of marsh islands allow floodwaters to flow with less resistance. i.e. wider channels.

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SAV Importance To Back Bay/Currituck Watershed 1. Improves water quality i.e. traps sediment, increases clarity etc. 2. Waterfowl Food source – seeds and plants 3. Essential Fish Habitat 4. Benefits to flood water mitigation, reduce duration of flooding events.

Questions?