The distribution of submerged aquatic vegetation (SAV) in Chesapeake Bay, its tributaries, and the Maryland and Virginia coastal bays of the Delmarva Peninsula, was mapped from black and white aerial photographs. These were taken between June and December 2006, at a scale of 1:24,000, encompassing 181 flight lines.

CHESAPEAKE BAY

For 2006, 23,941 hectares (59,160 acres) of SAV were mapped in Chesapeake Bay and its tributaries.

However, in 2005 a portion of the Bay was not flown due to adverse weather in the spring and summer; therefore, portions of the James River were not fully mapped in 2005.

All direct comparisons to 2005 in the report are restricted to only those regions that were mapped in both years. For comparison purposes, partial totals for 2006 have been computed for CBP segments, Bay zones, and the entire Bay using only those regions mapped for both years.

Notable changes in SAV distribution were measured between 2005 and 2006. SAV decreased 25% from 31,671 ha (78,263 ac) in 2005 to 23,903 ha (59,068 ac) in 2006 in the regions mapped for both years.

SAV decreased in all three (Upper, Middle and Lower) geographic zones delineated for Chesapeake Bay. In 2006, SAV increased in 13, decreased in 41, and remained unvegetated in 24 of the 78 CBP segments.

Upper Bay Zone

In the Upper Bay Zone (17 CBP segments extending south from the Susquehanna River to the Chester and Magothy rivers), SAV decreased 20% from 7,877 ha (19,465 ac) in 2005 to 6,286 ha (15,532 ac) in 2006.

One of the 17 segments (or mapped portions) increased by at least 20% and by at least 5 ha from 2005 totals:

69%, Northeast River (NORTF), 54 ha (2006) vs. 32 ha (2005)

Ten of the 17 segments (or mapped portions) decreased by at least 20% and by at least 5 ha from 2005 totals:

	23%, Bohemia River (BOHOH), 287 ha (2006) vs. 371 ha (2005)
	59%, Upper Chesapeake Bay (CB2OH), 176 ha (2006) vs. 433 ha (2005)
	41%, Sassafras River (SASOH), 350 ha (2006) vs. 597 ha (2005)
	55%, Bush River (BSHOH), 131 ha (2006) vs. 294 ha (2005)
	51%, Gunpowder River (GUNOH), 341 ha (2006) vs. 701 ha (2005)
	49%, Middle River (MIDOH), 93 ha (2006) vs. 184 ha (2005)
	70%, Upper Central Chesapeake Bay (CB3MH), 69 ha (2006) vs. 229 ha (2005)
	83%, Patapsco River (PATMH), 19 ha (2006) vs. 113 ha (2005)
	60%, Lower Chester River (CHSMH), 74 ha (2006) vs. 187 ha (2005)
	100%, Middle Chester River (CHSOH), 0 ha (2006) vs. 92 ha (2005)

One of the 17 segments remained unvegetated.

Middle Bay Zone

In the Middle Bay Zone (34 CBP segments extending south from the Bay Bridge to the Rappahannock River and Pocomoke Sound, and including the Potomac River), 12,407 ha (30,659 ac) of SAV were mapped for 2006. Comparing the same mapped regions between 2005 and 2006, SAV decreased 23% from 16,016 ha (39,577 ac) in 2005 to 12,407 ha (30,659 ac) in 2006.

None of the 34 segments (or mapped portions) increased by at least 20% and by at least 5 ha from 2005 totals.

Eleven of the 34 segments (or mapped portions) decreased by at least 20% and by at least 5 ha from 2005 totals:

	26%, Eastern Bay (EASMH), 229 ha (2006) vs. 311 ha (2005)
	55%, Mouth of the Choptank River (CHOMH1), 422 ha (2006) vs. 928 ha (2005)
	53%, Little Choptank River (LCHMH), 49 ha (2006) vs. 105 ha (2005)
	23%, Lower Central Chesapeake Bay (CB5MH), 1,048 ha (2006) vs. 1,369 ha (2005)
	52%, Honga River (HNGMH), 848 ha (2006) vs. 1,771 ha (2005)
	44%, Manokin River (MANMH), 94 ha (2006) vs. 166 ha (2005)
	28%, Big Annemessex River (BIGMH), 207 ha (2006) vs. 287 ha (2005)
	30%, Lower Pocomoke River (POCMH), 508 ha (2006) vs. 723 ha (2005)
	43%, Middle Patuxent River (PAXOH), 29 ha (2006) vs. 51 ha (2005)
	37%, Upper Patuxent River (PAXTF), 83 ha (2006) vs. 131 ha (2005)
	49%, Lower Potomac River (POTMH), 684 ha (2006) vs. 1,350 ha (2005)

Fourteen of the 34 segments remained unvegetated.

Lower Bay Zone

In the Lower Bay Zone (27 CBP segments covering the region south from the Rappahannock River and Pocomoke Sound regions to the mouth of the Bay), 5,248 ha (12,969 ac) of SAV were mapped for 2006. Comparing the same mapped regions between 2005 and 2006, SAV decreased 33% from 7,778 ha (19,221 ac) in 2005 to 5,211 ha (12,876 ac) in 2006.

Four of the 27 segments increased by at least 20% and by at least 5 ha from 2005 totals:

	88%, Lower Rappahannock River (RPPMH), 151 ha (2006) vs. 80 ha (2005)
	26%, Upper Pamunkey River (PMKTF), 298 ha (2006) vs. 237 ha (2005)
	100%, Mouth of the James River (JMSPH), 20 ha (2006) vs. 0 ha (2005)*
	318%, Upper James River (JMSTF), 90 ha (2006) vs. 22 ha (2005)

Six of the 27 segments decreased by at least 20% and by at least 5 ha from 2005 totals:

	52%, Western Lower Chesapeake Bay (CB6PH), 126 ha (2006) vs. 260 ha (2005)
	54%, Eastern Lower Chesapeake Bay (CB7PH), 1,513 ha (2006) vs. 3,294 ha (2005)
	90%, Upper Rappahannock River (RPPTF), 3 ha (2006) vs. 33 ha (2005)
	50%, Piankatank River (PIAMH), 114 ha (2006) vs. 227 ha (2005)
	25%, Mobjack Bay (MOBPH), 2,183 ha (2006) vs. 2,916 ha (2005)
	100%, Lynnhaven & Broad Bays (LYNPH), 0 ha (2006) vs. 8 ha (2005)

* Segment comparison restricted to areas mapped in both 2006 and 2005

Nine segments remained unvegetated in 2006.

DELMARVA PENINSULA COASTAL BAYS ZONE

In the Delmarva Peninsula Coastal Bays Zone (Assawoman, Isle of Wight, Sinepuxent, Chincoteague, and southern Virginia coastal bays), 4,524 ha (11,179 ac) of SAV were mapped for 2006. Since this region was not mapped in 2005, comparisons are with 2004, when it was last mapped. In this Zone, SAV decreased 36% from 7,033 ha (17,380 ac) in 2004 to 4,524 ha (11,179 ac) in 2006.

Two of the five segments increased since 2004:

	15%, Isle of Wight Bay (IOWPH), 145 ha (2006) vs. 126 ha (2004)
	73%, Southern Virginia Coastal Bays (SVCPH), 253 ha (2006) vs. 146 ha (2004)

Three of the five segments decreased since 2004:

	12%, Assawoman Bay (AAWPH), 199 ha (2006) vs. 228 ha (2004)
	10%, Sinepuxent Bay (SPXPH), 721 ha (2006) vs. 802 ha (2004)
	44%, Chincoteague Bay (CHNPH), 3.204 ha (2006) vs. 5,732 ha (2004)