Faherty, M.S.

Experimental Restoration of an Intertidal Oyster Reef in Wellfleet, Cape Cod, MA
Evaluating Three Reef Materials
Mark Faherty, Mass Audubon/Wellfleet Bay Wildlife Sanctuary
Mass Audubon is working with The Nature Conservancy, NOAA, and the Town of Wellfleet to restore a wild-set oyster reef on
intertidal flats owned by Mass Audubon, the first such attempt in Massachusetts. We are testing shell culch, reef balls, and
oyster castles in terms of their ability to attract and maintain a self-sustaining wild oyster reef and to increase local biodiversity.
Site Characteristics
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Intertidal, with 10 foot tidal range
Potentially harsh winter conditions – ice floes, freeze/thaw cycles
Held “1000 bushels” of oysters historically (Curley 1972)
Two acre “grant”, less than an acre covered in experimental materials
Open to commercial harvest after three years
Wild set in area precludes need for seeding
Study area map
showing the
restoration area plus
the two reference
areas for biodiversity
monitoring. Each
rectangle is roughly
one hectare.
Methods
A. Oyster density , growth, and survival
• Three treatments (culch, reef balls, oyster castles) in 9 replicate blocks
• Quadrat sampling of oyster density on culch
• Total counts on subsample of balls, castles
B. Biodiversity
• Sand cores, surface quadrats, shorebird and seabird surveys
• Sampled at restoration site plus two reference areas
C. Sediment Monitoring
• Nine sediment monitoring stations
D. Culch type comparison
• Two replicates each of pure oyster shell and surf clam culch
E. Disease testing
• Makin test for Dermo preformed in-house using volunteers
• MSX testing performed at Roger Williams University
Key Preliminary RESULTS:
Culch Type
Avg. Density
Avg. Length
Oyster
2129/sq. meter
23 mm
Surf Clam
3627/sq. meter
27 mm
Table 2. Surf clam culch caught a better set of spat
and showed faster growth than oyster shell culch.
Partners:
Reef Ball
Oyster Castles
Completed block
with 3 treatments
Setting up
October 2009
October 2009
a.
March 2010
Oysters/ m2
Treatment
Culch
Oysters/unit
(Actual)
794/sq. meter
794+
Total
Oysters
129k
Avg. Size
(mm)
23
Reef Balls
Castles
314/ball
115/castle
1570
1200
76k
60k
22
19
TOTAL:
265,000
(Theoretical)
March 2010
b.
October 2010
Winter
Oysters/unit Oysters/ m2 Total Avg. Size
Treatment Mortality (%)
(Actual)
(mm)
(Theoretical) Oysters
Culch
Reef Balls
Castles
66
25
45
142/sq. meter
69/ball
36/castle
142
345
360
TOTAL:
23k
17k
19k
59,000
25
24
19
October 2010
c.
Oysters/ m2
Treatment
Inverts Collected by Site by Year
for each bar, n = 20 cores
Number of Animals
• High set in each of first two
years: 800/sq. meter in 2009 and
~3000/sq. meter in 2010
• Sedimentation/winter mortality
very high on culch (66% mort.)
• Reef balls failed structurally over
winter (52% crumbled/sloughed
oysters)
• Roughly 265,000 wild oysters
were growing on the
experimental materials from the
2009 set
• After 15 months, ~190,000
oysters from 2 year classes.
Largest are 3+ inches
• Surf clam culch caught more
spat than oyster shell culch
• No evidence of MSX infection,
Dermo infection rate 33% but low
intensity
• Nekton sampling methods
(seining, throw traps, snorkeling)
not effective
Culch
Year 1
20
Culch
Reef Balls
Castles
15
10
2008
2009
5
Oysters/unit
(Theoretical)
Total
Oysters
Avg. Size
(mm)
63k
42k
82k
32
32
33
Year 2
112/sq. m 382/sq. m
67/ball
108/ball
48/castle 106/castle
494
540
1230
TOTAL:
188,000
0
Restoration
Reference
Rocky
Reference
Figure 1. Number of invertebrates (mainly
polychaetes) collected in cores. Number of animals
collected in the restoration site increased relative to
reference areas between 2008 and 2009.
Table 1 a - c. Table a. shows the number and sizes of oysters on the three
treatments in October 2009, after three months. Table b. shows winter mortality
and spring densities in March 2010. Table c. shows number and sizes of oysters by
year class after 15 months. Theoretical densities reflect the density of oysters
likely if the maximum number of reef balls and oyster castles were placed per
square meter.