PROJECT TITLE: Continuing Support for Inland Bay Shellfish Stock Enhancement and
Restoration Activities
REPORTING PERIOD: Final Report
FUNDING LEVEL: $13,217.00
July 30, 2005 – September 30, 2005
CIB Grant #: EPA CE99399-007
UD Code: MAST 432214
PARTICIPANTS:
John W. Ewart, Aquaculture Specialist (Project Manager)
Delaware Sea Grant Marine Advisory Service
Graduate College of Marine Studies, University of Delaware
700 Pilottown Road, Lewes, DE 19958
Phone: 302-645-4060; E-mail: <ewart@udel.edu>
Jim Alderman, Delaware Center for the Inland Bays (CIB)
EJ Chalabala, Delaware Center for the Inland Bays (CIB)
PROJECT OBJECTIVES:
1) Monitor growth and survival of different year classes of oysters deployed on the James Farm
Oyster reef
2) Conduct seasonal assays for MSX and Dermo pathogens
3) Organize and train and coordinate activities of citizen volunteer gardeners to produce a 2005
year class of juvenile oysters for deployment on the James Farm Oyster Reef
ANTICIPATED BENEFITS:
Determining the technical feasibility and potential for using aquaculture methods for shellfish
stock enhancement and replenishment will improve management options for state resource
managers.
Bivalve protozoan pathogens and the disease outbreaks (epizootics) they produce have
significantly impacted shellfish populations in Mid-Atlantic region and other estuaries along
the eastern seaboard. Current information on the occurrence and distribution of MSX, Dermo
and QPX pathogens will assist state fisheries managers to monitor populations of bivalve
shellfish valued for their commercial, recreational and ecological importance to Delaware’s
coastal bays.
PROGRESS OF THE WORK AND PRINCIPAL ACCOMPLISHMENTS:
Monitor growth and survival of different year classes of oysters deployed on the James
Farm Oyster reef (Objective 1)
The James Farm oyster reef was established during the summer of 2001 when 250 cubic yards
of surf clam shell was deposited on a 100 square foot (¼ acre) area of bottom to form a base
for stocking hatchery produced oyster spat on shell. The first planting of approximately 150
bushels of shell with oyster spat averaging 10 millimeters (shell height) occurred during
summer 2002 (Reef 1). The advent of the oyster gardening program during summer 2003
presented an opportunity to compare oyster growth and mortality between Reef 1 and a second
section of the shell base (Reef 2) planted with 10 millimeter spat on shell and supplemented in
the fall and subsequent spring with larger (30-50 millimeter) juvenile oysters produced by
gardeners during the 2003 – 2005 summer seasons. Clusters of oysters on shell are collected
seasonally during spring, summer and fall to measure growth and cumulative mortality. Oyster
growth and cumulative mortality data from 2002 to the present are summarized in Tables 1 and
2 respectively.
During the project year a volumetric method (4 Liters shell displacement) initiated in fall 2003
was used to equalize samples taken from Reef 1 and Reef 2. Both sections of the reef have
produced reproductively viable (spawning) adult oysters. Natural oyster recruitment, although
light, has been observed on both sections of the reef. Small oysters on Reef 1 are from natural
set during the last two summers. Wild oyster set on Reef 1 is typical of random low level
natural recruitment observed in other parts of Indian River Bay where rip rap or other hard
structure is present. Reef 2 oyster year classes are comprised predominantly from 2 seasons
(2003 &4) of oyster gardening (nursery culture) activity with some additional natural set as
well. Reef 1 samples contained a range of sub-market and market sized oysters after three
growing seasons. Annual supplementation of juvenile oysters on Reef 2 from two seasons of
the gardening program has produced oysters with an average size similar to those found on
Reef 1.
Reef 1
Date
Jun-02
Aug-02
Nov-02
May-03
Aug-03
Nov-03
Jun-04
Aug-04
Nov-04
Jun-05
Aug-05
SH (mm)
10
17.3
34.6
35.1
42.6
48.8
48.8
50.8
57.6
63.2
64.1
Reef 2
stdev
3.9
7.4
6.4
7.8
9.2
11.5
9.9
11.3
11.4
11.9
SH (mm)
10
30.8
28.8
46.5
53.2
56.9
57.2
stdev
5.8
8.7
9.4
8.5
9.2
13.0
Table 1. Average Growth (Shell Height) of James Farm Reef Oysters
Reef 1
Date
Jun-02
Aug-02
Nov-02
May-03
Aug-03
Nov-03
Jun-04
Aug-04
Nov-04
Jun-05
Aug-05
Reef 2
% Mortality stdev % Mortality
0
0
6.5
3.8
14.7
1.5
16.8
1.7
43.4
8.4
45.3
3.2
34.4
75.5
3.0
78.8
87.0
3.0
72.1
83.7
1.8
57.5
81.6
2.4
70.1
89.9
1.4
70.7
stdev
9.6
1.6
0.8
1.5
4.9
Table 2. Cumulative Mortality of James Farm Reef Oysters
In addition to anticipated losses from crabs, and oyster drills and other predators, two
significant mortality events occurred between May 2003 and November 2004: 1)
hypoxic/anoxic conditions created by excessive accumulation of macro-algae (Sea lettuce Ulva
and other species) on the reef during the summer of 2003; and 2) winter-kill when the normally
sub-tidal reef was exposed by extreme (-0.7 to -0.9) low tides coinciding with very low air
temperatures (4 degrees F) during January 2004.
These two natural environmental events caused catastrophic oyster mortalities approaching 80
percent between 2003 and 2004. A persistent smothering mat of “sea lettuce” (Ulva lactuca)
and other plant species covered the reef during most of the summer of 2003. The blanket of
macro-algae severely reduced water flow across the reef and increased sediment accumulation
leading to hypoxic and anoxic conditions and a 27 percent increase in mortality. A subsequent
very hard winter (rated as the 11th coldest on record) with extreme low tides and single digit
freezing temperatures, especially during January 2004, resulted in additional 30 percent to 40
percent winter mortality.
During the last project year (October 2004 – September 2005) cumulative mortality on Reef 1
was estimated at between 80-90 percent while mortality on Reef 2 has ranged between 60-70
percent. The lower mortality observed on Reef 2 is attributed to seasonal oyster gardening
supplements of additional juveniles. However, mortalities on both section of the reef were
affected by ever-present predation and were also influenced by another season of macroalgal
accumulation combined with unseasonably hot temperatures during most of the summer.
Additionally, losses of oysters and gear from theft/vandalism were noted in late spring. Visual
inspection of the reef on a large magnitude low tide showed that large central areas of the
bottom on Reef 2 were sufficiently cleared of oyster clusters (groups of juvenile oysters set on
a single oyster shell) to expose large areas of the surf clam shell base. Examination of the
corners and other peripheral areas of Reef 2 yielded remaining juvenile oyster clusters that
were subsequently collected and consolidated into a smaller area for better management and
observation. The extent to which theft and vandalism observed on the reef in Spring 2005
affected growth and mortality estimates is difficult to estimate. Poaching damage on the reef
appeared to be mainly confined to the Reef 2 section.
Conduct seasonal assays for MSX and Dermo pathogens (Objective 2)
Oysters from Reef 1 were collected for annual spring and fall/winter MSX (Haplosporidian)
assays and a late summer Dermo assay. The assays were completed at the Cooperative Oxford
Laboratory, Maryland Department of Natural Resources, Oxford, Maryland. Both the spring
and the fall/winter assays tentatively identified Haplosporidian costale (aka the Seaside
Organism or SSO). The pathogen was detected at prevalence rates of 20 percent and 33 percent
respectively. Oxford reported very light infections in both cases. Previous prevalence rates
during 2003 and 2004 have ranged between 10 – 27 percent. Differentiation between
Haplosporidium nelsoni and H. costale is not possible based solely on tinctorial histology; a
PCR assay is required. Oxford is not equipped to do PCR analysis.
Date
5/28/02
9/6/02
11/13/02
5/13/03
10/7/03
12/5/03
5/26/04
9/15/04
12/6/04
5/19/05
9/13/05
Pathogen
N
Prevalence
MSX/Dermo 100 0/100 (0%)
Dermo
30
0/30 (0%)
MSX
30
0/30 (0%)
MSX
30
6/30 (20%)
Dermo
30
7/30 (23%)
MSX
30
3/30 (10%)
MSX
30
8/30 (27%)
Dermo
30
9/30 (30%)
MSX
30
6/30 (20%)
MSX
30
10/30 (33%)
Dermo
30
28/30 (93%)
Comments/Infection Intensity *
for both pathogens
tentatively identified as SSO not MSX
1-3 Mean 1.7 *
described as a haplosporidian, not confirmed as MSX
described as a haplosporidian, not confirmed as MSX
1-6 Mean 1.2 *
described as a haplosporidian, not confirmed as MSX
described as a haplosporidian, not confirmed as MSX
1-7 Mean 3.2 *
*Oxford Laboratory Infection Intensity Scale: 1 (very very light) to 7 (very very heavy)
Table 3. Oyster Pathogen Summary
More troublesome is the dramatic increase observed in the prevalence rate for Dermo during
the last 12 months from 30 percent to 93 percent. The range of infections in the 2005 sample
covered Oxford Laboratory infection intensity scale from 1 (very very light) to 7 (very very
heavy) with an increased average infection rate of 3.2. This major rise in prevalence rate is
most likely a by-product of the stress placed on the oyster population by the combination of
exceedingly hot weather conditions and macroalgal accumulations on the reef over most of the
summer.
Haplosporidian infections by either MSX or SSO are generally not considered to be as
problematic or as lethal as Dermo. Two previous Dermo assays during 2003 and 2004 recorded
a slight increase in prevalence rates but the intensity of the infections remained relatively
stable. The 2005 Dermo assay is an ominous sign that pathogen activity is beginning to gain
significant momentum and will continue to do so especially if stressful summer environmental
conditions persist again during 2006.
Organize and train and coordinate activities of citizen volunteer gardeners to produce a
2005 year class of juvenile oysters for deployment on the James Farm Oyster Reef
(Objective 3)
During summer 2003, the Center for the Inland Bays received a small grant from the National
Fish and Wildlife Foundation Five-Star Restoration Challenge Grant Program to initiate a
pilot-scale oyster gardening program. The purpose of the program was to enlist and train a
group of volunteers for the nursery culture oyster spat for annual stock enhancement in support
of the James Farm oyster reef and for other Inland Bays restoration work. Other shellfish
restoration programs in the Chesapeake and elsewhere have demonstrated that raising oyster
spat to a to a larger size in Taylor Floats can significantly reduce losses to crab and other
natural predation.
Another goal of the CIB program was to increase community involvement and participation
and to educate the public about the important ecological services provided by oysters and other
bivalve shellfish. With the assistance of Inland Bay resident volunteers, oyster spat on shell
were deployed at more than 15 locations around all three bays during 2003 and 2004. During
the current 2004/05 project year, oyster gardening activity has nearly doubled to 29 locations
involving the volunteer efforts of 48 Inland Bay residents. In addition to returning volunteers,
new gardeners from Fenwick Island, South Bethany, the Bald Eagle Creek/Torquay Canal and
Guinea Creek areas of Rehoboth Bay and the Indian River Marina have joined the oyster
gardening program.
Oyster gardening orientation workshops were organized and conducted in late June at two
locations: Fenwick Island Town Hall and the College of Marine Studies Lewes. Because of the
unusually cool and wet spring, the University of Maryland oyster hatchery schedule was
significantly delayed. To keep the gardeners otherwise engaged until a 2005-year class of
oysters could be secured, approximately 10 bushels of small oysters from the 2004 season were
redeployed to gardening sites for another season of off-bottom culture. Hatchery produced
oyster spat for the 2005 season were eventually obtained in late August. In early September 77
bags of spat on shell (approximately 27 bushels) were transferred from the University
Maryland hatchery in Cambridge to the James Farm for distribution to gardeners and overwintering for the 2006 season.
As previously mentioned, clear evidence of theft and vandalism of oysters and equipment was
found for the first time since shellfish field work commenced in 1998. Losses included oysters
and gear from our boat slip area and the demonstration commercial grow-out area at Pasture
Point, and oysters from the reef. None of the other oyster gardening sites around the Inland
Bays were similarly affected.
Besides providing an optimum environment for nursery growth, the baskets of oysters and
shell in the Taylor Floats create excellent habitat excellent for grass shrimp, juvenile fish and
other small invertebrates. Since the start of the program volunteer gardeners have helped to
produce more than 30 bushels of juvenile oysters on shell for reef development. The systemwide distribution of oyster gardening locations has also greatly facilitated the monitoring of
Inland Bay water quality and the occurrence of shellfish pathogens.
The good to excellent oyster growth and survival that we have observed at different Inland Bay
oyster gardening locations has included some unanticipated sites like residential “dead end”
lagoon systems and the Little Assawoman Bay. Previous field surveys have confirmed that
natural populations of oysters, hard clams and other bivalves in the Little Assawoman are
extremely scarce. Episodic fluctuations in salinity, poor water exchange rates, zones of soft
mucky sediments high in silts and clays and low brood-stock biomass are believed to be
limiting factors.
Oyster gardening growth results and the excellent growth of hard clams planted in Little
Assawoman Bay in October 2003 and recovered in October 2005 demonstrate the effectiveness
and potential of using both off-bottom and in-bottom aquaculture methods for restoring
shellfish populations. Based on these results, the town of Fenwick Island has expressed interest
in additional oyster gardening and related shellfish restoration efforts. The Little Assawoman
Bay is unique in comparison to the other Inland Bays because it’s geography, low water
exchange and relatively closed nature offers good potential for larval retention and gradual
establishment of natural recruitment with the development of shellfish spawning sanctuaries.
Oyster gardening 2003 year class
2005 year class oysters
Hard clam growth in Little Assawoman Bay 2003-2005
WORK PLANNED:
This project has been funded for an additional 12 months (until September 30, 2006) and will
continue with the same objectives. Additional goals will be to further increase oyster gardening
participation and to establish oyster and hard clam spawning sanctuaries in Little Assawoman
Bay.
1) Monitor growth and survival of different year classes of oysters deployed on the James Farm
Oyster reef
2) Conduct seasonal assays for MSX and Dermo pathogens
3) Organize, provide training and coordinate activities of citizen volunteer oyster gardeners to
produce a 2006 year class of juvenile oysters for deployment on the James Farm Oyster Reef
and additional reefs established in the Little Assawoman Bay.
PUBLICATIONS AND OTHER OUTREACH ACTIVITIES:
Publications include 2 draft manuscripts that have been submitted for publication:
Kendall, Lindsay R., John W. Ewart, Paul N. Ulrich and Adam G. Marsh. 2005. Low incidence
and limited impact of the oyster pathogens Dermo and MSX on an artificial reef in Delaware’s
Inland Bays. College of Marine Studies, University of Delaware, Lewes, DE 19958.
(manuscript submitted to Estuaries).
Ulrich, Paul N., John W. Ewart and Adam G. Marsh. 2005. Incidence of Perkinsus marinus,
Haplosporidium nelsoni (MSX), and QPX in bivalves of Delaware’s Inland Bays and
quantitative, high throughput diagnosis of Dermo infections by QPCR. College of Marine
Studies, University of Delaware, Lewes, DE 19958. (manuscript submitted to Applied and
Environmental Microbiology).
Additional Publications:
Ewart, John W., Jim Alderman and EJ Chalabala. 2005. Special Report: Enhancing, Restoring
Inland Bays Shellfish - Inland Bays Applied Shellfish Research and Field Demonstration
Projects are Yielding Valuable Information. Inland Bays Journal. Fall 2005. 4 p.
Posted online at <http://darc.cms.udel.edu/ibog/cibnl10.05.pdf>
Fact Sheet: Delaware Center for the Inland Bays Oyster Gardening Program.
Posted online at < http://darc.cms.udel.edu/ibog/OGfactsheet.pdf>
Delaware Center for the Inland Bays Oyster Gardening Program Web site
<http://darc.cms.udel.edu/ibog/index.html> plus reports and other information posted at the
Delaware Aquaculture Resource Center’s section on shellfish stock enhancement and oyster
gardening <http://darc.cms.udel.edu/#oyster>.
Presentations:
Establishment of an Oyster Reef at the Delaware Center for the Inland Bays James Farm
Ecological Preserve: Lessons Learned (Jim Alderman and EJ Chalabala Co-Authors).
Presented at the 7th International Shellfish Restoration Conference. Charleston, South Carolina,
November 17-20, 2004.
A Community Based Approach to Delaware Inland Bays Shellfish Restoration and Water
Quality Monitoring (Joe Farrell, Ed Whereat, Jim Alderman and EJ Chalabala Co-Authors).
Presented at the 8th International Shellfish Restoration Conference. Brest, Brittany, France.
October 2-5, 2005. Posted online at < http://darc.cms.udel.edu/ibog/cibnl10.05.pdf>
Aquaculture Methods for Stock Enhancement, Restoration and Increased Production in
Delaware's Inland Bays (Jim Alderman and EJ Chalabala Co-Authors). Invited presentation
the CIB Scientific and Technical Advisory Committee (STAC) with recommendations for
priorities and opportunities as part of the CIB process to develop a research RFP.
Additional presentations on Inland Bays shellfish research and restoration to the University of
Delaware Academy of Lifelong Learning class on the Inland Bays; College of Marine Studies
Ocean Currents Summer Lecture Series; Fenwick Island Environment Committee chaired by
Councilwoman Martha Keller; Barnegat Bay (New Jersey) National Estuary Program; and 2
oyster gardening workshops (also open to the public) held in Lewes and Fenwick Island,
Delaware.
Other Related Outreach Activities:
Cooperative work between the Inland Bays Citizen's (water quality) Monitoring Committee
and the Oyster Gardening program to cover missing monitoring stations and to accommodate
water quality monitors interested in also participating with growing oysters. Several
individuals are currently doing both and a goal is to increase the number of volunteers doing
both water quality monitoring and oyster gardening.
Meeting with April Willey, April B. Willey, Volunteer Coordinator for the Retired and Senior
Volunteer program (RSVP). The RSVP program, administered in Delaware through the
Governor's Commission on Community and Volunteer Service in the State Office of
Volunteerism, is part of Senior Corps, a network of national service programs that provides
older Americans the opportunity to apply their life experience to meeting community needs.
RSVP is open to people age 55 and over and volunteers serve in a diverse range of non-profit
organizations, public agencies, and faith-based groups. Partners/Operations Local
organizations, both public and private, receive grants to sponsor and operate RSVP projects in
their community. Ms Willey is interested in the volunteer component of the oyster gardening
program and the possibility of directing RSVP financial support to it.
Participated in the Del Tech sponsored Upward Bound program for a day trip to the James
Farm. The visit included a ride to the James Farm Reef on the CIB pontoon/work boat and
discussion with Q&A on oysters and their importance to the Inland Bays.
Participated in the "Day in the Life of the Broadkill" project organized by Joe Farrell and Bill
Ullman, CMS. Used the CIB pontoon boat to conduct a field survey of oyster and other bivalve
shellfish resources in the river and assess other benthic invertebrates (with Doug Miller, CMS).
The Marian Koshland Science Museum of the National Academy of Sciences in Washington,
DC has invited CMS Dean Nancy Targett to present a public program related to the non-native
oyster issue since she served on the Review Committee for the NAS report on that subject.
They also indicated their interest in oyster gardening and reef restoration activities using the
native eastern oyster. Nancy suggested a joint presentation integrating both subject areas to
include information on Inland Bays shellfish research and restoration work. The joint
presentation idea was accepted and is tentatively scheduled for spring 2006.