This research has two goals. The first is to develop a better understanding of the
human health benefits and risks associated with cultured and wild seafood. The second
goal is to develop and transfer aquaculture technologies that permit economically
competitive production of seafood with safe contaminant levels and enhanced beneficial
fatty acid profiles. Learn
more about the background information for this project »
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We have expanded our expertise for understanding the human health-relevant relationships
between the risks of contaminants and the healthful benefits of long chain omega-3
fatty acid consumption. Samples of red drum collected from a variety of wild and
farmed, domestic and imported sources have been analyzed for fatty acids and contaminants.
Significant differences in fatty acid profiles were found, probably related to differences
in diet. Most contaminant levels were insignificant, although high levels of DDT
were found in farmed fish from two sources. A 62-sample survey of shrimp was completed
and awaits completion of fatty acid and contaminant analyses. A DHA-enriched finishing
diet study was conducted with red drum. Although the results are inconclusive, they
have led to improved experimental designs for future diet studies. A large study
raising red drum on diets in which fish meal/fish oil is greatly reduced or totally
absent is currently underway. While lipid analyses have not yet been conducted,
we are gaining valuable insight into improved operation of the HML Aquatic Production
facilities. Shrimp and feeds from a highly successful, organic certifiable diet
study were analyzed for fatty acids and chemical contaminants. Results will be published
soon in a refereed journal. In the search for approaches to develop more healthful
and nutritious cultured seafoods, studies have been expanded to investigate naturally
occurring microbial communities as supplemental, contaminant-free nutrition sources.
The objectives are to:
- Assess the variability of contaminants and beneficial fatty acids in a representative
finfish and crustacean. Red drum and shrimp are being collected from a variety of
sources—wild, farmed, domestic, and imported. The edible portions are analyzed
for contaminants (metals, pesticides, PCBs, PAHs, and PBDEs) and for their fatty
acid profiles; and
- Develop diets and feeding schedules to achieve a product that is economically competitive
with safe contaminant levels and enhanced beneficial fatty acid profiles. These
will be evaluated through a series of grow-out trials of red drum and shrimp in
the Hollings Marine Laboratory and at the South
Carolina Department of Natural Resource’s (SCDNR) Waddell Mariculture
The results are interpreted in terms of human health risks and benefits using US
EPA guidelines and through extrapolation from large, long-term human epidemiological
studies. Development of this approach will permit a comparison of different seafood
sources in terms of direct human health risks and benefits.
- During FY2004 wild red drum were collected at six “clean” and six “impacted”
sites in North Carolina , South Carolina , east coast Florida , west coast Florida,
Louisiana, and Texas . Farmed red drum were collected from three domestic sites
in Texas, Mississippi, and Florida and three imported sites in China, Taiwan, and
Thailand . During FY2005 fillets were analyzed by NOAA and NIST collaborators for
fatty acid profiles and contaminants: metals, pesticides, PCBs, PBDE’s, PAHs,
- Wild red drum have among the lowest levels of total lipids, DHA, and EPA of major
commercial and recreational marine finfish. Differences in fatty acid profiles of
fillets probably reflected differences in diets. Farmed fish have significantly
higher total lipid, DHA, and EPA levels than wild fish, and imported farmed fish
were higher for these parameters than domestically cultured fish. Farmed red drum
also displayed much higher levels of linoleic acid (LA) than wild-caught fish, reflecting
the large amounts of plant ingredients (e.g. soybeans, corn, etc.) in aquaculture
diets. Principal component analysis of nine major PUFAs clearly separated wild-caught
fish from farm-raised fish. Wild-caught fish from all locations clustered tightly.
Farm-raised fish from China and Taiwan separated clearly from domestically raised
fish and those from Thailand . This probably reflects the soybean-heavy commercial
diets typical of the domestic and Thai farms.
Interpretation of the large contaminants data set has not been fully completed.
We have examined it carefully in consultation with Dr. John Vena, chair of the University
of South Carolina ’s Department of Epidemiology and Biostatistics and he in
turn has conferred with colleagues in his department. We agree that the data should
be reported descriptively without drawing significant conclusions about any of the
sources. Most of the contaminants measured in the samples were below detection limits
and in almost all cases the values were well below USEPA screening levels or USFDA
action levels. The most dramatic exception occurred due to high levels of DDT-related
pesticides found in some of the red drum farmed in Southeast Asia . In one case
these levels exceeded the USEPA carcinogenic screening level for DDT compounds.
None of the other contaminants exceeded any human health standards. No obvious site
trends were observed for most classes of contaminants. Total PCBs were significantly
greater in fish taken from “impacted” sites in East Florida, North Carolina,
and South Carolina than from similar “clean” sites or from any Gulf
coast sites. Domestic farms showed higher PCB levels than southeast Asian farms.
We plan to explore these data more completely to focus on correlations among contaminants
and possible ways to examine cumulative effects of multiple contaminants. Since
red drum is the number one (by weight in 2004, NMFS) recreational fish caught along
the Southeastern and Gulf coasts, achieving a better understanding of the variability
in risks and benefits of its consumption will be significant to recreational and
subsistence fishers and the agencies that regulate the harvest.
- Shrimp is the number one seafood consumed by Americans. Shrimp that are readily
available to consumers in the southeastern U.S were collected from 62 sources. These
included a variety of domestic and imported, wild and farmed sources collected between
July and December 2005 to provide a good representation of stocks available to the
consumer. Reflecting shrimp consumption by Americans, farmed and wild L. vannamei
from domestic and foreign sources comprised the largest number of samples. Multiple
samples of wild L. setiferus, F. aztecus, and F. duorarum
from the Atlantic and Gulf regions and farmed imported P. monodon were
also collected. Laboartory analyses for fatty acid profiles and chemical contaminants
are not yet completed. Evaluation of these results should produce a significant
database that will yield insights into the PUFA levels and harmful chemical content
of shrimp from a wide range of sources.
- Diet studies of farmed red drum and shrimp began during FY2005. The goal is to reduce
contaminants by eliminating fish meal and fish oil in dietary formulations while
maintaining or enhancing the beneficial fatty acid levels of the final product.
A 12-week study was conducted to determine whether a finishing diet enriched with
DHA derived from a marine alga could alter the fatty acid composition of one year
old red drum at the end of grow-out. The conventional diet on which the fish had
been raised was top-coated with the algal-derived oil to raise the DHA level from
0.8% to 2.4%. Fish were fed either the conventional diet or the lipid-enhanced diet,
sacrificed at 3 week intervals, and composites of fillets were analyzed for fatty
acids. While initial results from this study appeared positive, detailed analyses
of the complete data set demonstrated an unacceptable level of variability. Some
of the archived fillets were re-analyzed individually using different procedures
for sample preparation. While the impact of the finishing diet remains inconclusive,
this study has provided valuable guidance for improving the design of future diet
studies. Some of these procedures involve identifying and monitoring changes in
individual fish, analyzing individual whole, skinned fillets rather than composites,
and increasing sample sizes at the expense of more frequent sampling.
- A larger diet study with red drum began in July 2006 and is currently underway.
The objective is to raise fish from 100g to 600g on diets with greatly reduced or
no fish meal and fish oil ingredients. At the end of the grow-out period some fish
will be switched to finishing diets to restore or enhance their levels of beneficial
PUFAs. A commercial diet containing 30-40% fish meal/fish oil is the control diet.
One test diet reduces the content to 5% fish meal, 5% fish oil. These ingredients
are eliminated entirely in the other test diets. One of these lacks DHA while this
fatty acid is supplied in the other diet by a DHA supplement derived from a marine
alga. All of the experimental diets are constructed from pure ingredients by OHH
Seafood personnel in the HML. Each of the original 456 fish, distributed among 24
1500 L tanks, was individually tagged, weighed, and measured. Growth parameters
and fatty acid profiles are being used to measure the relative success of the four
diets. A series of health problems has plagued the study almost from the outset.
While it can be demonstrated that diet treatment has had a significant effect on
the fish’s ability to resist disease, an effect due to apparent differences
in the recirculating filter systems is also significant. While the final outcome
of this study is not yet determined, valuable lessons are being learned that will
improve future studies in the HML Aquatic Production section.
- Research to design fish meal replacement strategies for shrimp mariculture
studies has also been conducted during FY2005. Pond cultured shrimp produced in
a study funded by the US Marine Shrimp Farming Program and Advanced Bionutrition
Corp. have been analyzed for fatty acid profiles and chemical contaminants though
the OHH Seafood Benefits and Risks program. The study evaluated a shrimp diet formulated
with organically certified, non-genetically modified ingredients. Fish protein and
lipids were replaced with plant proteins and algal-derived DHA. All shrimp
growth and production parameters related to the organic diet proved fully equivalent
to those for shrimp raised on the conventional fish meal based diet. Over 160 chemical
contaminants were measured and none were present in significant levels in shrimp
raised on either diet. The conventional diet provided significantly higher quantities
of EPA and DHA than the plant-based diet and the conventional diet shrimp reflected
this with higher levels of these beneficial fatty acids. However the relative ratios
of EPA and DHA in the shrimp compared to ratios in the diets suggest specific requirements
for amounts and ratios of these fatty acids in shrimp. Since, like humans, shrimp
are considered to have limited ability to synthesize EPA and DHA from shorter fatty
acids, it appears that shrimp either can selectively accumulate specific dietary
fatty acids or have access to a supplemental food source in the ponds.
- The results of the analyses conducted on this study may open new avenues for designing
feeds that enhance the level of beneficial fatty acids in the shrimp while ensuring
insignificantly low levels of chemical contaminants. The results of this study and
the OHH analyses will be published in the December 2006 issue of The Journal of
the World Aquaculture Society. These results also formed the foundation
for a spin-off project funded by the USDA Organic Program. This work will explore
the possibility of integrating specially designed diets with supplemental nutrition
supplied by managing the microbial communities of shrimp culture systems in order
to produce fully organic shrimp for the health-conscious consumer.
Transfer of Results
The results will be disseminated to user groups through appropriate media including
professional (both scientific and aquaculture) journals, regional, national, and
international meetings, news releases to public media, and workshops for human nutritionists
and toxicologists. The knowledge generated should be of value to consumers, regulatory
agencies, aquaculturists, and the medical community.
- Leffler, J.W., C.L. Browdy, and T.I.J. Smith, 2006. Risk Assessment. NOAA Inititiative
Examines Fatty Acids, Contaminants in Red Drum, Shrimp. Global Aquaculture
- Browdy, C.L., G. Seaborn, H. Atwood, D.A. Davis, R.A. Bullis, T.M. Samocha, E. Wirth
and J.W. Leffler. 2006. Comparison of Pond Production Efficiency, Fatty Acid Profiles
and Contaminants in Litopenaeus vannamei fed Organic Certifiable, Plant-based
and Fishmeal-based Grow-out Diets. Journal of the World Aquaculture Society,
- The Wild and Farmed Seafood Enigma: Exploring Human Health Risks, Benefits
and Opportunities for the Future. NOAA-OHHI National Conference. Charleston , SC.
January 2006. Presented by C.L. Browdy with T.I.J. Smith, J.W. Leffler, G. Seaborn,
and E. Wirth.
- The Wild and Farmed Seafood Enigma: Exploring Human Health Risks, Benefits
and Opportunities for the Future. Hollings Marine Laboratory Seminar. Charleston
, SC. February 14, 2006 . Presented by J.W. Leffler.
- Fatty Acid Profiles and Contaminant Loads of Wild and Farmed Red Drum: Assessing
Seafood Benefits and Risks. South Carolina Chapter of American Fisheries Society/
South Carolina Fisheries Workers Association. Charleston , SC. February 16-17, 2006.
Presented by J.W. Leffler with C.L. Browdy, T.I.J. Smith, G. Seaborn, and E. Wirth
- Human Health Benefits and Risks of Farmed and Wild Seafood. Mariculture Section
Retreat, Marine Resources Division, South Carolina Department of Natural Resources.
Bluffton , SC. March 1, 2006 . Presented by J.W. Leffler.
- An Ecosystem Approach toward Developing Environmentally-Friendly, Sustainable and
Economically Competitive Marine Shrimp Aquaculture. Grice Marine Laboratory Seminar.
Charleston , SC. September 7, 2006 . Presented by J.W. Leffler.
Public Information and Outreach
Several recent studies have suggested that farm-raised fish may carry higher health
risks than wild caught fish due to contaminants concentrated in the fishmeal-based
feeds on which they are raised. Our aquaculture studies seek to develop diets and
methodologies that will permit fish and crustaceans to be raised most of their lives
on no-fishmeal or low-fishmeal feeds. In order to ensure sufficient concentrations
of beneficial fatty acids we hope to use short-term finishing diets of various types
to boost EPA and DHA fatty acids to levels beneficial to human health. These methodologies
will be most useful when delivered to aquaculturists who will be able to produce
more healthful products.
For More Information
Contact: Gloria Seaborn, (843)762.8522
Contact: Ed Wirth, (843)762.8903
Contact: John Leffler, (843)762.8955
Contact: Craig Browdy, (843)953.9840