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Oysters and Fish - A culinary Combo with Environmental Imapct

Fish Monitoring of Restored Oyster Habitat along the Southeastern US Coast

There are plenty of reasons to love oysters. Many love eating them on the half shell, savoring their briny, sweet succulence, or gathering with friends for a fall or winter oyster roast. Fishermen appreciate the fact that oyster reefs provide vital nursery habitat for future catches of crabs, shrimp, finfish and many other commercial species, and that their filtering power improves water quality and health for aquatic life in general. 

Oysters are also a regional social and economic driver, with annual commercial oyster landings in NC, SC and GA providing over $8 million in fishery value in 2017 (though this is below historic dollar amounts). Indeed the humble mollusk is “a lusty bit of nourishment,” as the culinary writer M.F.K. Fisher famously wrote in her 1941 classic, Consider the Oyster, and more. The oyster is nourishment for the coastal ecosystem and the economy as much as for the hungry human at the oyster bar. Alarmingly, however, oyster populations are at risk. 

According to a 2011 Shellfish at Risk report by The Nature Conservancy, some 85% of oyster habitat has been lost globally, with most remaining oyster populations in poor condition. In the South Atlantic region (North Carolina through Florida), oyster populations are declining by 50 to 90%, largely due to overharvesting, disease and habitat damage and loss. 

The Need

Because healthy oyster populations are critical for healthy estuaries and fishery populations, for mitigating shore erosion through innovative living shoreline projects and for improving water quality, among other ecological and economic reasons, the Conservancy and its partners have prioritized oyster restoration and conservation in the South Atlantic Seascape. To date, 27 oyster reef restoration projects have been installed from NC to Georgia, covering 67 acres. The work has entailed monitoring of the projects to determine best practices and develop prototypes that can be replicated by other agencies. 

Oyster reefs have proved to be effective in mitigating erosion and maintaining a healthy estuarine habitat. They are promoted for their additional values as ecological habitat by providing crucial nursery habitat for recreationally and commercially important species, improving water quality, and providing food for numerous species. While the restoration work is promising, funding has been challenging. Federal grants necessary to expand restoration work from small-scale projects to ecosystem-level projects are competitive, and securing grants requires the ability to demonstrate the link between healthy commercial and recreationally important fish populations and oyster reef replenishment. Thus, the Conservancy has recently concluded a three-year study (2015 – 2018) to evaluate fish communities associated with restored oyster reefs in five southeastern locations. 

The Study

With primary funding support from Boeing, the Conservancy and its partners developed and implemented a regional fish productivity monitoring protocol to document the connection between restored oyster reefs, important fish species, and the marine food web. Working regionally and alongside university and state agency partners (University of North Carolina at Chapel Hill, South Carolina Department of Natural Resources, University of Georgia Marine Extension and Georgia Sea Grant), the Conservancy et al had the unique opportunity to aggregate data across seven sites, comparing fish communities around restored reefs with those at unstructured (non-reef) sites, as well as documenting differences related to various factors, including season (and related variables of salinity and water temperature), type of reef material (bagged shell, marl, cement coated crab pots, Oyster Castle®, and natural oyster reef) and site location. 

Nekton (i.e. swimming organisms) sampling was conducted seasonally between 2012-2017, and analysis incorporated spring, summer, and fall samples. A description of the monitoring methods is available in the practitioners’ guide: Sampling Nektonic Organisms Around Restored Oyster Reefs in the South Atlantic (Stone & Brown 2017). Organisms were identified to the lowest taxonomic level possible with total length recorded. 

The results revealed clear patterns in nekton community composition and abundance. By charting these patterns, researchers could begin to define the relationships between communities (assumed unburdened by random error). The sites monitored varied by state based on location, reef structure, season and tidal regime, yet despite these differences, the analysis shows significant variation in fish communities at structured vs. unstructured sites on multiple scales. This project increased our direct understanding of the link between fish communities and their utilization of oyster restoration sites in the southeastern estuaries.

The Results

On a state-by-state and regional scale, restored reefs had significantly more species than that of the unstructured (non-reef) controlled sites. Seventy-six finfish species and fifteen invertebrate species were collected. This included 26 managed fish species, demonstrating the link to commercial and recreational fishing. Managed recreational species included black drum, blue crab, red drum, sheepshead, southern flounder, spotted seatrout, stone crab, and striped bass, highlighting not only the importance of the species found but also the diversity of species. 

While oyster reefs are located in inshore coastal/tidal systems, eight of the total caught species are managed by the South Atlantic Fish Management Council (SAFMC), which focuses on offshore fisheries. This confirms a link between inshore and offshore habitats, emphasizing the importance of protecting and restoring oyster reefs not only to benefit inshore species, but also offshore species. 

Many of the species found in the study are economically important to the area given their management status and recreational and commercial value. Oysters, blue crab, shrimp, flounders, king mackerels, and snappers are all listed as key South Atlantic commercial species, and all of these species were found in our study within the restoration sites. Additionally, blue crab and shrimp values are tremendous for GA, SC, and NC, with blue crab valued at around $32.9 million in landings for all three states in 2017, according to NOAA National Marine Fisheries Service.

The study findings expand our body of knowledge about why larger scale oyster restorations are important, and further our understanding of the crucial ecosystem service role that restored oyster reefs have in fish production. By documenting a quantifiable economic value, this data will enable the Conservancy and others seeking to expand oyster reef restoration work to definitively communicate the value of oyster reef restoration to stakeholders, funders and managers. 

The project results also support broader Conservancy oyster efforts. Our global Mapping Ocean Wealth project evaluates the economic impact of marine habitats and species, including the role of oyster reefs for fish productivity (visit Mapping Ocean Wealth - Oysters). Analysis has shown that 12 fish species were enhanced by oyster reefs on the Eastern seaboard. Recognizing that oyster restoration can help increase fish population, the Conservancy’s Oyster Calculator helps set restoration goals. The results of the South Atlantic Seascape fish monitoring project have been used to improve the data behind the fish production portion of the Calculator, and thus, just as a small local oyster reef can make a broader ecosystem impact, this is another great example of local to global coordination. 

Looking Forward

While this project furthered our knowledge of the role restored oyster reefs play within and to fish communities, the small individual site data highlights the need for continued sampling and demonstrates the value of combining data for a more powerful analysis. This assessment emphasizes the value of a large and more biodiverse, comparable database to better understand the ways in which fish and other nekton use restored estuarine habitats. Continued sampling would provide more data for a larger dataset making the results between individual sites more statistically reliable. Monitoring of fish communities within oyster reefs has mainly been done on a state-by-state basis, making data difficult to compare. Continued and increased monitoring and additional analysis are vital for this study to succeed in the longer term and for broader impact.

Recent Publications:
Baggett, L.P., S.P. Powers, R. Brumbaugh, L.D. Coen, B. DeAngelis, J. Greene, B. Hancock, and S. Morlock, 2014. Oyster habitat restoration monitoring and assessment handbook. The Nature Conservancy, Arlington, VA, USA., 96pp.

Beck, M.W., R.D. Brumbaugh, L. Airoldi, A. Carranza, L.D. Coen, C. Crawford, O. Defeo, G.J. Edgar, B. Hancock, M. Kay, H. Lenihan, M.W. Luckenbach, C.L. Toropova, and G. Zhang. 2011. Oyster Reefs at Risk and Recommendations for Conservation, Restoration, and Management. BioScience 61(2): 107-116.

Grabowski, J. H., R. D. Brumbaugh, R. F. Conrad, A. G. Keeler, J. J. Opaluch, C. H. Peterson, M. F. Piehler, S. P. Powers, A. R. Smyth. 2012. Economic valuation of ecosystem services provided by oyster reefs. BioScience 62(10):900-909.

Philine, S.E., Z. Ermgassen, M.D. Spalding, R.E. Grizzle, R.D. Brumbaugh. 2012. Quantifying the Loss of a Marine Ecosystem Service: Filtration by the Eastern Oyster in US Estuaries. Estuaries and Coasts 36: 36-43.

zu Ermgassen, P.S.E., M.D. Spalding, B. Blake, L.D. Coen, B. Dumbauld, S. Geiger, J.H. Grabowski, R. Grizzle, M. Luckenbach, K. McGraw, B. Rodney, J.L. Ruesink, S.P. Powers, and R. Brumbaugh. 2012a. Historical ecology with real numbers: Past and present extent and biomass of an imperiled estuarine habitat. Proceedings of the Royal Society B on June 13, 2012. 

zu Ermgassen, P.S.E., M.D. Spalding, R. Grizzle, and R. Brumbaugh. 2012b. Quantifying the loss of a marine ecosystem service: filtration by the eastern oyster in U.S. estuaries. Estuaries and Coasts, DOI 10.1007/s12237-012-9559-y 

zu Ermgassen, P. S. E., M. D. Spalding, R. E. Grizzle, R. D. Braumbaugh. 2013. Quantifying the loss of a marine ecosystem service: filtration by the Eastern oyster in US Estuaries. Estuaries and Coasts 36:36-43.


 Further Reading