This project seeks to build upon Kramer’s efforts to develop a method for growing quahogs within the footprint of a floating oyster farm. We aim to replicate this work on three additional oyster farms in midcoast Maine, as well as to continue monitoring Kramer’s 2017 and 2018 quahog cohorts.
Objective 1: Test quahog grow out using oyster aquaculture techniques. Objective 1.1 Farmer orientation and training
Objective 1.2 Quahog deployment
Objective 1.3 Monitoring quahog growth and survival
Objective 1.4 Measuring environmental variables
Objective 2: Continue to monitor Kramer’s 2017 and 2018 quahog cohorts. Objective 2.1 Monitoring growth and survival
Objective 2.2 Harvest 2017 cohort
Objective 3 Quantify farm-scale production costs and model potential revenue. Objective 4: Conduct outreach to grow industry knowledge and market demand.
Objective 4.1 Existing farmer outreach
Objective 4.2 Industry outreach
If successful, we will have demonstrated that the incorporation of quahogs as a secondary crop is both viable and replicable across the midcoast Maine region. Furthermore, we will have provided three additional farmers with the knowledge and technology transfer needed to grow this species on their own farms and provided additional farmers the opportunity to see the technique first-hand through field trips.
The Gulf of Maine is experiencing rapid climate-driven environmental change that threatens the livelihoods of thousands of Mainers. Simultaneously, the diversity of Maine’s fisheries resources is at an all-time low (Steneck et al. 2011). The marine economy is over 75% dependent on the American lobster, which is showing signs of decline in the southern Gulf of Maine (Wahle et al. 2013). Marine resource diversification is essential for adapting to a rapidly changing ecosystem and ultimately promoting economic resilience for Maine’s coastal communities.
We believe that incorporating sub tidal quahog (littleneck clams) aquaculture into the existing footprint of an oyster farm is an opportunity for sea-farmers to diversify their crops by utilizing the vertical space of the water column. Most sea farms are mono-cultures using only the portion of the water column that maximizes growth. Adding a species with different environmental needs allows a farmer to expand in-place and benefit from additional products and increased resilience to disease and pests. This proposal builds upon Jordan Kramer’s effort to develop quahog and oyster polyculture (SARE projects FNE17-877, FNE18-901) by further testing and expanding this research to three additional farms. We have found that sea farmers are eager to engage in this work and believe diversification will be important to the future success of their farms.
Eastern oysters and quahogs are a good pairing for both husbandry and market. Small, intensive oyster farms (a large proportion of the region’s aquaculture) use floating equipment to grow oysters in the top few feet of the water column where strong currents deliver the most suspended plankton. Quahogs optimally grow in soft sediments and can be placed in rigid-plastic bags below an existing oyster farm (Fig. 1). In this arrangement, oysters and quahogs do not compete for food or space and the added species offers backup income if disease or pests decimate one crop.
The contained, sub tidal method of growing quahogs proposed by this project offers environmental and social benefits over the established aquaculture methods used on the east coast. In inter-tidal culture, clams are planted in netted plots on exposed mudflats, an area traditionally used for recreation and wild-harvest of clams and marine worms, leading to resistance from fishers and shore-front property owners. Growing clams below an existing oyster farm would avoid these conflicts. In traditional sub tidal culture, loose seed clams are harvested by dredging, disturbing bottom-dwelling species and habitat. Using sub tidal bags avoids the need for dredging.
Finally, quahogs are unique because they are most valuable at a small size, making them an attractive secondary crop for oyster farmers. Both oysters and quahogs are sold in the per-piece half-shell (raw) market, offering a considerably better price than the per-pound commodity market (where other clams and mussels are sold). Additionally, the raw market offers a premium for farm-grown over wild-harvested shellfish. A 2016 market analysis of Maine farmed shellfish found that seafood buyers prefer shellfish from the northeast and will pay a premium for Maine brand shellfish, indicating positive market growth potential for this sector (GMRI 2016).
In 2005, Northeast SARE funded a project that focused on the subtidal culture of surf clams (Spisula solidissima) and included a sub tidal polyculture of these clams with eastern Oysters (Baldwin 2005). In this study, both species were bottom-grown and shared space. Several approaches were tried to varying degrees of success, including growing clams in fabric mesh bags, shellfish trays, modified litter-boxes, and large nets to protect stock from predators. Adequate growth was seen in all but the fabric bags, but shellfish trays and litter-boxes were not
economically viable. Though the Baldwin project had similar aims to this proposal, surf clams have a very different biology from quahogs, preferring sand bottoms in high-energy systems (prevalent wave action) instead of soft mud. Furthermore, surf clams have a very different market from quahogs and command a lower price.
Sub tidal culture of quahogs (in the absence of oysters) has been attempted here in Maine as a portion of a USDA SBIR grant in 2010 (Porada 2010). In this approach, large plots were netted in the shallow sub tidal zone of Goose Bay. This project took place at the northern edge of the clam’s natural range, with marginal environmental conditions likely tempering growth (the study site proposed for this project is much warmer and sits within a highly productive wild quahog fishery area). The project did show that contained sub tidal culture of quahogs is possible in the state, albeit in waters incompatible with floating oyster gear.
Large-scale studies of polyculture (or multi-trophic aquaculture) are widespread, but focus on mitigating the negative effects of industrial fin fish or shrimp farming. In these trials macro-algae, marine worms, and/or shellfish are grown to filter and sequester waste from fish or shrimp. These systems have large outside food inputs and are not comparable to dedicated shellfish farms, where crops rely solely on naturally occurring plankton for food. Smaller scale approaches to polyculture in the region have focused on finding off-season crops, namely sea- vegetables, which typically need processing for sale and have an entirely different distribution from live shellfish.
The University of North Carolina Wilmington is currently testing polyculture of quahogs and oysters. However, this region has vastly different environmental conditions and the technique being tested uses a bottom-mounted rack and bag oyster growing system. In this approach, oysters and clams share equipment space on the bottom in both inter-tidal and sub tidal field sites. They are not segregated to different portions of the water column and, therefore, compete for food. Project results are not yet available.
Building on previous SARE projects:
SARE projects FNE17-877 and FNE18-901 tested the feasibility of growing quahogs in a polyculture with oysters in both sediments and surface waters (Kramer 2018, 2019). Results from this research showed commercial promise with clams projected to reach market size in two years, a favorable market price, low equipment costs, little labor burden, and acceptable seed retention/survivorship (40% for the 2017 cohort and 87% for the 2018 cohort). However, these projects were limited in their temporal and geographic scope. Fieldwork was conducted on one farm for just over 17 months, which was not long enough to follow the first crop to market. This proposal would test the suitability of this technique at multiple sites and would quantify underlying environmental differences. It would continue monitoring the original site to establish a firmer understanding of seasonal growth patterns (at both the surface and in sediments) and would follow the original clam crop to market, ultimately testing the economic assumptions presented in the original study.
Baldwin J (2005) Sub-tidal aquaculture of surf clams. USDA SARE project FNE05-542. https://projects.sare.org/sare_project/fne05-542/
GMRI (Gulf of Maine Research Institute). 2016. Maine Farmed Shellfish Market Analysis. Report.Gulf of Maine Research Institute, Portland, Maine. https://www.gmri.org/sites/default/files/resource/gmri_farmed_shellfish_final_with_cover_10.13.16.pdf
Kramer JM (2018) Integrated oyster and littleneck clam aquaculture to increase seafarm yield. USDA SARE project FNE17-877. https://projects.sare.org/project-reports/fne17-877/
Kramer JM (2019) Littleneck clam and American oyster polyculture: Economic viability and nursery Technique. USDA SARE project FNE18-901. https://projects.sare.org/project-reports/fne18-901/
Porada J (2010) Hard clam farming in eastern Maine: field experiments to evaluate biological & economic efficacy of field-based nursery and grow-out phases. USDA SBIR project 2010-02596. https://www.sbir.gov/sbirsearch/detail/16591
Stanley JG (1985) Species Profiles. Life Histories and Environmental Requirements of Coastal Fishes and
Invertebrates (Mid-Atlantic). Hard Clam. Maine Cooperative Fishery Research Unit Orono.
Steneck RS (1997) Fisheries-induced biological changes to the structure and function of the Gulf of Maine ecosystem. In: Wallace GT, Braasch EF (eds). Proceedings of the Gulf of Maine Ecosystem Dynamics Scientific Symposium and Workshop. RARGOM Report. p 151-165.
Steneck RS, Hughes TP, Cinner JE, Adger WN, Arnold SN, Berkes F, Boudreau SA, Brown K, Folke C, Gunderson L, Olsson P (2011) Creation of a gilded trap by the high economic value of the Maine lobster fishery. Conservation biology, 25:904-12.
Wahle RA, Brown C, Hovel K (2013) The geography and body-size dependence of top-down forcing in New
England’s lobster-groundfish interaction. Bulletin of Marine Science, 89:189-212.
Objective 1: Test quahog grow out using oyster aquaculture techniques.
Objective 1.1 Farmer orientation and training: Project leaders organized an initial meeting with farmers in August 2019 to discuss methodology, gear requirements, data collection, etc. All gear and quahog seed required for the project was distributed to farmers at this meeting.
Objective 1.2 Quahog deployment and grow out: Each farmer received 20,000 quahogs ranging in size from 5-15 mm shell length at the August 2019 training. We then worked with each farmer to prepare their gear/farm for deploying the quahogs. Initially, the quahogs were evenly split (10,000/bag) among two 2 mm plastic diamond mesh oyster bags (32 x 18 x 3 in). These bags were placed in floating cages on the surface for the first month of the project. We had expected to deploy surface and bottom treatments immediately; however, slower growth rates over the summer of 2019 delayed the deployment of our split treatments until late September. Once the quahog seed had reached a larger size, each farmer graded their seed using a 6 mm plastic mesh screen. All quahogs that retained on the screen were equally split into two surface and two bottom treatments. All treatments were overwintered (i.e., sunk to bottom) in early December 2019 and will remain there until March 2020, when monthly measurements will resume.
Objective 1.3 Monitoring quahog growth and survival: Quahog growth and survival was measured monthly from September-November 2019 (growth is not expected to occur from December-March when water temperatures fall below 5-6℃ (Stanley 1985)). Growth and survival were determined from 100 randomly sampled quahogs from each treatment (i.e., surface and bottom). Empty shells were used to calculate percent mortality.
Objective 1.4 Measuring environmental variables: We deployed a temperature logger on each farm that records hourly temperature measurements. In addition to this, we took monthly measurements of salinity, pH, turbidity, and chlorophyll on each farm using a Sonde, and we collected surface and bottom water samples and analyzed them at the University of Southern Maine using a fluorometer.
Objective 2: Continue to monitor Kramer’s 2017 and 2018 quahog cohorts.
Kramer’s 2017 and 2018 cohorts were monitored from September-November 2019 and will continue to be monitored in 2020. A portion of the 2017 cohort was harvested and sold at Harbor Fish Market in Portland, ME in the fall of 2019.
Objective 3 Quantify farm-scale production costs and model potential revenue.
This portion of the project will be conducted in the spring/summer of 2020.
Objective 4: Conduct outreach to grow industry knowledge and market demand.
This portion of the project will be conducted in the summer/fall of 2020.
Results are very preliminary at this point, as the quahog seed was deployed at the end of the growing season. However, we did see faster growth rates at the West Bath and Harpswell farms compared to the two Georgetown farms. We have not begun analysis of environmental variables, but it is possible that conditions in West Bath and Harpswell favor faster growth (e.g., warmer temperature or high chlorophyll content). We saw very high survival overall, often 100%. The highest observed mortality was 12% at the Harpswell farm in the month of October. Analysis of the environmental data may provide insights as to why this occurred. All other mortality measurements ranged from 0-2%.
The portion of Kramer’s 2017 cohort that was harvested and sold received a market price of $0.40/ea. This is ~$0.15/ea higher than wild harvest product. However, Kramer’s product was sold at a smaller size than wild harvest regulations allow, indicating a market niche. Interestingly, the market-size quahogs appear to be more fragile than their wild counterparts, so careful handling is necessary. We hope to explore this finding more in the summer of 2020.
These preliminary findings will be used to begin production and market analyses in the spring and summer of 2020.
It is too early to make conclusions from the data we have collected thus far. We can comment on the overall process thus far, which has been well received by farmer partners. Each farm was able to easily adapt to growing quahogs. Many more farmers have expressed interest in the project and the potential for crop diversification on their own farms.
Education & Outreach Activities and Participation Summary
We have received media coverage for this project from the following outlets:
- Associated Press: Environmentalists propose Mainers farm quahogs to beat pests: https://apnews.com/61bf6a06cdda4045a113c493f04b9076
- Heated: How to make the best fried clams ever: https://heated.medium.com/how-to-make-the-best-fried-clams-ever-35872b0ad0d3
- Maine Public Radio: Maine’s clam harvest: what is being done to improve health of Maine’s clam population? https://www.mainepublic.org/post/maines-clam-harvest-what-being-done-improve-health-maines-clam-population
- Landings: Quahogs tested as new Maine species: https://mlcalliance.org/2019/12/20/quahogs-tested-as-new-maine-species/
- Wicked Local: Plymouth-based Manomet Inc. tests hard-shell clams for replenishing Gulf of Maine fisheries: https://plymouth.wickedlocal.com/news/20191114/plymouth-based-manomet-inc-tests-hard-shell-clams-for-replenishing-gulf-of-maine-fisheries
Outreach in progress:
- Presentation at Milford Aquaculture Seminar, Shelton, CT, January 14th, 2020
- Presentation at Maine Aquaculture R&D&E Summit: Belfast, ME, January 17th, 2020
- Presentation at Maine Fishermen’s Forum, Rockport, ME, March 5th, 2020
We are currently working with the Bowdoin College Marine Biogeochemistry class on targeting the most pressing questions for farmers and developing sediment and water chemistry sampling protocols to address those questions.
We conducted the farmer orientation and training workshop in August 2019. The training was led by Kramer (farmer) and attended by the 4 farmers who are part of the project, as well as 2 additional farmers who are interested in growing quahogs. Dana Morse from Maine Sea Grant also attended the training.