A Partnership for Innovative Use of Emerging Species in Aquaculture

Progress report for ONE22-430

Project Type: Partnership
Funds awarded in 2022: $29,496.00
Projected End Date: 02/28/2025
Grant Recipient: University of Rhode Island
Region: Northeast
State: Rhode Island
Project Leader:
Dr. Coleen Suckling
University of Rhode Island
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Project Information


The project seeks to sustain the Atlantic sea scallop (Placopecten magellanicus) and Green sea urchin (Strongylocentrotus droebachiensis) industries in Maine through enhancing these emerging aquaculture sectors. To achieve this, the project will integrate the two species in shellfish grow out gear. The added benefit for this integration is that the green sea urchins will likely graze upon and therefore reduce biofouling on nets and shellfish. Subsequently we expect that this will result in the enhanced growth and therefore value of both the green sea urchins and the shellfish. To achieve this, we will conduct a range of growth trials using different densities of green sea urchins with trials to starting in May 2023. The green sea urchin seed are available at the University of Maine’s Center for Cooperative Aquaculture Research (CCAR) hatchery.



Project Objectives:

The project seeks to sustain the Atlantic sea scallop (Placopecten magellanicus) and Green sea urchin (Strongylocentrotus droebachiensis) industries in Maine through enhancing these emerging aquaculture sectors. 

To achieve this, the following objectives will determine whether:

1) Integrating Green sea urchin seed with Atlantic Sea Scallop seed during grow out can reduce biofouling on nets and scallop shells. We expect biofouling on scallop nets and shells to be reduced by up to 50% and 30-100% respectively.

2) This integration can enhance growth rates and the market value of both species by creating an additional $7kg-1 in scallops and $22kg-1 for sea urchins produced.


We will compare levels of biofouling in lantern nets that contain only scallops (control) or contain scallops and green sea urchin seed, using differing combinations of animal sizes and stocking densities to determine the best combinations. Treatment groups will be independently replicated in each farm at two scallop farms. The same approach will also be incorporated into an oyster farm to build on previous evidence for biofouling control needed for shellfish grower confidence. This work will be conducted through strong knowledge exchange and outreach efforts to the broad and diverse network of shellfish growers across the Northeast.


Atlantic Sea scallop (Placopecten magellanicus) production in Maine is largely based on an active fishery, but production is variable and has declined by about 7.5 million kg since 2019 (NOAA Fisheries landings data) despite strong and unmet demand. To work towards sustaining this regional industry, growth through aquaculture has shown tremendous success in recent years. For example, sea scallops are included on a fifth of the current experimental and standard leases issued by Maine Department of Marine Resources (DMR) and Maine has seen an increase of 262% since 2018 through Limited Purpose Aquaculture licenses (DMR, 2021). Aquaculture has also enabled a year-round supply to the market, thus closing the gap when the wild fishery is not active (May to November; Coleman et al., 2021). Despite the growing success, uptake, and application of sea scallop aquaculture, it is unanimously plagued by the major issue of biofouling during field grow-out. Sea squirts, sponges, tube worms, and barnacles are especially problematic on nets and on shells, with some species boring into shells (Fig. 1 in attachments). Farmers across Maine are greatly concerned that biofouling prevents shellfish from reaching their full commercial potential by >30% which in scallops (Ross et al., 2004) is equivalent to at least $7kg-1 missed opportunity (Fitzgerald, 2021). Biofouling can restrict and reduce water flow, and because it adds wet biomass to the external shell surface, the animals expend additional energy to open, which likely diverts energy from biological processes such as feeding, gas exchange, and waste removal, and negatively affects growth. Farmers presently spend time and money to combat biofouling, contributing to the heavy preponderance of labor as a driving expense in scallop farming (Coleman et al, 2021). 


This project focuses on the biological solution of integrating another commercially valuable species to potentially graze upon biofouling organisms and thus enhance growth to market, without detriment to scallop growth or quality. Green sea urchins (Strongylocentrotus droebachiensis) pose an extremely promising option as a low trophic species with low environmental impacts, and in sync with the low impacts of molluscan shellfish production. They offer strong potential for integration with Atlantic sea scallops. They naturally reside within Maine’s coastal waters, have overlapping optimal temperature requirements with Atlantic sea scallops (Eddy, 2015; Fitzgerald, 2021), have been shown to grow successfully through sea ranching or cage culture including in the types of gear used in scallop grow out (e.g. lantern nets; Cook and Kelly, 2007), and they have been successfully grown in polyculture with shellfish such as mussels (Mytilus sp.), oysters (Ostrea edulis), and scallops (Pecten maximus), where they’ve been shown to reduce biofouling by as much as 50% (Ross et al., 2004; McBride, 2005; Chopin et al., 2013; Harris, 2014; Sterling et al., 2016). The green sea urchin is one of the most valuable sea urchin species within global and regional markets; its edible roe, known as uni, can be sold as a processed product at $12-14 100g-1 and similar to oysters, green sea urchins can be sold as live, shell on  animals, fetching from ~$22 kg-1 up to $110kg-1. Uni quality is linked to dietary intake, and biofouling species on shellfish nets and shells offer additional protein for uni growth (Cook and Kelly, 2007; Suckling et al., 2011; Eddy, 2015). The green sea urchin production narrative has similar yet more dramatic parallels to that of Atlantic sea scallops. It has a drastically diminished fishery, declining from 18,000 t yr-1 (~$30m value) during the late 1990s to 900 t yr-1 ($6m value) today, and it is now heavily managed through strict harvesting regulations (e.g. catch size limitations of 52-76 mm and harvesting periods of only 15-40 days). Sea urchin demand is high and unmet, but declining wild stocks in combination with COVID have forced some of the few remaining smaller processors in the Portland area of Maine to exit the industry, posing an existential threat to the fishery. Green sea urchin aquaculture production is slowly emerging in Maine, with growing awareness of seed availability from the regional hatchery at the University of Maine’s Center for Cooperative Aquaculture Research (CCAR) in Franklin, Maine, though lack of green sea urchin grow out experience continues to slow adoption. Recent outreach efforts by the project team (Suckling, Eddy and Morse) have led to interest from >70 shellfish growers (scallops, oysters), including women in aquaculture, in experimenting with green sea urchin seed, highlighting demand and training needs.


Here we propose a partnership approach towards focusing on integrating these two emerging aquaculture species, Atlantic sea scallops and green sea urchins. This is a highly multidisciplinary topic that requires a broad team comprised of growers, green sea urchin hatchery producers, sea urchin and scallop researchers, and extension staff to bring needed expertise for resolving the issues of shellfish production biofouling, and to work towards sustaining these two important seafood industries in the region of Maine, which aligns with Northeast SARE’s outcome statement. While the primary focus is on enhancing growth and production of Atlantic sea scallops, this partnership will be important for the broader shellfish aquaculture community across Maine, by showcasing low trophic solutions towards reducing biofouling. We will therefore also build in a case study using oysters (Crassostrea virginica) to further build from previous biofouling control research to increase confidence in adopting these tools. In turn, this work will increase awareness of and confidence in green sea urchin production using strong knowledge exchange and outreach approaches to the broad sea urchin and shellfish stakeholder communities across the Northeastern US.



Click linked name(s) to expand/collapse or show everyone's info
  • Steve Eddy (Researcher)
  • Dana Morse (Researcher)
  • Anne Noll - Producer
  • Stewart Hunt - Producer


Materials and methods:

The full project team will meet virtually at the project start to refine experimental and logistical planning for the biofouling control trials at each farm. Online knowledge exchange will be provided by researchers and farmers, along with the identification of relevant resources needed for preparing all parties for growing sea urchins in open water grow out systems. This knowledge exchange will continue across the group via email and phone calls and ad hoc virtual meetings as needed throughout the project.


Green sea urchin seed will be reared at the University of Maine’s Center for Cooperative Aquaculture Research (CCAR) hatchery and transported in coolers to each farm site. Sea urchins will be transferred into grow out gear, such as lantern nets for scallop farms or dark sea trays for the oyster farm, consisting of separate compartments called tiers stacked into a column, with each tier separated by netting or mesh allowing for high vertical production capabilities.


This project will experiment with different combinations of shellfish sizes (small and large) and stocking densities of sea urchins per lantern net tier or tray. More specifically we will combine:


  1. Small scallops or oysters (<1”) with small sea urchin seed (<0.75”); 
  2. Larger scallops or oysters (1” shell height) with larger sea urchin seed (1” test diameter); and 
  3. Larger scallops or oysters (1” shell height) with small sea urchin seed (<0.75”). 


These size classes are commonly encountered for both types of seed across both of these emerging industries. Scallop seed of either size class will be stocked at 30% bottom coverage per tier following general protocols; oysters will be stocked at 100% bottom coverage. We will also assess the stocking density of sea urchins for each of the aforementioned size class combination groups, by stocking sea urchins at either 2, 4 or 8 sea urchins per tier following approaches outlined by Ross et al. (2004). All of these groups will be compared to control groups consisting of scallops or oysters without sea urchins. Each treatment group will be located within a replicate tier within a lantern net or dark sea tray stack, and replicated across three lantern nets or stacked tray systems (Fig. 3 in supporting materials) at each farm site.


Three experimental farm sites spread across Maine’s central coastal waters will be used to assess the success of reducing biofouling across an area where shellfish farming occurs, using the experimental designs and nets outlined above. The sites are as follows:


Site 1: The Darling Marine Center and the United States Department of Agriculture Experimental (DMC/USDA) Lease site at Lowes Cove, Walpole (Fig. 2). 1.7 acres in three tracts; the tract for this experiment is 1.0 acres in 18-30 feet of water. Temperatures achieve 18-20˚C maximum and salinities commonly above 28ppt.  This site is well protected and characterized by heavy fouling and will be used to integrate Atlantic sea scallops with green sea urchins in lantern nets.


Site 2: Casco Bay, Casco Bay Mooring. The farm is located in eastern Casco Bay. The site experiences salinities over 30ppt and temperatures reaching 18˚C.  Partially exposed site, and characterized by moderate fouling.  This site will be used to integrate Atlantic sea scallops with green sea urchins in lantern nets.


Site 3: Pemetic Sea Farms, Newbury Neck Site in Union River Bay, Surry (Fig. 2). This is a site with a limited Purpose Aquaculture License from DMR comprising up to a third of an acre of area with approval to grow oysters. This site will be used to determine whether the positive results yielded from Harris (2014) success in reducing biofouling in oysters (Ostrea edulis) can be repeated with a different oyster species, by integrating Crassostrea virginica with green sea urchins to tackle a persistent issue of aggressive biofouling from barnacles (Balanus crenatus) using dark sea trays, in which sea urchins can easily grow within (McBride 2005; Harris 2014).


Farmers will collect environmental data from their sites (e.g. temperature, salinity) as per normal farm operations. During mid-June and late-August, the farmers will thoroughly check the experimental gear and take photographs of biofouling for each group and briefly check the status and survival of sea urchins and shellfish. They will then meet virtually with the whole project team to update on the status of the experiments and use this as a knowledge exchange opportunity for any interventions that may be needed (e.g. replacing any mortalities of sea urchins with more seed for example and looking at environmental data to explain any potential issues/results). During October, the experiments will be terminated.


Sampling, data collection and analysis: 


During the project start and end, all shellfish (scallops and oysters) will be measured for their shell length, width and height and all sea urchins will be measured for the test diameters using a combination of vernier calipers and digital photography against a stationary ruler for scale for digital measurements using ImageJ (Shindelin et al 2012). Similarly, all nets will be photographed against a scale to qualitatively rank the level of biofouling (e.g. 1 = no fouling, 2, = some fouling, 3 = moderate fouling, 4 = heavy fouling) and identify biofouling species on nets. Fouling species and the gear tiers will be weighed wet and dry to quantitatively determine biofouling presence. Baseline and end of experimental samples of shellfish (n = 10 per replicate tier) and all sea urchins will be dissected. Shellfish wet tissue mass and sea urchin gonad mass will be weighed to determine impacts on market meat of the species. Following international reporting protocols, sea urchin gonad will be divided by the whole animal wet mass and expressed as a percentage. Gonad color will be compared against a sea urchin color card to qualitatively assess whether gonads are marketable in color (bright orange to yellow color) or not (dark brown, gray to black color; Suckling et al. 2011). All animal, biofouling and environmental data (e.g. salinity, temperature) and photographs collected by farmers and researchers will be collated and stored into a shared team Google Drive hosted by the University of Rhode Island which is backed up and has no storage restrictions. 

Data will be analyzed using R Studio to determine the treatment effects (seed size, stocking density) on biofouling, survival, growth, wet tissue mass, gonad index and color for shellfish and sea urchins and environmental data (temperature salinity) within each farm. Treatment differences will be analyzed using either Nested ANOVA via a General Linear Model or One-Way ANOVA after testing for normality and homogeneity of variance (p > 0.05) in R Studio. After significant ANOVA results, Tukey’s or Bonferroni’s Pairwise Comparisons will be utilized to determine which treatments differ for balanced and unbalanced data sets respectively. Non-parametric Kruskal Wallis tests will be carried out where heterogeneous residual variability remains after transforming data following Sokal and Rohlf (1995) or for qualitative data. Project approaches and results will be collated into a report and then discussed with the whole project team through a virtual knowledge exchange meeting to identify plans for how research and farmers will move forward with these results and to plan outreach efforts to the broader shellfish community across the Northeastern US.

Research results and discussion:

Site 1: The Darling Marine Center (DMC) did not amend their lease meaning that we were unable to conduct the trials during 2023. After correspondence with the Grant Director, a no cost extension was discussed as a solution to this, enabling the trials to take place instead during 2024. At the time for her project report, the PI submitted a no cost extension request to NE SARE and awaiting approval. In the meantime, DMC have submitted a lease amendment request and the team have coordinated plans for a potential experiment during 2024.

Site 2: Casco Bay, Casco Bay Mooring. This was a new partner added to the project after the original partner Vertical Bay LLC was unable to amend an experimental lease and meant that there was delay in starting the experiment until we found a new partner. This trial was implemented from June until August 2023. A team of graduate and undergraduate students are still processing the samples so we do not have final data yet. Preliminary results showed high survival of both scallops and urchins and no negative impacts on scallop growth when integrated with urchins, showing that these species can be co-cultured successfully.  The internal lantern nets were relatively clean but the external nets were  fouled, with no dramatically obvious results of reduced biofouling by the need eye - but further sample and data analysis are needed and ongoing to determine whether there were reductions or not.  Learning and building from this trial, the team are considering to use larger sized urchins at DMC to determine whether more drastic biofouling reductions can be observed. 

Site 3: The experiment at site 3, Pemetic Sea Farms, Newbury Neck Site in Union River Bay, Surry, ME was deployed in June 2023, but during September during a routine check, the grower's observed that all of the urchins and may of the small oysters had died, thus terminating this trial. We believe that the animals died due to severe storms in the area during that time and collated together temperature data from our data loggers with the experiment and environmental data collected by the Maine Department of Marine Resources. Collectively the data for this site showed that temperatures reached up to 26 degrees C, and salinity as low as 20 ppt. The unusually high summer temperature and extreme storm induced freshening of this coastal site which is normally 30ppt salinity were likely the reason for the mortality but it's difficult to tease apart whether one stressor after another, or the combination of the stressors were the cause of the mortality. Either way, this has been important by highlighting some aspects of tolerance of these animals and their suitability to host green sea urchins.


Research conclusions:

We sought to integrate green sea urchin seed  with various shellfish farms to co-grow species and reduce nuisance biofouling of shellfish. We were successful in showing that green urchin seed could be grown with Atlantic sea scallops and the grower wants to continue growing urchins showing. a positive change in practice at an experimental context. This has already brought awareness to 4 other growers who have requested green sea urchin seed for experimental grow out trials. We did not observe dramatically obvious reduction of biofouling, but have strategies we will apply in the next trials to work towards this goal.

Participation Summary
3 Farmers participating in research

Education & Outreach Activities and Participation Summary

1 Published press articles, newsletters
4 Webinars / talks / presentations

Participation Summary:

2 Farmers participated
6 Number of agricultural educator or service providers reached through education and outreach activities
Education/outreach description:

Extension agent, Dana Morse, will lead the outreach activities at the project start, midway and end point to disseminate project activities and goals and to provide information to the broad network of shellfish producers across the Northeastern US region. 


The project has trained two graduate students on shellfish integration technologies, an intern in shellfish and sea urchin farming, and  shellfish farmers in green sea urchin production. In addition, Morse and Eddy participated in a workforce training program called ‘Aquaculture in Shared Waters’ aimed towards fishers and other marine users.


Project progress and a final report will be made electronically available through institutional and team member websites and social media platforms (e.g. Instagram, Twitter, Facebook; University of Rhode Island, University of Maine Sea Grant, PI Suckling, Farmers), press releases, newsletters and webinar talks / conference or meeting presentations. For example, PI Suckling attended the National Shellfish Association meeting in Baltimore, MD and the Northeast Aquaculture Conference & Exposition (NACE) during 2023 and 2024 and presented project progress and preliminary results there (funds not requested or needed from USDA SARE for this conference). The NACE is the region’s largest aquaculture conference and trade shows in the Northeastern region which is attended by a broad regional stakeholder community including researchers, industry and students (>500 stakeholders).


The final report will be shared electronically with key opinion leaders and organizations across the Northeastern US, such as the East Coast Shellfish Grower’s Association, Maine Sea Grant, University of Maine Aquaculture Research Institute, University of Rhode Island Coastal Institute, and industry specific regional mailing lists (e.g. Sea Urchin Zone Council (industry led organization which advises the Department of Marine Resources), Sea urchin interest group which includes shellfish growers interested in growing sea urchins too, created from a Northeastern Regional Aquaculture Center funded project led by Suckling).

Learning Outcomes

2 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key areas in which farmers reported changes in knowledge, attitude, skills and/or awareness:

These are our collaborating farmers (Casco Bay Mooring and Pemetic Sea Farms). Pemetic Sea Farms still express interest to trial sea urchins. Casco Bay Mooring are keen to conduct more trials with sea urchins are in communications about developing one for submission to conduct this work but instead with Atlantic sea scallops and Green sea urchins. This work disseminated through talks and our engagement with a green sea urchin aquaculture  interest list has drilled more interest through enquiries and requests for seed.

Project Outcomes

4 Farmers changed or adopted a practice
5 Grants applied for that built upon this project
2 Grants received that built upon this project
$397,364.00 Dollar amount of grants received that built upon this project
3 New working collaborations
Project outcomes:

We sought to integrate green sea urchin seed  with various shellfish farms to co-grow species and reduce nuisance biofouling of shellfish. We were successful in showing that green urchin seed could be grown with Atlantic sea scallops and the grower wants to continue growing urchins showing a positive change in practice at an experimental context. This has already brought awareness to 4 other growers who have requested green sea urchin seed for experimental grow out trials. We did not observe dramatically obvious reduction of biofouling, but have strategies we will apply in the next trials to work towards this goal.

Assessment of Project Approach and Areas of Further Study:

We showed that green urchin seed could be grown with Atlantic sea scallops and because of this important result we believe that  the polyculture and integration of urchins and scallops are worth pursuing for diversifying crop production.  We have not fully answered the questions yet due to delays (see learner sections) and the need to find an alternative scallop grower (see methods update), but ongoing sample analysis may bring supportive data on this. In addition, due to our partner not gaining a lease amendment to conduct work, we are waiting for approval for a no cost extension to build upon these trials towards reducing biofouling.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.