Development of Integrated Seaweed and Green Sea Urchin Aquaculture for Diversification of Sea Farms in the Northeast

Progress report for ONE20-356

Project Type: Partnership
Funds awarded in 2020: $29,985.00
Projected End Date: 06/30/2022
Grant Recipient: Maine Seaweed Exchange
Region: Northeast
State: Maine
Project Leader:
Andrea Angera, Jr.
Maine Seaweed Exchange
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Project Information


Seaweed and shellfish aquaculture is a fast-growing industry in Maine, but most farms rely on only one crop and lack diversification options. Green sea urchins (Strongylocentrotus droebachiensis) represent an opportunity for multi-cropping on aquaculture farms, especially if seaweed can be cultivated on the farm for feed. This project proposes to develop integrated grow out strategies for green sea urchins and sugar kelp (Saccharina latissima) for existing oyster and kelp farms in Maine. Hatchery raised juvenile green sea urchins will be cultured alongside sugar kelp on two sea farms to determine growth rate, the feasibility of year-round production of algal feed, and to develop farm integration strategies for oyster and seaweed farms. Results will be shared with the industry through online media and through a one day workshop to be hosted by the Maine Seaweed Exchange.

Project Objectives:

Goal: To develop year-round integrated grow-out strategies for green sea urchins and sugar kelp that can be incorporated into existing sea farms in Maine. 

Objectives: This project seeks to:

Objective 1: Determine year-round growth rates of green sea urchins reared on farmed sugar kelp and wild set algae in sea cages at two different sea farm sites in Maine

Outcomes: Data will inform cultivation strategies and determine growth rates for urchin grow-out utilizing locally grown feed on sea farms in Maine 


Objective 2: Develop year-round cultivation strategies for sugar kelp and wild set algae to be utilized as feed for sea urchins

Outcomes: Strategies for successful year-round production of sugar kelp and wild set algae to be utilized as environmentally sustainable urchin feed


Objective 3: Characterize unique farm seasonality to determine integration needs and opportunities 

Outcomes: Farm management plans for oyster and seaweed farms in Maine to allow for successful urchin and kelp feed integration 


Once the fastest growing marine fishery in the US, the Maine green sea urchin fishery is another “boom and bust” cautionary tale. While Maine has had a small urchin fishery since the 1930’s, the fishery rapidly expanded in the late 1980’s, peaked in 1993 at 41 million pounds, then declined to 2 million pounds in 2018 (DMR, 2018). Efforts at reseeding wild populations were unsuccessful due to high predation (Leland et al, 2001), and wild stocks have not recovered. The increasing demand for high quality uni (sea urchin gonads), global market of $400 million, and limited wild resource presents an opportunity for aquaculture, but urchin aquaculture represents less than 0.01% of worldwide production (James et al., 2017). While several research trials have been conducted on urchin culture in Maine, there has never been an attempt to integrate urchins into existing seaweed and shellfish farms. We propose to determine the commercial feasibility of raising urchins in conjunction with seaweed for feed on existing sea farms, creating essential baseline data for the development of commercial integration of urchins onto sea farms. 

Maine has recently experienced an increase in seaweed and shellfish aquaculture leases, with the majority of farms cultivating only one crop.  Marine aquaculture leases are the most valuable asset to any ocean farmer. In Maine, the lease process can take several years, and represents a comprehensive process that requires considerable investment. By integrating new species into a farm, farmers can increase sustainability, profitability, and resilience of a sea farm. Currently, there are only a few crop options for seafarmers, each presenting challenges. Seaweed crops lack sufficient processing and marketing infrastructure, and are very low value at the dock, and shellfish can be closed from red tide biotoxin events, and can take several years to reach market size in the cold waters of Maine. 

Standard commercial aquaculture leases in Maine are divided into two categories; non-discharge and discharge. Non-discharge aquaculture includes seaweed and shellfish aquaculture, where organisms obtain all their food from the surrounding environment, requiring no additional inputs. Finfish aquaculture is discharge, introducing feed into the environment, requiring a pollutant discharge permit and additional oversight by the Department of Environmental Protection. Globally, efforts to cultivate sea urchins have included use of a pelleted feed, which is often made with fishmeal, which raises concerns about feed sustainability, nutrient loading in the environment,  and off-flavors introduced through feed. To avoid the complications of the discharge category, eliminate the need for additional nutrient loading in the environment, and to build sustainability into the culture system, we propose to cultivate kelp as feed for the urchins on the sea farms in conjunction with urchins. By cultivating sugar kelp year round, the farms will generate sufficient amounts of feed for an urchin crop. It is expected that sugar kelp and sea urchins can be cultivated as a secondary crop on both seaweed and shellfish farms to enable economic and species diversification for farmers. 


Click linked name(s) to expand/collapse or show everyone's info
  • Steve Eddy (Researcher)
  • Jordan Kramer - Producer
  • Sarah Redmond - Producer


Materials and methods:

Proposed Methods:

Experiments on urchin and kelp cultivation and seasonal farm integration will take place on an oyster farm and a seaweed farm at two geographically distinct sea farms in Maine. The Maine Seaweed Exchange will create and provide online data collection tools for the farmers; as well as create and generate project reports, data analysis, and outreach events.

Winnegance Oyster Farm is located in the New Meadows River in West Bath in a highly protected inshore site with strong tidal exchange. The farm has a maximum high-tide depth of 30’ (deeper than most oyster farms in the area, which average 15’). Surface-water temperatures in the summer reach as high as 21°C, though deeper portions of the farm remain in the tolerance range of urchins during warmer months (measured high of 17°C in Aug 2019). The farm consists of floating oyster cages and lantern nets that are tended on the surface from early April until the beginning of December. Oyster cages are overwintered on the bottom during winter months to avoid ice damage. Quahog clams are grown in the sediments year-round.

Springtide Seaweed’s farm site, located in Sorrento, is a relatively exposed site, with a five mile fetch to the east and south. The farm lease is located in deep water, at 80-90 feet, and experiences high surface summer water temperatures of 18°C and low surface winter water temperatures of -1.7°C. Springtide cultivates several species of kelp on submerged horizontal long lines suspended with buoys and held in place with moorings. Kelp seeding takes place in the fall (September-November) and harvest in the spring (March-June).

Due to Covid-19 disruptions in the sea urchin hatchery schedule at CCAR, new seed urchins will not be available at project start, so we will utilize juvenile urchins (approximately 30mm diameter) produced at the CCAR hatchery in 2019 in year one, currently housed at Springtide’s aquaculture facility. If new hatchery seed is produced by CCAR in year two, we will raise on the two sea farms and in the land based tank inside of smaller mesh nursery bags in the same manner as described above for juvenile urchins. 

Objective 1

Grow out strategies for juvenile urchins: Year 1: both farms will place 100 juvenile, 2 year-old, 30mm diameter urchins produced in the CCAR hatchery out on sea farms in the fall. Rigid stacked “lantern cages” will be developed for grow-out of juvenile urchins. Urchins will be stocked at a density of 5-10 urchins per layer, weighed and photographed upon stocking, and every two weeks thereafter for analysis with ImageJ image processing program to determine growth rates by measuring test diameter and weight. Urchin cages will be stocked with available wild set algae and farmed sugar kelp and monitored every week, and refilled as needed, keeping  track of algae feed (type, weight, condition) added to cages. 

Winnegance will integrate urchins into existing oyster operations and overwinter urchins in bottom cages. Springtide Seaweed will suspend urchins from longlines year round. Growth and feeding will be monitored through year two. It is expected that some portion of the urchins will reach maturity by year two, and can be analyzed for uni quality. 

100 juvenile urchins will also be cultivated in tanks at Springtide Seaweed’s aquaculture facility at an optimum growth temperature (10°C) and fed the same diet of farmed sugar kelp and wild set algae from farms in order to determine growth rates of tank raised versus farmed urchins. 

Objective 2

Natural macroalgal feed for urchins will be sustainably produced on farms year-round. Horizontal submerged longlines will be seeded with two different strains of sugar kelp (a downeast strain and a midcoast strain). Kelp seed spools, consisting of 2 mm kelp juveniles attached to twine wrapped around a length of PVC pipe, will be grown at Springtide’s seaweed nursery, and seeded onto horizontal long lines at each farm in the fall. 

Springtide and Winnegance will each seed a dedicated urchin line, and cultivate year round to determine feasibility of continual cultivation. Typically, kelp lines are taken in after harvest in the spring and farms are fallowed through summer months. It is expected that growth will slow in the summer when temperatures increase and nitrogen levels decrease, but then resume growth in the fall. Growth will be measured by taking representative samples every two weeks during farm season on each farm of each strain and measuring stipe length, blade length and width, and overall length. Lines will be monitored for biofouling organisms and plant health. Sustainable harvesting of lines for use as urchin feed will be conducted by either selectively thinning out densely seeded areas or by trimming ends of blades. The meristematic growth region for sugar kelp is located at the juncture of stipe and blade, so the plant will continue to grow when tips are trimmed. Wild set algae and biofouling organisms on kelp lines will be monitored through the year, and utilized as additional urchin feed. In addition, Winnegance will test specially designed settling gear designed to encourage wild set algae on the farm for use as urchin feed, to be set out in the spring and monitored through the growing season.  

Objective 3

Each farm will collect physical and biological environmental data year round to fully characterize farm sites for integration of sea urchins and algal feed. Temperature and light profiles will be developed for each site by affixing HOBO data loggers every 10 feet on an anchor line. Turbidity will be measured with a secchi disc every month of farm operation and surface water current velocity will be determined with drifter buoy Lagrangian measurements. Biofouling activity will be monitored by noting species and abundance every two weeks of farm operation. Farm activities will be outlined and analyzed for urchin and algal integration and optimization. A report describing the optimal integration strategies for oyster and seaweed farms will be created as a resource for the aquaculture industry.

Progress Report: January 15, 2021

The Maine Seaweed Exchange has provided a managerial role in the administration, organization, and execution of the project through regular planning and communication with project partners, managing orders and deliveries, and working to explore potential innovation for the project. Besides regular project activities, the MSE has initiated an internship program with three new undergraduate interns, who will be working to develop online data collection and sharing, webpage and social media development for the project, and outreach and education activities. The MSE is partnering with a technology company to pilot data sonde technology for aquaculture farms, and is planning on making these units available to partner farmers for environmental data collection on farms. The MSE is planning three upcoming online seaweed farming workshop in Jan, Feb, and March 2021, where the project will be highlighted and shared. 

Springtide Seaweed has been maintaining urchins from the CCAR nursery received on 7/12/2019  (hatched in early 2019) in tanks in their nursery, as well as field-raised cultures. On October 16th, 2020, Springtide Seaweed picked up a new batch of juvenile seed urchins from the UMaine’s Center for Cooperative Aquaculture Research (hatched in early 2020) and is currently cultivating them in shallow 4ft diameter tanks fed with kelp and wild collected seaweed. Two Springtide interns (one undergraduate, one post-graduate) have assisted with photographing of urchins for data measurements, and with field and tank maintenance.  

On November 2nd, Springtide picked up supplies from Hamilton Marine for the project, and delivered supplies, seeded kelp spool, and 100 urchins from the 2019 (approximately 21 months old) to Winnegance Oyster Farm for deployment. All urchins from 2019 and 2020 have been photographed, and will continue to be photographed for growth analysis throughout the year at both farms. 

Springtide Seaweed produced sugar kelp seed spools in their nursery in the fall of 2020 for both farms with parent plants sourced from midcoast and downeast Maine. Kelp was deployed in November (Springtide farm) and in December (Winnegance Farm) for cultivation through the winter months for urchin feed. Both farms have deployed temperature loggers, with more on the way for depth profiling. 

Winnegance Oyster Farm conducted several surveys of the local coastal area for wild populations of sugar kelp for sorus tissue collection in August, September, October, and November, but was unable to find any sufficient for seeding. The 2020 season was exceptionally warm, and could have negatively impacted local kelp populations. On November 3rd, Winnegance deployed urchins from Springtide into lantern cages with wild set algae for feed. The kelp spool was hung on the farm until December 3rd, when the long line was installed and seeded. The urchins were photographed on December 3rd. Winnegance built overwintering cages in November, and placed urchins in bottom overwintering cages on December 10th. Winnegance posted social media updates about the project on both Nov 3rd and Dec 3rd. 

Thus far, both farms are cultivating urchins through the winter, and the MSE is developing educational material for project outreach. Several interns will be involved in data collection, analysis, and outreach through their work with Springtide Seaweed and the Maine Seaweed Exchange. There is significant and increasing interest in new species for aquaculture, and it is expected that this project will continue to garner interest from both the general public and the aquaculture and seafood communities. 


Progress Report January 31, 2022

This project has been awarded an extension until 6/30/22. 

In spring of 2021, Winnegance oyster farm had a full, healthy line of kelp. Kelp was sampled in May and June and monitored through the summer. After June, kelp deteriorated rapidly, and hosted increasing growth of biofouling organisms. 

Sea urchins were brought up from overwintering cages in the spring and placed in lantern nets with seaweed, with 100% survival. By July, water temperatures were rising, but urchins survived until September/October, when they experienced a 100% mortality event. 

In January of 2021, Springtide began sampling kelp lines, and continued to sample through June. Urchins on farm were periodically checked, photographed, and fed, with 100% survival. In the fall of 2021, lantern nets became tangled and submerged around a mooring line, and were recovered several months later with very high survival, despite holes in the nets and heavy mussel sets. In the hatchery, urchins experienced a mortality event, with about 10% survival. Urchins will be monitored through June of 2022 to obtain a multi-year data set. 

Research results and discussion:

Data collection and analysis still ongoing as of Jan 30, 2022. 


At my site, kelp was only a reliable food source until mid August, after which saw the rapid breakdown of blades and fouling of ropes and remaining stipe. Though a small amount of stipe tissue was present until the end of the season (Nov. 30), results at my site point to the vulnerability of relying on a single species for urchin feed- with a potential gap in food availability from August until a new winter kelp crop.

Fouling in 2020 and 2021 was unusually heavy and did not follow prior patterns seen from 2014-2019. Unlike those years, where tunicate and sea vase fouling occurred in a single wave starting in late July and continuing through Aug, the last two seasons saw multiple “sets” of tunicates all the way into October. It is unclear how much this heavy fouling played a role in the loss of kelp. There is also potential that the fallow kelp line served as a reservoir for tunicates- as oyster cages on the line above were much more heavily fouled than cages on other longlines with the same air drying regimen. If this were a consistent effect, it would be a major drawback for farmers hoping to add this polyculture system an existing farm.

Wild set kelp persisted in surface waters on oyster cage throughout 2021. This kelp remained small (total length <24”) but did not foul or decompose despite spending the entire season in warmer water than the cultivated kelp.

Hands on urchin measurements were suspended in July on the advice of a technical advisor in order to avoid heat shock. Urchins were observed quickly during feedings to check for mortality. Mortality was not observed until September 30. At this check, 95% of urchins were lost. There were several potentially interacting sources of mortality- prolonged heat stress, rapid fouling that trapped waste and decomposing kelp in lanterns nets (smothering), and an unusual influx of fresh water (Photos). The surviving urchins were all in top tiers of lantern nets, in the warmest water (~1.5 m deep) and with the least decomposing kelp- which suggests temperature stress was not the only culprit. These urchins died after a second major rain event in mid October.


Both kelp and urchins thrived at the Springtide farm through the winter and spring. Kelp lines were sampled through June, and harvested and removed from the farm by July. Sea urchin lantern nets were fouled with algae, hydroids, and a major blue mussel wild seed set. Some lantern nets were lost for several months as they tangled around a mooring line and were hung down below the surface. Recovered lantern nets contained rips and holes, but most of the urchins were still present inside the nets, with very little mortality. Even when not fed intentionally, urchins survived in cages by grazing wild food, and by eating urchins. Although there were also starfish present in the nets, it appeared that they were feeding on the blue mussel seed set, and did not consume the sea urchins. 

Research conclusions:


The variable nature of the oyster site (extreme temperatures and salinity fluctuations) resulted in sea urchin mortality. Although kelp was a successful crop on this farm, it was only viable through May, as it quickly fouled and began to decay and host invasive species. Sea urchins are probably not going to be a viable crop on oyster farms, unless sited in cooler, deeper waters away from major freshwater runoff. 


Both kelp and urchins are viable co-crops on deep water, cold ocean sites. While kelp is abundant from February through July on the lines, there is a lack of feed source for the urchins from August through January. Sea urchins can survive by grazing on wild algae and mussel seed that settle inside the lantern nets, but major fouling on the nets can be a problem for water motion, and cages should be changed out at least once per year to avoid biofouling build up. 

Participation Summary
2 Farmers participating in research

Education & Outreach Activities and Participation Summary

3 Online trainings
5 Tours
4 Webinars / talks / presentations

Participation Summary:

20 Farmers
5 Number of agricultural educator or service providers reached through education and outreach activities
Education/outreach description:

The Maine Seaweed Exchange and partner farmers will share project activities and updates through social media postings of progress, and the Maine Seaweed Exchange will create a special page on their website describing the project and offering resources for growers. Interested audiences will include the general public, aquaculture farmers, chefs and restaurants, and potential new sea farmers. 

Near the end of the project, the Maine Seaweed Exchange will host three one-day workshops that will present and share results of the project from project data that has been collected, aggregated, and analyzed by the Maine Seaweed Exchange. This event will offer farmed seaweed and oyster snacks, and project participants (Winnegance, Springtide, Maine Seaweed Exchange) will present the work through videos, slideshows, and demonstrations. This workshop will be free and open to the public, with a target audience of existing seaweed and shellfish farmers. The MSE will invite sea farmers directly through an email invite, and share information about the event through Maine Sea Grant and the Maine Aquaculture Association. In addition to online outreach, collaborators will seek both press and opportunities to speak at local conferences.

Several educational talks were given in 2021 by Sarah Redmond (and Andrea Angera, through the Maine Seaweed Exchange) to a wide range of audiences. Although the talks focused on seaweed aquaculture, we included information about our work in sea urchin aquaculture as supported by Northeast SARE. 

Zoom talks:
Friends of Taunton Bay Webinar Series, “Seaweed Farming with Sarah Redmond”

6/7/21 The Friends of Harriet L Hartley Conservation Area, “Seaweed Aquaculture in Maine”

8/18/21 Monhegan Associates, “Seaweed Aquaculture in Maine"

In Person Presentation:
9/16/21 The Pour Farm, “Seaweed Farming in Maine”

Maine Seaweed Exchange online Trainings:
1-day Seaweed Aquaculture Intensive, by Sarah Redmond and Andrea Angera

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:

Gaining better understanding of the opportunities and limitations in cultivating sea urchins on different types of farm sites. 

Project Outcomes

2 Farmers changed or adopted a practice
1 Grant applied for that built upon this project
1 Grant received that built upon this project
$15,000.00 Dollar amount of grant received that built upon this project
2 New working collaborations
Project outcomes:

This project has given us a better understanding of how and where sea urchins can be integrated into existing sea farms. 

Assessment of Project Approach and Areas of Further Study:

While this project is still underway, we are gaining a much better understanding of the requirements and feasibility of cultivating sea urchins. 

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.