Progress report for FNE24-093
Project Information
Objective 1:
Determine the patterns of reproduction and spawning of farmed
urchins and correlate with environmental variables to better
understand seasonality.
Objective 2:
Develop a feeding regime that will ensure consistent high quality
uni at harvest.
Objective 3:
Test three different specific seaweed species to determine unique
flavor profiles to customize finishing diets.
Objective 4:
Develop harvest, post harvest handling, and marketing strategies
for farmed sea urchins.
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 the lowest levels yet in 2022, with less than 1 million pounds landed (DMR, 2022). 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) has a 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., 2016).
While various research trials have been conducted on urchin culture in Maine (CCAR, 2023), we are the first company to integrate green sea urchins as an diversification crop onto a commercial seaweed farm. Working in partnership with the University of Maine Center for Cooperative Research (CCAR), we have been growing hatchery-produced urchin seed in suspended lantern nets on our seaweed farm for the past 5 years, and now have several thousand urchins in different size classes that are ready or near ready for harvest. However, we need to develop the process to prepare, harvest, ship, and sell the market urchins at a higher price point than is typically received from wild harvested urchins. By providing a diet of select farmed seaweeds, we expect to develop an urchin farming system that will consistently produce the highest quality uni with optimal flavors, color, and texture. Consistency and control in uni yield and quality is unavailable in wild harvested urchins, and would allow for us to differentiate our product from existing markets and sell into premium markets.
Once we have established quality, consistency, and value of our farmed sea urchin crop, we will have completed the entire cycle of farming, from producing urchin seed in our hatchery, to growing the crop on our seaweed farm at sea, to preparing, holding, shipping, and selling our urchins. This will enable us to develop essential business plans for commercialization, and a preliminary economic feasibility report on the results of our work and current markets, to estimate potential economic viability of sea urchin farming. These business plans, reports, and farming techniques will be shared with the wider aquaculture community as a new diversification option.
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 their farm business. 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; 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, raising concerns about feed sustainability, nutrient loading in the environment, and off-flavors. 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, farmed seaweed produced on site can be used as a natural and effective feed for urchins. Both seaweed and sea urchins can be integrated into existing farms as alternative crops for diversification.
Cooperators
- - Technical Advisor
Research
Obj. 1: Our first objective is to determine the patterns of reproduction and spawning at our farm and to correlate patterns with environmental variables. This is important for understanding the reproductive cycles and some of the variables contributing to these cycles, to better predict natural cycles to optimize timing of enhancement and harvest.
Reproductive Cycles
Determine reproductive cycles through monthly urchin sampling. Sample monthly and bi-monthly from cages fed a mixed kelp diet to satiation (kelp always present in cages). Sample 3 urchins each from (2) replicate set of cages, transport in coolers, sample immediately. Measure total weight, test diameter, gonad weight, roe color and texture. Cages will be stocked at 100 urchins per cages, 10-15 urchins per level. Four cages will be prepared with the same size class, at or near harvestable size (Maine wild legal size min 52.4mm max 76.2mm) to create two replicates of two cages each. A total of 31 sampling trips will be taken (13 monthly and 9 bimonthly) requiring a total of 186 urchins for sampling.
We will also include sampling of the larger urchins, if numbers permit, and sample one urchin per month to compare with smaller size class.
Roe color, flavor, and texture estimated categorically by ranking. Gonad index (GI) calculated by, in wet weight: [(gonad wt / total wt)*100].
Ranked gonad color values: Three classes, corresponding to commercial grades
Ranked Flavor Data: Pleasant/unpleasant and taste/aftertaste categories, with descriptions
Odor: Pleasant/unpleasant categories, with descriptions. We will work with the 50-60mm size class, as numbers permit, as these should be harvestable in the upcoming season, but will also add the larger (60-70mm) size classes to our feeding and harvest trials in the first year to test larger urchins.
Environmental Data
Collect environmental data from farm site: extinction coefficient (Secchi disk), water temperature (onset data logger), salinity (refractometer), and photoperiod. Compare gonad index from sampling to environmental variables to determine seasonality of urchin gonadal development as correlated with environmental factors.
Obj. 2: Our second main objective is to develop a feeding regime that will ensure consistent roe at harvest. By providing a steady diet of optimized seaweed throughout the year, we expect that our farmed urchins will be consistent in roe quality and quantity, creating a new and superior product in contrast to the highly variable and inconsistent wild harvested urchins.
Consistent Feeding Regime Offer a diet of optimal mixed farmed kelp, sugar and horsetail kelp, to two sets of replicate cages on the farm, at 100% satiated. Sampling of urchin roe will be accomplished in Obj. 1. In addition, we will collect data on urchin size, density, and feed input throughout the project. Urchin size and growth will be measured by monthly sampling of 10 urchins from each replicate by taking photos and analyzed digitally with imageJ for test diameter.
Urchin Cage Design
Test an alternative urchin cage design. Lantern net cages are currently being used, but have a very short lifespan, as urchins can chew holes in the fabric netting. Test one or two urchin cage designs made with rigid plastic or coated metal mesh to try to find a better alternative to lantern nets. Build with rigid plastic mesh and stainless steel hog ties, zip ties, twine, and other materials available in the fishing/aquaculture industry. Test for ease of use, durability, and design out on farm by stocking with urchins and feed.
Kelp Farming
The two kelp species will be farmed on site near the urchin cages on suspended horizontal longlines. The kelp farming season typically takes place from September to June, with most of the kelp available from Feb-June. In the off season, July-Feb, we will utilize beach cast kelps, which are readily available locally after major storms, and frozen and dried farmed kelps if fresh kelp is not available. We will also plant lines of kelps in June to test the efficacy of off season planting for urchin feed.
Obj 3: Our third objective is to test specific seaweed species to determine unique flavor profiles to customize finishing diets. This information will help us determine enhancement strategies. If particular seaweed species lend specific desirable flavor profiles, we will better be able to control flavor at harvest.
Finishing Diets
We will test the most desirable seaweed species that we can grow on our farm, horsetail kelp (Laminaria digitata), sugar kelp (Saccharina latissima), and dulse (Palmaria palmata). We will feed 3 separate cages on a single seaweed species from Oct-Feb and sample 5 urchins monthly from each to determine flavor profiles, consistency, color, GI, and quality. Sampling will be done as in obj. 1 to determine GI, quality and flavor. Flavor profiles will be subjective and ranked on a flavor profile sheet with at least 5 tasters.
Seaweed Feed Production
Sugar kelp and horsetail kelp can be grown in abundance on longlines on our seaweed farm, as described in obj. 2. Dulse, a red seaweed, is morphologically much smaller than the kelps, with lower yields on longline systems. To ensure we have enough dulse for feeding experiments, we will cultivate dulse year round in tanks in our land based facility. We already cultivate dulse in our nursery year round for spore production, and can add additional tanks for feed production, optimizing conditions for growth and yield. We will set up dedicated dulse cultivation systems to optimize growth in tanks, at 10-12C, with filtered seawater, aeration for movement, light and 12:12 photoperiod, and regular seawater changes.
While fresh seaweed is preferred, there might be periods of low availability. We will test alternative forms by feeding fresh, dried, and frozen feed to urchins in tanks in our facility and monitoring feed consumption over time.
Obj 4: Our fourth objective will develop harvest, post harvest handling, and marketing strategies for farmed sea urchin.
Harvest and Handling:
When urchins are ready for harvest, transport in coolers from farm to land based facility, minimizing handling, exposure, or stress. Hold in fiberglas tanks with mixed kelp, ambient temperature seawater with aeration and low light until ready for shipping or sales.
Packing and shipping methods:
Seawater shipping methods: Trial shipping live urchins in seawater containers with gel packs. Determine best shipping practices and acceptable time frames. We expect that most urchins will require an overnight shipment, with immediate use, but will try to develop methods and systems to allow restaurants in Boston or New York to receive live urchins in good health after 48 hours. We will investigate alternative shipping options, including working with seafood distributors in Maine (like SoPo Seafood in Portland) that can offer overnight shipping to a wider audience.
Marketing:
Meet with potential customers with urchins for feedback. Visit 2-5 high end restaurants in Boston with samples of product for, as well as high end seafood markets and distributors in Portland. Create a business plan and economic analysis based on findings and updated market information.
Initiate Project: Project final agreement was not executed until May 9th, 2024, 2 months after planned start date. Project Period Activities 5/9/24 to 1/15/25.
Upon inspection of existing urchin nets on farm at project initiation, it was discovered that all of the lantern nets in use were damaged, allowing significant numbers of animals to escape. Sea urchins chew holes in the mesh fabric, and the heavy bio-fouling on the mesh weakens and damages the velcro and wire frames. It was therefore critical to secure urchins immediately by moving into new enclosures.
The lantern nets formerly used were no longer available for sale, so we traveled to Massachusetts to pick up a load of free lantern nets from another aquaculture farmer. These nets, however, were too small to hold any significant number of urchins, with mesh openings too large for some of the smaller urchins. While we may be able to use these nets in some of our research trials, we need larger cages to keep the urchins. We had to make our own urchin cages in order to secure the urchins and initiate the research objectives. Several different prototype cages were built and utilized before developing a final cage design. Over the course of 6 months, urchins were transferred from old lantern nets into new numbered urchin cages, and urchins were counted, sampled, photographed, and fed with fresh kelp. A full cage renewal was accomplished for all the urchins on the farm, along with a complete inventory, for a total of 6,170 urchins in 40 cages.
Obj. 1: Our first objective is to determine the patterns of reproduction and spawning at our farm and to correlate patterns with environmental variables. This is important for understanding the reproductive cycles and some of the variables contributing to these cycles, to better predict natural cycles to optimize timing of enhancement and harvest.
Reproductive Cycles
Determine reproductive cycles through monthly urchin sampling.
Initial sampling efforts have been exploratory, as we learn how to open live urchins, sample effectively, and observe and describe uni quality. Urchins were sampled in September, October, and November. Extreme winter weather in December and January has delayed sampling for these months. Gonad index increased from an average of 8.1% in September, to 16% in October, to 22.7% in November. Color of uni has been consistently yellow and orange, and flavors have been consistently pleasant with various flavor profiles. Texture of uni was consistent until November, when most of the uni started to become creamy, an indication that the prime period for uni had passed as the nutritive cells moved into gametogenesis.
Obj. 2: Our second main objective is to develop a feeding regime that will ensure consistent roe at harvest. By providing a steady diet of optimized seaweed throughout the year, we expect that our farmed urchins will be consistent in roe quality and quantity, creating a new and superior product in contrast to the highly variable and inconsistent wild harvested urchins.
Consistent Feeding Regime: While we initially were able to offer a diet of optimal mixed farmed kelp, sugar kelp and horsetail kelp, we were unable to continue to provide horsetail kelp. The horsetail kelp on the farm became so heavily encrusted with bryozoans and other organisms that it became unusable through the summer and fall. We were able, however, to continue to harvest farmed sugar kelp from our lines for feeding. Horsetail kelp may be only viable for fresh feeding in the spring months.
We collected initial data on urchin size and density as we moved all urchins into new culture cages. All cages were fed by filling with sugar kelp primarily, with smaller amounts of other available seaweeds. Urchin size and growth will be measured by sampling of 10 urchins from each cage by taking photos, and using calipers to determine test diameter.
Urchin Cage Design
Several different urchin cage designs were built and tested, utilizing different types of surface mesh and cage openings. All cages were based on a coated metal wire cylinder that is covered in a plastic mesh. We tried polypropylene deer netting (18mm mesh opening) and rigid plastic mesh (9mm, 4mm), and built cages to hang vertically with shelves, and horizontally with and without shelves. We suspended cages from the center and from the sides. The final design utilized a 9mm mesh, horizontally hung cage, with a flap on the end that opens for feeding and sampling of urchins. Each cage is suspended from a horizontal longline at about 5 feet depth in winter and 10 feet depth in summer, and held with one hardshell buoy at the surface. The new cages are easy to bring onto the boat for feeding, don't collapse, are resistant to urchin chewing, and foul less than lantern nets.
Kelp Farming: Sugar kelp, horsetail kelp, and dulse were planted out on the farm in the fall of 2024 for use as urchin feed in 2025.
Obj 3: Our third objective is to test specific seaweed species to determine unique flavor profiles to customize finishing diets. This information will help us determine enhancement strategies. If particular seaweed species lend specific desirable flavor profiles, we will better be able to control flavor at harvest.
We will test finishing diets in the upcoming year.
Seaweed Feed Production
Sugar kelp and horsetail kelp can be grown in abundance on longlines on our seaweed farm, as described in obj. 2. Dulse, a red seaweed, is morphologically much smaller than the kelps, with lower yields on longline systems. To ensure we have enough dulse for feeding experiments, we will cultivate dulse year round in tanks in our land based facility. We have set up dedicated dulse cultivation systems to optimize growth in tanks, at 10-12C, with filtered seawater, aeration for movement, light and 12:12 photoperiod, and regular seawater changes.
While fresh seaweed is preferred, there might be periods of low availability. We will test alternative forms by feeding fresh, dried, and frozen feed to urchins in tanks in our facility and monitoring feed consumption over time. We will work on testing these forms in the upcoming year.
Obj 4: Our fourth objective will develop harvest, post harvest handling, and marketing strategies for farmed sea urchin. This work will be accomplished during the last phase of the project.
Education & Outreach Activities and Participation Summary
Participation Summary:
10 students in an aquaculture training workshop gained experience and knowledge about sea urchin farming and uni sampling. All participants were either new farmers or interested in becoming new farmers.
1 seaweed farmer adopted new urchin cage design for her farm.
1 college student intern gained experience in sea urchin cage development, sampling, and feeding urchins.
Our own farm developed a culture system that protects urchins, eliminates escapes, reduces biofouling, and improved feeding efficiency.
Learning Outcomes
Sea urchin cage design and adoption, sea urchin sampling, sea urchin and seaweed feed seasonality
Project Outcomes
We held a three day aquaculture intensive workshop at our facility in October 2025, and sampled urchins with all the participants. This was an educational event, as we were able to get a wide range of sensory experiences and improved our uni sampling techniques. All of the participants were new farmers or people interested in becoming sea farmers, and sea urchin aquaculture was an area of great interest.
Our cages were also adopted by another seaweed farmer with a few experimental urchins in the fall of 2024.