Progress report for FNE22-018
This project seeks to build a technology that allows nearshore oyster cages on the bottom to be retrieved without vertical lines to surface buoys. This will be accomplished by developing a tethered remotely operated underwater vehicle (ROV) that will provide a real-time image of the cage on the bottom and will attach a lifting line to the cage for retrieval. The following objectives are proposed to complete this project:
- Identify the mechanical attributes of an ROV required to achieve the goals of maneuverability underwater, identification of unique bottom cage markings, and ability to attach a lifting line to a cage harness for retrieval;
- Design and construct an ROV that meets the qualifications outlined in Objective 1 (i.e. the OysterBot);
- Evaluate the OysterBot on a commercial farm to assess its capacity to replace surface lines for cage retrieval;
- Outreach this technology to other farms that are operating in nearshore waters.
The availability of the OysterBot concept will not only aid current subtidal farms in managing cage retrieval but it will also open up new areas for oyster farming by eliminating the vertical lines that will prohibit farm development where entanglements are a risk.
Recent reports project shellfish aquaculture has and will continue to proliferate in the northeast (GMRI 2016, CEI 2018), resulting in currently preferred areas becoming limited. As concluded in an evaluation of shellfish aquaculture in the northeast, farm growth will be affected by “location expansion constraints” (GMRI 2016).
Shellfish aquaculture is a sustainable and desirable farming activity. Hilborn et al. (2018) assessed the environmental impact of a variety of animal-sourced foods, including livestock, aquaculture and capture fisheries and concluded the lowest impact production systems were small pelagic fisheries and molluscan aquaculture. Furthermore, aquaculture could play a large role in sustaining our coastal communities (Love 2016). However, in assessing expansion of coastal aquaculture in the region, CEI (2018) reported that significant resistance to expansion in intertidal and shallow areas is due to “not in my backyard” attitudes of coastal residents.
An alternate area becoming more attractive for shellfish aquaculture is the nearshore, defined as deeper water located within 3 miles of but not immediately adjacent to the shoreline (Price et al. 2016). Nearshore farms have always been in existence, particularly along those shorelines with limited intertidal areas; however, interest is expanding. For example, New Bedford (MA) recently announced 8,400 acres of municipal waters were available for aquaculture development (CEI 2018) where an estimated 90% are in water depths of 15 to 30 feet.
While out of the viewscape of NIMBY landowners, nearshore farms are influenced by the same conditions as inshore sites although more exposed to high energy conditions (Price et al. 2016). Nearshore farm technology requires more robust and heavier cages suited for the challenging conditions and servicing heavier cages requires larger vessels deploying extensive vertical lines and buoys, similar to lobster fishing. The predominant technologies (floating, suspended or bottom tending) require an extensive array of vertical lines to anchor floating gear or to mark submerged gear. Vertical lines are a recognized risk to marine megafauna (Gentry et al. 2016, NOAA 2017); most listed as endangered or threatened and including sea turtles, primarily leatherback and loggerhead turtles (NMFS 2015); whales, with the North Atlantic Right Whale preeminent (Moore and van der Hoop 2012, NOAA 2016, Schreiber 2017); and, further south, manatees (Reinert 2015). Vertical lines in open waters are under intensifying scrutiny and regulation due to the risk of entanglements. Establishing a farm with vertical lines in nearshore waters will be severely limited or prohibited, as has happened with the lobster fishery (DMF 2021), unless we can develop technology to eliminate the lines, similar to the lobster fishery (Baumgartner et al. 2021).
Another aspect to vertical lines in aquaculture is the risk to the farmer. Between 1993 and 1999, seven lobstermen in the northeast drowned after being pulled overboard due to entanglement in lines on deck as the trap is released (NIOSH 2005). In a survey of lobstermen, 73% indicated that they had been caught in a trap line at some point in their careers (NIOSH 2005).
Following a “best of the worst” scenario expanding into nearshore farm sites (CEI 2018), it is imperative that those farms reduce or eliminate vertical lines. This was the case when BSS applied for a federal Letter of Permission for their Mattapoisett farm. Although right whales have never been reported in the area and sea turtles only rarely observed, BSS was required to reduce the number of vertical lines to 50% of the proposed number with the ultimate goal of removing them entirely from the site. To that end, we have been considering means to undertake ropeless shellfish farming in deeper waters. With this request, BSS proposes to develop ropeless oyster cages by retrieving them from the bottom using a remotely operated vehicle, the “OysterBot”.
In considering sustainable agriculture, this project addresses three of five SARE goals. They are:
- Reduction of environmental and/or health risks in agriculture
- Having a complex of lines on deck that are rapidly deploying overboard with the cage risks entangling the farmer and pulling him overboard. By removing the line, the risk to entanglement and drowning is removed.
- Improved productivity, reduction of costs and/or increase of net farm income
- Lines and buoys are an added expense to farm operations that can be eliminated with the elimination of vertical lines.
- Conservation of soil, improvement of water quality, and protection of natural resources
- Vertical lines in waters frequented by marine megafauna are a serious risk to the natural resource. With the development of ropeless oyster cages, that risk is significantly reduced for those threatened or endangered species.
Blue Stream Shellfish, LLC (BSS) is an enterprise operating two farms in southeastern Massachusetts. Seal Rock Farm is located in Buzzards Bay, 1 mile south of Brandt Cove (Mattapoisett, MA). Permitted in April 2021, Seal Rock covers 50 acres where oysters are grown in wire cages on the bottom at 20+foot depth. In August 2021, BSS took over West Island Farm, a 46-acre farm adjacent to West Island (Fairhaven, MA). West Island Farm is presently stocked with 4,000,000 oysters and sells 16,000 pieces per week, with sales expanding quickly. BSS possesses all licenses required to buy, sell and distribute shellfish nationally and internationally.
BSS operates a 20’x60’ processing barge, a 18’x30’ working barge, three skiffs (19’, 21’ and 25’) and a 25’ work boat. Shoreside facilities include a processing/packaging area along with office and workshop. The three members of BSS represent >100 years experience in aquaculture. Dr. Dale Leavitt oversees Blue Stream Shellfish LLC's efforts. Dale is an emeritus Professor/Aquaculture Extension Specialist (Roger Williams University, Bristol, RI) with >35 years experience farming shellfish. Through Dale’s outreach activities, he has assisted in training members of >50 shellfish farm start-ups in the northeastern U.S. Dale also maintained an active research program in aquaculture technology, including applying solar power to shellfish and finfish systems and improving shellfish hatchery/nursery protocols.
- - Technical Advisor (Researcher)
Objective 1 - Identify the mechanical attributes of an ROV required to achieve the goals of maneuverability underwater, identification of unique bottom cage markings, and ability to attach a lifting line to a cage harness for retrieval:
Drawing on the expertise of our Technical Adviser, the BSS farm team will develop a list of specifications that are required in the design of the OysterBot. These will cover details such as swimming speed/power and maneuverability of the ROV, resolution of the camera under ambient and enhanced light conditions, gripping strength of the robotic arm, ease of operation and other parameters that are deemed important during the design discussions. These criteria will be applied to the purchase and assembly of the OysterBot under Objective 2.
Objective 2 - Design and construct an ROV that meets the qualifications outlined in Objective 1 (i.e. the Oysterbot):
BSS proposes to assemble a collection of off-the-shelf components into the OysterBot that allows the operator to locate and lift oyster cages in nearshore waters (15 to 30 feet depth). Using the design criteria compiled under Objective 1, the BSS farm team will work with our Technical Adviser to identify and purchase the components needed to assemble the OysterBot. Based on a preliminary discussions, our Technical Adviser recommended that we investigate the components available through BlueRobotics (https://bluerobotics.com/). These are inexpensive but high quality components that are easy to assemble and operate and are routinely used by institutions such as the Deep Submergence Laboratory at the Woods Hole Oceanographic Institution (DSL-WHOI), where our Technical Adviser is employed as an Engineer II.
The one unknown in assembling the OysterBot will be the design and operation of the robotic arm that attaches the line to the lifting bale on the submerged cage. It will need to securely hold the lifting line in position as it descends to the cage but can attach the lifting line to the cage and subsequently release it from the ROV to allow the cage to be hoisted to the surface without tangling the ROV in the process. There are a few design options that are being considered and a final design will be selected in consultation with our Technical Adviser.
Objective 3 - Evaluate the OysterBot on a commercial farm to assess its capacity to replace surface lines for cage retrieval:
Initial training on operating the ROV will take place off the shoreside processing barge facility at the BSS West Island Farm. Training will include piloting the ROV and assessing its capacity to identify a marked cage and attach the lifting line to the cage bridle.
Evaluation of the OysterBot will occur at the BSS Seal Rock Farm in Mattapoisett, MA. This site is an open nearshore farm in ~25 feet of water. Initially, the general cage location will be identified using a down/side looking sonar on the vessel. The sonarbased fish finder has been successfully used to locate bottom cages on the Seal Rock Farm site as part of a SARE funded Farmer’s Grant in 2021 (SARE Project Number FNE-21-989). With the sonar, we will locate cages placed on the bottom to identify the area for deploying the OysterBot retrieval system. We will be able to clearly demarcate the location of large oyster cages on the bottom and, with integrated GPS, the precise location of bottom cages will be observed and recorded.
The cages will consist of large wire mesh structures populated with 9 or 36 stocked oyster bags and initially weighing in the vicinity of 300-500 lbs. The cages will be deployed in a set array on the bottom with approximately 20 feet of space between adjacent cages. In addition to those set up for OysterBot collection, we plan to install an equivalent set of identical cages with conventional surface buoys and 600 lb breakaway links, as is mandated by MA Division of Marine Fisheries for our site. At Seal Rock Farm we will install a minimum of 10 cages of each design to allow a comparison between the technologies in a replicated manner.
Once the location has been identified by sonar, the surface vessel will deploy the OysterBot to identify it via cage tag and attach a lifting line to a short (~1 foot) buoyed bridle affixed to the top of the cage. The OysterBot provides real-time video imaging to allow the on-deck operator to read the cage identification on the marked bridle to assure that the correct cage is being retrieved. Once confirmed, the OysterBot will attach a lifting line that it carried from the surface to the lifting bridle to allow the cage to be hoisted for maintenance or harvest.
The cages will be retrieved and handled approximately monthly to allow for maintenance on the oysters. Retrieving by OysterBot will consist of initial location by sonar, deployment of the ROV, identification of the cage, and attachment of the lifting line for hoisting. Handling of the conventional buoyed cages will consist of identifying the correct buoy and retrieving the buoy with surface line. The handling of the cages will be completed with the BSS vessel (F/V Phoenix), a 20' x 40' foot work barge equipped with a hydraulic crane and a 10” electric pot hauler.
Objective 4 - Outreach this technology to other farms that are operating in nearshore water.
BSS outreach effort targets new and existing farmers. Dale Leavitt is a retired Aquaculture Extension Specialist, formerly with Roger Williams University. In that capacity, for 24 years Dale has trained individuals associated with >50 shellfish companies in the northeast through his annual Applied Shellfish Farming course. The course was offered online and attracted 100+ participants annually. This project will be featured in the oyster culture section of that course. Additionally, Dale has collaborations with aquaculture extension agents and farmers throughout the region. He has gained these contacts through personal interactions over the past 30 years.
Our outreach will be introduced to farms in the region as BSS presents details of the OysterBot to industry members attending popular aquaculture meetings in 2022-24, i.e. the Northeast Aquaculture Conference and Exposition (NACE), the Milford Aquaculture Seminar, and/or the National Shellfisheries Association annual meeting (NSA). Dale will also prepare an article for inclusion in the East Coast Shellfish Growers Newsletter, published quarterly. Following those introductions, we will demonstrate the OysterBot and test the technology on a variety of farms in the northeast. BSS will visit any nearshore farm from Maine to New York that shows interest and invites us for a demonstration. With these farm visits, we can evaluate the performance of the system under a variety of farm conditions encompassing varying levels of visibility, depth, currents, etc. At the same time, we will demonstrate the technology to local farmers.
The goal for this study is to develop a ropeless retrieval system for oyster bottom cages in nearshore waters that works under all conditions. The successful completion of retrieving a bottom cage by ROV is the ultimate measure of success for the project. However, a primary consideration in comparing the two technologies (OysterBot vs. vertical line with buoy) is the time and ease of handling of each of the systems, from first identification of the cage to landing it on deck following retrieval. We will measure elapsed time for the full process of detection and retrieval for each of the cage systems for comparison between technologies. We will also maintain a log of observations in terms of ease of placement of the cage arrays on the bottom and ease/risk of handling while on deck with and without attached lifting line.
Objective 1 - Identify the mechanical attributes of an ROV required to achieve the goals of maneuverability underwater, identification of unique bottom cage markings, and ability to attach a lifting line to a cage harness for retrieval.
Drawing on the expertise of our Technical Adviser, the BSS farm team developed a list of specifications that were deemed important in the design of the OysterBot. These specifications cover details such as swimming speed/power and maneuverability of the ROV, resolution of the camera under ambient and enhanced light conditions, gripping strength of the robotic arm, ease of operation and other parameters that were suggested as important during the design discussions. These criteria are included in Table 1.
Objective 2 https://projects.sare.org/wp-content/uploads/Table-1_OysterBot-Wish-List.pdf- Design and construct an ROV that meets the qualifications outlined in Objective 1 (i.e. the OysterBot);
In collaboration with the Technical Adviser, BSS assembled a collection of off-the-shelf components for the OysterBot. Using the design criteria compiled under Objective 1 (Table 1), the BSS farm team worked with our Technical Adviser to identify and purchase the components needed to assemble the OysterBot (Table 2). The bulk of the components were available through BlueRobotics (https://bluerobotics.com/) (Figure 1).
Figure 1: Photo of assembled Blue Robotics ROV2 from promotional literature.
The ROV components arrived in May/June and the vehicle was assembled, primarily by our Technical Adviser, through the summer/fall of 2022. Since late September 2022, the OysterBot has undergone a series of test dives in the ROV test tank affiliated with DSL/WHOI. Numerous operational bugs were corrected as a part of the testing series. In December, the OysterBot was tested at a BSS farm site for further debugging (Figure 2).
The one critical factor in assembling the OysterBot is the design and operation of the robotic arm that attaches the line to the bridle on the submerged cage. To allow the cage to be hoisted to the surface without tangling the ROV in the process, the arm will need to securely hold the lifting line in position as it descends to the cage, attach the lifting line to the cage, and subsequently release it from the ROV. BlueRobotics offers a gripper arm for their ROV2 and we purchased and installed it on the OysterBot. We are in the process of testing this component to determine its ability to carry and attach the lifting line.
Objective 3 - Evaluate the OysterBot on a commercial farm to assess its capacity to replace surface lines for cage retrieval.
In December, preliminary field evaluation of the OysterBot began at the BSS West Island Farm in Fairhaven, MA. This site is a nearshore farm in ~12 feet of water. Initially, a general cage location was identified using a down/side looking sonar on the vessel. The sonar-based fish finder has been successfully used to locate bottom cages on the BSS Farms as part of a SARE funded Farmer’s Grant in 2021 (SARE Project Number FNE-21-989). With the sonar, we were able to locate individual cages placed on the bottom to identify the area for deploying the OysterBot retrieval system. The cages consist of large wire mesh structures populated with up to 18 stocked oyster bags and initially weighing in the vicinity of 300 lbs. and have been deployed in a set array on the bottom. We could clearly demarcate the location of large oyster cages on the bottom and, with integrated GPS, the precise location of bottom cages were observed and recorded.
During the initial field test, a cage location was identified by sonar and the surface vessel deployed the OysterBot to locate the individual cage. Because the OysterBot provides real-time video imaging, the on-deck operator was able to "fly" the OysterBot to the cage location and survey the cage positioning on the bottom (Figure 3) as well as trace the lifting bridle suspended at the top of the cage (Figure 4), to allow for future attachment of a lifting line. In addition to locating individual large bottom cages, the OysterBot was also successful in locating a series of smaller oyster bags that had been accidentally lost overboard due to cage damage following a storm (Figure 4). In a third effort (Figure 5), the OysterBot was able to provide images of a series of derelict cages discovered when surveying the farm site with sidescan sonar, thereby allowing us to retrieve those cages as we were able to discern their positioning and accessibility.
Future plans include the final step in the development of the OysterBot with the design of the lifting line and hook system for ROV attachment to individual cages on the bottom. This step will be undertaken in the spring as the field testing uncovered a few more bugs (e.g.. the auto-depth setting on the ROV) that need to be corrected at the DSL-WHOI test facility during the winter. Once a final product is available, initial training on operating the ROV that will take place off the shoreside processing barge facility at the BSS West Island Farm. Training will include piloting the ROV and applying its ability to identify a marked cage and attach the lifting line to the cage bridle.
Following training, the evaluation of the OysterBot as a tool for retrieving ropeless bottom cages will be completed during the spring/summer/fall of 2023. Simultaneously, outreach of the ROV coupled with sidescan sonar will be available for any interested farmers as we communicate the results of the project.
In constructing and evaluating the OysterBot, we proposed to assemble a technology that would be available to any nearshore oyster farmer that wishes (or is required) to utilize a ropeless technology for their oyster cage retrieval process. With an initial cost of under $10,000 as a onetime expense, it is significantly less expensive than the pop-up buoys currently being proposed for trap fisheries. If it is regulated that ropeless technology will be required for oyster cages in nearshore waters in locations where there is a risk of megafauna entanglements (essentially the entire coastline of the northeast), this may be a viable alternative to other technologies.
As the project has developed, there have been a few observations that seem relevant at this point in time. It is important to note that the components to be used for assembling the OysterBot are off-the-shelf technology that is non-proprietary in its application and readily available. However, it has become obvious that assembly of an ROV from component parts is not something that can be routinely completed by an individual with limited experience in mechanical and electronic assembly. The levels of cleanliness and attention to detail required during assembly may be problematic for an inexperienced assembly person. Furthermore, debugging the assembled OysterBot has proven to be necessary as mechanics, firmware, and software controls need to be adjusted for the individual build. While these tasks are not insurmountable, it does take a technical person to make these final adjustments and, again, are probably not achievable by an inexperienced assembler.
However, the resulting operational ROV appears to be very successful in advancing our goal towards ropeless cage retrieval, at this point in our preliminary evaluation.
Education & Outreach Activities and Participation Summary
Conducted a tour of the farm and discussed OysterBot application with NOAA Northeast Regional Aquaculture Extension (Zach Gordon) and MIT Sea Grant Aquaculture Extension (Danny Badger).
Discussed project with University of Maryland Shellfish Aquaculture Technology Specialist (Allan Pattillo). Dr, Pattillo invited us to present at the upcoming Robotics in Aquaculture session at the National Shellfisheries Association annual meeting in Baltimore, MD in March 2023. We have had an abstract accepted for this symposium (attached).
NSA Abstract: Developing the OysterBot for oyster cage retrieval