Tasks for the year were to: a) determine growout period of mussels to market size and evaluate product quality; b) continue refinement of seed procurement and seed handling; c) complete improvements on the project vessel for longline handling and lifting; d) evaluate the potential for aquaculture production of sea scallops and Belon oysters in suspension culture; e) compare the growth and production potential for all three shellfish species (mussels, scallops, oysters) of the existing growout site to existing culture operations in New England; f) conduct related shellfish sanitation and classification activities to advance the project to a commercial reality; and g) transfer information on the project to the scientific, aquaculture business and commercial fishing communities
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II. Seed collection and handling III. Gear improvements IV. Additional species V. Growth and production comparisons VI. Related activities VII. Technology/Information Transfer VIII. Difficulties Encountered A. Biological B. Engineering C. Institutional & Logistical IX. Anticipated Success in Meeting Proposed Objectives in Scheduled Project Period X. Tasks and activities for the next reporting period XI. Concerns or difficulties. XII. Photos & Graphs of data & materials collected (Figures 1-17).Mussel Growout- Growth of mussels on the submerged offshore longlines was monitored for three separate seed deployments during the reporting period. The first group of mussels was socked in early July 1999 with seed that were collected at the UNH Coastal Marine Laboratory beginning in July 1998. Figure 1 is a photo of this group of mussels taken in December 1999. Mussels from this group were allowed to grow until May 2000 when they were removed from the longline. Growth over the 10-month deployment was 41 mm, with a mean growth rate of approximately 1 mm/week, and mussels reached minimum market size of 50 mm in March 2000; approximately eight months after deployment. The second group of mussel seed were collected in June 1999, and were approximately 27 mm at the time of deployment in late October of the same year. This group was removed from the longlines in May 2000, and had grown to a mean shell height of 54 mm; an increment of 27 mm over seven months. Growth rates of the first two seed deployments were similar, and averaged approximately 1 mm/week. These data indicate that seven to eight months of longline growout is required for mussels to reach minimum market size if seed of 20-25 mm is deployed. Each foot of mussel sock yielded 4.2 lbs. of market-sized mussels. Based on these yields, and the number of socks that can be deployed from a longline (100 at 12 meters each), the projected maximum yield for a single longline is approximately 16,000 lbs. Mussels produced from the first two deployments were very clean (Figure 4) and of excellent product quality (Figure 5). Product quality was determined by comparing the cooked meat weight to the whole live weight of mussels, expressed as a percentage. Industry guidelines for a "select" mussel requires 40% meat weight or greater. Percent meat weight data are presented in Figure 6 (for the first) and Figure 7 (for the second) mussel deployment. Both groups far exceeded the 40% meat weight standard for select mussels, averaging 54% for the earlier deployment, and 58% of the later deployment, when they were removed from the longlines in May 2000.
Additional seed were deployed from the longlines in June 2000. Some seed for this deployment were removed from the fish cages during cage cleaning, and the rest came from collectors deployed at the UNH Coastal Marine Laboratory in June 1999. A total of 87 single mesh socks of 12-meter length (Figure 8) were deployed from the south line. Results to date have been excellent for the rope collected seed, and relatively poor for the seed from the fish cages. Seed from the rope collectors grew 16 mm in four months, at average densities of approximately 250/foot (Figure 9). While the growth of individual mussels that originated from the fish cage seed has been similar, the density of mussels growing on the outside of the socks has been much lower. The size of the fish cage seed was highly variable and the Spanish grader was unable to separate the largest seed from those at the 25 mm size. Consequently larger seed were socked with smaller seed in socks of inappropriate mesh size. Many of these mussels were unable to migrate out through mesh and attach to the outside of the socks. Interestingly, the fouling by hydroids was much heavier on the lower density socks (similar to the headline and seed lines shown in Figure 11), indicating that higher mussel density and resulting higher filtration capacity can greatly influence fouling. Since the project water sampling program has revealed seasonal water column stratification for temperature and food availability (as measured by chlorophyll a concentration), growth of mussels at the top, middle and bottom of the 12-meter sock was compared. Mean shell height of mussels measured in October 2000 was greatest at the top (42 mm) and declined with increasing depth (40.5mm middle and 39mm bottom). Top and bottom mussels were significantly different (ANOVA) but not top-middle or middle-bottom. These data somewhat supports the hypothesis that mussel growth is primarily influenced by temperature and food availability, however, further analysis of the data for the three vertical locations indicates that density may also be a factor. Highest densities were found at the bottom, and decreased with distance upward. Density will be included in any further analysis of growth rates.
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Seed collection and handling - Seed collectors were deployed in three locations during the reporting period. Approximately 800 ft of rope collectors were deployed from a raft at the same location used in 1998 and 2000 in Portsmouth Harbor. These seed have performed reasonably well though they are unlikely to be ready to sock before spring 2000. Two additional rafts were constructed and deployed in Hampton Harbor. Approximately 700 ft of collector line was hung from the two rafts. While the collectors did well, with high density and good growth, the water was very shallow at this location (less than five feet at low tide) and the collector ropes came in contact with the bottom at spring low tides. Consequently, predation by crabs became a factor as the seed grew. The final yield of seed was very low when the collectors were removed at the end of October. Approximately 1000 ft of rope collectors was deployed from the offshore longline in June 2000. After two months on the longline, heavy fouling by hydroids diminished optimism for any significant yield of mussel seed (Figure 11.). By October, however, most of the hydroid fouling disappeared revealing a dense set of mussel seed (Figure 12). Measurements taken in late October indicated that the seed had grown very rapidly in September and October (from 5 mm to 20 mm average shell height) are were ready to be removed and socked (Figure 13). This was done in December using the recently purchased New Zealand style continuous socking machine (Figure 14). This machine, which uses a rope core and biodegradable cotton mesh sleeve eliminated problems with out-migration of seed through polyethylene mesh and provided greater strength to the longer lines used in offshore operations. In addition, industry practitioners have documented a much greater efficiency for both socking and harvesting using the continuous method. We will continue to refine our strategy for the timing of seed collection. Deployment periods will include spring (April), summer (June), and fall (November) deployment so that we will have seed available for socking two to three times per year.
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Gear improvements - A number of equipment purchases and improvements to the longline handling equipment were made during the reporting period. An aluminum socking table and Spanish seed grader, previously borrowed from Maine consultants, were purchased. A 25 hp hydraulic power pack, final product declumper-grader, and continuous socking machine were purchased. All equipment will be made available for use by the Portsmouth Fishermen's cooperative. A stationary boom and fairlead system for the vessel's winch cable were fabricated and installed (Figure 15). This installation solved the problems encountered last year with lifting a fully loaded longline into the rollers. In addition, new heavy-duty starwheel shafts and wheels were purchased and installed, and new sock deflectors solved sock entanglement problems that were encountered last year (Figure 16). A lifting davit needed to assist with placement of the longline into the aft roller was fabricated and installed (Figure 17) and spring-loaded line keepers were fabricated added to fore and aft rollers to prevent the line from popping out of the rollers during inclement sea conditions.
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Additional species - Original plans to evaluate growth of sea scallops and Belon oysters at the offshore site have been postponed until spring 2001. We were unable to obtain small quantities (5,000) of uniformly sized (25 --- 30mm) animals from any of our sources. Spat collection gear purchased by the project in August was deployed by the Stonington Fishermen's sea scallop stock enhancement group in exchange for free scallop seed for the project in April 2001. Hatchery production of Belon oysters has been discontinued, therefore, we will not attempt to evaluate the potential for this species.
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Growth and production comparisons - Growth rates and production estimates for mussels were described in an earlier section of this report. Growth rates compare very favorably with those reported in New England and the Maritimes. Our estimates are that a 7-8 months growout period is needed for 20-25 mm seed to reach market size. A good seed production site can produce quantities of seed of 20-25 mm in 4-5 months. Therefore we project that a full production cycle from larval settlement to minimum market size can be as short as 12-15 months. The growout period reported for Maine raft culture is 18-24 months, similar to the time reported for PEI, Nova Scotia, and New Brunswick. Quebec reports approximately 24 months to market size, similar to what is reported for Newfoundland. Production for our operation is estimated at 16,000 lbs. per longline (120 m headrope) per year. Maine raft culture production is 60,000lbs for a 42' x 42' raft. Production estimates for inshore longlines (e.g. PEI) were not available for this report.
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Related activities - In consultation and coordination with the NH Department of Environmental Services, a water sampling and sanitary survey program was initiated in the fall of 1999 and completed in September 2000. The purpose of this activity was to certify the site so that the mussels could be sold, thus avoiding the problems encountered for the first two growout deployments where mussels were "bottom seeded" because the site was not classified and the product could not be legally sold. A commercial fisherman was trained by NH state personnel to collect water samples and a sufficient number of samples were collected and analyzed by the state FDA certified laboratory for sanitary classification. Project personnel (Richard Langan) also worked with DES personnel to provide material and data for a full sanitary survey and to establish a biotoxin monitoring station at the Isles of Shoals. The survey has been completed and we are now awaiting FDA's response to NH's application for a shellfish growing waters program. Additional activities for broad area classification are now in the planning stage with state personnel.
Additional activities have included planning for a HACCP analysis of the Portsmouth Fishermen's Cooperative for processing and distribution shellfish, and an economic analysis being conducted in conjunction with an EDA grant to Jeffrey Taylor, Director of the NH Office of State Planning for Coop expansion and diversification.
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Technology/Information Transfer - Numerous presentations were provided to a diverse group of audiences during the project period. These included invited oral presentations at:
Aquaculture America 2000 in February 2000 in New Orleans
The NOAA Milford Aquaculture Seminar in New Haven, CT in March 2000
WAS's Aqua 2000 in Nice, France in May 2000
Fish Expo in Providence, RI in October 2000
In addition, briefings on project progress were provided for the NH Coastal program, staffers of the Office of Senator Judd Gregg, and informal meetings with Fishermen's Cooperatives and groups of local fishermen.
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Difficulties Encountered - Despite the overall success of the shellfish culture component of the project, several difficulties have been encountered. They can be placed in three categories; biological, engineering, institutional and logistical.
Biological - The major problem in this category during the reporting period was fouling by hydroids, and starfish predation on the offshore seed lines. Neither problem was encountered last year, which reinforces the precautionary approach to large-scale commercial development prior to solving problems that may crop up over multiple production cycles. Fouling by hydroids, which affected inshore seed production in 1999, impaired initial seed growth, and to some extent juvenile growout. It also added weight to the lines, increasing maintenance costs for cleaning and adding buoyancy. Starfish settlement on one group (north line) of seed caused substantial mortalities.
Engineering - The major engineering problem encountered is maintaining proper buoyancy. Since virtually all suspension culture of shellfish takes place in protected waters, even submerged longlines are generally very close to the water's surface. Affordable, submersible buoys currently in production in Canada are only rated to a depth of 60'. For this project, our initial depth of the headline (and consequently the submerged floats) was 45'. As the mussels grow and add weight to the line, it can very quickly sink to depths below the capacity of the floats to provide buoyancy. When this threshold is crossed, the line quickly sinks and can even end up on bottom. Many floats have failed, which has added to the problem. Steel submersible floats rated to greater depths are available, but are very expensive. Two alternative approaches are an automated buoyancy compensation system (which may be prohibitively expensive) or a cheaper alternative to the submersible steel buoys. Both alternatives will be pursued.
Materials failure, in the form of sock breakage and shredding during the socking process also occurred. Socking materials manufactured by Fukui did not perform to their breaking strength claims, and one batch must have been defective, since nearly every sock developed a "run" during the socking process. The problem was addressed by using mesh socking from a different manufacturer, and running a piece of twine through the middle of the sock. Future problems will be avoided by using the New Zealand-style rope core with biodegradable cotton socking. The other engineering issue that has not been solved is harvesting. A 12 meter sock of market sized mussels can weight well over 200 lbs. Though all deployments since November 2000 have used the rope core method which lends itself to easier methods of retrieval at harvest, we will need to do something to harvest the existing single droppers of mesh socking.
The major institutional problem encountered is state and federal classification of the site for shellfish sale. With another harvest looming over the next month, this continues to be a serious problem for the credibility of the project. Lastly, the combined effects of weather, days of availability for faculty, staff, student assistance, and vessels have delayed some project activities.
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Anticipated Success in Meeting Proposed Objectives in Scheduled Project Period -Despite some of the problems cited above, overall prospects for project success are very good. We have demonstrated the feasibility of producing a high quality mussel in a reasonably short time period (12-15 months post set), and we have made advances in refinement of equipment and operations to accomplish the task. There are a number of challenges remaining (including the institutional difficulties cited above), however, we are confident that the project will be a success and will make significant contributions to commercialization of offshore mussel culture.
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Tasks and activities for the next reporting period
- Evaluate the potential for aquaculture production of sea scallops in suspension culture.
- Assess the potential advantages for coupling fish and shellfish culture.
- Conduct economic analyses and modeling
- Develop harvest methodologies
- Address the buoyancy issue cited above.
- Continue to work with state and federal agencies on permitting, classification and certification
- Continue coordination of project activities with other initiatives to transfer open ocean shellfish culture technologies to the user community.
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Concerns or difficulties- None, other than those discussed above. In general the project is going well and there has been substantial interest generated by the project results among the scientific community, the aquaculture industry and the regional fishing community. The potential for development of an offshore mussel aquaculture industry in the Northeast region looks promising at this point.
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Figure 1. A photo taken in December 1999 of mussels socked and deployed at approximately 21 mm on July 1, 1999. The mussels are approximately 42 mm in this photo.
Figure 4. A photo of live mussels removed from mussel socks in March 2000.
The mussels are from the July 1999 deployment and are approximately 54 mm in this photo.
Figure 5. A photo of cooked mussels taken in March 2000. These mussels were deployed on the offshore longline in July 1999 and are approximately 54 mm in this photo. The cooked meat weight is 52% of the whole live weight.
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Figure 8. A photo of a single sock deployed in June 2000 with seed of approximately 25 mm. The mussels in this photo, taken in October 2000, are approximately 40 mm.
Figure 11. A photo taken in August 2000 of the headline and seed collection lines. The lines are heavily fouled with hydroids, however, close examination revealed a set of mussel spat beneath and among the hydroid stalks.
Figure 12. An October 2000 photo of one of the seed collector lines depicted in Figure 11. Mussel seed overcame the heavy fouling by hydroids were approximately 20 mm when this photo was taken.
Figure 14. Photo of a New Zealand style continuous socking machine purchased by the project in October 2000. The machine was used in late November 2000 to deploy mussel seed collected at the offshore site (see Figure 12).
Figure 15. A photo of the stationary boom installed on the overhead of the F/V Rock & Roll. Blocks attached to the overhead and mast fairlead the main deck winch wire to the boom. This adaptation of existing deck equipment provides adequate lifting capability to handle a fully loaded longline.
Figure 16. Photo of the reinforced forward hydraulic starwheel hauler and fabricated sock and buoy deflector installed in June 2000.
Figure 17. Photo of the reinforced aft idler, fabricated lifting davit and sock/buoy deflector installed in June 2000.
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