Bay Scallop Culture as a Viable Diversification for the Aquaculture Industry

Table of contents

• Executive Summary
• Task 1: Improving operational efficiencies for the field nursery of bay scallops
• 1. Introduction
• 1.1 Specific objectives
• 1.2 Modifications to the OysterGro system
• 1.3 Seed transfer: Chinese hats or pizza trays
• 1.4 Seed performance: Surface or bottom deployment
• 1.5 Seed performance: Pizza trays versus Vexar bags
• 1.6 Conclusions
• Task 2: Defining the optimal production strategy for bay scallops in the OysterGro™ cage
• 2. Introduction
• 2.1 Materials and Methods
• 2.1.1 Experimental design
• 2.1.2 Statistics
• 2.2 Results
• 2.2.1 First grading
• 2.2.2 Second grading
• 2.2.3 Results: second grading to the end of the season
• 2.2.4 Comparison between sites
• 2.2.5 Size distribution
• 2.2.6 Fall growth
• 2.2.7 Dry weight
• 2.2.8 Temperature
• 2.2.9 Cadmium
• 2.3 Discussion and Conclusions
• 2.4 Acknowledgements
• Task 3: Wet holding of bay scallops at Mills Sea Foods and L’Etang Ruisseau Bar Ltd.
• 3. Introduction
• 3.1 Mills Sea Foods storage facility
• 3.1.1 Experimental design
• 3.1.2 System design
• 3.1.3 Monitoring
• 3.1.4 Holding conditions
• 3.1.5 Survival performance
• 3.1.6 Tissue weight assessment
• 3.2 L'Etang Ruisseau Bar
• 3.2.1 Experimental design
• 3.2.2 Monitoring
• 3.2.3 Holding conditions
• 3.2.4 Survival performance
• 3.2.5 Scallop condition
• 3.3 Conclusions
• Task 4: Shelf-life Trials: Aqualife and MAP
• 4. Introduction
• 4.1 AquaLife technology trials
• 4.1.1 Conclusions
• Task 5: Shelf-life Trials: Modified atmosphere packaging
• 5. Introduction
• 5.1.1 METHODOLOGY Phase I: Determining the Gas Mixture
• 5.1.2 Phase II: Pilot Scale Processing of MAP Scallops
• 5.2 RESULTS AND DISCUSSION
• 5.2.1 Raw Material
• 5.2.2 Vacuum Setting Determination
• 5.2.3 Gas Mixture Setting
• 5.2.4 Phase I: Determining the Gas Mixture
• 5.2.5 Phase II: Pilot Scale Production of MAP Scallops
• 5.3 CONCLUSIONS
• 5.4 RECOMMENDATIONS
• Task 6: The economic feasibility of bay scallop culture
• 6. Introduction
• 6.1 Economic model
• 6.2 Section 3-Product type by source, volume and selling price
• General Conclusions

Executive Summary

The project proposes to develop operating procedures for the commercial scale aquaculture production of bay scallops, Argopecten irradians irradians, from nursery grow-out through to juvenile grow-out, holding and shipment of live product to market. It brings together four industry partners from rural coastal communities of New Brunswick NB, L’Étang Ruisseau Bar Ltée (ERB), Shippagan, NB, Mills Sea Foods Ltd., Bouctouche, NB, King Aquaculture Ltd., Richibouctou Village, NB and Jaillet Aquaculture Ltd., Bouctouche, NB. It is intended that this species will become a viable diversification alternative for the oyster growers in NB as well as for the several processors who are in demand of new products and diversity. 
 
L’Étang Ruisseau Bar Ltd operates the only commercial scale hatchery in Canada for the production of bay scallop seed. The key underlying objectives of the proposal are to evaluate existing production infrastructures and equipments, in particular, the OysterGro cage technology to produce the bay scallops from nursery through to adult grow-out, and to develop the wet holding protocols which could be used in existing under-utilised land-based infrastructures to commercially hold and eventually ship live bay scallops throughout the winter season. 

In brief, this project proposes to develop the protocols to enhance the grow-out of Bay scallops utilizing the OysterGro cage as a means for diversification for the oyster grower in NB.  The focus will be to optimize the densities and define the suspension position and timing, in the water column, on two aquaculture sites with very different bay conditions (King Aquaculture Ltd., and Jaillet Aquaculture Ltd). Furthermore, the protocols to commercially hold bay scallops for extended periods during the winter months, utilizing existing infrastructure with slight modifications, will be defined using infrastructure at Mills Sea foods Ltd and L’Etang Ruisseau Bar Ltd. Finally, extending the shelf-life of the bay scallop, once out of water, from the normal 6 days to weeks will be imperative in order to reach distant markets with the best quality product, and thereby is a key objective of this project. The results from this project will be immediately evident and useable by the entire aquaculture industry for the commercial aquaculture production of bay scallop in New Brunswick. A full cost analysis and economic model will also be provided for each stage of the process: grow-out, holding and shipment.

Task 1
Improving operational efficiencies for the field nursery of bay scallops

1. Introduction

Over the past decade, L’Étang Ruisseau Bar (ERB) has developed reliable protocols for producing commercial quantities of bay scallop seed (2-3 mm) in the hatchery. However, ensuring that the seed reach 7 mm in the field by late June is a critical step for the production of market-sized bay scallops (>50-mm) by mid-October. ERB had experimented with various nursery tray systems and deployment times, but in 2009 the OysterGro system was used to deploy some of the collectors currently used in the production process. Preliminary results suggested that this strategy was superior to the standard approach of transferring seed to window-screen trays in Aquamesh bottom cages. 

The objective of this trial was to produce large numbers of >7-mm bay scallop seed for transfer to 4-mm bags by mid-to-late June. The seed were produced in the ERB hatchery in March 2010 and reared in tanks until late May when conditions were suitable for deployment in the field (Baie St-Simon Sud). The first step was to adapt the OysterGro system to deploy the Chinese hat collectors used in the hatchery for the settlement of the bay scallops. In addition another series of OysterGro structures (5-mesh high) were purchased to hold the round window-screen ``Pizza trays`` typically used to deploy loose 3-mm seed from the hatchery. The plan was to compare the yield and size of seed recovered from the Chinese Hat collectors and the Pizza trays deployed in the OysterGro cages at the surface versus the Pizza trays deployed in the traditional bottom cages. Another objective was to determine whether commercially-available Vexar bags (2-mm mesh) were a suitable alternative to the relatively expensive custom-built Pizza trays.

1.1 Specific objectives

1. Design modified versions of the OysterGro cage for holding Chinese hat collectors and Pizza trays.
2. Determine whether bay scallops perform better if transferred to the OysterGro cage directly on the Chinese hat collectors or in Pizza trays.
3. Compare the growth and survival of juvenile bay scallops deployed in Pizza trays in the modified OysterGro system versus in cages deployed on the bottom.
4. Evaluate the performance of bay scallops deployed in Pizza trays versus Vexar bags.

1.2 Modifications to the OysterGro system

Ten OysterGro cage structures were modified to allow deployment of Chinese Hat collectors from the hatchery. These "oversize" versions are 33 mesh units long by 19 units wide by 10 units high. The collectors are not heavy and the structure did not require additional floatation. Problems were encountered with the window-screen mesh bags used to contain the Chinese hat collectors which were apparently damaged by rubbing against the Aquamesh structure. However, the blue nylon bags remained undamaged by abrasion over the 3-week deployment period (June 1-22).

1.3 Seed transfer: Chinese hats or pizza trays

The typical ERB strategy for transferring juveniles to the field was to remove them from the Chinese hat collectors in the hatchery and stock them in Pizza trays. This involves taking the collectors apart and banging them against the wall of a tank to dislodge the scallops; it should be noted that approximately 10-15% typically exhibit damaged/broken shells following this procedure. Alternatively, the collectors can be deployed directly in the field in mesh bags; this small mesh size is necessary to retain the juvenile bay scallops that become detached from the collector. An important advantage of the modifed OysterGro cages was the option to safely deploy the collectors in shallow water without the risk of their touching bottom and suffocating some of the scallops. 

On June 1 one Chinese hat was transferred directly to the field in the modified OysterGro, while a second hat from the same tank was taken apart and the scallops dislodged. They were then graded and placed in six 2-mm mesh Pizza trays (approx 5000/tray) and four 1-mm mesh Pizza trays (approx 7500/tray) for transfer to the OysterGro structure. The results of this preliminary trial suggested that the seed grew better when left undisturbed on the collectors as opposed to being transferred to Pizza trays prior to deployment. Growth rate and the proportion of >7-mm scallops ready for transfer to 4-mm Vexar bags was higher on the collector than the Pizza tray. Although the initial number on the Chinese hat could only be estimated from the matched collector, it also appeared that the yield or survival was higher when the scallops were left undisturbed. The lower survival in the 1-mm trays versus the 2-mm trays may reflect losses due to shell damage during the removal process. It was also noted that in terms of labour, it was generally easier to dislodge the scallops from the collector at larger size when their shells were heavier. It is also conceivable that they may be less vulnerable to shell breakage at this larger size.

1.4 Seed performance: Surface or bottom deployment

Two trials (May 26 and Jun 1) were undertaken to determine whether bay scallops deployed in Pizza trays performed better than in the OysterGro cages deployed at the surface or in the standard ERB bottom cages.

One problem previously encountered with Pizza trays in bottom cages was the tendency for the mesh to become fouled with sediment, particularly during periods of high wave activity. It was suspected that the associated reduction in flow/food supply was negatively impacting the scallops' growth performance. The results of the two 2010 trials indicated that while the difference in final shell height between the scallops deployed at the surface versus the bottom was only 1.3 mm, this translated into a substantial difference in the proportion ready for transfer to a 4-mm bag on June 22. Note that the lowest growth rate and survival were observed in the trays deployed in bottom cages on May 26; these were noticeably more fouled than those deployed in the OysterGro structure. Statistical analysis (ANOVA) of the results from the two trials (May 26 and June 1) indicated significantly better growth (p<0.001) in the trays/bags deployed at the surface than on the bottom. 

1.5 Seed performance: Pizza trays versus Vexar bags

One objective of these trials was to determine whether commercially-available Vexar bags (2-mm mesh) might be a viable alternative to the relatively expensive custom-built Pizza trays. In the June 1 trial scallops were deployed in Vexar bags as well as Pizza trays at both the surface (OysterGro) and on the bottom (Aquamesh structure). Statistical analysis (ANOVA) of the results indicated no significant difference in overall growth performance of scallops reared in Pizza trays (6.19 mm) versus Vexar bags (6.17 mm).  However, the best performance in terms of growth rate, yield of 7-mm scallops and survival was observed in Pizza trays deployed in the OysterGro structure. Note that additional comparative data on pizza trays versus Vexar bags will become available from the other sites in this project.

1.6 Conclusions

The best seed performance was observed on the Chinese hat collector transferred directly from the hatchery to the OysterGro cage. Although not assessed quantitatively in these trials, it was also noted that scallops transferred on Netron collectors from the hatchery to the OysterGro performed equally well. Access to these modified OysterGro units will lead to a change in the standard deployment strategy for bay scallop seed from the hatchery to the field site, seed will be left attached to collectors whenever possible and only individuals attached to the walls of the tanks will be dislodged and transferred to the field in Pizza trays. Moreover, the trials indicated that the OysterGro system was preferable to the bottom cages for deploying the Pizza trays. Sediment accumulation in the tray was substantially lower at the surface; this is particularly important for the 1-mm mesh Pizza trays which tend to foul very quickly when deployed in the bottom cages. A third advantage of the OysterGro system is the ability to deploy 4-mm bags with young juvenile bay scallops (>7 mm) in the surface zone. Otherwise these bags must be deployed on tables or in Aquamesh structures on the bottom which requires a higher labour costs.

Task  2
Defining the optimal production strategy for bay scallops in the OysterGro™ cage

2. Introduction

In 2008 the inventory of the New Brunswick industry was evaluated at 100 million oysters and the OysterGro™ cage was being used by nearly 85% of oyster producers from the South Eastern area involved in suspension aquaculture (pers. comm.). The bay scallop is a species which has great potential for New Brunswick because it grows rapidly and reaches commercial size in six months. This species has been identified as an excellent candidate for diversifying the revenue of shellfish farms. The bay scallop has been cultivated in lantern nets and pearl nets in the Maritimes, the United States and other countries in the world. In New Brunswick, aquaculturists would prefer to cultivate bay scallops using the equipment already in their inventory as they have expertise in operating this system and it functions well in their bays. In this project, the OysterGro™ cage will be evaluated for the culture of bay scallops as the system is multipurpose; it floats at the surface but can also be deployed on the bottom resting on the floats. In 2009, Jaillet Aquaculture conducted a rearing trial with bay scallops in the OysterGro™ cage and obtained promising results. This project will aim to define the commercial production parameters for bay scallops in order to maximize the use of this system.

2.1 Materials and Methods

2.1.1 Experimental design

One hundred thousand juvenile bay scallops (Argopecten irradians irradians) were obtained from the hatchery belonging to L'Étang Ruisseau Bar Ltée, Shippagan (N.-B). On June 10 2010 the juveniles were transferred and deployed at two rearing sites: Bedec (King Aquaculture, MS-0017) and Bouctouche Bay (Jaillet Aquaculture, MS-1191). Initial shell measurements (length, width and height) were obtained using calipers. The mean size of the bay scallops was 3.50 ± 0.76 mm. The juvenile bay scallops were placed in <pizza> trays at a density of 4000 scallops/tray and in vexar ® bags (1.5 mm mesh size) at a density of 2000 scallops per bag. Two vexar® bags or <pizza> trays were placed in each compartment of an OysterGro™ cage. At both sites, the <pizza> trays and the vexar® bags were placed in suspension and on the bottom at the start of the experiment.

The scallops were graded and transferred to vexar® bags of a larger mesh size twice during the season: 1st grading - June 28 2010 (2.5 weeks after deployment) and 2nd grading - July 19 2010 (5 weeks after deployment). After the first grading (5-mm mesh), the bay scallops were placed in 4-mm vexar® bags at a density of 2000 scallops/bag and returned to their original position in the water column. After the second grading (12-mm mesh), the scallops were placed in 9-mm vexar® bags at 5 different densities in triplicate. These densities were 80, 100, 120, 150 and 200 scallops/bag. At that time, some of the scallops which had been reared in suspension since the beginning of the experiment were transferred to the bottom.  Thus 3 rearing strategies were evaluated: 1) in suspension; 2) on the bottom; and 3) in suspension at the start but transferred to the bottom following the switch to 9-mm vexar® bags. To establish a control using the traditional method for rearing bay scallops in New Brunswick, 9-mm bags of scallops were also deployed on <rebar> oyster tables at the 2 experimental sites.

Before each grading, 15 scallops from each bag or <pizza> tray in each level in the water column were measured for shell length, width, and height. Survival was estimated on 3 samples of 100 scallops taken at random from the bags and the <pizza> trays. The percentage of scallops which had reached the desired height was determined at each grading. Whereas the OysterGro™ cage has 2 levels with 3 vexar® bags per level, only 4 vexar® bags were evaluated per cage at the final sampling: the 2 bags in the middle, 1 on the exterior on the lower level and 1 on the exterior on the upper level. At each sampling event, the same parameters were evaluated, with the exception of the 15 scallops per bag taken for assessment of whole weight at the end of the trial in October.
 
The biofouling which accumulated on the scallops was assessed and documented at each sampling event. Temperature was recorded in suspension and on the bottom using a Vemco Minilog recorder. Salinity was monitored at both sites using a Star-ODDI probe. Although the trial was supposed to end in mid-October 2010, a few bags from each density in suspension and on the bottom were left until the end of November to estimate the growth during this period. Shell size (length, width, and height) as well as whole weight was evaluated after this one additional month of growth.

A sample of scallops from each site was evaluated for cadmium content by the Research Productivity Council (RPC) before being transferred to the wet-holding facility. Tissues from 20 scallops were pooled, frozen and sent to the RPC laboratory (Fredericton, N.B.).

2.1.2 Statistics

The normality of the data was tested with the Shapiro-Wilk test. A two and three-way analysis of variance was used to test for the statistical significance of the various factors (site, position, system and density). When a significant effect was noted, the Bonferroni test was applied to detect differences between the means. These analyses were carried out using the SPSS 13.0 software (Chicago, IL, USA).

2.2 Results

2.2.1 First grading

The first grading was conducted 18 days (June 28 2010) after the initial juvenile deployment on June 10 2010. The results indicated a difference in shell growth between the 2 sites; the Bouctouche site had higher growth than the Bedec site (p<0.01). Growth was higher in the vexar® bags than in the <pizza> trays (p=0.012), and at the surface than at the bottom (p<0.01). The scallops grew very rapidly over this short period. Shell length varied from 5.8 to 9.7 mm among sites and systems, which corresponded to an increase of 2.3 to 6.2 mm. Growth rate was equivalent to 0.34 mm/day for the best-performing combination (i.e. Bouctouche - vexar® bags in suspension). Mortality rates for the different groups varied from 1.6 % to 8.2 % between the two sites. A significant effect on mortality was observed for the three factors: site, system and position in the water column. The Bedec site had a higher mortality than the Bouctouche site (p=0.002), i.e. 3.2 to 8.2 % at Bedec versus 1.6 to 7.0 % at Bouctouche. The comparison between the two juvenile grow-out systems indicated that the <pizza> trays had a higher mortality than the vexar® bags (p=0.018). The systems deployed in suspension had lower mortality than those on the bottom (p<0.01). 

At the first grading, the number of scallops which had reached the desired size (≥5 mm) was determined before transferring them to a 4-mm vexar® bag. A significant difference in this parameter was observed between the sites (p<0.01), the positions in the water column (p<0.01) as well as the interaction between these 2 factors (p<0.01). The Bouctouche site showed a higher percentage (91 %) of >5 mm scallops than the Bedec site (59.7 %). The systems in suspension had a higher recovery of >5 mm scallops than those deployed on the bottom.

2.2.2 Second grading

The second grading was conducted in the week of July 19 2010, or 5 weeks after the initial deployment of the juveniles. During this period the bay scallops were reared in vexar® bags in suspension and on the bottom. The scallops attained a shell length of approximately 11.0 to 20.5 mm, which represented a growth rate of approximately 7.5 to 17.0 mm since the start of the trial. Site, position in the water column, as well as their interaction had a significant effect on growth performance (p<0.01). At both sites, the scallops reared in suspension (17.3 mm at Bedec and 20.5 mm at Bouctouche) grew better than those reared on the bottom (8.7 mm at Bedec and 14.6 mm at Bouctouche). The Bouctouche site showed better growth than the Bedec site. Mortality rates were low and similar at the two sites. The scallops reared in suspension had a lower mortality than those reared on the bottom with values ranging from 0.05 to 2.1 %.

As in the case of the first grading, the results of the second grading on a 12-mm mesh provided an indication of the proportion of scallops which had attained the desired shell height of >12 mm, suitable for transfer to a 9-mm bag. Both site and position had a significant effect on this value (p<0.01). Bouctouche had a greater percentage of scallops >12 mm than did Bedec. Rearing scallops in suspension was more effective at producing individuals large enough to be transferred to 9-mm bags than was the bottom-rearing strategy. Scallops reared on the bottom at Bedec had the lowest growth rate and thus fewer individuals attained a suitable size for transfer to 9-mm bags. Only 3 (80, 100 and 120) of the 5 densities were evaluated on the bottom at this site.

2.2.3 Results: second grading to the end of the season

After the second grading, the bay scallops were stocked in 9-mm mesh vexar® bags at 5 different densities (80, 100, 120, 150 and 200 per bag). At that time (July 19), the experimental lots reared at the surface were re-deployed at the surface, those reared on the bottom were re-deployed on the bottom, and a third lot which had been reared at the surface were transferred to the bottom. The results of these three strategies were evaluated at both production sites.

2.2.4 Comparison between sites

No biofouling was observed on the scallops grown at Bedec, but heavy fouling developed at Bouctouche in August, both on the Oystergro™ cages as well as the vexar® bags. The cages and the bags were cleaned several times, but there was a heavy set of oyster spat which survived on both the bags and the scallops. Comparisons of bay scallop performance between the two sites revealed significant differences in terms of shell length and whole weight. It should be noted, however, that the whole weight of the scallops at Bouctouche was likely overestimated due to the biofouling on the shell. The variation between sites was consistent for the two shell parameters; Bouctouche (60.8 mm, 31.1 g) had a higher shell length and whole weight than Bedec (57.0 mm, 22.4 g). At both sites, scallops reared in bags on oyster tables (experimental control) achieved a higher shell length and whole weight than those reared using the various alternative strategies. In the case of the OysterGro™ cages, scallops reared in suspension performed better than those reared on the bottom or transferred from the surface to the bottom partway through the trial. The lowest density of 80 scallops/bag (62.18 mm; 30.56 g) had the highest estimates of shell length and whole weight at both sites. No significant difference was detected between the next two densities of 100 scallops/bag (58.95 mm; 26.46 g) and 120 scallops/bag (58.58 mm; 26.35 g). The lowest estimates were observed at the highest density or 200 scallops/bag. Mortality rates were similar for all the rearing strategies at the Bedec site (0 to 0.98 %) whereas losses were slightly higher at Bouctouche (0.18 to 3.24 %), possibly due to the presence of sea stars in some of the bags.

The mean weight of scallops/bag harvested in October was calculated for each site, stocking density and position in the water column. It should be noted that the mean weight for the Bouctouche site was overestimated because of the oyster set on the scallops. At Bedec, rearing scallops in suspension offered the best yield in terms of weight whereas the combination of suspension followed by bottom rearing was preferable at Bouctouche.

2.2.5 Size distribution

Note that because the market for this species is still under development, a specific market size has yet to be defined. If the plan is to sell bay scallops at >60 mm, then suspension culture at 80 scallops/bag offered the highest percentage of market size product at Bedec (80%). This yield was similar to that obtained from the lowest density bags on the oyster tables (83.3%). At Bouctouche, 90% of the scallops grown at the lowest density on the bottom attained a size >60 mm. If the commercial market size were to be set at >55 mm, the majority of the scallops at both sites would have been suitable for marketing at the end of the study. 

2.2.6 Fall growth

Certain bags of scallops were left in suspension and on the bottom in October in order to assess the level of growth between this date and mid-November. Little change was observed except in the case of those left at Bouctouche. It is possible that the cleaning of the cages and the bags in October reduced the level of feeding competition in the higher density treatments thereby allowing better access to the available food. In general, however, production gains were minimal during this period.

2.2.7 Dry weight

Tissue dry weight was evaluated for the various stocking densities of scallops reared in suspension and on the bottom. The results indicated a marked difference between the two sites; scallops grown at Bouctouche had a significantly higher dry tissue weight than those grown at Bedec. In general, scallops reared in suspension (1.68 g) had higher values than those reared on the bottom (1.34 g), and those reared at the lowest density had the highest tissue weight.

2.2.8 Temperature

Temperature was monitored in suspension and on the bottom throughout the study. Profiles were similar at the two sites and the different depths in the water column. Bouctouche had slightly higher values (5.2 to 23.6 °C) than did Bedec (4.7 to 22.9 °C), particularly in July-August. Salinity was monitored in suspension at both sites, but the data from Bouctouche were considered unreliable because of the heavy fouling. The only salinity data reported are thus from July. At Bedec, the highest salinity was observed in August (25.05 ‰) and the lowest value in November (17.11 ‰).

2.2.9 Cadmium

Cadmium levels are an important criteria for export to Europe; specifically the concentration in bivalve molluscs must be less than 1.0 mg/kg (see the Position paper by Seychelles on the level of cadmium in bivalves set by the EC, 2002 and the Canadian Food Inspection Agency website). Cadmium levels in the bay scallops at both sites were below the critical threshold; mean estimates were 0.380 mg/kg for Bouctouche and 0.321 mg/kg for Bedec. 

2.3 Discussion and Conclusions

The results of this study demonstrated that bay scallops can be successfully reared in OysterGro™ cages. A mean size of 60 mm was attained in 4 months (131 days), from June 10 to October 20 2010. The results also indicated that the yield of market size scallops varied between sites as did the optimal rearing strategy. The best juvenile growth was observed in suspension at both sites, prior to the second grading or the transfer to 9-mm mesh bags. The preferred strategy for the final grow-out phase varied depending on the site. The best performance was obtained in suspension at Bedec, but on the bottom at Bouctouche, probably as a result of the biofouling at the surface. In terms of yield the preferred density was 80 scallops/bag but levels of 100 and 120 scallops/bag also gave acceptable results. 

Based on this study, juvenile growth was better in the vexar® bags (1.5-2 mm mesh) than in the <pizza> trays at an initial stocking density of 4000 scallops per system. It should be noted that it is more difficult to remove the scallops from the inside of the bags than from the <pizza> trays. Moreover, these bags do not hold their shape as well as larger mesh vexar® bags. They tend to collapse and lose their rectangular structure, which may interfere with the flow through the mesh and thus the scallops' growth. We suggest finding a method to ensure the rigidity of the bag, or constructing two bags out of one; i.e. a more compact shape may be less susceptible to deformation. 

The bay scallop has considerable commercial potential not only because of its rapid growth but also its very low mortality rates. At Bedec the cumulative mortality in the best-performing strategy (i.e. suspension at 80 scallops/bag) was 3.46 %. In the best-case scenario at Bouctouche (i.e. suspension followed by bottom rearing at 80 scallops/bag), the cumulative mortality was 3.58 %. These low mortality levels are impressive in a species that grows so rapidly.

At the Bouctouche site, a heavy layer of fouling developed on the cages, the bags and the scallops over the course of the study. This fouling, particularly the oyster set, likely reduced the growth of the scallops and rendered them unfit to sell as whole product.  Many sites in this region are very productive, but these high food levels not only promote shellfish growth, but encourage the development of fouling organisms. Changing the cages and the vexar® bags after the settlement of oysters and barnacles is an option, but augments the labour cost. An economic evaluation of this strategy would be feasible using the model developed in this project. Another option would be to sell these scallops as a shucked product, assuming that the price was sufficient to make this strategy profitable.

The fall trial in which the scallops were left to grow for another month (mid-October to mid-November) did not increase their size or weight substantially. It may be less risky to remove the scallops from the site in October in order to avoid the onset of ice and the disturbance associated with high winds. Following this first year of trials with rearing bay scallops in Oystergro™ cages, there are various other strategies which could be explored:

• Purchase of larger seed at the same time in June
• Trials with lower juvenile stocking densities (i.e. 1000, 2000 and 3000 scallops/bag) to determine whether higher growth rates could be achieved at a reasonable cost
• Trials with lower stocking densities following the second grading (i.e. 500 and 1000 scallops per 4-mm vexar® bag)
• Given that the scallops reared on oyster tables showed excellent growth, modify the OysterGro™ cages for use on the bottom but at a height similar to that of the tables - this option would be particularly interesting to evaluate at the Bedec site

2.4 Acknowledgements

This study was financed by the Aquaculture Innovation and Market Access Program (AIMAP), the Industrial Research Assistance Program of the National Research Council (NRC-IRAP), the New Brunswick Department of Agriculture, Aquaculture and Fisheries and Entreprise Kent. Thank you to the various staff members of the two aquaculture operations, King Aquaculture, Inc. and Jaillet Aquaculture Inc., as well as the shellfish research group at the Coastal Zone Research Institute: Mélanie Degrâce, Josée Duguay, Roxanne Thériault and Mathieu Landry for their excellent work and collaboration.

Task 3
Wet holding of bay scallops at Mills Sea Foods and L’Etang Ruisseau Bar Ltd.

3. Introduction

The long-term wet holding of shellfish has received little attention in the scientific literature, probably because most areas of the world do not have to deal with extensive ice coverage over an extended period of time. In Atlantic Canada, mussels are often stored in wet-holding facilities during the winter, but typically for a 2-wk period because of the fast inventory turnover. Bay scallops grown on the east coast of New Brunswick reach market-size in October but do not survive the winter under the ice, which often develops by mid-November.  Wet holding is thus a necessity in order to extend the marketing window for this whole live product. The overall objective of this study was to define the protocols for holding large quantities of bay scallops for at least five months of the winter season (i.e. November to March).

Previous attempts to over-winter bay scallops in the field in eastern NB (i.e. wild storage) have consistently resulted in a complete loss of inventory, typically by late December depending on the advent of ice coverage (Mallet, pers. obs.). In contrast, bay scallops were successfully over-wintered in the field until late March for several consecutive years in Lunenburg Bay, Nova Scotia (Mallet, pers. obs.). Similarly, under experimental conditions, bay scallops were successfully wet-stored indoors in trays at the Marine Research Station, Sandy Cove, Nova Scotia. It should be noted that the temperature in these indoor trials never decreased to sub-zero levels. Furthermore, bay scallop broodstock in eastern N.B. have been maintained indoors in tanks at ambient temperatures from the end of November to mid-January when they are transferred to conditioning systems with minimal losses (Mallet, pers. obs.). We believe that there is sufficient evidence to suggest that bay scallops have the biological capacity to survive in a wet-holding facility for an extended period of time. However, there is a complete lack of information on the environmental parameters required to successfully establish a commercial wet-holding system for this species. This study was to designed to evaluate different strategies for the winter storage of bay scallops at two commercial facilities: Mills Sea Foods in Bouctouche, N.B. and l'Etang Ruisseau Bar in Shippagan, N.B.

3.1 Mills Sea Foods storage facility

Shellfish processors, such as Mills Sea Foods (Bouctouche, N.B.) are looking to diversify their markets and products in order to increase their bottom-line. Several such processors in NB and Atlantic Canada, have existing infrastructures designed to hold and/or depurate shellfish species, and while very expensive to maintain, they are rarely utilized to full capacity and often rest idle for several months of the year. The development of a bay scallop industry in NB could offer Mills Sea Foods and others processors a valuable opportunity to diversify their product base. Not only would this require minimal investment in infrastructure modification, but these companies already have in-house expertise with respect to the monitoring and holding of various shellfish species. 

3.1.1 Experimental design

On November 16 2010 approximately 1550 lbs of market size bay scallops were obtained from King Aquaculture (Bedeque Bay) for the wet holding trials. The scallops had been graded in mid-October and maintained in floating boxes (Loktek) at a density of approximately 40 lbs/box. The scallops were passed through a washer onto a conveyor where they were screened to eliminate any dead or broken individuals. Live scallops were then transferred to holding trays at four stocking densities: 10 lb, 20 lb, 30 lb and 40 lb per tray. Trays of each density were stacked on a pallet with an empty tray on the bottom of each stack. The trays were labelled A, B, C, D starting from the bottom. The pallets loaded with trays were transferred into 5000-L holding tanks at three overall stocking densities: 200 lbs/tank, 500 lbs/tank and 1000 lbs/tank. The highest density (1000-lb) was comparable to commercial stocking levels for holding softshell clams (i.e., 40 trays @ 30 lb/tray).

3.1.2 System design

The Mills storage facility is equipped with a large underground reservoir (13,000 L) which can be filled from the Bouctouche estuary at high tide or whenever the salinity conditions are acceptable. During the intervening period, sand-filtered sea water is circulated through a series of 5000-L holding tanks and UV-treated as necessary should depuration be required.

Water is supplied to each holding tank through a manifold at one end. An internal bulkhead ensures that the water enters at the base of the tank, from where it passes through the product and out through an opening near the surface at the far end. Air is supplied to the first compartment in the tank to ensure that the water is well oxygenated before entering the main area.  

3.1.3 Monitoring

Temperature probes (Vemco Minilogs) were deployed in each of the three holding tanks on November 19 2010. A Seastar temperature / salinity probe was also deployed in one of the tanks. Salinity and oxygen levels in the tanks were also monitored daily.

Bay scallop survival was assessed every 2 wk from December 6 2010 through February 4 2011. The number of mortalities removed at each sampling event and the number of survivors at the end were counted to determine the total number of scallops per tray. These values were used to calculate survival curves for each treatment over time. Total weight of live scallops remaining in each tray was also documented following the removal of mortalities. An analysis of variance (ANOVA) was used to determine whether tank stocking density or tray stocking density had a significant impact on survival.

Initially, and then approximately at 2-wk intervals, five scallops were taken from two trays per treatment (level A and B) for assessment of condition. Note that the survival calculations were corrected to account for the removal of these individuals. The scallops were measured (shell height), weighed (whole live weight), separated into shell and tissues (wet weight) and the tissues dried for 48 h at 60oC (dry weight). Condition (g/mm) was estimated as tissue dry weight (g) divided by shell height (mm). ANOVA statistics were used to determine whether tank stocking density or tray stocking density had a significant impact on scallop condition.

3.1.4 Holding conditions

The plan was to try to maintain the scallops at 2-5oC in the holding tanks for as long as possible. Problems were encountered in November-December due to heavy rainfall which resulted in abnormally low salinity levels in the incoming water. To avoid exposing the scallops to these conditions, it was necessary to switch from flow-through to recirculation mode for several days at a time or until the salinity increased to acceptable levels. In this case the pumping action caused a steady increase in water temperature. Hence the bay scallops were exposed to a wide range of temperatures (2-14oC) during the first seven weeks in the holding tanks (November 16 - January 4). When it was finally possible to switch to flow-through mode, the temperature was relatively stable (2-7oC) (January 4 to February 4 2011).

3.1.5 Survival performance

The biomass of bay scallops declined steadily according to a similar pattern in all three tanks; after five weeks 42% of the original weight remained (Dec 22 2010), and after ten weeks only 8% remained (Jan19 2011). The trials were terminated on February 4 2011 when <1% of the scallops remained. The similarity in survival profiles among tanks indicated that tank stocking density was not a critical factor in determining bay scallop survival. In other words the environmental conditions experienced by the scallops were similar in all three density treatments.

Whereas there was no variation in bay scallop survival among tanks (p=0.20), tray stocking density had a significant effect on survival (p<0.01). Specifically there was a noticeable decline in survival with increasing tray stocking density, regardless of tank stocking density.

3.1.6 Tissue weight assessment

The bay scallops were sampled initially on November 16 2010, and then again on December 8, December 22, January 6 and January 19. Neither tank or tray stocking density had any significant effect on scallop condition, whole weight or water content with the exception of water content at the final sampling. Unexpected trends were observed in this group of scallops; for instance, their condition actually improved after being transferred to the storage tanks. The fact that these bay scallops gained weight during this initial period would suggest that they may have been in relatively poor condition at the outset of these trials. This would be consistent with earlier measurements of dry weight for the Bedec bay scallops which showed substantially lower values than those from the Bouctouche site.

3.2 L'Etang Ruisseau Bar

ERB (Shippagan, N.B.) has been producing commercial quantities of bay scallops since 2005 and has made several previous attempts to conduct large-scale wet-holding trials. For example, in November 2007 market-size bay scallops were transferred from the field to a commercial wet holding system operated by Chiasson Aquaculture (Miscou N.B.). This system, originally designed for holding mussels, was based on 600-L Xactics tanks stacked three units high. Seawater (40-50 L/min) was supplied to the uppermost tanks from the water distribution system and flowed down through the shellfish, through the tank sub-floor or false bottom and exited via a stem pipe to the tank below. Trials were conducted from November 2007 to February 2008 with various types of trays and racks as well as loose scallops (300 lbs per tank), but without any significant success.

In 2009 another series of wet-holding trials were conducted at the new ERB storage facility (Shippagan, N.B.). In this case bay scallops were placed in stacking tubs (40 lbs per tub) with ambient seawater supplied on the upper level and draining down through the stack via internal stem pipes. Significant losses were observed after two weeks in these tubs whereas oysters stocked at similar densities in the same system exhibited no mortality over several months. In the present study the two main objectives were to assess an alternative tray design equipped with aeration as well as investigate the possible advantages of pre-heating the storage water.

3.2.1 Experimental design

On December 9 2010 bay scallops were brought into the plant from floating tubs in the field and dead or damaged scallops were removed. Batches of 15 lbs, 20 lbs and 25 lbs were placed in stacking Dark Sea trays as well as the stacking tubs used in the 2009 trials. The bottom tray in each stack of Dark Sea trays was modified to include an air delivery hose. Note that this modification was based on the design of the AquaLife container system. The trays were labelled A through F starting from the bottom. Three stacks of six trays were placed in two 2000-L tanks, one receiving ambient seawater and the other, heated ambient seawater.  The water was heated by adding a titanium coil with running 8oC freshwater to the main reservoir. The tubs with ambient water were stacked three-high similar to the 2009 trials.

3.2.2 Monitoring

Temperature probes (Vemco Minilogs) were deployed in each of the three treatments on December 9 2010. A Seastar temperature / salinity probe was also deployed in one of the tanks but the salinity data were unreliable. Temperature, salinity and oxygen levels in the tanks were monitored using a YSI meter at each sampling event. Bay scallop survival was assessed weekly from December 14 2010 through March 9 2011. The number of mortalities removed at each event and the number of survivors at the end were recorded to determine the total number of scallops per tray. These values were used to calculate survival curves for each treatment over time.

Initially, and every 2 weeks thereafter, five scallops were taken from two trays per treatment (levels A and D) for assessment of condition. Note that the survival calculations were corrected to account for the removal of these individuals. The scallops were measured (shell height), weighed (live weight), separated into shell and tissues (wet weight) and dried for 48 h at 60oC (dry weight). Condition (g/mm) was estimated as tissue dry weight (g) divided by shell height (mm). ANOVA statistics were used to determine whether the holding temperature or the tray stocking density had a significant impact on scallop condition.

3.2.3 Holding conditions

The plan was to maintain the scallops in the heated treatment at approximately 1 to 3oC while those in the ambient seawater treatments (ambient-air / tubs) experienced temperatures in the 0 to -1.5oC range. Note that the scallops were placed in the "heated tank" on December 9 at the start of the trial but the ambient water temperature remained relatively warm through December; the mean temperature in the ambient-air tank was 1.38+1.33oC versus 0.97+1.35oC in the stacking tubs. Apparently the addition of the air raised the water temperature by approximately 0.4oC. The system for heating the water was installed on January 1. Apart from a few days in mid-February when the freshwater pump failed, the temperature remained in the range of 1 to 4oC until March 9. Salinities remained in the 22-28 o/oo range for the duration of the trial. Oxygen saturation levels were consistently higher in the two aerated systems (96-106%) than in the stacking tubs (79-105%). The supply of water to the heated tank was approximately 12 L/min compared to 20 L/min in the two ambient systems.

3.2.4 Survival performance

At the ERB facility all three experimental factors: holding temperature (p ), storage system (p ) and stocking density (p ) had a significant effect on bay scallop survival. The best overall recovery (approximately 30%) was observed in the heated system at stocking densities of 15 or 20 lbs per tray. An increase in mortality was observed in most treatments by the third week of February, approximately 10 wk into the trial. The beneficial effect of the slightly higher storage temperature became evident towards the end of January (wk 7). Survival was higher in the Dark Sea trays than the stacking tubs. 

3.2.5 Scallop condition

Initial samples of the bay scallops were taken on December 9 2010, and a subsequent sampling was done on Dec 24 2010. At that time none of the experimental factors including the holding system, the holding temperature and the stocking density, had a significant effect on scallop condition, whole weight or water content. A similar analysis of variance on the tissue data from Feb 02 2011 indicated a significant difference in whole weight among holding systems and a significant difference in water content among holding systems and stocking densities. By the final sampling day (Feb 23 2011) all three experimental factors had a significant effect on the tissue characteristics. 

In general, there was a decline in scallop condition, whole weight and water content over the course of the study. Although this was expected, we did not anticipate the greater decline in the DST system versus the tubs. Overall, the scallops in the heated system showed the greatest loss in condition, possibly because the higher temperatures and/or the variation in temperature were stressful.  Likewise, whole weight declined by approximately 8 g per scallop in the DST system versus 3 g in the tubs. Water content is a general indication of stress in shellfish; for example, bay scallops held at ambient temperature tended to have highly retracted mantles towards the end of the study which was consistent with their relatively low water content. Note that whereas survival was higher in the heated DST system, final estimates of condition, whole weight and water content were lower than in the stacking tubs.  It is possible that only the strongest scallops survived in the stacking tubs and hence these were the ones that were sampled. 

3.3 Conclusions

Progress has been achieved with the wet holding of the bay scallop at L’Étang Ruisseau Bar.  In the past, massive mortalities would occur soon after the fall transfer into the wet holding tanks. One of the overriding factors observed in this study at both Mills Sea Food and ERB is the effect of the tray / tub stocking density: trays stocked with greater than 20 lbs of bay scallops consistently exhibited lower survival. In past years, trays were typically stocked with 40 lbs of bay scallops thereby leading to high rapid losses as well as conditions (i.e. contaminated water from decaying scallops) unsuitable for the sale of the product. 

Another positive development has been the development of a modified Dark Sea Tray following the design of the Aqualife System. This stacking tray system with air injected at the bottom did enhance the overall survival of the bay scallops; in addition, other ancillary observations were the lack of shell discoloration and the lack of smell associated with decaying tissues. It is likely that the highly oxygenated seawater prevented the development of anaerobic sulfur-producing bacteria. This meant that the marketing window for bay scallops held in storage was augmented substantially from two to more than eight weeks. Finally, the results indicated that bay scallops held at 1-20C temperatures had a higher survival than those held at ambient (-1.0oC) temperature.

At the Mills Sea Food wet holding facility, issues were encountered with several seawater parameters which may have led to a higher than expected mortality at the beginning of the study; in particular, exposure to low salinity levels, near 100/oo as well as higher fluctuating seawater temperatures which may have caused a physiological stress. Yet, another factor which needs to be considered is the condition of the bay scallops as they entered the wet holding facility. Scallops used in the Mills wet holding trials originated from the Bedec site, but bay scallops from the Bouctouche site held in the same facility for the Modified Atmosphere Packaging trials appeared to exhibit lower mortality. It should be noted that a highly significant difference in condition (tissue weight standardized for shell height) was noted in the field trials between the Bedec (1.1 g/mm) and the Bouctouche sites (1.9 g/mm). Although the initial higher mortality observed at the Mills operation was likely caused by fluctuating seawater conditions, the lower number of days to reach a LD50 level (50 days) as compared to ERB (70 days) could be accounted for by the relatively lower initial condition of the scallops.

Task 4
Shelf-life Trials: Aqualife and MAP

4. Introduction     

The shelf-life of bay scallops, once removed from the water, is only six days at refrigerated temperatures. This short period barely allows sufficient shipping time to reach markets in the US and Canada, and undermines any effort to establish new markets in Europe. Hence, one of the key objectives of this project was to investigate proven technologies for extending the shelf-life of a fresh product. The two options were Modified Atmospheric Packaging (MAP), which is currently utilized by Canadian Cove in PEI for mussels, and the AquaLife system (http://www.aqualife.nu/), a patented technology designed to ship live product to Asia and Europe in controlled environment containers. This process has been successfully applied to shellfish such as lobster. 

4.1 AquaLife technology trials

On October 28 market-size bay scallops from the Bouctouche grow-out trials were delivered to East Jeddore (N.S.) where the AquaLife operation was currently based. A refrigerated MAERSK shipping container equipped to support the AquaLife storage tanks was delivered to the plant. Inside each AquaLife tank is an internal structure consisting of a stack of half-moon perforated trays sitting on a stainless-steel base fitted with an air-distribution system. The blue circular air line has very small holes drilled along its length to ensure that air bubbles up through the product and maintains a highly oxygenated environment.

For the preliminary trial bay scallops were loaded into the stacking trays at 30 or 40 Kg per tray to determine whether stocking density affected survival. The trays were transferred to the Aqualife tank which was then placed in the shipping container using a forklift. The tank was hooked up to the air line and the water recirculation system and the lid was sealed for 15 days. 

On November 12 2010 the AquaLife tank was drained and opened and the scallops were removed for assessment. Given that there had been no water exchange for two weeks, the majority of the product looked excellent with no sign of shell discoloration or odour. The only evidence of mortality was in the bottom of the trays stocked with 40-lbs; in this case the weight of scallops may be too high to allow for the lower ones to open. There was no evidence of gaping and some of the scallops were tightly interlocked suggesting that the muscle was still strong. Upon opening the tissues appeared plump and the muscle fibres twitched as would be expected in a healthy scallop. There was no indication that this product would not be marketable upon arriving at the desired destination.

4.1.1 Conclusions

The establishment of a technology designed to move large quantities of bay scallops to distant markets is essential to the development of the bay scallop sector. Being able to move product in seawater at a competitive price to airfreight offers an interesting scenario to reach the European market which has an affinity for this product. After 15 days in these tanks, the product seemed vigorous, healthy and the meat quality was very high. It should be noted that the bay scallops used in this trial came from Jaillet Aquaculture and these scallops had an excellent condition factor. We believe that it will be important to develop good indicators of condition in order to insure that every shipment of product to distant markets is a success.

Task 5
Shelf-life Trials: Modified atmosphere packaging

5. INTRODUCTION

The client, Mr.Andre Mallet, represents four aquaculture scallop industry partners from rural coastal communities in NB, L’Étang Ruisseau Bar Ltée (ERB), Shippegan, NB, Mills Sea Foods Ltd., Bouctouche, NB, King Aquaculture Ltd., Richibouctou Village, NB and Jaillet Aquaculture Ltd., Bouctouche, NB. The group is interested in testing the use of modified atmosphere packaging (MAP) technology on aquacultured scallops. MAP processing is used extensively in Europe to extend the live shelf life of mussels. The primary benefits of MAP to the mussel industry, are in extending the live shelf life of the product from 12 days to 18-20 days. Recently, this technology has been introduced to the aquaculture mussel industry in Canada where it has allowed the industry to expand markets in the retail sector.

The assistance of the Centre for Aquaculture and Seafood Development (CASD) was requested to evaluate the application of MAP (modified atmosphere packaging) technology for the purpose of extending the shelf-life of live farmed Bay scallops from 6 days to 21 days. For this project the CASD compared the shelf life of scallops packaged using the current industry method and scallops packaged in vacuum bags with various MAP gas mixtures.

The project was carried out in two phases:

• Phase 1: Evaluate gas mixtures used in the mussel industry for MAP processing of bay scallops (Argopecten irradians irradians).
• Phase 2: Conduct a pilot test using the mixture from phase 1 that provided the most significant benefit.

This report outlines the results of the phases 1 and 2 of the project.

5.1.1 METHODOLOGY Phase I: Determining the Gas Mixture

This experiment was designed to identify optimum gas mixtures including O2, CO2 and N2, that would provide high quality, live scallops with a 10-14 day shelf-life. This extended shelf-life will allow the New Brunswick companies to access non-traditional markets in Canada, U.S and Europe. The gas mixtures tested included:

• 80% Oxygen-20% Carbon Dioxide (Canadian Patent)
• 70% Nitrogen-30% Oxygen (Italian Mixture)
• 60% Oxygen-40% Carbon Dioxide (European Patent)

Initial testing was required to determine the optimal vacuum setting to properly evacuate the atmosphere without crushing the scallops while preventing the scallops from gaping. To evaluate the MAP gas mixtures, live scallops were packaged in 1 lb x 6 mil poly bags and flushed with the test gas mixture before sealing. The MAP product was placed in chilled storage at 2-4OC and evaluated over a 10 day period.

To evaluate the benefits of MAP processing, the MAP samples were compared a set of control samples for shelf-life. The control samples consisted of scallops that were packaged using the current industry method. The procedure for the packaging of the control samples:

• Receipt of live scallops
• Culling of dead and critically weak animals
• Weighing scallops into Styrofoam boxes and layering with soaker pads wetted with salt water
• Place into chilled storage

MAP samples and control samples were evaluated for shelf-life on Days 1, 3, 5, 7, 9 and 11. The scallops were evaluated on the following criteria:

• Appearance
• Package odour
• Number of live & dead
• Drained weight of scallops
• Package atmosphere
• MAP processed product only

The optimum gas mixture identified in phase 1 was used for the pilot scale trial conducted during phase 2.

5.1.2. Phase II: Pilot Scale Processing of MAP Scallops

Based on the results from phase 1, the client was requested to provide CASD with approximately 200 lbs of live bay scallops. For this process, the scallops were packaged in lots similar to what would be anticipated in a commercial process. Currently, aquaculture bay scallops are distributed to markets in Styrofoam containers with 5 lbs of scallops per container. Thus, for this pilot production run scallops were packaged in 5 lb poly bags and flushed with the MAP gas mixture prior to sealing. The gas mixture used for this process was determined in phase 1.

As in phase I, the shelf-life of the product was evaluated to determine the benefit of MAP processing for live farmed bay scallops. The MAP processed scallops were compared to scallops packaged using the current industry method. The shelf-life evaluation consisted of removing scallops on Days 1, 3, 5, 7, 9 and 11. Scallops were evaluated based on the following criteria:

• Appearance
• Package odour
• Number of live & dead
• Drained weight of scallops
• Package atmosphere
• MAP processed product only

5.2 RESULTS AND DISCUSSION

5.2.1 Raw Material

The client supplied the live farmed bay scallops to CASD in two shipments, one shipment for phase 1 was received in October 2010, and a second shipment for phase 2 was received in January 2011. For each shipment the scallops were inspected upon receipt to determine if they were of acceptable quality, placed into chilled storage and MAP processed that day.

Prior to processing the scallops for the shelf-life evaluation, weak and dead animals were culled and the weight recorded. The remaining animals were then packaged in either the MAP or control format and placed in chilled storage.
                        
There was a significant difference in both the appearance and condition between the two shipments of live scallops; the scallops in the first shipment were moist, clean, and mostly free of settlement and showed clarity in the drained water in the pack. The second shipment appeared dry. The shells were dirty and full of spat settlement, and were sitting in dirty, brown coloured water. There was also evidence of a slight fecal odour when the box was first opened upon its arrival at MI. It is worthy to mention the level of spat settlement on the second shipment of scallops. The two shipments were visibly different in their condition with very little culling required on the first and quite substantial effort required on the second. The animals in the second shipment were much weaker and gaping. Anecdotal evidence coupled with the clients’ comments, suggests it is normal for scallops to be in a weakened condition during winter months.

5.2.2  Vacuum Setting Determination

Introducing MAP gases to a package can be completed by direct flushing with inert gases or through a process whereby the existing atmosphere is removed using a vacuum and the MAP gas is injected into the package then sealed. The latter process of using a vacuum and flushing process provides a more consistent result than flushing alone.

The MAP packaging system at the Marine Institute uses the vacuum & flushing process. When a package is processed using this system, the final appearance of the package is similar to that of a vacuum packaged product. In developing the process, the first step was to determine the maximum vacuum strength that would keep the shells closed but not crush them.

5.2.3  Gas Mixture Setting

The system used to package the scallops was the Multivac packaging system. This system produces a MAP product by initially drawing a vacuum. Once the vacuum is drawn the gas mixture is flushed into the package. This method of MAP processing utilizes a minimal volume of gas as compared to flushing only.

The MAP gas used in this project was comprised of a ratio of carbon dioxide, nitrogen and oxygen. To vary the ratios of each gas to obtain the desired mixture the Smith mixing valve was used. To achieve the correct ratio, the user determines the appropriate dial setting for each valve by referencing the desired gas mixture on a reference chart.

For each gas mixture, test samples of the scallops were produced to verify the accuracy of the dial settings. The packaged scallops were processed through the packaging cycle and tested for actual gas mixture percentages using the PBI Dansensor Checkpoint O2/CO2 Gas Analyzer. When the results were in the range of plus or minus 2% of the desired gases, the dial setting was recorded. If the gas mixture did not meet the % gas specifications, adjustments were made to either the flush time or dial setting on the mixing valve. Any adjustments were recorded for future processing.

5.2.4 Phase I: Determining the Gas Mixture

In this phase of the project three gas mixtures were evaluated to determine which mixture provide the most significant benefit to shelf-life extension for this product. The gas mixtures tested were:

• 80% O2-20% CO2
• 60% O2-40% CO2
• 70% N2-30% O2

For this test, 1 lb packages of scallops were processed and packaged in 6 mil poly bags. This product was MAP processed and labeled; noting the gas mixture in the package. The product was then placed in the chill room for the duration of the shelf life testing.

To evaluate the benefit of MAP processing on shelf-life extension, MAP scallops were compared to a control sample which consisted of scallops packaged using the current industry method. On sampling days, two packages of MAP scallops were removed and checked for appearance, tightness of bag and actual atmosphere. The package was then opened to check odour, appearance of scallops and released water, live/dead testing and final weights.

For the control sample, scallops were placed in a Styrofoam box in pre-weighed individual layers separated by soaker pads and gel packs. The weights of each layer were recorded and the boxes were closed and placed into the chill room at 2-4 OC. On sampling days, one layer from the Styrofoam box was removed. The control sample was weighed and evaluated for odour and the number of live and dead scallops.

Evaluation of the MAP processed scallops consisted of the following:

• Assessment of package appearance
• Testing of the gas atmosphere inside package
• PBI gas analyzer was used to test the gas environment
• Immediately after opening the package the odor of the product was evaluated
• Weight of free water in the package was recorded
• The number of live/dead and damaged scallops was determined

The 60% oxygen and 40% carbon dioxide mixture outperformed the other two gas mixtures yielding a shelf-life of 9-days in the 1 lb packages. The control sample had significant mortalities on day 7 of the shelf-life test. Thus, the shelf-life for this packaging method was determined to be 6 days. The complete shelf-life data tables are included in Appendix A.

5.2.5 Phase II: Pilot Scale Production of MAP Scallops

Based on the results obtained from phase I of this project it was determined that the 60% oxygen and 40% carbon dioxide gas mixture provided the most significant increase in the product shelf-life. This gas mixture was subsequently used in phase 2 for the pilot production run. The client established that an appropriate package size for the live MAP scallop product was 5 lbs, based on his knowledge of customer purchases.

For the pilot production run, the client was requested to send fresh, purged scallops to CASD. Upon receipt, the CASD technologist inspected and evaluated the scallops. The product was then packaged and MAP processed using the 60% oxygen and 40% carbon dioxide gas mixture.

The 1 lb packages of scallops were packaged such that the scallops were arranged in a single layer and all the animals were oriented with the cup side down. For the 5 lb packages, although a significantly larger bag was used, it was not possible to place the scallops in a single layer and have all al the animals properly oriented.

In addition to the packaging issues, the volume of free water in the 5 lb packages was significantly higher than what was seen in the 1 lb packages. The water, which was released by the scallops, was very cloudy in appearance and contributed to the fecal odour in the package. This free water may have contributed to the shorter than anticipated shelf-life obtained for this product.

The shelf-life for the control sample was estimated to be 3 days. The product was considered spoiled due to a strong fecal odour present in the package. In comparison, the MAP processed scallops had an estimated shelf-life of 5 days. The mortalities increased significantly on this sampling day and a strong fecal odour was present in the package. Although a distinct fecal odour was present in the package at day 3, upon rinsing the scallops with clean water the fecal odour disappeared. Therefore, it was determined that the fecal odour was a result of the free water which had accumulated in the package.

MAP processing has the potential to increase shelf-life of live shellfish by approximately 50% of the normal expected shelf-life. In this case, the MAP processing did increase the shelf-life of the live scallops by the expected duration. This is compared to what the shelf-life normally would have achieved without MAP processing (i.e. the control sample). Thus, in comparison to the control sample, which had a shelf-life of 3 days, the MAP processed scallops had a shelf-life of 5 days which is more than a 50% increase.

However, in comparison to the results achieved in the initial trial using 1 lb packages, the anticipated shelf-life of 9 days was not achieved in the 5 lb packages. The shorter shelf-life obtained in the 5 lbs packages was attributed to the condition of the scallops (i.e. second shipment of scallops received in January 2011) upon arrival at MI. When preparing live scallops for MAP processing, it is critical that consistent product quality and handling protocols be strictly adhered to.

5.3 CONCLUSIONS

It has been shown that MAP processing can provide an expected increase in shelf-life of 50% of the normal expected shelf-life. In the initial trail, the 60% oxygen and 40% carbon dioxide (European patent mixture) gas mixture provided the expected increase in shelf-life for the bay scallops. The other MAP gas mixtures tested also extended the shelf-life of the scallops, but only by approximately 17%.

In the pilot production run, the European patent mixture was used to MAP process 5 lb samples of scallops. As was shown in the initial trail, this mixture did provide the additional shelf-life extension. However, the shelf-life of both the MAP sample and the control sample were significantly shorter than the shelf-life obtained in the initial trial.

To obtain the maximum shelf-life extension it is critical that consistent product quality standards and handling protocols be adhered to. Handling protocols, such as purging process, packaging protocols, etc., must be developed and strictly followed.

5.4 RECOMMENDATIONS

Based on the results of this study the following recommendations are submitted for review and consideration.

Develop protocols for purging scallops prior to MAP processing
The scallops utilized in the pilot production run (i.e. second shipment) were assessed to be lower quality than the product received initially (i.e. first shipment). One of the key concerns was the amount of waste products in the water released by the scallops. The contaminant in the water significantly increases the bacterial load in the package (strong fecal odour) and can negatively impact the shelf-life of the live scallop.

Develop product quality criteria for product destined for MAP processing
To obtain the maximum shelf-life, the scallops packaged in the MAP environment should be assessed as the premium quality with respect to appearance, liveliness and condition. Developing a standard to assess product quality would ensure a consistent product quality and maximum shelf-life for this product.

Evaluate tray packaging versus poly bag for MAP Scallops
The packaging of large volumes of animals per package presents challenges with respect to factors that impact shelf-life. The larger poly bags used in the pilot production run resulted in the product being jumbled together and scallops being immersed in the waste water released by the scallops during storage. Using a tray can potentially reduce the adverse effects identified when producing the larger commercial package.

In this case, bags were used as neither the client nor MI was able to source a small number of the appropriate trays and film. Unfortunately, packaging suppliers require minimum order quantities and in this case, the cost of the MAP trays would have exceeded the project budget. Therefore, bags were used from the CASD’s store of packaging supplies.

Task 6
The economic feasibility of bay scallop culture

6. Introduction

A program built with the Excel program was developed to track the costs from the planting of bay scallop seed through two density sortings to the harvesting of the bay scallop for a farm-gate cost. The following assumptions were followed:

• Aquaculture operations would be performed by persons and /or companies that are actively fishing and have the necessary equipment and personnel at their disposal.  Accordingly, vessel and equipment costs are based upon the useful life of the assets and the percentage usage during the season.
• Interest is calculated on all costs to reflect the cost of deploying capital to the project.  The cost of new vexar bags and new cages are included in the interest calculations. Amortization amounts for existing equipment are used in the interest calculation to reflect the incidental usage.
• Density sorting accounts for stock over 5 and 12 mm that were replanted. Any stock smaller than these sizes were not considered.
• The final recovery at harvesting included all scallops over 55mm but did not include any smaller scallops recovered or recoverable.

6.1. Economic model

The calculations show the lowest farm gate cost for a 55-mm scallop is $0.15 for a density count of 200 on the bottom and for a density count of 150 in suspension. The difference between strategies in the farm-gate cost per scallop is however small and one should note that a fixed number of bay scallops (17) were used to estimate the farm-gate cost per lb. We do know that bay scallops reared at high densities tend to have lower whole weight and to be of lower quality. Input cells in the model can however be changed to reflect the likely lower number of bay scallops required to make one lb at the lower densities.

6.2. Section 3-Product type by source, volume and selling price

I performed an internet search and developed a listing of companies that appeared to produce, to process or to sell live bay scallops in the shell. Japan, China and South America seemed to be in the frozen market solely and market information was vague and generally not available. I decided not to proceed any further in these areas and concentrate on the closer markets due to product shelf- life concerns and freight costs.

Canada and the United States
I performed a web search of companies in the eastern USA and Canada and determined there were only a few participants. I reviewed the following company websites and contacted them:
Clearwater Seafoods:

Halifax N.S.- frozen product only from Chile

Pec-Nord Quebec: Minimum of 5Kg can be purchased - Cocktail 5-6cms 16-24 in a pound. No replies were received to emails and calls made.

Taylor Seafoods Mass: I received no information after various emails and a conversation. The website indicated in their marketing information a costed recipe for Scallops Monique showing a markup of 300% on 8 Taylor Bay Scallops in the shell. The cost for each scallop was listed as $.40 each.

Their website contained the names of 10 restaurants. We were able to enter 7 restaurants websites and looked for Bay scallops in the shell in the menus listed. There was no listing that clearly indicated live in the shell bay scallops.

Northern Wind Inc.Mass: No fresh bay scallops. Frozen product is purchased  from China and Peru.

Seatrade International Ltd. New Hampshire: Their company deals with sea scallops only.
www.farm-2-market.com/live-in-the-shell-bay-scallops: The product is sold for $20 a dozen (Feb 3, 2011)

Sayle’s Seafood Fish Market Nantucket Mass: Sells fresh Nantucket Bay Scallops for $13 a pound (Oct 22, 2010)

CTI Assessment prepared for Rhonda Dillon IRAP dated January 28, 2011
I reviewed this report which gave an overview of the market. There is little market information on live in the shell bay scallops. There are only a few players in this market space which appears to be driven by the upper tier restaurant industry. This is supported by the IRAP-NRC project paper “Market Assessment for Cultured Scallops” presented by Tim Jackson, NRC-ARAP Atlantic & Nunavut on February 4th 2011.

Conclusion
The market for live in the shell bay scallops is not well defined or established. Markets appear to have been established by producers within their local geographical area. Accordingly, market prices are not available except on a spot basis. Market acceptance and the development of market demand will be the next step in determining the volumes and prices that can be obtained. The project was ceased at this time.

General Conclusions

The commercial development of a new live product such as the bay scallop from seed production to the market is a long and complex process. Each species has strengths and weaknesses and the challenge is to address the various roadblocks which prevent their large-scale commercialisation. This project was useful in tackling several biological issues related to the bay scallop and provided results to improve the process of bringing this product to market. Some highlights of this project are:

• An improved field nursery technology and procedures will increase the inventory of large seed earlier in the season thereby translating into larger scallops in the fall – this provides a more valuable product to the grower and decreases the cost of production.
• An alternative technology for rearing bay scallops to market size – issues still need to be addressed but the proof-of-concept has been validated.
• Improved wet-holding technology and protocols provide the means to extend the marketing window for selling scallops during the winter months.
• A promising technology to ship large volume of whole live bay scallops to distant markets; in particular, the Aqualife system seemed well-suited to extend the short shelf-life of the bay scallop. The MAP technology has also been shown to improve the shelf-life of bay scallops by 50%.
• An economic model which suggests a reasonable production cost for the bay scallop in a new grow-out technology.

Bay scallop seed are produced in a shellfish hatchery in March, moved to the field site in early June and reach a market size > 55-mm by October 1. In addition to its fast growth rate, this product is of excellent quality and very attractive. Like most scallops however, the shelf-life for a whole live product is short, approximately 6 days, thereby imposing a severe constraint on the ability to move a large inventory to distant markets. A second constraint on the bay scallop is their inability to withstand temperatures <0oC. In this project, we have managed to substantially improve the wet-holding system and procedures for maintaining the bay scallop in storage – this has effectively increased the marketing window for this product by eight weeks. The successful trial of the bay scallops in the Aqualife technology suggests that it may be feasible to move a large inventory of bay scallops to distant markets. We are therefore confident that important commercial developments will be occurring within the bay scallop sector in the upcoming years as significant distribution lines are secured.