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Optimization of Hatchery-Nursery Practices for Production of Sea Scallop Spat in 10-m³ Tanks in Newport

Final Report
Fermes Marines du Québec Inc
AIMAP 2012-Q01

Summary

This project is the second phase of the AIMAP project submitted by Fermes Marines du Québec Inc. (FMQ) in 2011. FMQ's operations involve producing sea scallop spat in Gaspesie, using an innovative hatchery-nursery method consisting of 10- m³ tanks. The planned production steps correspond to scallop development stages: broodfish conditioning, spawning, larval and post-larval culture and transfer to the sea or sale, including the production of the different microalgae required for good growth and a good survival rate. As this is the first hatchery-nursery for sea scallop on this scale in Canada, the culture methods andsystems used will entail several elements that are totally new to the industry, such as 10-m³ tanks and an intermediate culturing area for settlement. These innovative processes will improve the competitiveness of the company, which is targeting an annual production of 25 million spat. FMQ also aims to stimulate the development of this culture and the introduction ofsea scallop spat marketing in Atlantic Canada, thereby increasing and stabilizing mariculturists' current supply. 

The project involves optimizing hatchery-nursery practices to improve survival rates, larval quality, bacterial reduction and profitability, while establishing reliable and reproducible protocols to promote the hiring of skilled labour in the region. To achieve these goals, two main activities were identified:

Activity 1: Performance optimization of the 10- m³ larval tanks

The objective of this activity was to successfully produce sea scallop larvae in 10-m³ culture tanks. Concretely, the objective of the activity was to achieve an excellent larval survival rate by determining the best culture densities for the various growth stages and establishing appropriate maintenance frequencies. Apart from visual observations of growth with a microscope, survival rate and food availability could be carried out in-situ. A cooperation agreement was concluded with Dr. Réjean Tremblay's laboratory at the Institut des sciences de la mer de Rimouski, Université du Québec (UQAR-ISMER) to validate and also transfer to FMQ the technique for monitoring larval triglyceride levels by simple observation with an epifluorescence microscope, which is used by some French oyster hatcheries. UQAR-ISMER's participation involved analyzing each batch of larvae by taking biochemical measurements of classes of lipids and fatty acid profiles to ensure that there was no essential fatty acid deficiency and to validate the microscope's coloration index with computer imaging analysis software at the hatchery.

Activity 2: Use of a settlement room and optimization of nursery equipment

The objectives of the activity were to assess settlement room performance and provide for a transition in culture operations for larvae ready to metamorphose. This stage generally takes place in the hatchery or nursery, and it involves problems for the culturing program since larvae are very sensitive during the settlement stage (high mortality during metamorphosis), and therefore an appropriate system is required (mechanical filtration, UV sterilization recommended, etc.). Once post-larval metamorphosis is terminated, we observe better larval survival because the larvae are much less sensitive when they reach their adult morphology. By adding a settlement room, we can therefore enable the post-larvae to complete the metamorphosis stage without the need to encumber the nursery with an elaborate filtration and sterilization system. An additional advantage of this technique is that it frees up the hatchery area to receive new larvae. The second objective of the activity was to assess nursery performance by testing new culture structures (plastic cages) created by FMQ, as compared to traditional collectors. These structures are immersed in the settlement room tanks and serve as a settlement substrate for metamorphosing larvae. Culture performance was evaluated after the cages had been moved to the nursery, where the post-larvae spend a few months until they reach a size of 7 mm.

Outcomes: During the course of our AIMAP project, which aimed to improve hatchery practices in 10-m³ tanks, changes were made several times. Outcomes of the first two spawnings were much poorer than we had anticipated. As a result, the company reassessed some procedures requiring the physical handling of the larvae. We quickly realized that the switch from 1-m³ tanks that were 3′ high to 10-m³ tanks with a height of 10′ had an unplanned and unexpected impact on larval velum (a scallop larva's swimming system), which was damaged and even disintegrated during handling because of the drop.

To resolve this problem, FMQ adopted a new method for collecting the larvae during the third spawning by changing the type of collection sieve and using flexible piping with a smaller diameter to siphon them up so that they would be ejected more slowly. Although this seems to have somewhat reduced the physical shock to the larvae during collection, results were still not up to par. FMQ therefore set about creating a multilevel collection sieve support system to reduce to the maximum the shock to the larvae when they were caught in the sieve and so protect their velum. Although results with this system seemed to be good for the fourth and fifth spawnings of the season, they were mixed because of the small quantity of roe collected. FMQ had not planned for so many spawnings and lacked broodfish so late in the year (at the end of the fall). Broodfish kept in a tank and derived from the fishery (i.e., wild broodfish) were used for the second spawning (hatchery broodfish and broodfish from the natural environment had already spawned during the season) and roe quality seemed to be mediocre (low survival rate at day 4). 

A human resources position not originally budgeted for was created so that physical alterations could be made to the system and new larval collection equipment developed. Spawning took place at the beginning of the 2013 season and a comparative analysis of motricity and visual appearance was carried out to determine which larval collection method produced the best outcomes. The multilevel system, together with collection through the tank drain, had no impact on the larvae. They were still intact when collected and started swimming again a few minutes after being removed from the collection sieve. With this system, ascendant larvae rose to the surface, after which the water level in the sieve decreased by a few centimetres. All the other siphoning systems had a negative impact on the larval survival rate. Furthermore, the multilevel collection system using the drain reduced the amount of handling and the risk of cross contamination. We have used this method since the beginning of the 2013 season and production outcomes in terms of both growth and survival have greatly improved.

Because of the small number of viable larvae throughout the season, we were unable to carry out the portion of the project involving UQAR – which was carried out during the 2013 season – because, although we had acquired the equipment needed for this purpose, we would have been forced to sacrifice too large a percentage of the viable larvae to conduct the project, which would have made it impossible to interpret the test results. We entered into a second agreement in this regard with Dr. Réjean Tremblay of UQAR-ISMER in the winter of 2013.

Our biologist became pregnant during the course of the project, and the CSST deemed the environment in which the larvae were cultured to be detrimental to her so she had to go on maternal health risk leave of absence. Given the nature of the monitoring required during the fourth and fifth spawnings, FMQ chose to replace its biologist by an aquaculture technician in order to increase the frequency of larval monitoring. In short, throughout the course of the project, we were able to increase the quantity of larvae produced, but the company must improve several aspects concerning the hatcheries and the handling of the mounting brackets, as well as obtaining more statistics on the performance of the various collectors used in the nursery.

1.0 Introduction

Most Quebec scallop currently marketed is derived from the fishery although the resource is not very abundant as it has been overfished in the past. With fishery management, wild stocks stabilized at the end of the 1990s and the beginning of the 2000s but, due to the fragility of the native populations, they never became abundant enough to meet demand, beyond local demand. The establishment of a hatchery-nursery mainly makes it possible to meet the increasing demand of the mariculture industry in Quebec and, eventually, in Atlantic Canada, where supply is insufficient to develop the market despite strong demand. Scallop is a species of shellfish that consumers crave, on both the Canadian and international markets, and selling prices are good. In view of this, aquaculture is a way to ensure species sustainability and market development.

The only supply of scallop spat hitherto available in Quebec for culturing and sale on the markets has been collected naturally. This is one of the main reasons why the shellfish industry has developed slowly in Quebec and Canada. Because of the considerable year-to-year fluctuations in natural collection volumes, dependence on natural collection has not resulted in a very reliable supply for the industry, and this instability is a disadvantage to producers. This situation directly impacts the growth of the sea scallop culturing business, which has never been able to realize its full potential.

FMQ aims to produce as many as 25 million spat annually in its hatchery-nursery, which will result in a good balance between supply and demand for Quebec scallop in the province. The implementation of innovative procedures will lead to the development of new companies that grow out scallop, thus enabling Quebec and Canada to positionEastern Canada as a responsible and sustainable producer of farmed scallop.

What is innovative about this project is the choice of culture equipment and systems for the hatchery-nursery for sea scallop (Placopecten magellancius) in Canada. Several of the procedures and techniques we have implemented have never been used in Canada's shellfish hatcheries for any species. Concretely, the system involves the use of 10-m³ tanks and a settlement room to optimize individual growth and survival rates. It should also be pointed out that production of the food (phytoplankton) consumed by the scallop will also be designed on the basis of innovative sixth-generation procedures (technology imported from England), which will maximize both quality and density of the different microalgal cultures required, thus reflecting the company's strengthened determination to improve its environmental performance. 

The company hired an experienced biologist to incorporate the procedures and operations that have proved their worth for scallop culture in the leading European and Asian countries in this field, as well as the latest scallop hatchery advances developed by Dr. Réjean Tremblay and Dr. René Robert. It is, however, understood that adjustments to local conditions will be needed; these techniques have been closely monitored and tested to assess and improve culture performance.

The project's objectives are in accordance with AIMAP priorities and fit in perfectly with the themes of Sustainable Production, Green Technology and Diversification. These themes are described in detail in the following paragraphs. 

1.1 Sustainable production: Improvement in the quality and supply of progeny

Broodfish are selected for their rapid growth and good health. To ensure genetic variability, broodfish were collected by means of the traditional method. They will be added to existing stocks, thus preserving the genetics of native scallop in the area where they are lowered into the water, facilitating their survival when cultured and promoting genetic diversity in the natural environment.

Furthermore, the development and implementation of culture protocols based on advanced technologies for larval reproduction and survival enables us to increase productivity and means that the company will be able to apply the knowledge developed to othershellfish species covered by its aquaculture licence. Production capacity based on this innovative methodology is sufficient to provide a reliable and stable supply to any company wishing to enter the culture field.

1.2 Green technologies:

This ecological awareness is fundamental to FMQ and has led to the acquisition of a number of energy-efficient construction procedures, that is:

  1. The hatchery has a passive solar wall so that building air is preheated.
  2. A geothermal system has been incorporated to heat the process water.
  3. An impressive plate heat exchanger system has been installed to recover energy from the process water.
  4. And, finally, an automated system to manage the water supply and the entire system reduces energy loss during all the procedures and permits ongoing monitoring of production parameters.

1.3 Diversification – East Coast

Sea scallop culture is nevertheless still underexploited in relation to the production capacity of the Maritime Provinces. Observation of scallop aquaculture production volumes makes it obvious that production of this species is clearly below potential environmental capacity.

A bio-economic analysis of aquaculture production of sea scallop showed that the main constraint on this industry in Atlantic Canada is the fact that no reliable annual supply of large volumes of spat is available at reasonable commercial prices. FMQ is therefore targeting a species of undisputed potential in terms of the marketing of both spat and market-ready scallop. It should also be pointed out that scallop was selected by the 2011-2015 National Aquaculture Strategic Action Plan Initiative (NASAPI) as a diversifying species. 

1.4 Commercial justification and project impact

1.4.1 Technological context

It is undeniable that the project as a whole is based on existing knowledge acquired from three years of work performed at the experimental hatchery and by different companies that culture scallop (for example, Pec-Nord Inc.) in Canada and elsewhere. However, there are still some weaknesses, which must be overcome to ensure adjustment to the specific requirements of sea scallop and to local environmental conditions. These weaknesses, which are technical as well as scientific, will be overcome through the work done by the project biologist and technicians. Solving these shortcomings will increase culture performance and enable us to identify clear specific methodology that is reproducible from year to year. By these means, the company's productivity will increase and it will then be able to provide mariculturists with a stable supply of spat, which will trigger more rapid growth in the scallop industry in the Atlantic maritime regions.

1.4.2 Equipment for large volumes – 10-m³ tanks

Canadian shellfish hatcheries usually choose their culture equipment based on price although they also replicate the equipment used for scientific research, to remain in familiar territory. As a result, Canadian hatchery tanks for sea scallop are mostly small, with a maximum capacity of 1 m³, even though research has never shown this type of tank to be effective. When FMQ staff members travelled to Norway and visited the Scalpro scallop hatchery at the Marine Research Institute (translation of the Norwegian term Havforskninginstituttet), they found that it had much better scallop larval growth and survival rates than those obtained in Canada. The Scalpro director confirmed that these excellent survival and growth rates were directly related to the choice of tanks, which had a capacity of 3.5, 5 and 8 m³ in the experimental system. The director also indicated during a discussion of the matter that it would be best to increase the capacity of the Institute's larval tanks. He strongly suggested using 10-m³ tanks to improve the condition of cultured larvae. Furthermore, during a similar discussion with the director of the scallop hatchery in Tinduff, France, René Robert confirmed the Norwegian director's comment.

These statements corroborate information published by the FAO: Installation and operation of a modular bivalve hatchery: “In general, the larger the tank the better; it is preferable to minimize the surface area to water volume ratio as surfaces tend to have higher numbers of bacteria.” (FAO, 2007). Another necessary consideration is that a higher capacity provides a more stable environment for all the key parameters in larval development (i.e., temperature, salinity, feed ratio and culture density). 

1.4.3 Use of settlement rooms and nurseries

Natural collection involves immersing collectors in the sea when scallop larvae become benthic and try to settle to a substrate to attain their adult morphology. This technique for obtaining a supply is laborious and costly. It is also of rather chancy reliability because Canadian research has shown year-to-year fluctuations in numbers of young scallop collected. An industry with a fixed and stable supply cannot be founded on this operating model. Furthermore, with natural collection it is very difficult to move organisms between Canadian regions or provinces because invasive species might be transferred. This constraint prevents a supply of scallop spat from reaching the market, a situation the company has experienced directly a few times during the last few years.

The second approach used – the one advocated by FMQ – is the use of a hatchery in which adult scallop spawn in land-based facilities and in which the resulting larvae are cultured. However, in most current Canadian hatcheries only scallop in the larval growth stage are cultured, following which the steps involved in natural collection are followed, that is, the collectors are immersed in the tanks when the larvae are ready to settle in the hatchery, and they are transferred to the sea to continue growing in their natural environment.

This method is very expensive and this recurrent expense could be avoided. It also considerably reduces a company's productivity because organism growth in the sea and the survival rate are much poorer than in land-based facilities since, on land, it is possible to control culture parameters.

In Norway, use of a land-based nursery and a settlement room (i.e., an intermediate stage between a hatchery and a nursery) boosted culture productivity and profitability. The modular culture system created by the addition of this area is less time-consuming and produces more larvae due to the succession of spawnings. The effectiveness of a nursery has been demonstrated several times in European and Asian countries that are world-wide leaders in the production of young scallop. A Quebec company on the Lower North Shore has tried to simulate a nursery by installing outdoor tanks. The results have been very promising but not optimal because the nursery, being outdoors, was exposed to temperature fluctuations. The use of settlement rooms and indoor nurseries represents an innovation for supplying the market with young scallop ready to be transferred to the sea and grown out.

1.4.4 Culture densities, concentration of food in the tanks, feeding frequency, expected general survival and growth

In an industry that uses an animal resource for production purposes, all the issues envisioned require technical and scientific calibration. Any research to increase the performance of an aquaculture company aims to improve culture conditions because anticipated success is directly measured in terms of excellent organism survival and growth rates.

This is why commercial operations will focus on optimizing culture conditions in order to maximize survival and growth. The scientific weaknesses to be overcome pertain directly to the use of 10-m³ tanks, settlement rooms and nurseries. The broodfish conditioning, spawning and larval culture stages must also be monitored by the work team by adapting the scientific literature to local conditions. The greatest effort will therefore focus on larval settlement and scallop's post-larval stage. 

The biologist's work will include culture densities, feeding frequency and food concentration in the tanks so that he can create optimal and reproducible culture conditions. The basic parameters required for success involve determination of organism density in the culture area and feeding.

Another very important parameter is a biochemical one, larval lipid content. The importance of lipid content and, specifically, polyunsaturated fatty acid (PUFA) percentage is widely stressed in the literature. Recent work on sea scallop suggests that larvae must accumulate more than 20 ng of triglycerides per larva by day 20 in order for metamorphosis to occur.

Other physicochemical and microbiological parameters concerning water quality must also be monitored (presence of Vibrio parahaemolyticus, temperature, tank water renewal frequency, oxygenation and frequency and method for sorting the larvae and post-larvae). Some tests have been contracted out to the UQAR-ISMER laboratory under the supervision of Réjean Tremblay so that we can obtain data that cannot be observed in situ.

2.0 Methodology

2.1 Activity 1: Optimization of 10-m³ larval tank performance

Activity objective:

To ensure successful production of sea scallop larvae in 10-m³ culture tanks. Concretely, the objective of the activity is to ensure an excellent larval survival rate by determining the best culture densities for the various growth stages and establishing adequate maintenance frequencies.

Several factors were observed for purposes of monitoring the larvae:

Daily:

Every 2 days:

2.1.1 Culture program:

We performed several comparative tests, changing the times for draining and disinfecting the tanks, that is, doing this every 2, 3 or 4 days. For the company, minimizing the number of larval tank water changes decreases operations requiring labour. It also cuts water consumption and hence heating, filtration and pumping since a large quantity of water is required every time a tank is drained. Our tests in this regard were not very conclusive and they will have to be redone because we obtained the best results with the tanks that were maintained least frequently. However, we can also see a correlation between these results and the results of observations of larval motricity and survival rates following tank water changes. The results throughout the first culture year were far poorerthan those we had previously obtained with 1-m³ tanks. Monitoring prior to and after tank water changes revealed that our siphoning method destroyed larval velum, the system that enables them to swim, filter and feed during their first few stages. The result was a dietary deficiency and most of the larvae died once their food reserves had been depleted. However, larvae that had been handled the least grew normally. Yet we also observed more contaminants in these tanks and an abnormally high mortality rate as the cycle progressed. Tests showed that vibrio sp. was much more common in the infrequently maintained tanks (maintenance every 4 days) than in those that were maintained every 2 days.

2.1.2 Handling of larvae:

Outcomes of the first two spawnings were much poorer than we had anticipated. As a result, the company reassessed some procedures requiring the physical handling of the larvae. We quickly realized that the switch from 1-m³ tanks that were 3′ high to 10-m³ tanks with a height of 10′ had an unplanned and unexpected impact, as previously discussed, on larval velum, which was damaged and even disintegrated during handling because of the drop.

To solve this problem, FMQ adopted a new method for collecting larvae during the third spawning by changing the type of collection sieve and using flexible piping with a smaller diameter to siphon them up so that they would be ejected more slowly. Although this seems to have somewhat reduced the physical shock to the larvae during collection, results were still not up to par.

FMQ then set about creating a multilevel collection sieve support system to reduce to the maximum the shock to the larvae when they were caught in the sieve and so protect their velum. Different modules can be added or removed, depending on the height of the water in the tank. The difference in the water level in the sieve and the tank can always remain slight. Furthermore, since the method involves a sieve supply line connected to the tank drain instead of a siphon system, all the handling required to start siphoning can be avoided, as can any possible contamination. Although results with this system seemed to be good for the fourth and fifth spawnings of the season as far as velum was concerned, they were mixed because of the small quantity of roe collected. FMQ had not planned for so many spawnings and lacked broodfish so late in the year (at the end of the fall). It was therefore decided to repeat the tests in the 2013 season. During this season, the system proved superior in terms of both ease of operations and quality of the larvae collected, as their velum was no longer damaged.

2.1.3 Larval lipid monitoring:

Development of a hatchery-nursery such as FMQ's ensures a more regular supply of spat for the Quebec shellfish industry. However, production of scallop larvae in a hatchery is still a very problematic procedure as larvae of this family of shellfish are very sensitive to the quality of their environment and the food they get, much more so than ostreidae larvae, for example. This is why it is helpful to develop tools to optimize production by real-time monitoring of larval development. And this is the procedure we are developing through our work calibrating a colorimetric index, which indicates larval triglyceride levels through simple observation with an epifluorescence microscope.

It should be pointed out that the main energy reserve of sea scallop larvae consists of lipids, as is the case with the vast majority of bivalves. Furthermore, roe lipid content has been found to be related to the percentage of D larvae and the number of abnormal larvae that hatch. Larval survival for the first 10 to 15 days thus depends on roe quality, which can then affect the number that reach metamorphosis, the critical phase in larval development. The importance of lipid content and, specifically, polyunsaturated fatty acid (PUFA) percentage is widely stressed in the literature. There are different classes of lipids, reserve lipids such as triglycerides and lipids in the membrane structure, such as phospholipids and sterols. Recent work on sea scallop suggests that larvae must accumulate more than 20 ng of triglycerides per larva by day 20 in order for metamorphosis to occur. But how can we be sure that the larvae meet this criterion without performing tedious biochemical tests? A simple fluorescence-based triglyceride assay has been validated recently in oyster larvae (Crassostrea gigas). If the triglycerides are stained, percent cover in the larvae can be estimated by analyzing the microscope image. In this way triglyceride concentration can be estimated in just a few hours. This work has demonstrated a direct linear relationship in oysters between this staining method and chromatographic assays. Preliminary work on a closely related species, Pecten maximus,encourages us to develop this technique for Placopecten magellanicus.

During the 2012 season, although FMQ had acquired all the necessary equipment to carry out in situ tests and although there was an agreement with UQAR-ISMER, lipids were not monitored. There were two reasons for this: first, it was impossible to order the equipment before the project started, which would have made it eligible for funding and, given the delivery times, we received and set up most of the equipment in time for the fourth spawning. As already mentioned, the very small quantity of roe produced in the 2012 season during the fourth and fifth spawnings prevented the company from collecting enough larvae for testing purposes without seriously impacting the other parameters and the company's business operations. The company therefore decided to carry out the experiments involving UQAR-ISMER in the 2013 season, using a good-quality batch so that all the necessary tests and the post-metamorphosis monitoring could be performed. During the 2013 season, samples of different batches of larvae, collected on days 2, 6, 11, 20 and 30, were monitored and tested. In this way we will be able to verify whether, as in the case of Crassostrea gigas, there is a direct relationship between the fluorescence percentage in the larvae and triglyceride levels detected by the biochemical tests.

The colorimetric index corresponds to the ratio of lipid surface area stained with Nile red to a larva's total surface area. The test method is fairly simple compared to biochemical tests. To obtain good estimates, 50 to 100 larvae in each sample have to be stained. It is essential to use fasting larvae so that algae ingested do not interfere with the fluorescence measurements. Nile red staining is simple and fast. The Nile red stain and the larvae merely have to be placed together for 90 minutes, then rinsed and the stain fixed with formol. The effect lasts for up to four hours. When a green filter is used (450-490 nm of excitation and emission of 515-565), together with an epifluorescence device, lipid droplets contained in the larvae fluoresce. Analysis of the image shows the lipid droplet area in relation to total larval area. These percent cover results can be directly compared to the triglyceride levels found on biochemical testing.

For the moment, we only have the preliminary results of the colorimetric testing of the larvae. FMQ tests the batches on an ongoing basis whereas the biochemical tests will only be performed when all the culturing has been completed, in July and August. The real lipid level results compared to the quantity of spat ready to be transferred to the sea will only be known in February 2014, once all the laboratory tests have been performed, compiled and analyzed. Even so, the visual and non-scientific observations have shown that the batches with the most staining seem to produce the best results.

2.1.4 Monitoring of feed rations:

We purchased a Coulter cell counter for phase 1 of the AIMAP project to monitor phytoplankton production, a measurement that comes under “procedure optimization and verification.” As expected, with this apparatus we could evaluate the production capacity of the phytoplankton area, establish accurate feed rations for the larvae and post-larvae and monitor the consumption of the organisms in the tank in order to optimize culture procedures.

2.1.4.1 Production capacity of the phytoplankton area

As the production system in the phytoplankton area enables ongoing harvesting, it is important to be familiar with the cell densities of each species cultured in order to establish the basic feed rations to be provided to the organisms, since these densities vary regularly. Samples were collected from each phytoplankton harvesting tank every day and cell density analyzed with the apparatus. These were the data used for the daily assessment of the quantity of food given to the young scallop.

2.1.4.2 Establishing feed rations

The Coulter counter enabled us to establish accurate feed rations, based on phytoplankton cell concentration. The rations, which are expensive to produce, enable the larvae to develop well and build up good energy reserves. It is important that the larvae not be underfed. But they must also not be overfed because surplus food in the culture tanks causes contamination and also increases production costs. A ration can be based on cell concentration rather than phytoplankton on culture medium volume simply by knowing the cell density in the harvesting tanks and the desired cell density in the culture tanks. If the Coulter counter had not been used, feed rations would have been determined by phytoplankton volume alone, which would have decreased the degree of accuracy. For example, for a 30-litre ration of food, cell density is 2 cells per ml and the total number of cells in the ration will be 60,000. However, with a density of 6 cells per ml, there will be a total of 180,000 cells in the 30-litre ration. It is therefore clear that, if the ration for a tank of larvae had been based on volume alone, and 30 litres of phytoplankton had been provided every day without cell density being known, it would have been impossible to know with any accuracy whether the quantity of food each batch received was the same in order to rule out this variable when studying the other parameters (temperature, larval density, method for collecting the larvae). With the Coulter counter, phytoplankton volumes distributed to the larvae varied from day to day so that the larvae and post-larvae always received the same number of cells.

2.1.4.3 Monitoring consumption of the organisms in the tank

Still with the aim of optimizing culture procedures, phytoplankton consumption was monitored with the Coulter counter. To begin with, daily monitoring was performed to determine how long it took for the organisms to consume a given ration. Feeding frequency was established on the basis of the data obtained so that food was provided in the tanks of larvae and post-larvae every day at the same times. A sample of water was then collected from each tank before each feeding to determine the remaining number of phytoplankton cells. By knowing the cell density in the harvesting tanks in the phytoplankton culture area and the desired rations, the right quantity of food could then be added, depending on the needs of each tank.

2.1.4.4 Advantage: less time-consuming procedure and more accurate data

Spawning occurred at various times during the year, making it possible to try out different feed rations made up of different species of phytoplankton. These tests could be done quickly and accurately thanks to the Coulter counter, and this method was less time-consuming than the traditional method of counting cells, in which an individual counts each sample, using a microscope. For example, it can take up to 15 minutes to count a sample manually whereas the Coulter counter can analyze the sample completely in only two minutes. While manual counting only provides an approximate cell count, the Coulter counter not only gives us an exact cell count, but can also provide various helpful data, such as frequencies of phytoplankton cell sizes, which enable us to estimate whether or not the larvae can ingest the food they are given.

2.1.4.5 Main difficulties:

While phytoplankton cells can be counted very easily with the Coulter counter, the device itself is difficult to calibrate. The main problem arising during the activity entailed assembling the apparatus, which is supplied in separate pieces, and calibrating it. A representative of the manufacturer generally comes to install a Coulter counter after it is received by the company. However, the supplier's head office was too distant from the hatchery and the apparatus was set up with telephone support only. After much trial and error and many calls, the Coulter counter was ready and testing could begin.

2.2 Activity 2: Use of a settlement room and optimization of nursery equipment

No results can be presented at the moment for this phase of the project because the results for the 2012 season detected no difference between the structures, and the low volumes produced in the hatchery portion made it impossible to manage large numbers of collectors and thereby improve the means of handling them. Budgets for this portion were instead earmarked to improve the handling of the larvae, as described in section 2.1.1, and to alter the building's automation features, enabling us to optimize hatchery system productivity (Being the first part of the culture cycle, hatchery operations have to be perfectly under control before settlement room and nursery operations start). More work will be done on this activity in the 2014 season. During the 2013 season, FMQ again focused on increasing hatchery performance, which resulted in a clear increase in the number of larvae metamorphosing.

3.0 Conclusion

Much work remains to be done! However, with these encouraging outcomes and with the monitoring equipment, we can constantly improve our technique for producing sea scallop spat. The gradual but ongoing improvement in our production and success rate are indicative of this project's major positive impact on FMQ and show that the results will have an important incidental effect of increasing medium- and long-term scallop production in Quebec and also in Eastern Canada. There are so many variables: mechanical variables involving the facilities, physicochemical factors involving the water, biological factors involving the broodfish and their health, roe quality and genetics that it is very difficult, with a project of this scale, to determine causes and effects in relation to one single variable. However, the culture program, monitoring protocols, tools and the monitoring we have put in place and/or modified thanks to this project, certainly allow FMQ to position itself for success, which would have been difficult without the contribution of Fisheries and Oceans Canada to the project.

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