The Development and Assessment of Optimized Land-Based Tank Farming of Atlantic Halibut in Canada

Canaqua Seafoods Ltd

Table of contents

• Executive Summary
• Introduction
• Methods
• Infrastructure Upgrades
• Grading Procedures
• Results and Discussion
• Infrastructure Upgrades
• Grading Procedures
• Conclusions

Executive Summary

Over the next few years, Canaqua Seafoods Limited will improve production efficiencies of Atlantic halibut aquaculture through the incorporation of innovative management tools and rearing facilities into their existing land based grow out farm in Advocate Harbour, Nova Scotia.  This initial phase of the project focused on enabling Canaqua Seafoods Limited to mechanically grade their halibut. This required infrastructure upgrades and installations. These were successfully completed; and the large halibut on the farm were graded and populations were monitored for several months post grading in order to assess the effect of size grading on performance. The set up for grading small halibut was also initiated.

Grading had the clear and desired effect of reducing variation. Reduced population size variation increases feeding through the diminution of feeding hierarchies; and it improves fish stock management by improving accuracy of biomass and mean fish size estimations. It aids the determination of feed rations, the allocation of optimum feed size and the monitoring of fish performance and health. Soon after the fish were graded, growth rates seemed to increase with steady improvement through the winter months. There was a real reduction in time and effort required to grade the halibut when compared to the earlier manual grade techniques which likely would not even have been feasible at this stage of production.

Introduction

Research on halibut culture was initiated more than 20 years ago in Canada. Hatchery production, the original bottleneck to its commercial realization has become standardized in Canada resulting in consistent production of juveniles recognized internationally for their quality. Canada is also home to a superior broodstock development program that utilizes the latest in selective breeding technology. Despite these efforts and their obvious successes, aquaculture of Atlantic halibut remains fixed in a pre-commercial stage. This contrasts halibut production in Norway which continues to expand with nearly 1500 metric tonnes being harvested in 2007.

Atlantic halibut tolerate intensive land based grow out well. But advancements in production efficiencies will improve financial returns for this species which already has a tremendous recognized market potential.

Canaqua Seafoods Limited is a private Nova Scotia company, which was incorporated in April 2006 and commenced operations in September 2006. The business represents the next phase of growth for land based farming of Atlantic Halibut in Nova Scotia. Its goals are to develop world-class aquaculture facilities in Nova Scotia and produce Atlantic halibut for the North American market. The company is located in Advocate Harbour, Nova Scotia, Canada, on a 50 acre approved aquaculture variance site. Canaqua Seafoods Limited represents a unique opportunity for aquaculture in Nova Scotia. Its water sources include both seawater and fresh water wells. Such water sources allow the provision of pathogen free water to the site. The sea water wells also provide pristine quality water which is thermally stable thereby reducing the need for high energy chilling as is required for most land based sites.

This project is part of a proposed multi-year comprehensive study that will address a chief constraint of the halibut industry by focusing on improving production efficiencies through the incorporation of innovative management tools and rearing facilities. It will eventually include the installation of a modern, low cost, low energy water re-use system.

This report details an initial phase of this study. Limitations to funding allowed only one critical aspect of halibut production to be examined, namely the grading of halibut for improved production. As stated in Annexe A of the contribution agreement signed July 17, 2009: “The contributions from AIMAP will cover only the purchase of equipment designed to facilitate the innovative halibut grading system, tankhouse covers and related infrastructure .… An additional application to AIMAP is planned for fall 2009 to complete the full 16 tank system…”. It is notable that the building of the rearing tank system will be required in order to meet all deliverables of the project particularly: the demonstration of land-based halibut farming in an innovative, low cost, low energy water re-use system, an analysis of the inputs and outputs of the operation and how they relate to environmental impact/performance, identification of the optimal rearing conditions for halibut in recirculation systems, including water quality parameters, analysis of power usage for pumping and heating, analysis of feed inputs and characteristics and volume of effluent.

In a land-based, halibut grow-out facility, energy (to pump water) and feed costs are major components of the total cost of production. Both can be lowered if growth rate is optimized.  Energy costs are reduced because fish reach marketable size in a shorter period of time.  Optimized growth rates occur when available feed is utilized efficiently by all individuals in the population. Faster growing populations tend to have lower feed conversion ratios (FCR’s). Reduced costs lead to increased profitability – the yardstick of success in any commercial venture. Failure to optimize growth rate may be the ultimate difference between profitability and insolvency.

The growth rate of fish in a tank is most often determined by either bulk sampling (more common) or individual sampling (less common) for weight over some fixed time interval (e.g. monthly). Both methods will yield estimates of average size at each interval and changes in mean size between intervals. Only the latter can be used to estimate changes in population variability. Best husbandry practice dictates that feed size should increase in direct proportion to increased fish size.

When there is wide variation for size among the fish within in a tank, feeding hierarchies develop rapidly. Larger, dominant fish eat first and will consume the bulk of the feed. Smaller, subordinate fish must wait until the larger fish are sated before they even get a chance to feed. Many don’t get enough feed. The bigger fish grow at a faster rate than the smaller fish and variation increases. Increasing feed size as a response to average size in ungraded or poorly graded populations may result in feed that is too large to be eaten by smaller fish. This will only exacerbate an already bad situation. The halibut at CanAqua Seafoods Ltd. had reached this stage.

Previously, grading for size at CanAqua Seafoods Ltd. was done manually. Halibut were netted by hand to a grading table as it is not practical to move large halibut using existing fish pump technology. Individuals were sorted by eye and different size grades were then directed down appropriate chutes or flumes to the grow-out tanks. The fish flowed from the grading table, through the flumes and into the various tanks by gravity. The process was subjective, relatively slow and involved more than desirable handling of the fish. The results were noticeable; but stress levels for both the fish and personnel were unacceptably high.

Mechanical graders designed for flatfish are available. Mechanical graders eliminate subjectivity and are much gentler – thereby reducing the handling stress of grading. Successful application of a mechanical grader should improve production efficiencies. Grading for size is a proven and important husbandry tool that helps to optimize growth rates. When all fish in a tank are of a similar size, all fish have an equal opportunity to feed. Grading for size helps to retard the development of feeding hierarchies. This leads to more efficient feed utilization and faster growth rates.

This study introduced a mechanical grading system for halibut to an existing halibut rearing facility in order to improve grading efficiency and ultimately improve fish performance.

Methods

In order to use a mechanical grader, it was necessary to make a number of changes in the CanAqua Seafoods infrastructure.

Infrastructure Upgrades

1. Construction of two new tanks measuring 15.25m in diameter by 1.8m deep (50 ft by 6 ft) designed specifically for grading, hereinafter referred to as grading tanks. The grading tanks installation required lengthening of existing freshwater and saltwater supply lines, and establishing effluent connections with existing effluent system.
   
   Innovations in the design and construction of the grading tanks included:

• A new water level control system that directs effluent through a valve “ladder” with valves controlling water depth at specific levels.
  
  
• Improved tank access
  Modified service (feeding) bridges in each tank were engineered to include supports by wooden trusses with a 6.7m span (25 ft) from the tank rim to a centre support structure. A slightly larger raised porch allows servicing of both tanks from a single structure. The existing production tanks have one porch per tank.
  
  
• Modified tank design.
  The grading tanks are wider and shallower than previously used production tanks to improve fish access.
  
  
• Water supply improvements
  Additional water supply was required to service the new tanks. This was met by upgrading salt water wells to improve their pumping reliability. The installation of corrosion-resistant, threaded PVC casings mated to threaded stainless steel wellscreens were anticipated to reduce corrosion problems that were causing serious water supply problems. The original well construction used untreated steel casings and wellscreens held in place by friction. Over time, corrosion through the casing and/or the accidental displacement of the wellscreens allowed sand and gravel to infiltrate the wells. The result was premature wearing and breakdown in the submersible pumps and motors and the obstruction of water flow through distribution plates in the de-gassing structures. Back-up pumps and motors were also supplied in order to provide water service to the new tanks and grading equipment. The forks on the fork lift were upgraded to include a rotator to improve mobility of graded fish.
  
  
• Oxygen supply improvements
  Oxygen supply to the tanks was to be provided with a highly efficient oxygen generator system (AirSep Model AS-J500 Series PSA Oxygen Generator and Kaiser Air Screw Compressor)
  
  Additional upgrades to the facility associated with grading smaller fish included:
  
  
• VAKI mechanical live fish grader complete with Heathrow fish pump.

Grading Procedures

After completing the infrastructure upgrades a mechanical grader (Melbu Tech, Large Flatfish Grader) was set up adjacent to one of the grading tanks. The grader yields three grades and was adjusted to the following tolerances:

• The small grade included halibut weighing less than one kilogram.
• The medium grade included halibut weighing between one and two kilograms.
• The large grade included halibut weighing more than two kilograms.

Typically, all production tanks on the farm are in use. To create space to receive the three grades, the next step was to transfer all of the halibut from three tanks into a grading tank. This completed the set-up for the actual grading operation.

Prior to grading, the water level in the grading tank was lowered to a workable level. There were four or more people in the tank using dip-nets to manually transfer halibut from the tank to the grader. There were two people ensuring that the fish moved freely over the grader belt. There were three people counting graded fish as they emerged from each grade chute and dropped into the various water-filled, insulated boxes. One person was assigned to move and dump graded fish to the production tanks and bring boxes of water back to the grader. One person continually filled empty boxes with water. The grading operation was interrupted whenever a box had to be moved and when more fish were added to the grading tank.

Following the infrastructure upgrades and the initial set up, there were very few mechanical problems to deal with. As a result, one full grading cycle of Canaqua’s total halibut fish population (n=35,000 fish) was completed.

Results and Discussion

Infrastructure Upgrades

The infrastructure upgrades represent significant advancements over the previous systems:

• Valve ladder
  This system is an important improvement over the stand-pipe technology utilized in the production tanks. Tanks can be drained completely only by opening the bottom valve. While more costly to install than a stand-pipe, the valve ladder eliminates the possibility of a catastrophic loss that can occur if a stand-pipe becomes unseated or is left out too long due to human error.
  
  
• Improved tank access
  The modified feeding bridge is much stronger and safer than existing bridges in the production tanks. The double access porch resulted in a net savings in materials and increased labour efficiencies as two tanks can be accessed at the same time for feeding, water quality checking etc..
  
  
• Modified tank design.
  The grading tanks are wider and shallower than our production tanks. This increases surface area and makes it simpler to put halibut in and take them out of a tank. Water in the grading tanks also drains to a workable level much more quickly. Because the grading tank walls are lower than those in the production tanks, the grading station can be set up at ground level. In addition to simplifying fish handling, there is a significant improvement in worker comfort and safety.
  
  
• Water supply improvements
  The saltwater well upgrades have completely eliminated the infiltration of sand and gravel into the wells and allowed the new tanks a reliable supply of water.
  
  
• Forklift upgrade
  The rotators for the fork lift made it possible direct different size grades into insulated plastic boxes. The boxes could then be transported and dumped into the appropriate grow-out tank in a very efficient manner, avoiding additional handling or re-netting of the fish.
  
  
• and g. The oxygen supply improvements and Vaki grader arrived only recently and no assessment of their performance has yet been possible. It is anticipated that the oxygen supply improvements will reduce the price of oxygen from $0.85/m3 to $0.12/m3, representing an estimated annual savings of $43,000. The Vaki grader and fish pump will provide Canaqua Seafoods with the option of bringing in smaller “nursery sized” halibut and save on the per unit cost of the incoming juveniles

Grading Procedures

Despite the mechanization, the grading was quite labour intensive with the actual grading operation taking approximately three weeks and eleven people each day. However, a manual sort would have taken several months and an equivalent number of bodies.

The mechanical grader was consistent at sorting the fish into the three size categories. There were fewer miss-sorts using the mechanical grader than were observed during our earlier manual grade. There was no measurable mortality induced by the grader. The fish were handled gently and resumed feeding within five to ten hours. These are both reliable indicators that grading stresses were kept to a minimum.

The low-sided grading tanks made it possible to scoop fish directly from the tank to the start of the grader belt. In the higher sided production tanks this would not have been possible. It would have taken an intermediate step. Finally, the grading equipment was stationary so that the fork rotator on the fork lift improved efficiency. Time was saved because it was not necessary to move from tank to tank and re-set flumes.

An indicator of improved productivity can be seen by examining weight sampling results pre- and post-grade. In the months preceding grading, within-tank variation had become so great that monthly averages became impossible to interpret. Sample means showed a decrease every second month. This is not a real trend but a reflection of error in the sampling due to extremely large size variation within a tank. A very large and unrealistic sample size would be required to overcome this error.

Grading had the clear and desired effect of reducing variation. Reduced size variation improved population management by improving accuracy of biomass and mean fish size estimations. These are necessary for appropriate feed rationing, feed size allocation and determining fish performance and health. Reduced variation also improves feeding behaviour because the probability of feeding hierarchies is reduced. Increased feeding was noted by observation.

Prior to grading, the fish growth rates appeared to be slowing down. Exact determination of the severity of the problem is difficult to quantify because weight sample results had become inconsistent and often illogical as explained above. After the fish were graded, growth rates appear to have improved, but the supporting weight sample data is not suitable for statistical comparisons. We noticed steady improvement through the winter months. Pre-grade our largest halibut weighed about 2.5 kg.  We now have fish in the 4.5 to 5.5 kg weight range.

We judge the recent grading operation as successful. There was a real reduction in time and effort required to grade the halibut when compared to our earlier manual grade. Without this project it may not have even been feasible to manually grade the tank populations at this stage of production.

Conclusions

The infrastructure improvements that were intended to make it possible to mechanically grade halibut at CanAqua Seafoods Limited were successful. Grading of large halibut was performed within a reasonable timeframe and resulted in a reduction in size variation of fish populations. Labour associated with grading and fish husbandry has been reduced and most significantly, growth rate of fish has improved suggesting that feed conversion efficiency has been enhanced.

Atlantic halibut is listed as a priority species of the 2008/09 AIMAP Innovation Priorities. This project addressed the innovation priorities of Species Diversification and Sustainable Production by improving production efficiencies for Atlantic halibut aquaculture. Increased operational efficiency will result in a reduction of time to market and reduction of costs. This, along with other improved efficiencies expected from the next phases of the proposed multi-year project, are anticipated to increase interest from investors in the private sector. Renewed investment will promote expansion of the halibut aquaculture industry to increase its global competitiveness in halibut production, entitling Canada to be a central player internationally in the production of a high quality, high valued white fleshed fish.

Of most need for ensuring improved production efficiency for Atlantic halibut is consistent provision of optimum rearing conditions. Therefore, the next step in this project should focus on ensuring a sustained thermal regime for Atlantic halibut at the Advocate Harbour site by using a water re-use system with efficient water heating and water treatment equipment. It is anticipated that the supply of a sustainable increased thermal regime will result in a reduction of 5 months off the current 35 month production cycle seen at the Advocate Harbour site.