Commercial Scale Deepwater Holding and Pre-Harvest Finishing System for Oysters

Final Report

Odyssey Shellfish Ltd
AIMAP-2010-P30

Table of contents

Executive Summary
Introduction
Methods / Solution / Results
Conclusion

Executive Summary

In 2006, Odyssey Shellfish Ltd developed a prototype ‘finishing’ system for oysters that assisted in mitigating occasional spikes in water quality, and therefore added an extra layer of food safety confidence.  The prototype system pumped cold seawater from 25 meters depth (below the thermocline), and circulated it in holding tanks by pumping water through microbubbler units, ultraviolet (UV) lights, and sand filters for 48 hours immediately pre-harvest.  These methods proved effective in their objective, and the proponent decided to scale up and improve the system for increased production efficiencies at a commercially viable level.

This AIMAP funded project involved (1) the scaling up of the prototype system (from roughly 7,000 dozen oysters per week) to a more efficient, process integrated, and commercially viable system (able to process over 20,000 dozen per week); and (2) the promotion of the system across the industry as a model for an additional proactive level of food safety for cultured shellfish.  This project contributes to the advancement and competitiveness of the Canadian aquaculture industry by pro-actively addressing a potential threat to food-safety through an industry-driven shellfish quality assurance process.  The second-generation (commercial scale), highly energy efficient system will be showcased as an innovative husbandry process that could be scaled up or down, or made modular to suit any and/or all shellfish growers’ needs.

Introduction

The microbial flora of oysters (like that of all filter-feeders) is determined by the microbial flora within the seawater that they inhabit, and ingest as food.  In terms of food safety, it is important that cultured shellfish are grown in seawater containing minimal numbers of microbes that may cause illness to the humans that consume them. 

Shellfish growers in BC harvest product from their farms when the water quality meets the standards of the Canadian Shellfish Sanitation Program (CSSP); in other words, when the ‘area’ is open for harvesting.  However, a farm can be classified as approved for harvest (open) by Environment Canada (under the CSSP), and potentially still experience high fecal coliform counts.  This potential contamination of waters within the vicinity of a farm site can occur as a result of concentrated visitations of birds, seals, or other unknown or unpredictable event.  Of concern is the possibility that contaminated oysters may not be detected by random inspections.  If unknowingly contaminated oysters are delivered to market, they could adversely affect the health of the final consumer, which would lead to serious damage to the business and reputation of the shellfish industry in general.  This project has highlighted the development of a cost-effective method of accelerating the decrease in fecal source bacterial numbers in seawater, and consequently in oysters.  It is not considered a verified method of purging animals of impurities; rather, it is considered a ‘finishing’ process whereby oysters are delivered to market with a higher degree of quality assurance, and food safety confidence.

In 2008, Odyssey Shellfish Ltd developed a prototype finishing system that has proven capable of mitigating these occasional spikes in water quality and therefore adds an extra layer of food safety confidence.  This AIMAP funded project has improved on the prototype system and has magnified its scale to enable processing product at commercially viable volumes.  Production has grown more efficient and has grown from a capacity of 7,000 dozen oysters per week to potentially more than 20,000 dozen per week.  In addition, the second-generation system has proven its scalability, and therefore its potential to be integrated into the operations of any oyster farm site in Canada. 

The unique and innovative process involves pumping cold seawater from 25 meters depth (below the thermocline), and circulating it in large custom fiberglass holding tanks.  The flow of water into the tanks is delivered via Microbubbler units, which generate microscopic bubbles, to aerate the water.  For 48 hours pre-harvest, oysters are held in the closed-circuit system in which water circulates through the microbubbler units, as well as UV lights and sand filters for further water clarification. 

A key aspect of this finishing system is that the oysters are harvested from within an area classified as open for harvest under the CSSP.  The finishing system is not a requirement for food safety; rather it simply increases the confidence in food safety and quality assurance of the product for human consumption.  Gaining this increased level of food safety across the sector will positively affect the reputation of Canadian shellfish, and subsequently increase the overall value of such products in domestic and international marketplaces.  In terms of the AIMAP program sustainability goals, this project (1) will create an increased supply of Canadian shellfish with high level of food quality and safety (sustainable production); (2) will increase production efficiency and allow for a future opportunity of conversion to three-phase electrical shore-power (green technology) for the proponent; and (3) may be applied to any species of bivalve mollusk or filter feeding organism (species diversification), theoretically at any shellfish farm site.

Methods / Solution / Results

The project is expected to exceed expectations in terms of production efficiencies and systems integration.  The section below outlines the deliverables and describes progress towards overall completion.

We purchased and secured a 40 metre long by 16 metre wide barge on the farm site in 2010 that would serve as the platform for the Microbubbling system, among other integrated husbandry systems.  In January 2010 the barge was anchored and secured according to a professional anchoring plan. 

Fabrication and installation of Microbubbling project systems began shortly thereafter and was completed by January 2012. 

Systems include electrical generation, water circulation through UV lights, and microbubbler units within large fiberglass tanks.  The project also involved the fabrication of custom designed tray stack modules, which each house four cylindrical deepwater grow-out tray stacks.  The modules are then hoisted from a deepwater holding area alongside the barge onto the barge deck (using the overhead crane) and into the fiberglass tanks for finishing.

As of January 31st, 2012, testing is being completed to determine most effective water flow rates and ideal placement of the microbubbler units within the tanks.  However, the system is not yet commissioned fully, and therefore it is not possible to determine effectiveness at finishing oysters as proposed.  Given the current knowledge of the process (based on the prototype system) and its scalability, we anticipate the same, if not more effective results.

The system is expected to exceeded production estimates and will be able to process more than 20,000 dozen oysters per week.  This is excellent, as production from the farm site is increasing as other improvements to the site are developed including seed nurseries, and grow-out techniques, which have improved survivability.  We expect to reach maximum production capacity by summer of 2013 as the ancillary infrastructure (and oyster seed) capacity is installed and attained.

Communication of the project has been done through industry networks (the BC Shellfish Growers Association) and subsequent communications will be issued after project completion.  These may include filming the system in operation, and interviewing key people associated with the project.

Conclusion

For both shellfish growers and consumers to have confidence in the consumption of bivalve mollusks, products delivered to market must be of consistent quality and high level of food safety.  The Canadian Food Inspection Agency (CFIA), Environment Canada, and Fisheries and Oceans Canada (DFO) jointly administer the Canadian Shellfish Sanitation Program, with the goal to protect consumers from the health risks associated with the consumption of contaminated bivalve molluscan shellfish.  However, despite high levels of control and monitoring to ensure food safety at the regulatory level, there remains random, unpredictable events (such as a flock or birds or sea lions settling on shellfish harvesting rafts) that could potentially affect quality standards.  Given that consumer safety and product quality assurance are paramount to the success of a shellfish farmer’s business, this project was developed to provide another pro-active layer of food safety to the product going to market.

Circa 2008, Odyssey Shellfish Ltd (the AIMAP Recipient) developed a prototype finishing system that has proven capable of mitigating these occasional spikes in water quality and therefore adds an extra layer of food safety confidence.  This AIMAP funded project has improved on the prototype system and has magnified the scale to process product at commercially viable volumes.  Production has grown more efficient and has grown from a capacity of 7,000 dozen oysters per week to potentially more than 20,000 dozen per week.  In addition, the second-generation system has proven its scalability, and therefore potential to be integrated into the operations of any oyster farm site in Canada.