Scientific research on farmed oysters

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Science is the key to an environmentally and economically sustainable aquaculture industry. Fisheries and Oceans Canada scientists and researchers have examined the potential impacts of clam aquaculture on the marine ecosystem, including the potential effects and benefits of clam harvesting and predator protection techniques. Multi-disciplinary research has also been undertaken to study all aspects of the clam culture cycle, including seeding, rearing, over-wintering, and harvesting.

Innovation

A mechanized grading technology for oysters exceeded industry expectations: the automated grading equipment increased production by nearly three times the amount possible with hand-grading, concurrent with a 65 per cent decrease in production costs, and steady overhead and labour costs. The new 3-D imaging technology provided higher grading standards and increased consistency.

  • Canadian Aquaculture R&D Review article: 2011

A research team set out to develop new, high-quality shellfish aquaculture raft designs that would enhance economic profitability and environmental sustainability for industry in British Columbia using state-of-the-art materials and computer simulation techniques.

  • Backgrounder, Canadian Aquaculture R&D Review article: 2009

The oyster gluing process was improved by developing technology for drying oysters, assessing the use of warm glue, and developing a floater for the glued oyster rearing structure.

  • Canadian Aquaculture R&D Review article: 2011

Real-time histology sessions using VNC technology and Skype were examined by researchers in Prince Edward Island as potential networking solutions for producing more reliable and sensitive methods for detection of pathogens in oysters, clams, and other molluscs.

  • Canadian Aquaculture R&D Review article: 2007

A multi-functional, closed-loop storage facility for shellfish was developed in New Brunswick to store shellfish while making it possible to decontaminate the product and maintain the health of coastal areas. The system removes bacteria and dissolves organic matter while aerating and circulating the water, which minimizes the risk of introducing disease and invasive species and allows for the implementation of a more effective and flexible product certification program.

  • Canadian Aquaculture R&D Review articles: 2009, 2011

Integrated multi-trophic aquaculture

The idea of growing finfish, shellfish, and marine plants together for the benefit of the environment and all three crops is known as integrated multi-trophic aquaculture or polyculture. Canadian researchers are studying various aspects of this model, including combining the rearing of Pacific Oysters and sea cucumbers in British Columbia to reduce the amount of organic deposition underneath shellfish farms while producing a secondary cash crop.

Production

A one-year project was conducted by researchers in British Columbia to examine the efficiency of expanded clay aggregate and lava rock as a new method of growing bivalves (Pacific Oysters and Manila Clams) in suspended culture. It is thought that by utilizing this method, both biofouling and shell deformities will be reduced.

Research was undertaken to document the annual shell growth of various size classes of near market-size oysters grown in suspended culture and to evaluate strategies to augment the proportion of saleable product in order to improve net productivity and economic viability. The study also evaluated the effectiveness of brine dipping in eliminating various fouling organisms such as barnacles and mussels.

A multi-disciplinary research team evaluated the growth performance of various size grades of oysters from the same year class originating from two different New Brunswick seed sources, as well as four size grades of oysters reared using two grow-out systems and exposed to different localized environmental conditions. By comparing the growth and survival profiles of the various size groups, the research team sought to determine an appropriate strategy for identifying and culling true “slow” growers.

Oyster seed (spat)

An adaptation of the French ‘cup’ technique for the collection and production of oyster spat was tested in New Brunswick in order to mechanize the operation and reduce costs. The tests confirmed that the technique improves the productivity of collection and the mechanization of operations. The cup-collectors also make it possible to address key constraints for establishing a sorting strategy to select the individuals most likely to grow successfully.

  • Canadian Aquaculture R&D Review article: 2009

A research team set out to quantify the setting rates of oyster pediveligers in field bouncing buckets and to compare this innovative remote-setting approach with a more conventional approach. The goal was to demonstrate that the newly settled spat in the buckets could grow into large seeds by the fall of the same year.

Cultivation gear

In 2009, researchers from New Brunswick began a two-year project that compared an offshore and inshore site for oyster aquaculture using the French string technique. This project aimed to evaluate whether oyster shell growth rates and reproductive rates are similar between offshore and inshore sites.

Researchers investigated the effectiveness of lowering oyster culture trays to a depth where the temperature is lower and harmful algae are less concentrated to mitigate the mortalities to oyster stock that can be caused by algal blooms. As part of the research, the team aimed to find the optimum depth to which oysters should be lowered in order to maintain oyster growth. Results of the research were intended to help oyster growers to manage summer stock mortalities by making decisions based on simple environmental monitoring and tray movement.

In 2009, a new study was launched to assess the performance of oysters to attain market size that are glued on strings and cultured in suspension on two New Brunswick leases: an exposed offshore environment near Stonehaven and a sheltered inshore environment in Caraquet Bay.

The efficiency of four experimental floating gear types in deterring birds was tested between 2006 and 2008. The research was undertaken after routine sampling in 2004 found the presence of bird fecal matter deposited on a number of floating bags, which resulted in a new requirement of oyster farms to convert floating gear into non-floating gear a few weeks prior to the marketing of oysters. Complementary research also examined whether “microbubblers” could reduce microbial contaminants (fecal source bacterial and other microbes) of oysters in seawater, but the results of the research indicated that these low-pressure aeration devices were not directly effective.

  • Research abstracts (project 1, project 2), Canadian Aquaculture R&D Review article: 2007
  • Fact sheet (research results): Does Microbubble Aeration Reduce Potential Oyster Microbial Contaminants in Seawater?

A research team investigated the relationship between floating oyster bag turning frequency, fouling levels, organic sedimentation rates, and oyster quality in order to increase understanding of oyster farm management of floating oyster bags. The objective of the research was to improve productivity and minimize environmental impacts of floating bag equipment. Complementary research in this area involved the development of a prototype for a flipping device for OysterGroTM cages to reduce production costs and the labour-intensive process entailed with flipping cages to control cage biofouling.

A new machine that uses hot water to control marine biofouling in oyster cultivation in New Brunswick was developed. Another study investigated whether biofouling control methods such as heat exposure or desiccation significantly impact oyster productivity. The findings of the study indicated that mortality was higher in juvenile oysters subjected to hot-water or desiccation treatments than in adults subjected to the same treatments.

Potential effects and benefits of oyster culture on wild fish and shellfish and/or the marine environment

A research team consolidated data collected through the Shellfish Monitoring network and to analyze the strengths and weaknesses of this tool in providing the Habitat Protection and Sustainable Development team with scientific advice to enable them to conduct environmental risk assessments of shellfish aquaculture activities on the marine habitat. Based on the results, a long-term and sustainable Shellfish Monitoring Network will also be designed.

Multi-year field experiments are examining the recovery dynamics of eelgrass exposed to oyster cultivated in suspended bags, as well as off-bottom, in order to provide advice to Fisheries and Oceans Canada’s Habitat Management team. The project also seeks to develop best management practices to guide the industry in mitigating any effects of oyster culture on eelgrass populations.

Research was undertaken between 2006 and 2008 to determine if the current stocking density of cultivated oysters (2,000 oyster bags per hectare) can deplete food resources within the farm at some point during spring, summer and fall. Factors, such as currents and water temperature, were studied as part of this project. A subsequent study evaluated the effects of increasing stocking densities on oyster productivity, such as shell growth, and the environment, such as biodeposition over three years to determine whether culture density could be increased beyond 2,000 bags per hectare.

Researchers in British Columbia monitored particulate deposition rates, sediment geochemistry, and benthic faunal communities at a deep-water, suspended Pacific oyster farm to understand the benthic impacts. Results indicated that the increased organic input from the farm was not leading to consistently reducing sediments or sulfide accumulation in comparison with other locations with the area. The results also indicated that benthic communities were not exhibiting any changes that would be associated with organic enrichment of the sediment.

  • Canadian Aquaculture R&D Review article: 2007

A two-year project was undertaken between 2002 and 2004 to evaluate the scale of benthic disturbance caused by the use of non-permanent oyster culture gear used on two sites. The sedimentation rate and quality was collected on the control sites as well as from areas that use different culture practices.

Aquatic invasive species

A two-year project was undertaken between 2010 and 2012 to evaluate various risk mitigation measures for the potential introduction of an invasive alga, in order to facilitate bivalve spat transfer requests in Eastern Canada.

An environmentally friendly machine to eradicate invasive species in the oyster industry is being developed that would use the current water table and a heating method without the use of pesticides or toxins.

  • Canadian Aquaculture R&D Review article: 2009

Tunicates can damage oyster culture gear and harm stocks. Research is contributing to the development of management strategies and rapid response procedures.

Animal health

In New Brunswick researchers are conducting a three-year project to assess variations in the health and condition of oysters in response to environmental changes, in order to identify critical periods of physiological stress. This will help in the development of management plans and best practices to help oyster producers reduce mortalities and optimize resource utilization, ultimately improving the environmental sustainability of the New Brunswick oyster culture industry.

Researchers are testing the development of a modified assay for use in temperate waters to evaluate the immune status of bivalves using biomarkers. This assay will be used to assess the stress tolerances among oyster stocks with varying levels of heterozygosity. Results from this research will contribute to the accurate identification of stocks with increased tolerance to stressful conditions.

A multi-disciplinary team of researchers tested the stress response of Pacific oysters exposed to high temperature and harmful algae in laboratory conditions, and the environmental conditions that may elicit a stress response in oysters at a farm site. The research was undertaken to be able to predict and avoid the occurrence of irreversible stressors that lead to large-scale mortalities of BC cultured shellfish.

Researchers tested whether cultivated oysters and mussels begin feeding at a similar temperature in the spring, and whether the feeding rates of oysters exposed to low temperatures was uncorrelated to animal size. The study was intended to provide a scientific basis for developing the approach for managing shellfish closures by species in Canada.

Multinucleate sphere X (MSX)

Since the onset of MSX oyster disease, Fisheries and Oceans Canada’s Shellfish Health Unit and the Nova Scotia Department of Agriculture and Fisheries have worked intensely on testing shellfish for MSX in order to provide scientific advice for disease management.

A collaborative government-industry research team initiated a breeding program for MSX-resistance oysters in the Bras d’Or Lakes oyster population with four objectives: initiate a rotational breeding plan with oysters from specific sites; test the progenies in field sites; consider impacts of future breeding in quarantine to obtain hybrids; and make recommendations for an expansion and/or continuation of the breeding program and for future restoration programs.

Research was undertaken to determine precisely the time-temperature-salinity combinations needed for appropriate gametogenesis and spawning in MSX-infected oyster broodstock. The study was critical for the success on the on-going breeding program for resistance to MSX, and to refine timing and zoning of oyster management activities within the Bras d’Or Lakes.

Results from a five-year study on two parasites affecting shellfish aquaculture in Atlantic Canada suggested that documentation of the distribution of MSX on oysters, and monitoring of mortalities due to the disease, was essential to allow aquaculture activities to continue while protecting uninfected stocks.

Malpeque disease

A two-part investigation was undertaken by researchers to develop molecular-based tools for the diagnosis of Malpeque disease. The first part of the project aimed to confirm the presence of the pathogen in infected oyster tissues by isolating small parts of its genetic material. Using these data, the second part entailed the development of a ‘polymerase chain reaction’-based test to determine the presence or absence of the pathogen from animal tissues.

Product quality

Researchers from New Brunswick are developing tools to evaluate the shelf life of the American Oyster. Results from this project will help to identify optimal storage conditions to avoid rapid loss of quality.

Various chemical parameters in the tissue of American oysters over-wintered at sea, in tanks and in cold storage were monitored between 2010 and 2011 to study the parameters likely to cause physiological stress and to alter the flavour of the oysters. Preliminary results suggested that during winter, the valves open almost imperceptibly in oysters held at sea and in tanks, and in spring, valve activity is triggered when the water temperature reaches 1-7°C. The results also suggested that digestive gland lipids were the most important energy reserve used by the oysters during winter.

  • Canadian Aquaculture R&D Review article: 2011

Research was undertaken to develop management tools for oyster cadmium levels. The study entailed: an investigation of the variability of cadmium concentration among oysters, oyster tissues, sites, and depths and examination of the relative concentrations of cadmium in the stomach, and other body tissues; and an investigation of the potential cadmium pathway of uptake by phytoplankton and subsequent transfer to oysters. Results of the research indicated that cadmium was primarily concentrated in gut tissues. Particulate matter was not found to be a significant source of cadmium in oyster and was actually negatively correlated Cadmium in oyster tissues was found to be inversely correlated with temperature.

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