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Technology Transfer, Adaptation and Implementation of Washington state Mechanical Clam Harvesting Technology to the BC Shellfish Farming Sector

Post-project performance evaluation
AIMAP-2009-P11
The BC Shellfish Growers Association

Table of contents

Executive Summary

Clam digging technology in BC has been lagging behind other parts of the world, where mechanical harvesters have been employed for decades. In BC, beaches are still dug manually with long-tined rakes. Clam growers struggle to find people willing to harvest clams because this job is very labour intensive and the wages depend on how many clams the diggers are able to find (paid per pound). Mechanical clam harvesters will increase the speed, efficiency, and profitability of growing clams in BC. The mechanical harvesters are able to harvest more clams in less time and with far fewer people. This advantage could allow growers to be more competitive in global seafood markets. In order to start the mechanization process, the BC Shellfish Growers Association purchased a prototype mechanical harvester and then modified the design to produce a second harvester, which better suits the conditions of BC’s clam beaches.

Both the environmental and socioeconomic considerations of the mechanical clam harvesters were taken into account. An environmental impact assessment was completed and the harvesters were shown to be no different than manual harvesting in terms of their environmental impact. The negative socioeconomic impacts of the harvesters were also found to be minimal.

As a result of this project, mechanical clam harvesting technology is now available to shellfish growers in

BC. This technology will allow the clam growing sector to more effectively harvest their product and give them a competitive advantage in the market place. This project was possible thanks to funding by the DFO Aquaculture Innovation and Market Access Program (AIMAP).

1. Introduction

In order for BC’s shellfish growers to compete in global markets, advances need to be made that can decrease costs and increase harvesting and processing efficiency. Clam harvesting technology, in particular, has been lagging behind in research and development. In BC, clams are still dug by hand using long-tined (10-15cm) rakes. This method is inefficient and labour intensive. For this reason, it is very hard to find and retain labourers. Clam harvesting has been mechanized successfully in many other clam-exporting nations, such as Italy and France. The technology transfer, adaptation and implementation of Washington State mechanical clam harvesting technology to the BC shellfish farming sector was a large leap towards increasing efficiency for clam growers.

The Manila clam (Tapes philippinarum) is the most commonly grown clam species in BC. They require two years of growth to reach a marketable size and are then sold on both North American and global markets. The clams are grown in the low portion of intertidal beaches in a variety of substrates. Muddy and sandy beaches are an idea substrate for both clam growth and clam digging, but many of the clam beaches on Vancouver Island are pea gravel and rock. The mechanical harvester prototypes that were trialed are only able to harvest clams on sandy and pea gravel beaches. The rocky beaches will still need to be harvested manually.

Clam diggers are paid per pound of clams harvested and the work is very labour intensive.   For these reasons, diggers prefer “hot spot” beaches, which means that they will only dig where there is a high density of clams. The mechanical harvesters would be operated by a fulltime employee and they are not labour intensive to operate. For these reasons, the mechanical harvester is more likely to result in the entire beach being harvested and therefore more clams retrieved. It is also thought that the harvesters will make the low density clam areas more productive for subsequent years by aerating the substrate.

A prototype mechanical clam harvester, designed by Taylor Shellfish Ltd., was trialed on eastern Vancouver Island clam beaches from July 2008 to August 2009. This prototype will be referred to as the Mark I harvester in this report. The Mark I harvester was used as a baseline from which to design a mechanical harvester than was better suited to BC beaches. A second prototype was built with these design upgrades in mind. The second prototype will be referred to as the Mark II harvester in this report. The harvesters dig clams by penetrating the substrate with a vibrating, grated shovel. The shovel retains the adult clams while some of the juvenile clams, non-target organisms and substrate fall back through the grate. The retained portion moves along a conveyor belt and onto a sizing screen where the remaining juvenile clams, non-target organisms and substrate fall back onto the beach. The adult clams are deposited in a collecting basket where they can be sorted and bagged.

This Mark I harvester is estimated to do the work of 8 manual diggers and the Mark II harvester is estimated to do the work of 15-16 manual diggers. The mechanical clam harvesters are more efficient, faster and require fewer employees to operate.  All of these factors could significantly increase profits for clam growers in BC.

However, before the mechanical clam harvester can be used on an industrial scale in BC, an environmental impact assessment had to be completed and the socioeconomic implications were taken into account. This report will 1) provide a detailed description of the project; 2) discuss the environmental considerations of the mechanical clam harvester in BC, including the results of the environmental impact assessment; 3) discuss the socioeconomic implications of the mechanical clam harvester in BC.

2. Project Description

2.1. Partners

Names: Roberta Stevenson and David McCallum
Company/Organization: BC shellfish Growers Association (BCSGA)
Position:  Executive Director and R&D Coordinator
Contribution: Project management

Name: Richard Hardy
Company/Organization:  Pentlatch Seafoods Ltd.
Position: General Manager
Contribution: Technical advice on technology development, modification and application

Name: Gordy McLellan
Company/Organization:  Mac’s Oysters Ltd.
Position: President
Contribution: Technical advice on technology development, modification and application

Name: Keith Reid
Company/Organization:  Odyssey shellfish Ltd.
Position: President
Contribution: Technical advice on technology development, modification and application

Name: Leo Limberis
Company/Organization:  Limberis Seafoods Ltd.
Position: President
Contribution: Technical advice on technology modification and application

Name: Dr. Steve Cross
Company/Organization:  Aquametrix Research Ltd. / Pacific SEA Lab
Position: Executive Director
Contribution: Advice on scientific aspects including EIA

Name: Tom Broadley
Company/Organization:  IEC Collaborative Marine Research & Development
Position: Co-owner and CEO
Contribution: Advice on technology modification and application

2.2. Key members of the project team

Name: David Stirling
Company/Organization:  Aquametrix Research
Position: Environmental Consultant
Contribution: Environmental impact assessment (EIA)

Name: Chris Barker
Company/Organization:  Taylor Shellfish Ltd.
Position: Professional Mechanical Engineer
Contribution: Mechanical harvester engineering and design

Name: Derek Deidricksen
Company/Organization:  Forbidden Alloy Products Ltd.
Position: Owner
Contribution: Mark II mechanical harvester fabrication

2.3. Technology transfer, adaptation and implementation

2.3.1. Phase I – Purchase and importation (transfer) of the Mark I harvester

The BCSGA purchased the Mark I mechanical clam harvester from Taylor Shellfish Ltd. in Washington State after a brief trial in August of 2008. The Mark I harvester was purchased for $45,000 USD. The BCSGA and industry partners agreed that the Mark I design was a useful template from which to make modifications as well as represent future prototypes during an environmental impact assessment.

The mechanical clam harvester works by penetrating a vibrating, grated shovel at the front of the machine into the beach substrate. The harvester is powered by a diesel engine and propelled by a hydraulic track system. Adult clams move onto a conveyor belt while juvenile clams and small non- target organisms fall through the grate of the shovel and sizing screen. The clams move a along conveyor belt and fall into a collecting basket at the back of the harvester. Here the operator is able to sort marketable clams from non-target organisms and damaged clams while simultaneously operating the harvester.

Chris Barker of Taylor Shellfish Ltd. traveled to Bayne Sound in order to train local operators on proper usage and maintenance of the Mark I harvester. The local operators were then responsible for operating and maintaining the machine during the 2009 field trials.

2.3.2. Phase II – Field trials and design modifications (adaptation) of Mark I harvester

The Mark I harvester was initially trialed in August 2008, before it was purchased by the BCSGA. It was trialed again in January/February 2009 and July/August 2009 in order to complete the environmental impact assessment and to experiment with possible modifications for the Mark II design. The environmental impact assessment was completed by David Stirling.

Based on the 2009 field trials of the Mark I harvester, the following modifications were deemed necessary for the Mark II harvester:

Increased horse power in order to gain speed and more effectively penetrate substrate

The Mark I harvester was designed for the muddy beaches of Puget Sound, not the course sand and pea gravel beaches of BC. The more difficult substrate was overworking the track system and in many instances the machine was not able to effectively penetrate the substrate. The Mark II harvester has an 18 horse diesel engine and is able to harvest at approximately 5-7mph depending on the substrate.

Increased shovel and screening efficiency

Both the shovel and the sizing screens were deemed too small in the Mark I design and were made deeper in the Mark II design. The sizing screen on the Mark II harvester is also interchangeable.

Increased use of ‘green technology’

Containment trays were placed around both the fuel tank and the hydraulic fluid tank in the Mark II harvester in order prevent leakage into the marine environment in the event of a spill. This was not a design component of the Mark I harvester.

Bio-based hydraulic fluid was also discussed as an option for the Mark II design, but bio-based hydraulic fluids tend to solidify due to the moisture of the marine environment and plug hydraulic pumps. Instead a more environmentally friendly petroleum-based hydraulic fuel (Chevron clarity AW46) was chosen for the Mark II harvester.

Adjustments to decrease noise pollution

The Mark I design utilized pins and bushings to connect the steel components. The pins and bushing created a loud rattling noise. This noise could be heard from further distances than the engine of the harvester. The industry partners and engineers decided that the bushings and pins should be replaced by flat bars in order to reduce noise pollution in the Mark II design. Because of this modification, the Mark II harvester is quieter than the Mark I harvester, despite having a larger engine. Sound insulating materials were not used in the Mark II harvester design, but could be added later or incorporated into future prototypes.

Adjustments to reduce juvenile clam and non-target species mortality

Adjustment to shovel width relative to track width

The shovel on the Mark I harvester extends beyond the width of the tracks. As the shovel picked up substrate, juvenile clams and non-target organisms fell back through the grate onto the ground. Some of this tilled area was then run over by the tracks. This led to organisms being crushed before they had the opportunity to dig back into the beach. The industry partners and engineers decided to contain the shovel between the tracks, rather than having them overlap in the Mark II harvester.

Moving controls from the back to the side

In the Mark I design, the operating controls are at the back of the machine, which meant the operator would walk over the freshly tilled substrate and therefore would crush juvenile and non-target species. In the Mark II design, the operating controls were built on an adjustable the arm that could be accessed from the side of the tilled area. This would prevent operators from walking on the freshly tilled substrate and therefore prevent juvenile and non-target species mortality.

Adjustments to reduce visual impact

The track mark of the Mark I design was no longer visible after the tide had come in and receded twice. The Mark II harvester was designed to have an even shorter lasting track mark. The track area of the Mark I harvester is 420 sq. inch and the track area of the Mark II harvester is more than three times the size (1364 sq. inch). However, the weight of the Mark II harvester is not three times the weight of the Mark I harvester. This means less weight per area of track and therefore a lighter imprint on the substrate from the Mark II harvester than the Mark I harvester.

2.3.3. Phase III – Production and fabrication of Mark II design (implementation)

The Mark II harvester was fabricated by Derek Deidricksen, Forbidden Alloy Ltd., Courtenay, BC. Derek has been designing and fabricating equipment for local shellfish farmers for many years, which made him an obvious choice for this project. The Mark II mechanical clam harvester that Derek built is more user friendly, more environmentally sound, and more efficient than the Mark I harvester.

The BCSGA is very pleased with the Mark II harvester and the industry partners are excited to utilize it on their beach tenures.

3. Environmental Considerations

3.1. Literature Review on Environmental Impacts of Mechanical Clam Harvesters

Many different types of mechanical harvesters have been utilized to harvest clams around the world. Some of these include the Italian ‘rusca’(Pranovi et al., 2003; Badino et al., 2004), the rotating drum harvester (Badino et al., 2004), the hydraulic clam dredger (Coen, 1995), the escalator harvester (Coen, 1995), and the suction dredger (Kaiser et al., 1996; Spencer et al., 1998).

In most studies the mechanical clam harvesters showed minimal short-term impacts and there were few reports of long-term impacts. The harvested area generally returned to original species diversity and abundance 7-12 months after harvest (Kaiser et al., 1996; Spencer et al., 1998). In a comprehensive review of the mechanical clam harvesters, Coen (1995) concluded that there are no long-term, chronic environmental effects. He further concluded that the short-term effects are minimal and no different than ambient levels of natural variability, such as tides and storms. Coen’s conclusions were based on the following ecological issues associated with mechanical clam harvesters:

  1. Resuspension/turbidity
  2. Direct burial/smothering
  3. Contaminant release
  4. Nutrient release
  5. Change in water quality
  6. Disturbance of infauna
  7. Effect on economically important finfish and crustaceans

Tarnowski (2001) also reviewed the literature for mechanical clam harvesters in order to evaluate the environmental implications of using a hydraulic escalator dredge in Maryland. Tarnowski found that the impacts are highly dependent on how much erosion the beach naturally receives. Impacts are minimal on high erosion sites and more lasting on calmer or more stabilized sites, such as where sea grasses are present. Generally Tarnowski found that the trench was gone within 2-3 months, but can last up to three years; the maximum distance for sediment deposition was 75 feet; cultch can either be buried or exposed depending on the site; and contaminants are unlikely to build up. Tarnowski did find that the harvester can expose juvenile clams and non-target organisms to predators, but that motile species can quite easily bury themselves back into the freshly aerated substrate. Finally, Tarnowski found that clam mortality was reduced with hydraulic escalator dredge for hard clams (1 in 2,000). Mortality dropped from 50% with hand harvesting to 5% with the hydraulic escalator dredge for soft clams and juveniles were also rarely damaged.

Pranovi et al. (2004) found the short-term effects of mechanical clam harvesting to be more severe with an increase in suspended particulate matter, total carbon, organic carbon, total nitrogen, and sulfide concentration as well as a decrease in macrofaunal density. Ferns et al. (2000) also quantified the decline in non-target organisms and some of their predators after a mechanicall cockle harvester was used in South Wales. They found that cockles could be harvested more efficiently, but that there was a decline in non-target species on the beaches. Some species were significantly depleted for more than 50 days while others were significantly depleted for more than 100 days (Ferns et al., 2000). They also found a decrease in seabird predators for 50-80 days after the harvest, after an initial increase due to exposed non-target organisms immediately following the harvest. A sister-study found the long-term effects of the mechanical harvest on cockle stocks to be negligible (Cotter et al., 1997).

While it is useful to review the environmental performance of mechanical clam harvesters in other parts of the world, an environmental impact assessment for an intertidal clam harvester on British Columbian beaches was still necessary. Many of these other harvesters have a very different design. For example most are designed to harvest subtidal clam whereas the prototypes being trialed in B.C. harvests clam on intertidal beaches during low tide. This alone will make a big difference in sediment transport, fauna density and diversity, and trough/track resonance time. In addition, the trench on intertidal beaches is much smaller to begin with because many of the other common mechanical harvesters spray water at high pressure into the sediment to suspend clams. This creates a large trench compared to the grated shovel on the BC intertidal prototypes.

3.2. Environmental Impact Assessment for British Columbia

The environmental impact assessment was completed by David Sterling as part of an M.Sc. thesis. The results are presented here and a more comprehensive description of the methods and additional discussion can be found in the technical report by David Stirling, which was submitted with this report.

The three beaches sampled were Comox Beach, Royston Beach and Ships Point. Both the manual and mechanical harvesting techniques were used at each of the three beaches on 15mx30m plots. The manual harvest was conducted by the same eight clam diggers at all three sites. The study started in August of 2008 and was completed in August of 2009 with two summer sampling periods and one winter sampling period.

Before any data was collected, an oceanographic survey was conducted. This survey determined the direction and velocity of tidal flow. Based on this survey, transects were placed in the direction of tidal flow at each beach for both manual and mechanical harvesting plots. Sampling stations were placed along the transects at 1, 10, 25, 50 and 75 m (in the direction of the tidal flow) starting at the edge of the harvest plots. There were also two reference stations for each treatment at each beach.

Three replicates for each parameter were collected at each sampling station before and after a clam harvest. These parameters were sediment chemistry (sulfide concentration, redox potential, and sediment grain size), sedimentation (sediment accumulation), and biological condition (macrofauna and meiofauna abundance and diversity).

3.2.1. Sediment Chemistry
3.2.1.1. Total free sulfide concentration and REDOX potential

The results were highly variability within transects, within beaches and between beaches for both total free sulfide concentration and REDOX potential (eH), with no significant differences between manual and mechanical harvesting detected. Some of the variability in these samples may be attributed to the probes used. These probes are more effective in mud than in sand and gravel and most samples were primarily sand and gravel. Additional error may be attributed to the variation in temperature, which ranged from 14.6°C to 25.7°C. Temperature has an influence on eH results.

3.2.1.2. Sediment grain size

The sediment grain size analysis suggested that a higher percentage of mud and lower sediment density are correlated with increased sediment accumulation. This result was only found in some of Stirling’s trials and would require further research. However, the result is logical as small, less dense particles are likely to move more easily with tidal flow.

This finding becomes important when interpreting the sedimentation results.

3.2.2. Sedimentation - sediment accumulation

Sediment was collected in buried canisters, which were 21 cm high with an 8 cm diameter. The canisters were buried with a 1-2 cm rim left above the sediment level. The canisters were left on the beach long enough for the tide to come in and go out once. Some significant differences in sedimentation were found between manual and mechanical harvesting plots. However, this trend was found in the pre-harvest data only with the exception of Royston beach. The pre-harvest data is the control and

therefore does not represent any difference between the manual and mechanical harvesting methods.

At Royston beach, there was a significantly higher sediment volume at the manual harvest plots than the mechanical harvest plots at the 10, 25 and 50 m stations post-harvest. This result may suggest that manual harvesting has a higher environmental impact, in terms of sedimentation, than mechanical clam harvesting. Alternatively, Stirling attributed the difference in sedimentation to the higher percentage of mud at the manual harvest portion of the beach. Stirling found that a higher percentage of mud leads to increased sedimentation rates (see section 3.2.1.2.).

Stirling did some additional data collection to support his finding. He measured sedimentation pre- and post-harvest at Base Flats, a commercially farmed clam beach (tenures owned by Pentlach Seafoods Ltd and Mac’s Oysters Ltd.). At Base Flats, Stirling found no difference in sediment volume before and after the mechanical clam harvest.

In further support of the low environmental impact of the mechanical clam harvester, Stirling found that:

  • The mechanical post-harvest plots had a more uniform distribution of sediment than the manual harvest plots (pre- and post-harvest).
  • More sedimentation was caused by the clam netting  than by the mechanical clam harvester
  • Storm events caused a sediment flux four times that of the mechanical clam harvester.

It should be noted that the sedimentation results are from the 2008 and 2009 summer sampling periods only, not the winter sampling period. This is because all of the canisters were completely filled with sediment for all stations during the winter sampling.

3.2.3. Biological condition - macrofauna and meiofauna abundance and diversity

Sediment cores were taken at Comox Beach , Royston Beach and Ship’s Point. These cores were taken both pre- and post-harvest and preserved. The samples were later used for taxonomic analysis of both macrofauna and meiofauna. Stirling was able to identify most organisms to species or family. The results of these data were highly variable and no significant trends were detected. This means that Stirling found no difference in infaunal abundance or diversity between mechanically and manually harvested clam beaches.

Keith Reid of Stellar Bay Seafoods Ltd. observed that the mechanical harvesters decreased juvenile clam and non-target species mortality during beach trials. The manual diggers rake substrate towards them and then walk forward through it.  This means that they are stepping on freshly exposed organisms. The operator does walk through the freshly tilled path when the Mark I harvester is used because the controls are at the back. Also, the tracks drive over a portion of the freshly tilled sediment. This could lead to some juvenile and non-target species mortality. However, the Mark II harvester is designed so neither the operator nor the tracks will make contact with the freshly tilled substrate. This will allow the juvenile clams and non-target species to easily burrow back into the aerated substrate before being crushed.

Also, the manual diggers create mounds of substrate. These mounds are dense and compact, which makes it difficult for juvenile clams and non-target organisms to burrow back into the substrate. The mechanical harvesters leave a uniform patch of aerated substrate, which will allow the juvenile clams and non-target organisms to easily burrow back into the substrate.

4. Socioeconomic considerations

The environmental impact assessment detected no difference between the impacts of mechanical and manual clam harvesting. However, the socioeconomic implications of replacing the mechanical harvesting method with the manual harvesting method also need to be considered. The major socioeconomic implications are profitability, job creation, job satisfaction, noise pollution, esthetic quality of the beach, and public perception.

4.1. Profitability

The mechanical clam harvester shows great potential for increasing the profitability of farming clams in BC. Currently, BC clam growers are struggling to compete in global markets. The mechanical method is faster, will harvest and aerate low density areas of the beach, reduces loss due to mortality, and decreases labour costs. With the mechanical harvester, 1-2 people can complete a job that required 8- 20 manual harvesters, while retrieving more of the clams, in better condition and less time. These factors could dramatically increase profits for the clam farmers.

However, the costs associated with the mechanical clam harvester must also be considered.  The Mark I harvester was purchased for $45,000 and the Mark II harvester cost approximately $90,000 to build. This is a large initial expense to clam growers. Keith Reid, Stellar Bay Seafoods Ltd., explained that the expense would be easily worth it for the larger growers in the area, but smaller growers would be more likely to contract the use of mechanical harvesters or share the expense with other small growers.

In addition to the initial cost of the mechanical harvesters, there is fuel, maintenance, and support infrastructure. The Mark II harvester is estimated to get 40 miles per gallon of fuel depending on the difficulty of the substrate and harvesting depth. Derek Diedricksen, the fabricator of the Mark II harvester, estimated that the harvester would require $2,000 to $3,000 worth of repairs annually, in addition to the cost of fuel. He also commented that the tracks have too many moving parts to be galvanized and would therefore likely need to be replaced every five years. He estimated the track replacement to cost $12,000. Finally, the support infrastructure required includes a boat to transport the harvester to the beach and a fresh water tank/pressure washer to remove salt and sand after each use. All of these expenses need to be factored in when clam growers consider the benefits of mechanizing their harvesting practices. According to Keith Reid of Stellar Bay Seafoods Ltd., the math supports the mechanical harvester for larger beaches.

4.1. Job creation and job satisfaction

Having 1-2 people do the job of 8-20 benefits the tenure owners, but removes jobs from the community. This is one of the draw backs of the mechanical clam harvester. This is also an issue that media outlets may emphasize, which will further influence public perception.

The other side of this argument is job satisfaction. Currently, tenure owners find it difficult to find and retain labourers to harvest clams. One grower even had to rely on a foreign worker program in the past, through which the employer had to pay for flights, housing, visas and wages for 18 Vietnamese workers. This is because manual clam harvesting is labour intensive and the wage is uncertain (60-70 cents/lb).

In addition the clams are harvested during low tide, which means workers are harvesting at irregular times throughout the day and night. Finally, clam harvesting only provides contract employment, which means workers are not guaranteed work and there are no benefits provided. Because workers are paid per pound, it is not uncommon for diggers to put rocks and damaged clams into their bags.

While there may be fewer jobs available on the beaches where the mechanical clam harvester is adopted, the jobs will require training and more highly skilled labourers and therefore will demand a higher wage. According to Keith Reid, Stellar Bay Seafoods Ltd., the operator would be full time staff and be responsible for operation and maintenance of the mechanical clam harvester. It is important to note that the mechanical clam harvester cannot be used on all beaches. Small beaches and rocky beaches will still need to be dug by hand. It is not cost effective to transport and operate the mechanical harvester on very small beaches and the harvester is not able to penetrate the substrate on rocky beaches.

In summary, the mechanical harvester will not be displacing people from their jobs. It is very difficult for employers to find and retain clam diggers and there will still be clam digging contracts available because the mechanical harvesters are not suited to all beach types.

4.2. Noise pollution

Community members have expressed concern over noise pollution caused by the mechanical clam harvester and this issue may become exacerbated when the harvesters become more common on the beaches. The harvester has the same decibel rating as a lawn mower. From more than 100m, the harvester is no longer audible over ambient noise level. The Mark II harvester is quieter than the Mark I harvester because the loud bushings and pins were replaced by flat bars, which do not rattle against the steel. Future prototypes will be even quieter as there is potential for more insulating materials to be put around the engine.

Currently, upland home owners complain to the BCSGA about the noise pollution caused by manual diggers. Music and chatting from diggers during night tides have been a major point of conflict. It is hoped that the monotonous drone of the mechanical clam harvester will be less disruptive to upland owners than large groups of diggers on the beach during the night.

4.3. Esthetic quality of the beach

There may be concern over the impact of the mechanical clam harvester on the esthetic quality of the beach. The harvesters do leave tracks on the beach in a regular pattern, which may be considered unnatural to community members and visitors. However, these track marks will only remain obvious until the tide had come in a receded again and any sign of harvesting activity will no longer be visible after two tides for the Mark I harvester. The tracks will disappear sooner for the Mark II

harvester because there is less weight per area of track on this machine.

4.4. Public perception

The mechanical clam harvester may be received poorly by the public for a number of reasons. Job loss, noise pollution and beach esthetics are three reasons already touched upon. In addition, the public may view the machinery as negative and invasive; the public may assume that the harvester can be used on any beach (not only clam tenures); and the public may perceive a negative effect on infauna as well as damage to the ecosystem and ecosystem processes.

Mechanization of the clam harvesting industry may receive additional criticism because it is considered aquaculture and may be associated with the negative media attention on salmon farms. Many residents of British Columbia are already skeptical of aquaculture, which could lead to increased resistance to developments that appear to intensify farming efforts.

The environmental impact assessment has shown the environmental concerns to be unwarranted. However, the general public will not be familiar with the studies leading up to the use of the mechanical clam harvester.  For this reason, public education and outreach may reduce negative public perception. The BCSGA has been and will continue to educate the public about the mechanical clam harvesters through their website, the Tidelines Quarterly Newsletter, their annual workshop and at various conferences.

5. Conclusions

The BCSGA is very pleased with the technology transfer, adaptation and implementation of Washington State mechanical clam harvesting technology to the BC shellfish farming sector. The Mark II harvester is much better suited to the clam beaches of BC than the Mark I harvester and will be very beneficial to local clam growers. The Mark II harvester will be able to harvest a beach 2-3 times faster than the manual method and 1-2 people will be able to do the job of 15-16 manual diggers. While growers will have the initial expense of purchasing the machine and ongoing maintenance expenses, they will save a huge amount on wages and will not have to struggle to find diggers.

The results of the environmental impact assessment show that the mechanical harvesters have the same environmental impact as manual harvesters and additional discussion indicates than it may even be lower. The mechanical harvesters also have minimal negative socioeconomic impacts. This new technology has the potential to greatly improve the clam growing sector in BC.

6. References

Badino, G., Bona, F., Maffiotti, A., Giovanardi, O., Pranovi, F. 2004. Impact of mechanical clam harvesting on a benthic habitat: evaluation by means of sediment profile imaging. Aquatic Conservation and Freshwater Ecosystems 14, 59-67.

B.C. Shellfish Growers Association. 2008. Environmental assessment of mechanical clam harvesting vs hand method. Retrieved from [http://www.bcsga.ca/news/environmental-assessment-of-mechanical-clam-harvesting-vs-hand-method]

Coen, L.D. 1995. A review of the potential impacts of mechanical harvesting on subtidal and intertidal shellfish resources. South Carolina Department of Natural Resources. Retrieved from [http://www.ecsga.org/Pages/Sustainability/Coen%2095%20review.pdf]

Cotter, A.J.R., Walker, P., Coates, P., Cook, W., Dare, P.J. 1997. Trial of a tractor dredger for cockles in Burry Inlet, South Wales. ICES Journal of Marine Science 54:72-83.

Ferns, P.N. Rostron, D.M. Siman, H.Y. 2000. Effects of mechanical cockle harvesting on intertidal communities. Journal of Applied Ecology 37:464-474.

Kaiser, M.J., Edwards, D.B., Spencer, B.E., Infaunal community changes as a result of commercial clam cultivations and harvesting. Aquatic Living Resources 9:57-63.

Pranovi, F., Libralato, S., Raicevich, S., Granzotto, A., Pastres, R., Giovanardi, O. 2003. Mechanical clam dredging in Venice lagoon: ecosystem effects evaluated with a trophic mass-balance model. Marine Biology 143:393-403.

Pranovi, F., Da Ponte, F., Raicevich, S., Giovanardi, O. 2004. A multidisciplinary study of the immediate effects of mechanical clam harvesting in the Venice Lagoon. ICES Journal of Marine Science 61:43-52.

Spencer, B.E., Kaiser, M.J., Edwards, D.B. 1998. Intertidal clam harvesting: benthic community change and recovery. Aquaculture Research 29: 429-437.

Stirling, D. 2010. Technical summary: mechanical clam harvesting for coastal British Columbia: environmental implications.

Tarnowski, M. 2001. A literature review of the ecological effects of hydraulic escalator dredging. Maryland Department of Natural Resources. Fisheries Technical Report Series 48. Retrieved from [http://www.ecsga.org/Pages/Sustainability/Tarnowski2001(rev2006).pdf]

Date Modified: 2012-08-30

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