The ECO-Bath Cage System: Eco-Friendly, Safe and Cost-Effective Ectoparasite Control in Finfish Aquaculture Operations

Final Report

Admiral Fish Farms Ltd.
AIMAP-2010-M04

Table of contents

Project Summary
Project Rationale & Objectives
Project Description
Phase I Tank Trials
Phase II: Design of an Eco-Friendly Bath Solution
Phase III: Field Trials of the ECO-Bath System
Salmon Treatment
ECO-Bath System versus Well Boat Comparison
Communications
Research Team
Conclusions & Next Steps

Project Summary

The ECO-Bath System was conceptualized to address shortcomings present in the use of other bath treatment methods. The design incorporates the following components to maximize fish welfare, environmental stewardship and bath treatment efficacy:

• Modified AEG Containment System provides a fixed bath volume with external debris skirt
• Double impermeable tarp with internal transfer net retains treatment bath water
• Water circulation and filtration minimizes water quality deterioration and removes organics/cleared sea lice
• Nitrogen reducing oxygen infusion reduces stress on crowded fish
• Proven fish pumps that are gentle on transferred fish with no scale loss
• Versatile dewatering to and from treatment bath systems while retaining treatment water
• Integrated method to bind or eliminate remaining pesticides active ingredient when all site treatments are completed

Initial tank trials were completed at the Huntsman Marine Science Centre to verify that the very high oxygen, low Total Gas Pressure (TGP) environment did not cause acute or chronic issues for treated salmon or that the pesticides compounds were not toxic in this environment. Results verified that used a very high oxygen (250-350% saturation) and TGP (103-120%) environment did not cause mortality of exposed salmon. Further, there was no difference in mortality to fish or efficacy of the treatment pesticides (killing and/or removing sea lice) between fish treated with Salmosan and Alphamax in combination with a high oxygen/TGP environment or in an ambient oxygen environment. Unfortunately, use of hydrogen peroxide was not trialled with the ECO-Bath System following tanks trials as it appeared to remove the protective mucous coating from the exterior of exposed fish and their gills. Tank trial results provided a sufficient level of comfort to precede with the ECO-Bath System design process and prototype field trials.

Dye studies were completed to ensure that the tarp was indeed impermeable to the contained pesticides and to measure the degree and rate of mixing within the ECO-Bath System. The treatment water within the ECO-Bath System was relatively well mixed by one hour following injection of the dye. Therefore, a one hour mixing period was adopted after introducing pesticides to the system but prior to transferring fish for treatment based on the dye study results. This practice will ensure an appropriate bath treatment is completed to clear sea lice infection while minimizing the opportunity for sea lice to build resistance to the treatment pesticides.

A trial was completed to treat sea lice infected Atlantic salmon using Salmosan within the ECO-Bath System. The calculated oxygen uptake during the trial was 0.23 g O2/h/kg fish, which is less than the generally accepted oxygen uptake of 0.3 g O2/h/kg fish required by unstressed fish. Dissolved carbon dioxide was also monitored throughout the trial and never reached 1 part per million (ppm) providing a further indication that the treated salmon were not experiencing any stress during the ECO-Bath System treatment with Salmosan. Treated salmon were unstressed during the treatment due to the handling methods developed and presence of a high oxygen saturation environment maintained during the treatment period.

The total removal of all life stages of sea lice on treated salmon within the ECO-Bath System using Salmosan was 75.5%. The most dramatically affected life stage was mobile sea lice, which was removed at a rate of nearly 81% within 24 hours of the ECO-Bath System treatment. Removal of other sea lice life stages were also positive from the ECO-Bath System treatment with more than 61% of the chalimus sea lice and nearly 55% of the adult female sea lice removed 24 hours post-treatment. Also note that all sea lice that were physically dislodged from treated salmon while contained within the ECO-Bath System would not be returned to the ocean environment as sometimes can be the case when treating sea lice in tarps or well boats. With the ECO-Bath System, any sea lice (dead or alive) that are removed from salmon while within the system would be eventually filtered from the bath water and not pose any further threat for reinfection on otherwise treated salmon.

Just nine salmon mortalities were collected 24 hrs post-treatment or 0.38% of the treated population. Chronic long-term mortality following treatment within the ECO-Bath System was also not evident in the treated salmon population as can sometimes be the case post-treatment. This low number of mortalities following any treatment is remarkable and can be attributed in the ECO-Bath System due to the handling methods developed and use of the PurGRO2® oxygenation units to maintain the treatment bath water O2 concentration.

Significantly less pesticides are required to treat sea lice infestation when using the ECO-Bath System compared to tarp and well boats given the ability of the ECO-Bath System to retain pesticides between treatments on a specific day and requiring just a 1/3rd top-up to continue treatments on the same site on subsequent days. The ECO-Bath System also holds promise to integrate a filtration system to completely remove the pesticide active ingredient after an entire site has been treated rather than releasing any of the pesticides to the environment following treatment. Trials using a pressurized carbon filter resulted in a significant reduction in the amount of pesticides with 99.79% removal of Alphamax and 99.99% of the Salmosan removed.

Our results provide a dramatic contrast between the use of the ECO-Bath System and cage tarps or well boats to treat sea lice infested Atlantic salmon with Salmosan. The quantity of pesticides required to treat a cage and site in the ECO-Bath System is significantly less than that required in a cage tarp or well boat. The associated costs to purchase the pesticides and possible environmental impacts are also less with the ECO-Bath System in a direct comparison. The ECO-Bath System will allow treatment of fish in a wider water temperature range given its capability to control the O2 concentration within the treatment water. Finally, the ECO-Bath System is expected to be available to the industry at a fraction of the cost to purchase a well boat making it feasible to maintain site-specific treatment capability to control sea lice infestation while eliminating biosecurity concerns associated with transfer of sea lice and other pathogens between sites when sharing a common treatment platform.

Project Rationale & Objectives

Sea lice (predominantly Lepeophtheirus salmonis) have a global economic impact on salmonid aquaculture of over US$100M annually through loss of stock, product downgrades at harvest and costs involved in monitoring and managing infection. A sea lice epidemic recently occurred in New Brunswick (NB) as local sea lice populations became resistant to in-feed treatment using Slice. Going forward an Integrated Pest Management Plan will be necessary to assist the industry, which will require access to a toolbox of pesticide treatments including in-feed and bath options. However, industry and government both require assurances that environmental impacts will be minimized as the effort to contain sea lice damage increases. Recent bath treatment attempts using full tarps proved difficult to obtain and maintain effective dose concentrations in the sea cage environment given the high organic loads found naturally in the Bay of Fundy, NB region while well boats have been employed by some companies but this method tends to be very capital intensive. Both of these strategies also release used pesticides directly into the environment following treatment with new pesticides required for each subsequent treatment.

We proposed to develop an eco-friendly, safe and efficient “ECO-Bath System” that would require movement of sea lice infected Atlantic salmon from grow-out to bath to grow-out cages. We were directed in our design and technical approach to ensure the ECO-Bath System must:

• Minimize fish stress and eliminate mortality during the entire treatment process.
• Effectively kill and remove all sea lice from treated fish.
• Operate in a cost-effective and efficient manner to ensure adoption and use throughout the local, national and global aquaculture industry.
• Dramatically reduce the total quantity of pesticides to a fraction of that presently required to treat an entire aquaculture site.
• Fully contain the treatment bath water including removed sea lice and pesticides after the treated fish stock is removed.

In addition, the conceptual design of the ECO-Bath System would provide several critical aspects of treatment that would be unique among other present bath treatment strategies including: 1) an ability to remove natural organics in the treatment water, 2) maintenance of high oxygen levels during the treatment period to enhance fish welfare, 3) a method to minimize the amount of pesticide used for treatment, and 4) removal of the pesticide from the treatment water at the end of repeated treatments.

Project Description

The project was split into three primary Phases:

Phase I: Tank Trials to Determine Pesticide Potentiality

Objective – To determine changes in pesticide efficacy associated with infusion of ultra high levels of oxygen in treatment bath water.

Phase II: Design of an Eco-Friendly Bath System

Objective – To design the ECO-Bath System that meets strict criteria associated with pesticide containment, fish welfare and ease in operation for use on commercial salmon farms while marrying three sets of technologies including the fish pump/dewatering table/treatment baths, treatment water circulation/filtration system, and ultra high oxygen infusion system.

Phase III: Field Trials of the ECO-Bath System

Objective – To use a prototype commercial scale ECO-Bath System to treat Atlantic salmon and develop the necessary protocol for safe and efficient use of this system within commercial aquaculture operations.

Phase I tank trials were completed at the Huntsman Marine Science Centre with input from other project personnel and funding from the New Brunswick Innovation Foundation. Phase II primarily included input from the equipment supplier companies, NB Department of Agriculture, Aquaculture & Fisheries and Admiral Fish Farms to ensure that the prototype system would meet the needs of commercial farm operations and fish health concerns. Phase III was completed on an Admiral Fish Farms site with input from the DFO St. Andrews Biological Station to complete dye studies involving the ECO-Bath System and NB DAAF to monitor fish health and complete water sampling to measure pesticide concentrations during the trial.

Phase I Tank Trials

Large amounts of oxygen are required for bath treatments to reduce fish stress while being treated in overcrowded situations. Plate diffusers are an inefficient method and inclusion of several ceramic plate diffusers in a treatment cage still frequently results in low oxygen levels. This subsequently results in curtailing of the treatment period and the containing tarpaulin released prematurely. None of the standard methods to infuse oxygen in the aquaculture industry are particularly efficient at simultaneously infusing oxygen and removing significant quantities of nitrogen gas from water. However, the inVentures Technologies PurGRO2® technology uses a unique method to infuse gas into liquids to produce very high levels of oxygen while simultaneously removing nitrogen. Intuitively, infusion of oxygen and removal of nitrogen from the treatment water will help to lower fish stress while densely stocked for treatment.

The inVentures Technology oxygen infusion system provides a method by which oxygen can be very efficiently infused into water at levels many times greater than any standard oxygen infusion technology presently in use in aquaculture. The PurGRO2® technology can provide culture environments with nearly unlimited amounts (700-800% saturation) of oxygen, while simultaneously removing significant quantities of nitrogen gas from the processed water. Removal of nitrogen from the treatment bath is equally important to reduce the Total Gas Pressure (TGP) and otherwise makes oxygen uptake by fish difficult and causes nitrogen saturation of fish blood. The inVentures PurGRO2® technology would greatly reduce fish stress during cage treatments but could also affect pesticide potentiality or toxicity to Atlantic salmon during treatment. These pesticide effects were tested before field trials on commercial fish populations were conducted.

Scaled ECO-Bath Experiments in Tank Trials

A series of in-tank/laboratory trials were completed in July-September 2010 to verify that the 1) high oxygen/TGP environment did not adversely affect the treated fish in any acute or chronic way, 2) high oxygen/TGP environment did not potentiate the pesticide dose, rendering it more lethal to treated fish, and 3) efficacy of the pesticide used was enhanced in the high oxygen/ TGP environment. Salmon were exposed to treatments with Salmosan, Alpahamax and hydrogen peroxide, in combination with the PurGRO2® environment. Further, methods to remove pesticide compounds from treatment water were trialed. Finally, in order for the ECO-Bath System to work optimally, pesticide concentrations within the treatment bath must remain stable during the treatment period and the treatment tarpaulin must remain impermeable to water to achieve this aspect. We tested the selected tarpaulin material to be used in the ECO-Bath System to verify that it was indeed impermeable with no leakage.

The goal of all experiments was to provide scaled down conditions, as closely as possible, that were considered characteristic of the treatment environment provided by the ECO-Bath System. Four of the proposed experiments were completed to determine possible changes in the efficacy of chemical treatments on fish health (survival) and sea lice removal/mortality including: a) infused O2 alone vs. control; b) H2O2 (hydrogen peroxide) + infused O2 vs. control; c) Deltamethrin (AlphaMax®) + infused O2 vs. control; and, d) Azamethiphos (Salmosan) + infused O2 vs. control. A final experiment was completed to test the efficacy of freshwater to remove an appreciable number of sea lice over a feasible period of time in a treatment bath (one hour).

Tank Trial Conclusions

Several conclusions can be derived from the experiments performed to test the operating parameters of the ECO-Bath System as follows:

• Experiments verified that a very high oxygen (250-350% saturation) and TGP (103-120%) environment did not cause mortality of exposed salmon.
• There was no difference in mortality between fish treated with Salmosan and Alphamax in combination with a high oxygen/TGP environment and those treated with Salmosan and Alphamax in an ambient oxygen environment.
• No difference was observed in the efficacy of the compounds in killing and/or removing sea lice between fish simultaneously exposed to high oxygen/TGP environment and sea lice infected fish treated in an ambient oxygen environment.
• Hydrogen peroxide use was discontinued, in part, as it appeared to remove the protective mucous coating from the exterior of fish and their gills. This has also been recorded at sea cages using hydrogen peroxide and further thought must be given to the approach to take while using hydrogen peroxide in the ECO-Bath System.
• Freshwater trials were added but did not remove appreciable numbers of sea lice in a short period of time.
• The proposed heavy nylon, urethane-coated tarpaulin material proved impermeable to the pesticides used in the experiments and a full-scale ECO-Bath tarpaulin was manufactured following these results.

Phase II: Design of an Eco-Friendly Bath Solution

General design incorporates the following components to maximize fish welfare, environmental stewardship and bath treatment efficacy:

• Modified AEG Containment System provides a fixed bath volume with external debris skirt
• Double impermeable tarp with internal transfer net retains treatment bath water
• Water recirculation and filtration minimizes water quality deterioration and removes organics/cleared sea lice
• Nitrogen reducing oxygen infusion reduces stress on crowded fish
• Proven fish pumps that are gentle on transferred fish with no scale loss
• Versatile dewatering to and from treatment bath systems while retaining treatment water
• Integrated method binds or eliminates remaining pesticides active ingredient when all site treatments are completed

The AEG Containment Systems required minimal overall design changes except that each beam needed to be much shorter for proper deployment within the small treatment bath collar. A double tarp system was also developed to provide redundancy to the system while holding pesticides during an extended treatment period as necessary. An Aqualife fish pump was chosen due to its ability to pump fish from a relatively loose seine thereby reducing stress and gentle handling of the fish inside the pump to reduce damage and possibility for handling mortality. The dewatering system was specifically designed such that pumped fish would be upwelled onto the table and a swivel arm would direct transferred fish in either of two directions with minimal hose handling after the entire system is positioned – from the grow-out cage to the treatment bath cage or from the treatment cage to the grow-out cage after treatment. Of course, the Aqualife pump also pumps a large quantity of water during the fish transfer process and so it is imperative that this transfer water is easily handled by the dewatering system so that pesticide treatment water is properly returned to the bath cage while ocean water is not allowed to enter the bath systems to prevent an overflow of treatment water. Solids removal is critical to overall success as the recent experience in NB shows that the active ingredient in some pesticides binds with natural organic material in the cage environment rendering it inactive. Finally, the inVentures PurGRO2® system is deployed in duplicate for each ECO-Bath System bath to supply ultra high oxygen water to help alleviate fish stress during treatment while removing nitrogen and therefore providing an appropriate total gas pressure.

In practice, two complete ECO-Bath Systems might be required on each site due to the time required to move fish to each treatment bath followed by the required soak time and then returning the treated fish to the grow-out cage. Logistically this process may be difficult while using a single bath system and to complete daily cage targets. In this case, fish will be seined into the bath units until the grow-out cage is corked as necessary to remove the last fish for treatment. An empty cage could be left within the mooring grid to allow this approach to treat all cages efficiently on the site. An alternative approach might be to dedicate a single ECO-Bath System permanently to each site so that the crew can continually treat fish along with completing other site tasks (i.e., treatment can occur in tandem with net cleaning) and remove artificial time constraints to the overall treatment schedule. Dedicated site-specific ECO-Bath Systems are feasible when comparing the cost per unit to the total cost associated with acquiring a well boat.

Phase III: Field Trials of the ECO-Bath System

Field trials of the ECO-Bath System followed completion of Phase I tank trials and meetings associated with Phase II design activities. Two complete ECO-Bath Systems were available but the components of only a single ECO-Bath System were deployed for the prototype trials discussed in this report including an internal transfer net, double tarp and external debris skirt coupled with all required plumbing associated with the filtration and oxygen infusion systems and purpose built dewatering table.

Initial Operations

Many of the system components were operated independently before additional studies were completed to monitor water mixing, fish movement and finally salmon treatment. The water circulation and filtration system was operated on numerous occasions to ensure that all plumbing was properly completed and without leaks. The fish pump and dewatering table were also operated for similar reasons particularly when the system would be transferring treated salmon from the ECO-Bath System to the grow-out cage and requiring return of all pesticides treated water back to the bath system. Finally, the ECO-Bath System circulation, filtration, oxygenation, fish pump and dewatering table were all positioned on the barge deck to allow optimal use of the components while enhancing fish welfare and system functionality.

Dye Studies

DFO staff have used fluoroscein dye to monitor mixing during sea lice treatments in well boats and salmon cages as the dye is a more cost-effective and non toxic measurable surrogate for the pesticide compound. The first dye study simply involved pouring dye directly around the inside perimeter of the tarpaulin and looking for obvious leakage of the highly visible fluoroscein dye to the outside water. This study demonstrated no visible permeability of the tarpaulin similar to results from tarpaulin trials completed at the Huntsman in Phase I.

A follow-up dye study occurred on 28 July 2011 with DFO SABS personnel to monitor the degree of mixing within the ECO-Bath System but in the absence of fish. Mixing of the treatment water is imperative to ensure that the administered pesticides is distributed appropriately throughout the bath system for an effective bath treatment and enhanced fish health while diminishing the opportunity for sea lice resistance to occur to any specific treatment pesticide compound.

Salmon Treatment

System Performance

On 21 October 2011 the first Atlantic salmon were pumped to the ECO-Bath System, held for a set time indicative of a pesticides treatment and then pumped back to the grow-out cage. The filtration/oxygenation systems were started two hours prior to beginning fish transfer so that the bath water could begin its circulation and have organic materials filtered from the water, which would be necessary if pesticides were added to the treatment cage. Approximately 2,350 salmon having an average weight of 1 kg were transferred across the dewatering table and into the ECO-Bath System in less than 30 min using the Aqualife pump.

The crew began to seine the salmon in the ECO-Bath System about 30 min after entry to the bath and the fish pump turned on to begin transfer back to the grow-out cage approximately one hour after completing the entry fish transfer. Salmon transfer from the bath cage to the grow-out cage required about 30 min to complete. This pace was acceptable for the first trial and theoretically meant that the first salmon in could have been present in the bath cage for about two hour if it were the last salmon to return to the grow-out cage.

Our primary concerns with this trial were the ECO-Bath System oxygen levels and the capability of the PurGRO2® system to maintain oxygen at or above an acceptable level in the relatively large volume involved. These concerns are magnified as the salmon are highly stressed from the transfer process and from being contained within the tarp. The oxygen levels also remained high within the tightly seined population of fish during the return transfer with measurements consistently remaining higher than 130% saturation. In total, 1.45 kg of oxygen was transferred to the bath cage using the PurGRO2® system with about 0.744 kg of this oxygen consumed during the trial, including the fish pump. The calculated oxygen uptake between 11:30 am-12:15 pm was 0.23 g O2/h/kg fish. This quantity of oxygen is less than the generally accepted 0.30 g O2/h/kg fish that would be consumed by unstressed fish. Dissolved carbon dioxide was also monitored throughout the trial and never reached one ppm providing further indication that the transferred fish were not experiencing any stress during the trial.

Results from this initial fish transfer trial provided sufficient information and confidence in the ECO-Bath System components to move to the next project stage and conduct a pesticides treatment. On November 14, 2011 the project team completed its first treatment of Atlantic salmon with the ECO-Bath System. The same approximately 2,350 sea lice infected Atlantic salmon having an average weight of one kg were treated with the pesticide Salmosan (i.e., Azamethiphos) using a target dose of 0.3 ppm and target treatment period of one hour.

A similar strategy was used as in the initial salmon transfer trial but with a goal to be more efficient so that the entire treatment process might be completed within the time period required when using pesticides. The filtration system was started more than one hour before salmon transfer began to allow circulation of the bath water and filtration of organic material. Algae within the bath cage increased the O2 levels overnight and so the PurGRO2® systems were placed on idle and would infuse O2 only as required. An appropriate quantity of Salmosan was introduced to the bath cage in less than five minutes using a separate pump and flat hose with holes pierced along its length and extended across the surface of the bath cage (similar to the introduction of fluoroscein dye during the earlier dye study).

Salmon transfer started about one hour after the introduction of Salmosan to give ample opportunity for the pesticide to mix throughout the bath volume based on results from the earlier dye study. The first fish were transferred using the fish pump at 11:06 am with the final salmon moved to the treatment bath at 11:32 am. The crew started to seine the treated salmon using the internal net at 12:00 pm to begin movement out of the ECO-Bath System. The treated salmon were continually crowded in the direction of the fish pump with the final fish transferred out of the Salmosan treatment water at 13:10 pm. The total theoretical treatment period for the first salmon in could be as long as about two hours if it were also the last salmon taken out of the treatment water. Movement of salmon in the ECO-Bath System process must be quicker and we fully expect this to be the case as more experience is gained by the crew and less time is required to monitor the system as is the case during this development stage. However, we were also not concerned about the health of the treated salmon based on the results from the tank trials completed earlier at the Huntsman.

Oxygen measurements were again taken throughout the entire treatment trial. The single O2 probe was consistently moved in the treatment bath such that O2 was measured directly within the seined area where the salmon were gradually corralled to enable transfer out of the ECO-Bath System. The oxygen results were similar during the treatment trial with pesticides as the earlier fish transfer trial. The calculated oxygen uptake between 11:30 am-12:00 pm was 0.23 g O2/h/kg fish. This quantity of oxygen is less than the generally accepted 0.3 g O2/h/kg fish required by unstressed fish. Dissolved carbon dioxide was also monitored throughout the trial and never reached one ppm providing a further indication that the treated salmon were not experiencing any stress during the ECO-Bath System treatment with Salmosan. The oxygen saturation did drop below 100% during the treatment trial; however, the PurGRO2® systems were kept on idle during the trial. If another bath treatment was planned for immediately following the treatment then the PurGRO2® systems would have been activated to keep the oxygen saturation levels elevated to ensure low fish stress during subsequent bath treatments within the ECO-Bath System.

Biological Response

Developing an environmentally sensitive ECO-Bath System would be pointless if removal of sea lice does not meet or exceed results acquired from bath treatments using tarps or well boats. Pre- and post-treatment sea lice counts provided very positive results that exceeded our expectations.

Data provides a clear indication of the overall success of the ECO-Bath System to treat sea lice infestation of Atlantic salmon using the pesticide Salmosan. The ECO-Bath System treatment trial occurred on November 14, 2012 and the pre-treatment count was completed within two hours prior to this treatment. The total removal of all life stages of sea lice on treated salmon was 75.5%. The most dramatically affected life stage was mobile sea lice, which was removed at a rate of nearly 81% within 24 hours of the ECO-Bath System treatment. Removal of other sea lice life stages were also positive from the ECO-Bath System treatment with more than 61% of the chalimus sea lice and nearly 55% of the adult female sea lice removed 24 hours post-treatment.

These results are generally better than actual sea lice removal results in the local industry while using Salmosan in tarps and well boats in 2010 and 2011. The present label for Salmosan states that 20 g per 100 m3 is allowed in tarps or 0.2 ppm. However, the local salmon aquaculture industry has been permitted to provide a treatment dose of 0.3 ppm of Salmosan in tarps as it is proving very difficult to attain the target concentration of 0.2 ppm in tarps due to the large and variable volume involved in a tarp and the high concentration of organic material naturally present in the Bay of Fundy. We used this same permitted 0.3 ppm dose as the ECO-Bath System is essentially an advanced tarp strategy; however, in our specific case we in fact reached and maintained this permitted tarp concentration of 0.3 ppm. This capability compares with the fixed volume within a well boat but the higher Salmosan concentration is likely one factor that provided the impressive ECO-Bath System sea lice clearance results. An additional factor that likely attributed to the superior ECO-Bath System results is the fact that the salmon soak time within the treatment was longer as already discussed. Together, a higher Salmosan concentration and longer treatment period provided increased efficacy of Salmosan to treat sea lice within the ECO-Bath System.

A major concern for the industry would be whether increased Salmosan efficacy within the ECO-Bath System might negatively affect treated salmon survival. However, our results provide sufficient evidence to set aside this concern. Just nine salmon mortalities were collected 24 hours post-treatment or 0.38% of the treated population. This low number of mortalities following any treatment is remarkable and provides impressive results for the ECO-Bath System given this was the first treatment trial using the prototype system and the water temperature was 10oC. Of course, our treatment stocking density (7.8 kg/m3) was considerably lower than a target density for commercial treatments but we do not anticipate a significantly higher mortality rate given that the treatment bath O2 concentration will not be depleted while using the PurGRO2® oxygenation units. Chronic long-term mortality was also not evident in the treated salmon population as can sometimes be the case post-treatment.

Finally, it should be noted that all sea lice that were physically dislodged from treated salmon while contained within the ECO-Bath System would not find themselves returned to the ocean environment. This can sometimes be the case when treating sea lice in tarps or well boats whereby sea lice are removed from the salmon but not killed and released to the ocean environment for possible reinfection following treatment. With the ECO-Bath System, any sea lice (dead or alive) that are removed from salmon while within the system would be eventually filtered from the bath water and not pose any further threat for reinfection on otherwise treated salmon.

Pesticides

Water samples were taken before, during and after the salmon treatment trial to confirm that the target Salmosan concentration was reached. Samples were sent to RPC for laboratory analysis using accepted solvent extraction and analysis by liquid chromatography/tandem mass selective detection methods to measure the concentration of Azamethiphos (the active ingredient in Salmosan). Results indicated that Salmosan was mixed throughout the ECO-Bath System as expected following the previously described dye study and the target pesticide concentration was also reached and maintained throughout the treatment trial.

In general, water samples indicated Salmosan concentrations more consistent than bath treatments in tarps and higher than well boat Salmosan concentration used locally to treat for sea lice. The NB salmon farming industry is permitted to introduce Salmosan in tarp treatments at a concentration that would provide 0.3 ppm but with the hope to reach the required dose of 0.2 ppm given the high quantity of natural organic material present in the waters of the Bay of Fundy. We followed this same procedure as the ECO-Bath System is also a tarp albeit integrated with water filtration and oxygenation components. Our ability to reach and maintain a dose concentration of at least 0.3 ppm provides the most convincing evidence for the capability of the ECO-Bath System to filter natural organic material from the bath water and therefore a superior treatment environment in stark contrast to simply placing a tarp around the grow-out cage volume.

Some Salmosan was detected within the ECO-Bath System water prior to introducing the treatment dose. However, we expect this essentially negligible quantity originated from the pump/hose used to deliver Salmosan that would have been used previously at another location. Water samples taken 10 and 20 minutes into the treatment period provided identical concentrations of Salmosan indicating that sufficient organic material had been removed from the treatment water so that none of the active pesticide ingredient was bound and therefore lost during the treatment. An identical measure also provides further evidence that the treatment water/pesticides were fully mixed as was expected from the previous dye study.

Sample #4 was taken on the next day following the treatment trial (24 hours after the introduction of Salmosan to the ECO-Bath System) and showed a reduction in Salmosan to 0.22 ppm or 39% reduction in the pesticide concentration. This reduction is entirely attributed to the oxidizing effect of the sun on the Salmosan active ingredient Azamethiphos. Our results suggest that multiple cage treatments could occur on the same day with little requirement to top-up the Salmosan concentration; however, approximately 1/3 of the target dose of Salmosan would need to be added to the ECO-Bath System if treatments were to continue on the next day to maintain a target Salmosan concentration.

Pesticides Removal

As described, significantly less pesticides are required to treat sea lice infestation when using the ECO-Bath System compared to tarp and well boats given the ability of the ECO-Bath System to retain pesticides between treatments on a specific day and requiring just a 1/3 top-up to continue treatments on the same site on subsequent days. This ability of the ECO-Bath System affords salmon farming companies an enormous amount of environmental benefit not previously enjoyed when it comes to sea lice bath treatments. However, the ECO-Bath System also holds promise for the complete removal of the pesticide active ingredient after an entire site has been treated.

Huntsman staff completed the initial trials using activated charcoal in a passive filter to remove pesticides from water. Their results were very encouraging and led NB Department of Agriculture, Aquaculture and Fisheries (DAAF) personnel to continue with these efforts at the Huntsman during the project period. Two trials were completed to remove pesticides using activated carbon: one using Salmosan and one using Alphamax. A significant reduction in the amount of pesticides was achieved using carbon filtration under pressure. Resultant pesticide removal exceeded expectations with 99.79% removal of Alphamax (14,000 ppm start to 29 ppm after filtration) while 99.99% of the Salmosan was removed by the pressurized carbon filter (310,000 ppm start to 20 ppm final concentration). The starting concentrations of Alphamax and Salmosan were obviously much higher than concentrations used for sea lice treatments; however, these excessive starting concentrations were used to ensure that the final concentration of each pesticide was indeed detectable during laboratory water analysis but similar percentage reductions should be expected using the treatment concentrations of each pesticide. These results provided the impetus for NB DAAF to obtain additional funding to continue with research into the removal/denaturation of pesticides in treatment water and additional methods to absorb/denature used pesticides have also been explored. These efforts are outside of the scope of this specific ECO-Bath System project.

The ECO-Bath System lends itself well to integration of a passive or active filter that would absorb/remove pesticides active ingredient after an entire salmon site involving numerous sea cages has been treated. The ECO-Bath System continually pumps water from the middle of the bottom tarp in the bath cage to the filtration/oxygenation components and back to the bath cage to create a small current within the bath cage and subsequent mixing. Integrating a suitable passive/active filter would be achieved by adding the filter in line with this water movement at the end of sea lice treatments. This will allow the bath water with pesticides to pass directly through the filter to remove the entire active ingredient followed by safe disposal on land rather than to the ocean environment. Theoretically, if the filter was consistent in giving a high degree of removal as seen in the reported early studies then filtered bath water could simply be pumped to the ocean free of pesticides as the bath cage is pumped dry following treatment. Any possibility to entirely remove pesticides following treatment has eluded the industry in the past while using tarp or well boat treatments.

Water sampling results also indicated that leaving the ECO-Bath System with direct exposure to the sun will also result in deterioration of the pesticides active ingredient over time – at least in the case of Salmosan. Our results indicate that about 1/3 of the Salmosan active ingredient deteriorates each day through oxidation and therefore only about 0.0047 ppm of the Salmosan active ingredient will remain after 10 days of having direct exposure to the sun (assuming a starting concentration of 0.3 ppm). Solar degradation (oxidation) is not a preferred method of pesticide removal; however, oxidation lends itself as a possible method for pesticide removal while using the ECO-Bath System, which is not the case while treating with tarps or well boats. This would especially be the case if a dedicated ECO-Bath System is maintained on each grow-out site and therefore not requiring a complete breakdown after completing an entire site treatment before moving to the next site.

These results provide a clear indication that the ECO-Bath System might also provide a means for use of other pesticide compounds that are presently not allowed while using tarps or well boats due to their potential negative effects to the marine environment. The ECO-Bath System affords the possibility to remove the entire active ingredient for each and every possible pesticides compound that might be added to the fish farmers toolbox to more effectively manage sea lice infestation as part of a responsible Integrated Pest Management Plan.

ECO-Bath System versus Well Boat Comparison

Reported results provide a dramatic contrast between the use of the ECO-Bath System and cage tarps or well boats to treat sea lice infested Atlantic salmon with Salmosan. The average salmon farm in NB will have:

• 315,000 salmon present typically in 10 cages (about 31,500 salmon per cage)
• Operators will plan to raise these salmon to a target live weight of 5 kg (157,500 kg biomass per cage)

The ECO-Bath System and well boat both have two compartments (baths or wells, respectively) to treat infested salmon with each compartment having:

• Approximately 300 m3 of treatment volume
• Average target treatment density for salmon is 80 kg/m3
• A calculated weight for each compartment per treatment is 24,000 kg
• This weight of salmon will allow 4,800 individual fish in each bath/well at the target live weight harvest size of 5 kg
• These optimal target numbers will require 7 baths/wells to complete a bath treatment of a typical salmon cage population in NB of harvest size salmon without exceeding a target treatment density of 80 kg/m3

Up to this point, the comparison between the ECO-Bath System and well boat is essentially identical. However, the quantity of pesticides required to treat a cage and site in the ECO-Bath System is significantly less than that required in a well boat. Of course, the costs to purchase the pesticides and possible environmental impacts are also less with the ECO-Bath System.

The well boat strategy requires that the full dose of pesticide (e.g., Salmosan) be added for each individual well treatment as the treatment water is flushed out of the well during return transfer of the treated salmon to a grow-out cage. The ECO-Bath System maintains the treatment bath water during the return transfer of treated salmon to the grow-out cage. This strategy allows the operator to reuse the same pesticides for subsequent bath treatments on the same day to complete a full cage bath treatment. Our treatment trial only involved a single movement of salmon to the bath and a limited number of water samples for analysis. A next step required in the ECO-Bath System development must involve multiple uses of the bath water to treat infected salmon on the same day coupled with an aggressive water sampling regimen. This will allow us to more fully understand the expenditure of pesticide active ingredient in subsequent bath treatments on the same day to treat an entire cage of infected salmon. However, even if a portion of the pesticide is expended during each subsequent treatment then the total ECO-Bath System pesticide requirement to top-up between treatments is still expected to require a fraction of the total pesticide required to treat an entire site using well boats (i.e., if hypothetically 1/3 of the total pesticide is expended during each treatment then the total Salmosan required to treat a typical cage using 7 baths would be 242 g compared with the 560 g required for the same well boat regimen or nearly 57% less pesticide than that required in a well boat cage treatment).

Based on our present data, the savings of Salmosan between treatments each day and 2/3 savings day-to-day will provide the industry with a significant financial savings while using the ECO-Bath System due to a dramatically lower requirement for Salmosan to treat entire sites. Of course, lower quantities of pesticide will also provide significant environmental benefits and there are further gains possible with the ECO-Bath System if none of the pesticides are released to the ocean environment following site treatment due either to active removal of the pesticide through an absorption filter or leaving the pesticide to oxidize over several days in direct sunlight (note that leaving the ECO-Bath System to allow pesticides oxidation will require installation of a small meshed top net to ensure that no animals/birds inadvertently find their way within the ECO-Bath System).

Additional noted benefits from using an ECO-Bath System within farm operations include:

• The optimal target treatment conditions within a well boat are provided in 6-8oC water. The ECO-Bath System will not be restrained to this small optimal range given its capability to control the O2 concentration within the treatment water. In fact, the ECO-Bath System treatment trial was conducted in water temperature of 10oC with exceptional results.
• The ECO-Bath System is expected to be available to the industry at a fraction of the cost to purchase a well boat (possibly as low as 5% of the cost to purchase a well boat). This more cost-effective purchase price allows justification to acquire site-specific ECO-Bath Systems that will provide more frequent and consistent sea lice treatments throughout the industry while better mitigating any concerns associated with biosecurity and cross-contamination between fish farm sites.
• Some might argue that the well boat provides a more secure compartment for treatments; however, this has been mitigated in the ECO-Bath System design by integrating a double tarp layer to provide containment redundancy and the entire bath is surrounded by a debris skirt to prevent any possible damage from passing debris.

Communications

Numerous discussions have occurred related to the ECO-Bath System with government agencies, therapeutant suppliers and fish farming companies that appear to have an interest in the ECO-Bath System for direct use within local farming sectors and specific companies.

Formal presentations at industry meetings include:

• Atlantic Canada Fish Farmers Association Invitational Research Meeting (focus on sea lice), December 1, 2010, Fairmont Algonquin Hotel, St. Andrews, NB.
• Atlantic Canada Fish Farmers Association Annual General Meeting and Workshops, November 29-30, 2010, Fairmont Algonquin Hotel, St. Andrews, NB.
• New Brunswick Salmon Growers Association Sea Lice Research and Development Workshop, January 21-22, 2010, Fairmont Algonquin Hotel, St. Andrews, NB.

Research Team

Dr. Amber Garber is with the Huntsman Marine Science Center and was the Project Coordinator. Garber was responsible for project oversight and coordination. Garber also oversaw Huntsman technical staff during tank trials.

Evan Kearney served as the Project Manager reporting to AIMAP and was the main contact for Admiral Fish Farms. Kearney was involved in project meetings and coordinating Admiral staff during field trials.

Bill Hogans provided support in protocols and testing at the Huntsman (Phase I). He was also particularly involved in the set-up of the prototype circulation and filtration system.

Chris Bridger and Phillip Dobson are partners in AEG Innovative Solutions Inc. and both individuals were involved in project meetings, conceptual and component designs for the ECO-Bath System, coordinating AEG fabrication staff and participating in field trials. AEG retains the intellectual property rights of the ECO-Bath System through patents and will market the system for global sales.

James Snider, Craig Glassford and Wade Campbell are partners in inVentures Technologies Inc. and were involved in project meetings, coordination of inVentures fabrication staff and participation in tank and field trials particularly regarding the PurGRO2® oxygenation system.

Clarence Blanchard is the owner of Future Nets & Supplies and was actively involved in the manufacture of the system tarp.

Dr. Michael Beattie and Kathy Brewer-Dalton work with the NB Department of Agriculture, Aquaculture & Fisheries and both individuals, along with other NB DAAF staff, participated in project meetings and responsible for overseeing development progress from a fish health and pesticides use perspective.

Dr. Fred Page and staff of the Department of Fisheries and Oceans, St. Andrews Biological Station were involved with the ECO-Bath System project to complete and analyze dye study results to identify any technical issues with the system (e.g., permeability and mixing) and provide required information to various regulatory agencies.

Funding for the ECO-Bath System development project was provided by the DFO AIMAP, NBIF and the participating companies/organizations.

Conclusions & Next Steps

1. The ECO-Bath System holds tremendous promise as a tool within an aquaculture Integrated Pest Management Plan. Next steps to further refine the ECO-Bath System include:
• Continuing field trials in the 2012 treatment season with the Admiral Fish Farms prototype ECO-Bath System to:
• Gather further data regarding pesticide depletion/usage between successive bath treatments and overnight;
• Train additional personnel in the optimal use of the ECO-Bath System and its various integrated components; and,
• Apply for permission to use other pesticide options for field trials while using the fully contained and eco-friendly ECO-Bath System.
2. AEG is presently completing fabrication plans that include a purpose-built barge with integrated plumbing for all of the ECO-Bath System components. Project partners plan to continue our collaborative efforts to deploy a final commercial ECO-Bath System using many of the components already present from this project but with the capability to treat all salmon sizes expected within commercial operations.