Transport & Dispersal of Deltamethrin Treatment of Atlantic Salmon

Table of contents

• Executive Summary
• Conclusions
• Introduction
• Activity 1: Determination of dispersal of sea lice control product
• Introduction
• Summary and Conclusions
• Activity 2: Determination of rate of mixing, concentration of sea lice control product within a treated cage during treatment and temporal dilution of sea lice control product using AlphaMax® (deltamethrin) (2009)
• Introduction
• Discussion and Conclusions
• Activity 3: Monitoring the impact of AlphaMax® (deltamethrin) on sentinel species including american lobster (Homarus americanus) in the field
• Introduction
• Summary and Conclusions
• Activity 4: Effect of sea lice control product on mussels at an Integrated Multi-Trophic Aquaculture site
• Introduction
• Conclusions
• Activity 5: Laboratory study on fate and partitioning of the active ingredient of various sea lice bath treatments. (2010)
• Introduction
• Summary, Conclusions and Recommendations
• Mixing and deltamethrin concentrations during treatment
• Effluent dispersal
• Overall
• Benefit of AlphaMax® Research for the Canadian Salmon Farming Industry

Executive Summary

In the fall of 2008 and throughout 2009 the salmon aquaculture industry within southwest New Brunswick suffered from an outbreak of sea lice. As part of the management strategy aimed at controlling sea lice abundance, the province of New Brunswick applied to the Pest Management Regulatory Agency (PMRA) for the emergency registration of the sea lice bath theraputant, AlphaMax®, with active ingredient deltamethrin. Bath treatments, either skirts or tarps, for the application of chemical therapeutants, have been a standard procedure for salmon industries in various nations (Chile, Norway etc.). General assumptions associated with their use include that the product is applied, becomes well mixed within the tarped or skirted cage and reaches target concentration, on a regular basis.

PMRA approved the emergency registration for AlphaMax® in Southwest New Brunswick with a number of usage restrictions, and with requirements for designing and implementing a monitoring, surveillance and research program. The province of New Brunswick in collaboration with the PMRA, Fisheries and Oceans Canada (DFO), Environment Canada (EC) and the Atlantic Canada Fish Farmers Association (ACFFA) (formerly known as the New Brunswick Salmon Growers Association) therefore designed monitoring and surveillance studies to help ensure the proper use of the product and issue early warnings of potential adverse effects on the environment. Aquaculture Innovation and Market Access Program (AIMAP) funding was awarded to fulfill part of the regulatory research requirements in the following five categories:

• Activity 1: Determination of dispersal of sea lice control product
• Activity 2: Determination of rate of vertical mixing, concentration of sea lice control product within a treated cage at the time of release and temporal dilution of sea lice control product
• Activity 3: Impact on sentinel organisms
• Activity 4: Effect of sea lice control product on mussels at an Integrated Multi-Trophic Aquaculture site
• Activity 5 (Amendment): Laboratory study on fate and partitioning of the active ingredient of various sea lice bath treatments

This report identifies the research, monitoring and surveillance that was undertaken to fulfill these requirements.

Field studies were concentrated at three farm sites located in Aquaculture Bay Management Area 2a, representing different hydrographic regimes, farm configurations and cage sizes. AlphaMax® skirt treatments at one cage per test site were intensively studied. Researchers accompanied site crews who followed standard industry treatment procedures. The AlphaMax® product was mixed with seawater in a 1 m3 container and pumped into perforating hoses that extended across the diameter of the cages. Target exposure was a concentration of 3 ppb for 40 minutes. At the end of the 40 minutes, the skirt was removed and water flow entered, dispersing the chemical.

Mixing and concentrations inside treatment cages (Activity 2):
Water samples were taken at four different stations around the inside periphery of the treatment cages at multiple times during the treatment and following skirt removal. Deltamethrin concentrations measured inside the skirt during treatment varied among stations, never reaching a constant state and reached a maximum concentration of approximately 10 % of the target deltamethrin concentration. Following skirt removal, AlphaMax® remained detectable in the cage up to at least an hour after treatment, though at one cage it was undetectable by half an hour and another it may have been longer than an hour.

Dispersal (Activity 1)
Following the removal of the skirt, the dispersal of the product was investigated with the collection of water samples in the estimated effluent plume. Sediment samples were collected pre- and post-farm treatment regimes (i.e., treatment of all cages on farm). An evaluation of current speeds and flow direction during and after treatment was accomplished through the use of current meters and surface drifters. At one site, current data and flow direction were available for subsequent treatments at the same site. The water samples collected in the estimated plume detected deltamethrin at only one of the three test sites. No deltamethrin was detected in sediment samples; however, exposure to deltamethrin was unknown.

The characterization of flows around fish farms found that the mean current speed at the time of treatment trials ranged from 1.5 to 11.5 cm·s^-1. Current speeds within the treatment cages during treatment were lower than outside the treatment cages. An estimation of the time taken for the product to flush from the treatment cages varied among sites. Based on the water chemistry data taken within the treatment cage following skirt removal (Activity 2), the flushing rates were comparable to estimates produced with the current data at Sites B and C. At the site where current data was available for multiple cages, the current direction and speed varied considerably among treatments.

Impact on Sentinel organisms (Activity 3 and 4)
Sentinel species arrays containing multiple marine organisms and lobster cages were deployed at distances up to 200 m away from the treatment cages at the three test sites and at two reference sites. While the organisms at the test sites were deployed for the entire site treatment regime, current meter data used to estimate exposure was only available for the intensively treated cages, with the exception of one site where current meter data was available for the entire treatment regime. Projections of plume direction and speed were derived from the current and drifter data indicated that sentinels were exposed for brief periods of time from treatments at a subset of cages. No mortalities or damage among the organisms were attributed to exposure to AlphaMax®.

In order to explore the uptake of deltamethrin by organisms co-cultured with salmon, like mussels, grown as part of Integrated Multi-Trophic aquaculture (IMTA) systems, mussels were collected at one of the test sites and an additional adjacent IMTA site following site treatment regimes. No deltamethrin was detected in tissue samples, however exposure experienced by the mussels was unknown.

Biological and Chemical Partitioning of Active Ingredient (Activity 5)
Indications that field use of deltamethrin was not achieving target concentrations in bath treatments inspired preliminary trials into the uptake of the active ingredient by chemical and biological elements present in sea cage environments. These trials failed to produce conclusive results, but provided useful direction for next steps. Future work should begin with a lab phase to study product fate (i.e., binding characteristics of active ingredients and stabilizers as well as biological availability of active ingredients) in a spectrum of conditions experienced in the field to determine whether the potential for relationships between various facets of water chemistry and product fate exists. If any of the above are validated, field studies should then be considered.

Conclusions:

These preliminary investigations have yielded considerable information concerning the application, mixing, and dispersal of the product and have highlighted the difficulty in assessing exposure.

It is now clear that the product is not becoming well mixed inside the cage and target concentrations are not being met. Dilution of the product following skirt removal inside the cage and outside the cage is not well understood. Dispersal of the product is site specific, and influenced by parameters including currents, wind, fish stocking density, bio-fouling, etc. Further methods need to be developed to conduct relevant sentinel studies. Biological and chemical partitioning of the product is complex and requires further investigation, along with all of the above phenomena.

(Please note some work in these areas is already underway as part of several different research projects)

Introduction:

The New Brunswick salmon aquaculture industry has responded to a number of fish health challenges throughout its history, including the control and management of sea lice. All farms in the Bay of Fundy are monitored on a regular basis for fish health by private veterinarians, fish health biologists and the NB DAAF fish health staff.

Several species of sea lice occur naturally in the Bay of Fundy. They are parasitic on various wild and cultured fish species. To control outbreaks of sea lice, an integrated pest management (IPM) approach is being implemented by the New Brunswick salmon farming industry, similar to strategies used in the agricultural sector. This includes the use of aquaculture bay management areas for coordinating fallowing and stocking, as well as relying on the naturally cold water temperature during the winter months to disrupt the sea lice life cycle. A final component of IPM is the use of chemical therapeutants, when deemed necessary. In order for chemical therapeutants to be efficient and efficacious as part of the IPM, the availability of multiple products is considered vital to prevent resistance from building in sea lice populations and therefore minimize the need of chemical treatments. Bath treatments, either skirts or tarps, for the application of chemical therapeutants have been a standard procedure for salmon industries in various nations (Chile, Norway etc.). General assumptions associated with their use include that the product is applied, becomes well mixed within the tarped or skirted cage and reaches target concentration, on a regular basis.

The NB DAFF and salmon farming industry have been working closely with the Federal government in order to access alternative chemical therapeutants for sea lice control. Several chemicals are used in salmon farming jurisdictions in other areas of the world. A review of these chemicals led to the selection of AlphaMax®, with active ingredient deltamethrin, a product used in other salmon farming countries. The approval of pesticides such as deltamethrin for use in Canada is the responsibility of the PMRA of Health Canada. The NB DAFF applied to Health Canada for access to AlphaMax®. The PMRA considered the value and safety of AlphaMax® before permitting its limited use. The assessment included a scientific review of the literature, with risk assessments on both human and fish health and potential environmental impacts.

In May 2009 PMRA approved a limited use of AlphaMax® for a defined geographic area (ABMA 2a – 2007, 2010 year class) in Southwest New Brunswick. There were several restrictions placed on the approval including: a- use was restricted to 13 sites in the ABMA 2a and 3a region; b- no site located within 3 km of an active lobster pound was permitted to use this product; 3- hydrographic information had to be used to limit the overlap of plumes following treatment and 4- sites were advised to treat on an outgoing tide. In addition to these restrictions the approval required a monitoring, surveillance and research program to be undertaken. This program included:

1. Determination of chemical concentrations in the cage at time of treatment
2. Determination of rate of vertical mixing within a treated cage
3. Collection of treatment data: including pre and post treatment sea lice counts
4. Surveillance for determination of dispersal following release
5. Monitoring impact on sentinel organisms
6. Laboratory studies on lobster toxicity

The province in collaboration with the PMRA, DFO, EC and the ACFFA designed monitoring and surveillance studies to help ensure the proper use of the product and issue early warnings of potential adverse effects on the environment. AIMAP funding was awarded to fulfill part of the regulatory research requirements in the following categories:

Activity 1: Determination of dispersal of sea lice control product

Activity 2: Determination of rate of vertical mixing, concentration of sea lice control product within a treated cage at the time of release and temporal dilution of sea lice control product

Activity 3: Impact on sentinel organisms

Activity 4: Effect of sea lice control product on mussels at an Integrated Multi-Trophic Aquaculture site

Activity 5 (Amendment): Laboratory study on fate and partitioning of the active ingredient of various sea lice bath treatments

This report identifies the research, monitoring and surveillance that was undertaken to fulfill these requirements. The report takes the form of a series of separate manuscripts, directed at each of the questions.

Activity 1: Determination of dispersal of sea lice control product.

Introduction:

The PMRA approved an emergency use of AlphaMax® in Aquaculture Bay Management Area 2A under the condition that several monitoring, surveillance and research initiatives be undertaken to help fill knowledge gaps associated with the efficacy, transport and dispersal and environmental effects of AlphaMax®. The objectives of this activity were to determine the concentrations of product in effluent plumes, to estimate flow direction and speed during the time following product release using current meters and drifters and drogues, to determine if any product remains in the near site sediments post treatments, to conduct zooplankton tows for future analysis and finally to provide this information to further refine FVCOM hydrographic modeling.

Summary and Conclusions:

Current information, sediment samples and effluent water samples were gathered from treatment trials conducted at three separate farm sites, designated Sites A through C, in the southwest New Brunswick area. Some difficulties were encountered in association with the measurement of the near surface current. The current meters suspended within the treatment cages experienced changes in the depth at which they were suspended. During the time period when the Site B trial cage was skirted the current meter appeared to have been raised to the near surface such that the current data from this time period was not reliable and hence was not included in current analyses. Some of the near surface data collected by the ADCPs moored in close proximity to the treatment cage was also of poor quality and was not included in the data analyses. This data was thought to have been influenced by the near surface acoustic interference associated with the presence of treatment vessels, cage infrastructure or bio-fouling. Despite the loss of some data there was sufficient information gathered to characterize the flow during and after the treatment period.

The characterization of flows around fish farms found that the mean current speed at the time of treatment trials ranged from 1.5 to 11.5 cm·s^-1. Current speeds within the treatment cages during treatment were lower than outside the treatment cages. The mean current speed within the treatment cage during the treatment trials was less than 5 cm·s^-1. During all three trials the currents were relatively weak, usually being less than 10 cm·s-1. At Site B, in the three hours post treatment for cages #1-10, mean current speeds varied per treatment cage from 2.1 to 21.6 cm/s and median current speeds from 1.8 to 23.7 cm/s.

The rate at which the theraputant was flushed from the treatment cage ranged from 4.7 to 14.1 minutes for Site B, with the 4.7 minutes corresponding to the time for the water to transit across the diameter of the polar circle cage and the 14.1 minutes being three times the e-folding time scale associated with the assumption of continuous mixing throughout the cage, to 6.2 to 18.6 for Site A and 17.8 to 53.3 for Site C.

The drift trajectory of the treatment theraputant over the six hour period immediately following the lifting of the treatment tarps at trial treatment cages was characterized by the empirical drifter data as well as progressive displacement trajectories estimated from the moored current meters.

At the two sites (Sites B and C) where both drifter and progressive displacement data existed, the drifter and progressive displacement trajectories were similar for the initial few minutes to an hour or so after the lifting of the skirts. After that the drift trajectories and progressive vector trajectories began to diverge with time, due presumably to spatial variation in the water circulation that was captured by the drifters but not by the current meters.

At Site A, the drift pathlines estimated from the current meters following the treatment and skirt removal at the trial cage all flowed in the southwest direction. Current meters were recovered from the site before additional AlphaMax® treatments were conducted at the site and hence plume pathlines for treatments other than the Cage 5 treatment could not be estimated.

Drifters released from around the treatment Cage 6 at Site B moved away from the cage toward the northeast. Pathlines estimated from the current meters deployed at this site also indicated an initial easterly drift, evolving to southeasterly, following skirt removal at Cage 6. For subsequent treatments at the other cages on Site B, progressive displacement pathlines were estimated from current meter data. The estimated trajectories varied in direction from southwest, south, southeast, east to northeast.

Drifters released from around treatment Cage 14 at Site C moved away from the cage toward the southwest and pathlines estimated from the current meters deployed at this site also indicated a southwest drift

In two of the three treatment cases the current meter and drifter data indicated the initial drift direction was from the treatment cage toward other cages in the farm site. At Site A the drift was through five other cages and at Site C it was predominantly through one cage. At Site B the treatment cage was located at the end of a column of cages and the drift was away from the cages.

Plankton samples collected at Site A in the estimated plume remain to be analyzed.

Due to logistical complexities, no dye markers were used in this study.

The water samples taken following drogues post skirt removal at test cages at Sites A and B showed no detectable deltamethrin present, while low concentrations were detected in some water samples taken at Site C.  In order to understand the rates of dilution and vertical and horizontal dispersion of the product more intensive water sampling in the plume is needed or studies involving the use of surrogate dispersion agents like dye.

Deltamethrin was not detected in sediment samples collected in the vicinity of treated sites.

Activity 2: Determination of rate of mixing, concentration of sea lice control product within a treated cage during treatment and temporal dilution of sea lice control product using AlphaMax® (deltamethrin) (2009)

Introduction:

Bath treatments are a widely used in the application of chemical therapeutants in the salmon aquaculture industry. It is critical to understand, from an efficacy and resistance point of view, what exposure of the product the fish and sea lice are receiving during and after treatment. The objectives of this Activity were to determine the spatial and temporal evolution of the chemical concentrations of AlphaMax® (deltamethin) inside skirted cages, to compare deltamethrin concentrations achieved with the target dosage, and to quantify deltamethrin concentrations at the time of release.

Discussion and Conclusions:

• At Sites A, B and C, at individual sampling times, deltamethrin concentrations among the four sampling locations within the cages varied up to 28 fold between the highest and lowest measured concentrations. Concentrations at a majority of individual sampling stations do not appear to have stabilized during the treatment period. This indicates that the product did not become well mixed during the treatment period.

• How fish react to zones with higher deltamethrin concentrations compared to zones with lower concentrations is unknown.

• Concentrations reached within the cage were well below the target of three parts per billion (3 ppb). Prior to skirt removal, the average deltamethrin concentration (standard deviation) at Site A was 0.30 ppb (0.1); at Site B it was 0.06 (0.01), and at Site C 0.15 ppb (0.05). It is unclear why target concentrations are not being met; the product may not be well mixed in the mixing tank prior to application causing uneven dispersion within the cage; it may be sinking and escaping through the bottom of the skirt, or reacting with elements within the water. Also the product may not disperse as well to the cage periphery, where the sampling stations were located.

• Based on average deltamethrin concentrations inside the cage during treatment, it was estimated that field treatment exposures, are to 11 % (Site A), 10 % Site B, or 7 % (Site C) of an ideal exposure.

• These findings could have important consequences for treatment efficacy as well as for resistance building in sea lice populations. Further studies examining the uptake or breakdown of the active ingredients are suggested (beyond Activity 4 in this report) as well as determining fish behavior relative to chemical concentrations

• Concentrations being released from the skirt were approximately 10 times less than target concentration (less than 0.5 ppb).

• By ten minutes post skirt removal, the concentration of active ingredient was diluted between 1 and 22 x at Site A, between 2 and 4 x at Site B, and between 2 and 22 x, at Site C compared to the pre skirt removal concentrations.

• The active ingredient, deltamethrin, was undetectable within the cage in samples taken more than 10 minutes after skirt was removed at Site B, and after one hour at Site C. At Site A, deltamethrin concentrations between 0.014 ppb and 0.07 ppb (two orders of magnitude below target concentration) were detected at 30 minutes post skirt removal, and by the subsequent sampling point, 3 hours after skirt removal, the product was undetectable.

• More sampling points during treatment and post skirt removal would allow for a better understanding of the temporal dilution. It seems the product was already somewhat diluted before the pre-skirt removal water samples were taken, impacting the length of time the product was detected in the cage.

• Further work needs to be completed on the development of product application methods to achieve a quick and even delivery of product in cages. (Please note: Further studies on mixing are currently underway with NB DAAF and DFO using dye as an indicator of overall mixing within tarp and skirted cages. This work has also been completed in the well boats and results will be available in another report.)

Activity 3: Monitoring the impact of AlphaMax® (deltamethrin) on sentinel species including american lobster (Homarus americanus) in the field

Introduction:

Current knowledge of impacts to non-target organisms in field situations is limited. To better understand the impacts of AlphaMax® on non-target organisms in situ, sentinel organisms, including sea urchins, crabs, mussels, starfish and periwinkles, and lobsters of different size ranges, were placed around test sites and monitored during AlphaMax® site treatment regimes. The objectives of this Activity are to report on the impact of AlphaMax® on the sentinel organisms during and subsequent to treatment exposure as well as long term effects of treatment exposure on molting and reproductive processes in lobster. Finally, this Activity summarizes the assessment of exposure to sentinel organisms, from projections of plume direction and speed derived from current and drifter data.

Summary and Conclusions:

All sentinels, from AlphaMax® test sites and references sites, were living and accounted for at the end of the trial periods, with the exception of some escapees, lost tubes and cages, and minor incidence of predation. No mortalities in sentinel species (including lobster) were associated with proximity to AlphaMax® treatments. The lobsters continued normal life processes once transported back to DFO St Andrews.

Although the sentinel cages were deployed in locations that had the potential to be exposed to the effluent plume, the actual exposure depends upon the exact location and nature of the currents at the time of treatment release. These currents vary with the phase of the tide and over small horizontal spatial scales, particularly in some locations and in relation to cage site infrastructure.

Despite these challenges and limitations, the drift trajectories observed and estimated at for the three intensive trial treatments, i.e., one at each of the three sites, indicated that the effluent plume at only one of the treatment sites (Site A) passed through the sentinel cages and at Sites B and C the effluent plume associated with the trial treatment was unlikely to have exposed the sentinel cages. At Site B, current meter data was available to estimate displacement trajectories associated with the treatments conducted at all of the cages on the site. The sentinel cages may have been exposed for five of the ten treatments. The potential for exposure from plumes associated with non-trial treatments at Sites A and C could not be assessed due to the lack of current meter data during the treatment times.

Due to the uncertainty of exposure and the resulting difficulty in drawing conclusions from sentinel work, it would be suggested that further sentinel studies include some additional method of assessing exposure (i.e., taking water samples during potential exposure periods or using indicators like dye to estimate exposure).

Activity 4: Effect of sea lice control product on mussels at an Integrated Multi-Trophic Aquaculture site

Introduction:

In response to the outbreak of sea lice in southwest New Brunswick, the PMRA conditionally approved the use of chemical therapeutant AlphaMax® to be part of the industry’s integrated pest management strategy. However, salmon are not always grown in isolation; approximately 10 % of salmon farms in southwest New Brunswick are IMTA farms, a system where multiple species from differing trophic levels are grown in spatial proximity, to capitalize on by-products produced by one species to provide nutrients for others. Species involved in IMTA systems vary from seaweeds to various bivalve species, including mussels, all which can be marketed commercially. Concerns were raised about the potential impacts of registered sea lice control products for salmon, like AlphaMax®, on other species. The purpose of this study is to investigate the chemical uptake by mussels by analyzing mussel tissues for AlphaMax® residues.

Conclusions:

No AlphaMax® residues were located in the IMTA mussels collected; however their exposure to AlphaMax® effluent plume is unknown. Further, many factors can influence bio accumulation and detection of pyrethroids in tissues including lipid content and bioavailability once bound to sediments.

Activity 5: Laboratory study on fate and partitioning of the active ingredient of various sea lice bath treatments. (2010)

Introduction:

Chemical therapeutants are being utilized as part of a pest management plan for salmon growers in their fight against sea lice. The salmon industry is not achieving target dosage in a predictable manner for sea lice products like AlphaMax® in bath treatments, resulting in reduced efficacy, the need for more frequent treatments and higher probability of development of resistance. It has been suggested that the chemical is binding to substances in the sea water. The intent of this study is to explore the partitioning of the active ingredient among biological material like fish and bio-fouling, organic solubles, solids and water and ultimately determine the fate of the active ingredients for sea lice chemical theraputants. Success may allow veterinarians to correct for environmental factors that impede achieving target dosage.

Summary, Conclusions and Recommendations:

These preliminary investigations have yielded considerable information concerning the application, mixing, and dispersal of the product and have highlighted the difficulty in assessing exposure.

Mixing and deltamethrin concentrations during treatment:

At Sites A, B and C, at individual sampling times, deltamethrin concentrations among the four sampling locations within the cages varied up to 28 times between the highest and lowest measured concentrations. Concentrations at a majority of individual sampling stations do not appear to have stabilized during the treatment period.

The mean current speed within the treatment cage during the treatment trials was less than 5 cm·s^-1.

The water sampling data indicates that the product did not become well mixed during the treatment period.

Concentrations reached within the cage were well below the target of three parts per billion (3 ppb). Prior to skirt removal, the average deltamethrin concentration (standard deviation) at Site A was 0.30 ppb (0.1); at Site B it was 0.06 (0.01), and at Site C it was 0.15 ppb (0.05). It is unclear where the product is going; it may be sinking and escaping through the bottom of the skirt, reacting with elements within the water, or not reaching the cage edge where the samples were taken from. Whether or not the product was well mixed prior to application may also impact the dispersion of the product within the cage during delivery.

Based on average deltamethrin concentrations inside the cage during treatment, it was estimated that field treatment exposures, are to 11 % (Site A), 10 % Site B, or 7 % (Site C) of an ideal exposure.

The mean current speed outside the treatment cage during the treatment trials varied from 1.5 to 11.5 cm·s-1 and the median varied from 1.2 to 12 cm·s^-1.

These findings could have important consequences for treatment efficacy as well as for resistance building in sea lice populations. How fish react to zones with higher deltamethrin concentrations compared to zones with lower concentrations is unknown and studies to date on biological and chemical compartmentalization of AlphaMax® in seawater have been inconclusive. Further studies examining the uptake or breakdown of the active ingredients are suggested (beyond Activity 4 in this report) as well as determining fish behaviour relative to chemical concentrations

Future work on the biological and chemical partitioning of deltamethrin in seawater should begin with a lab phase, with artificially spiked samples to study product fate (i.e., binding characteristics of active ingredients and stabilizers as well as biological availability of active ingredients) in filtered vs non filtered water, and to determine whether the potential for relationships between various facets of water chemistry and product fate exists. Also further trials should attempt to recreate the spectrum of levels of organics experienced on salmon production sites and evaluate potential relationships to product partitioning. If any of the above are validated, field studies should then be considered.

Further work needs to be completed on the development of product application methods to achieve a quick and even delivery of product in cages.

Effluent dispersal:

Concentrations being released from the skirt were approximately 10 times less than target concentration (less than 0.5 ppb).

By 10 minutes post skirt removal, the concentration of active ingredient was diluted between 1 and 22 x at Site A, between 2 and 4 x at Site B, and between 2 and 22 x at Site C compared to the pre-skirt removal concentrations.

The active ingredient, deltamethrin, was undetectable within the cage in samples taken more than 10 minutes after skirt was removed at Site B, and after one hour at Site C. At Site A, deltamethrin concentrations between 0.014 ppb and 0.07 ppb (two orders of magnitude below target concentration) were detected at 30 minutes post skirt removal, and by the subsequent sampling point, 3 hours after skirt removal, the product was undetectable.

The estimated rate at which the theraputant was flushed from the treatment cage ranged from 4.7 to 14.1 minutes for Site B, with the 4.7 minutes corresponding to the time for the water to transit across the diameter of the polar circle cage and the 14.1 minutes being three times the e-folding time scale associated with the assumption of continuous mixing throughout the cage, to 6.2 to 18.6 for Site A and 17.8 to 53.3 for Site C. Based on the water chemistry data taken within the treatment cage following skirt removal, the flushing rates were comparable to estimates produced with the current data at Sites B and C.

More sampling points inside the cage during treatment and post skirt removal would allow for a better understanding of the temporal dilution and the appropriateness of the use of proxies or models like e-folding time scales. It seems the product was already somewhat diluted before the pre-skirt removal water samples were taken, impacting the length of time the product was detected in the cage.

The current speeds within the treatment cage over the six hour time period immediately following the treatments were either less than the current speeds recorded outside the cage or similar to the outside speeds when these speeds were less than about 10 cm·s^-1.

In all environmental monitoring treatment cases the current meter and drifter data indicated the initial drift direction was from the treatment cage toward other cages in the farm site. At Site A the drift was through five other cages and at Site C it was predominantly through one cage. At Site B the treatment cage was located at the end of a column of cages and the drift was away from the cages.

Water samples taken following drogues in the estimated plume showed no detectable deltamethrin present at two sites and low concentrations at one site.
 
During all three environmental monitoring trials, the mean currents were less than 22 cm·s^-1.

Deltamethrin concentrations were undetectable in sediment samples taken 75 and 100 m from study sites.

No AlphaMax® residues were located in the IMTA mussels collected; however their exposure to AlphaMax® effluent plume is unknown. Further, many factors can influence bio accumulation and detection of pyrethroids in tissues including lipid content and bioavailability once bound to sediments.

Due to the temporal and spatial patchiness of dispersal from salmon cages the lack of detection of chemical outside the cages should not be interpreted as the product not being present. Field sampling needs to be done using a dye tracer in order to properly follow the plume and identify appropriate sampling locations. Subsequent studies have been conducted combining dye, current meters and water sampling.

Organisms in the sentinel arrays and lobster cages showed no signs of impact of AlphaMax® exposure. Current meter and drifter data suggest that sentinels on Site A were exposed at least once to the AlphaMax® plume, Site B sentinels were likely exposed for at least two treatments; and possibly up to five, and Site C is uncertain. However, there is uncertainty as to the degree of exposure that the sentinels at the treatment sites received.

Due to the uncertainty of exposure and the resulting difficulty in drawing conclusions from sentinel work, it would be suggested that further sentinel studies include some additional method of assessing exposure (ie taking water samples during potential exposure periods or using indicators like dye to estimate exposure).

Overall:

It is unclear where the product is going; it may be sinking and escaping through the bottom of the skirt, reacting with elements in the water, or not reaching the cage periphery where the samples were collected. Dilution of the product following skirt removal inside the cage and outside the cage is not well understood. Dispersal of the product is site specific, and influenced by parameters including currents, wind, fish stocking density, bio-fouling, etc. Further methods need to be developed to conduct relevant sentinel studies. Biological and chemical partitioning of the product is complex and requires further investigation, along with all of the above phenomena.

(Please note some recommended research and monitoring work is already underway as part of several different research projects)

Benefit of AlphaMax® Research for the Canadian Salmon Farming Industry

Currently the Canadian salmon farming industry is severely hampered by the lack of alternative sea lice control products that are critical to a well structured integrated pest management program for sea lice.  This problem is not restricted to New Brunswick; however, the emergency registration of AlphaMax® for sea lice control in New Brunswick in 2009 provided a much-needed research platform to begin to assess this product for application as part of an IPMP.

The research and scientific monitoring conducted as part of this comprehensive assessment of AlphaMax® has made a significant contribution to Canadian understanding of this product.  The research funded was critical to support PMRA’s Emergency Registration for AlphaMax®.  The findings from this project are now available to support further Emergency Registrations for AlphaMax® in all Canadian jurisdictions.  This project provided regulators and the industry with the ability to identify further knowledge that needs to be gained through additional research and monitoring. The results from this work and future work will support the eventual registration of this product in Canada.

This was the first time that a sea lice bath treatment has been so closely monitored and researched in Canada.  In addition to gaining a greater understanding of the product itself, the project contributed to a greater understanding for regulators, risk assessment officers, and industry itself to understand farm management dynamics and how these products could be used as part of an integrated approach.  This program provided a template for the efficient evaluation of other sea lice bath treatments and treatment methods – which benefits not just New Brunswick but other areas in Canada.

The salmon farming industry in New Brunswick directly benefited from having access to a new sea lice bath treatment at a time when there were very few options available for treating sea lice.  The evaluation of AlphaMax® provided an opportunity to not only study its effectiveness in eliminating lice under a variety of environmental conditions, but also looked at methods of application to support optimal treatments and mixing of the product was also evaluated.  From information learned during the course of the trials, farmers have already begun to invest in improved technologies for the delivery of treatments intended to increase efficacy and further minimize environmental impacts (i.e., enclosed tarp systems and well boats).  Industry developed new collaborations with a range of stakeholders regionally, nationally and internationally. This information has been shared across the Canadian industry and the technology transfer from this project has been significant. The New Brunswick industry has been very open in communicating results of this work, operating procedures and other lessons learned with their colleagues across the country.   

Findings from this research project has also enabled the communication of accurate information to other marine resource users across the region to demonstrate that the salmon farming industry will ensure our fish health management practices do not have an impact on populations of wild species in our marine systems.