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

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 and verified that very high oxygen (250-350% saturation), and a low Total Gas Pressure (103-120%) environment did not cause acute or chronic issues for treated salmon, or that the pesticides compounds were not toxic in this environment. 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.

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. Based on the results, a one hour mixing period was adopted after introducing pesticides to the system but prior to transferring fish for treatment. This practice ensured 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. Treated salmon were unstressed during the trail due to handling methods developed and the high oxygen saturation environment that was 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 treatment. Removal of other sea lice life stages were also positive from the ECO-Bath System with more than 61% of the chalimus sea lice and nearly 55% of the adult female sea lice removed 24 hours post-treatment. With this system, any sea lice (dead or alive) that were removed from salmon were eventually filtered from the bath water and did not pose any further threat for reinfection on the treated salmon.

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 allows for the treatment of fish in a wider water temperature range given its capability to control the oxygen concentration within the treatment water. Finally, the ECO-Bath System is expected to be available to the industry at a fraction of the cost of a well boat, making it feasible to maintain site-specific treatment capability to control sea lice infestation while eliminating bio-security concerns associated with transfer of sea lice and other pathogens between sites when sharing a common treatment platform.

Recipient: Admiral Fish Farms Ltd.

Total Project Cost: $729,812
           
DFO-AIMAP Contribution: $280,000

Other Financial Support:

• Recipient: Admiral Fish Farms Ltd. - http://admiralfishfarms.com/
• Government of New-Brunswick: NB Department of Agriculture, Aquaculture and Fisheries (NBDAAF) - http://www.gnb.ca/0027/index-e.asp
• Private industries: Engineered Aquaculture Solutions (AEG) - http://www.aeg-solutions.com/; inVentures Technologies Inc. - http://www.gasinfusion.com/

For more information please contact the AIMAP regional coordinator
Maritimes Region: Cindy.Webster@dfo-mpo.gc.ca