Developing an Innovative Underwater/Above Water High-pressure Spray System to Treat Vase Tunicates (Ciona intestinalis) Fouling on Cultured Mussels

Final Report
Somers Island Blues Inc
AIMAP 2012-G03

Summary/Abstract:

The objective of this project was to develop a prototype underwater sprayer system to improve upon current above water spray systems. It was conducted under the Aquaculture Innovation and Market Access Program (AIMAP) and also with assistance from the Aquaculture Technology Program with PEI Fisheries, Aquaculture and Rural Development (PEI DFARD). The work was performed by Murray River Precision Works, Cardigan Bearing and Steel and Chris Somers. The results of the underwater spray system revealed that the high-pressure seawater nozzle, in a contained shroud, filled with continuous high volume, low-pressure air, removed fouling, such as the vase tunicates. It was concluded that the method of using air and high-pressure in an underwater spray system did remove fouling from cultured mussels with little or no damage to mussel socks, compared to the traditional above water sprayer system.

Introduction:

This report has been written to show the cost and development of the High-Pressure Spray System. It will analyse the results of the project and make any recommendations that are necessary. The objectives of the report are to educate the targeted market on the components of the sprayer and how the sprayer is an advantage to the mussel industry. The report will examine the development of the sprayer and what alterations had to be made to improve efficiency of the equipment.

Methodology:

An innovative treatment system for the vase tunicates has been developed and built with the assistance of AIMAP and PEI DFARD. Without their encouragement and assistance a PEI Mussel Grower in a tunicate affected area would not be able to accomplish such a project financially. Because of the unknown risks associated with such a project, I am under the impression that such a system has not been attempted in the past. Mussel growers are looking for the best solutions to eradicate the tunicates from their mussel lines, so an underwater sprayer idea has been considered, but never developed. With this new technology all mussel growers will be able to treat their mussel crops, while underwater, for fouling. This method will reduce the abundance of mussels that are lost due to the traditional above water spray systems. If this new piece of equipment is utilized by using the proper de-fouling regiments, the mussel grower will yield higher mussel weights from their crop.

The high-pressure spray system utilises water injected through an oscillating nozzle in a semi enclosed shroud. The shroud has the same circumference as the oscillating nozzle; therefore, a determined distance from the nozzle to its point of impact must be maintained with a certain volume of air. This volume of air must be controlled individually for the entire thirty two nozzles that are underwater, as each nozzle is lowered into the water at different depths. Some are as close as six inches to the surface of the water compared to others that may be as deep as nine feet. Each depth requires a certain amount of pressure and volume to fill each shroud with enough air to prevent the seawater from entering that shroud. If the air pressure and volume are not sufficient the seawater will enter the shroud and the spray pattern of the nozzle would not reach the point of impact on the mussel socks. If this should occur the nozzles would not clean that portion or area of the mussel sock. Each shroud that contains the nozzles has its own valve to control air pressure and volume. Once these parameters are set there should be no need for them to be altered unless the depth of each nozzle was to change, which would be highly unlikely.

The air pressure and volume is easily controlled by the engine running the air pump. Water pressure can also be controlled by the throttle on its separate engine. This way each supply system can change its own performance individually. With each separate water pump and air pump every RPM seeing will have different outcomes or cleaning effects on mussel socks. For example, higher rpms on a water pump would produce an increased aggressive wash. If the rpms are too low the air pump would not supply enough air to work. A minimum amount of air is required for the equipment to produce results. In retrospect too much air may cause mussel socks to rise to the surface prior to being washed thus not being effective.

An abundance of effort has been put into regulating the air volumes, nozzle placement and shroud dimensions. I have been concerned regarding the supply hoses leading to the sprayer box. All the necessary hydraulic and high pressure hoses are located under the deck. This was also done in order to supply the hoses to the sprayer as neatly as possible. It was difficult to anticipate exactly where each line should run freely up nine feet to its above spray position and to its underwater position. A problem that occurred in a test run was the pinching and abrasion of the supply lines. To correct this I need to incorporate a roller system on the sprayer for the supply lines to operate freely.

Conclusion:

A full season of maintaining tunicate fouling on my mussel farm would present me an evaluation of the operation of the water sprayer system. Even though each season is different year to year, due to water temperature and winter mortality of the vase tunicate I can do my own evaluation with underwater treatments for the full season on routine lines. On adjacent lines I will perform the above water treatments to see which sprayer is more successful.