Sustainable Expansion of Freshwater Fish Farming in Lake Diefenbaker Adapting the iCage to Freshwater Trout Culture

Table of contents

• Wild West Steelhead
• Key Project Objective # 1: Adapt and Develop Strategies, Practices and Tools Related to the Submergibility Functions of the iCage
• Successful Installation of iCage Units
• Adaptation of OOSI Sea Water Submergence Techniques to Freshwater Operations & Submergence Trials
• Technology Transfer and Training WWS Staff
• Development, Implementation & Testing of Overwintering Strategy
• Development & Testing of Submerging Strategy During Spring Break-Up
• Key Project Objective # 2: Develop and Implenent Strategies to Adapt the iCage to the Early Stages of the Steelhead Trout Growth Cycle
• Successful Installation of iCage Units
• Successful Design, Installation and Testing of Nursery Strategy
• Successful Tow Test of the iCage Units
• Successful Transfer of Fingerlings from Nursery Cage into Juvenile iCage Set-Up
• Key Project Objective # 3: Assess the Applicability of iCage Biomass Management Tools to Freshwater Fish Production
• Produce Complete Production Curves
• Additional Information
• Fish Performance
• Net Maintenance
• Stocking Into and Harvesting From iCages
• Conclusion

Wild West Steelhead

Three iCages’s were installed at Wild West Steelhead’s (WWS) farm site in Lake Diefenbaker in 2010 to test their effectiveness at addressing some of the unique environmental challenges faced by the Canadian freshwater cage culture industry. 

The following report summarizes the successes and challenges of the project as outlined by the three Key Project Objectives

Key Project Objective # 1: Adapt and Develop Strategies, Practices and Tools Related to the Submergibility Functions of the iCage:

Successful Installation of iCage Units: 

Installation began in June 2010 and was completed by August 2010. The unique structure of the iCage poses challenges with assembly, and requires trained personnel, including a considerable amount of diving time. Furthermore, both the shape and material limits the amount of assembly which can be completed at source, resulting in higher labour costs for assembly and installation on site, as compared to traditional square surface cages, which typically can be assembled on site by farm staff.

The three-point mooring system for the iCages is effective, though complicated.  Mooring installation was hampered by standing submerged trees on the bottom of the lake, remnants of the pre-flood landscape, as well as the depth of the site.  At 35m, dive times were severely limited. WWS and OOSI are in discussions on how to simplify and improve the mooring system by switching the cages to a two-point mooring configuration. This change has the potential to both reduce installation time and simplify the submergence process.

Adaptation of OOSI Sea Water Submergence Techniques to Freshwater Operations & Submergence Trials:

Upon completion of installation, submergence trials were initiated. There were two challenges encountered during these trials. The first problem involved slippage of the tom float anchor when fully charged. The configuration of the mooring lines results in significant horizontal forces on this anchor as buoyancy in the tom float is increased. This resulted in movement of this anchor block toward the cage, along the mooring line. The net effect then being that the tom float rises in the water column, without pulling the cage under water. To remedy this, additional ‘back-up’ anchors were installed behind the tom float block to prevent movement.

The second problem involved a lack of reserve buoyancy in the iCage. This caused the cage to actually sink and sit on bottom when submerged. The cage was originally designed to be positively buoyant in seawater, even with the rings completely flooded, in order to prevent sinking once submerged. With freshwater being less dense than seawater, the reserve buoyancy is lost.  Additional buoyancy compensators were added to the end of the axles to prevent this from occurring.

The first submergence trial was carried out on September 28th. The cage was submerged to a depth of 24’ and remained submerged for a period of approximately 20 hours. Upon resurfacing, the fish were jumping very actively for a period of about 10 minutes, after which point their swimming behavior returned to normal. It is worth noting that the pen had been fed in the morning and submerged in the afternoon. The excessive jumping behavior may have resulted from the fish not having had sufficient time to adjust swim bladder buoyancy after the meal. The second submergence trial was performed on November 15, 2010, and remained submerged for 48 hours. This time fish were starved for a period of two days prior. Upon resurfacing, there was noticeably less jumping action than experienced with the first trial.  There were no adverse affects on the fish as a result of either of the submerging trials.  

Technology Transfer and Training WWS Staff

Select employees have been trained on the rotation procedure as well as how to raise and lower the operating height of the cage in the water.  Diving staff have also gained experience on mooring inspection and mortality removal.

Development, Implementation & Testing of Overwintering Strategy

Servicing the three iCages during the winter months was relatively easy. The cages remained at the surface during the winter months and ice free conditions were maintained in and around the structure of the cages via the use of aeration lines. Each cage had an airline installed from the surface to the lowest submerged arch. The upwelling action maintained ice free conditions throughout most of the winter. One small issue encountered with this method was that the lowest arch was not always directly centered below the middle of the iCage, so portions of the cage frame were still frozen in the ice, while, other areas were ice free some distance from the cage. A simple remedy for this is to install the air line on the axle inside the cage. With this set-up, the upwelling stream would always remain centered in the cage regardless of cage (arch) orientation.

In addition to aeration lines, extension hoses were installed from the lower ring valve to the surface, adjacent to the above water ring valve, in order to allow buoyancy adjustments to the rings from the surface without the use of divers. This proved very effective and adjustments to the operating height of the cages were easily made throughout the winter months. 

Additional access zippers were installed in each cage to allow easy access into the cages for divers. The pens were then “locked” in position using buoys to prevent cage rotation and to ensure that the diver access door remained at the surface during the winter months. Ramps were built to allow access to the cage over the open water for diving operations.

Feeding during the winter months was accomplished by either hand feeding, which is possible with the reduced feed intake at this time of year, or with the use of a blower.

Development & Testing of Submerging Strategy During Spring Break-Up

Potentially, the most significant benefit offered by the iCage to freshwater cage producers in Canada is the ability to submerge the cages below ice during spring thaw. Wild West Steelhead has, along with other sites in Canada, experienced both equipment damage and fish loss as a result of moving ice colliding with cages. This mass of moving ice is typically only a few inches thick, but can cover a very large surface area and carry enormous momentum when moving. Having the ability to submerge the cages just a few feet below the surface of the lake eliminates this most significant risk.

Two of the three iCages were submerged two days prior to ice break-up without incident.  Additional mooring problems on the third cage resulted in that cage being only partially submerged the following day, with the highest point protruding only a few inches above the surface of the lake. During break-up ice was shifting on the lake for a period of approximately two days. The cage which did not completely submerge actually surfaced slightly higher through the ice during this time due to a lock malfunction on the valve for the tom float airline.

While this was not planned test, it did prove interesting. As moving ice would hit the cage it acted as in inverted pendulum, submerging and resurfacing as the ice moved over top of it and away. There was no damage, as a result, to either the frame or the netting and no adverse affects on the fish. The two submerged cages were resurfaced after approximately one week, again, with no ill effects on the fish. 

Key Project Objective # 2: Develop and Implenent Strategies to Adapt the iCage to the Early Stages of the Steelhead Trout Growth Cycle.

Successful Installation of iCage Units

See discussion under Key Project Objective #1.

Successful Design, Installation and Testing of Nursery Strategy

This component of the project involved designing, installing and operating a net insert inside of the main net on one of the three iCages. One potential benefit provided by this strategy is potential cost savings. iCage nets are constructed with Dynema material which is stronger and lighter making it more expensive than traditional nylon. Small mesh nets which are required for juvenile trout (fingerlings) contain more material per square foot than grower nets and as such a full sized fingerling net would be very expensive and limit the cage to production of small fish only. Having juvenile net inserts that could be installed inside any iCage frame, regardless of the main net mesh size, increases the versatility of the cage and allows production of fish of any size from that cage.

A fingerling net insert was designed with approximately one meter of space between the main net and the insert. This provided approximately 900m3 of cage volume inside the insert.  Fingerlings were stocked in the cage and fed for approximately two months, at which point they were released into the main net and the insert was removed.

This strategy, while proven possible, did pose challenges and it became obvious fairly quickly that it was not a strategy worth pursuing. The most significant problems occurred while feeding. Trout are very active and competitive surface feeders. With this net configuration, there is only a very small amount of surface area provided for feeding inside the juvenile net. This created significant surface competition and the resulting currents would push feed pellets outside of and away from the iCage. To increase the area available for feeding, the cage was raised higher but this made rotating and working the cage more difficult. To remedy this issue the feed rate was slowed to reduce surface activity, thereby reducing to potential for feed wastage. In addition, reinstallation of the insert was labour and diving intensive and for these reasons it was decided not to further pursue this strategy.

Successful Tow Test of the iCage Units

Cages were towed from the assembly site to the final mooring site, both with and without nets installed. Cages have not been towed while stocked with fish; however, based on experience with towing empty cages, no problems are anticipated. It was found, as would be expected, that the cages tow much easier, the higher they are floating in the water.

Successful Transfer of Fingerlings from Nursery Cage into Juvenile iCage Set-Up

Approximately 66,000 fish with an average weight of 100 grams were successfully transferred from a transport cage into the iCage juvenile net insert without incident. The design of the insert is such that it and the main net share a common opening for the transfer door. A swim tunnel was sewn onto the transport net and the iCage door opening and the fish were pushed into the net insert. This practice is very similar to that used with traditional square cages and was easily adapted to the iCages.

Key Project Objective # 3: Assess the Applicability of iCage Biomass Management Tools to Freshwater Fish Production.

Produce Complete Production Curves

Using historical production records from WWS, growth curves for large trout were produced. This data is presented in the Appendix. 

It was originally planned that this data would form part of the inputs required to develop the Integrated Biomass Optimization System (iBOS) program. The purpose of this program is to improve inventory management by providing real-time feedback on such indicators as farm biomass, feeding requirements, and environmental nutrient inputs and impacts, as well as projecting production based on feed and environmental conditions.

Due to time constraints brought on by the operational issues described above, we were not able to complete the additional activities as described in the project proposal. 

Additional Information

Fish Performance

Two of the three iCages received fish on August 15, 2010. Due to high water temperatures at the time and the later than planned stocking date, fish could not be counted into each cage independently. Rather, a total of 49,400 fish at 600 gram average weight were split between the two cages by swimming them into the cage. Mortality and feed records later indicated that the split was approximately 60%-40% with approximately 30,000 in one cage and 20,000 in the other. 

Fish were fed from August 2010 to June 2011. On June 20, 2011 a sample was taken and the average weight was calculated at 1,332 grams. This places feed conversion for the period between 0.92 and 1.45, depending on the actual number of fish in the cage. This, however, will not be determined until conditions allow an actual count of the fish in the cages, planned for this fall.

At this point, based on the weight sample taken and visual observations, the fish performed at least as well as those in traditional square cages.

Net Maintenance

The nets on the iCages require little maintenance with respect to cleaning, despite not having any form of anti-foulant applied. Rotating the cage was carried out manually at first, however, it was discovered that when moorings are operating properly, wind activity alone was enough to rotate the cages and maintain clean nets. Manual rotation was only required during extended periods of low wind speeds.

Stocking Into and Harvesting From iCages

Two of the most routine activities involved with operating a cage culture operation involve stocking fish into and removing fish from cages. The unique structure and enclosed net of the iCage’s pose challenges and require a different approach, especially for removing fish. 

Stocking fish into the iCage, as discussed earlier, is not significantly different from the way it is done with square surface cages. It simply involves sewing a swim tunnel between the iCage and the transport cage, and pushing the fish from one to the other. While there is the additional step of rotating the iCage to correctly position the harvest door, all other procedures are essentially the same, and can be accomplished in a reasonable amount of time.

Transferring fish out of the iCage poses a considerably larger challenge. On June 20, 2011 OOSI and WWS staff attempted to transfer fish out of one of the cages using a specially designed seine net and techniques developed by OOSI staff. The procedure involves placing the seine inside the iCage net, lacing it to the harvest door and to a portion of the cage itself to hold the seine in position. Once laced into position, the cage is rotated and the seine acts as a paddle gathering the fish as it rotates around the axle of the cage. 

It should be noted that site conditions were very poor at the time due to strong currents and very poor lake visibility caused by higher than normal local runoff. This hampered operations to the extent that the seining and transfer was aborted and the majority of the fish left in the iCage. It became obvious during the exercise that, even under ideal conditions, this technique is not operationally efficient. Furthermore, the requirement to have divers in the cage, working between the main net and the seine, poses safety concerns. WWS and OOSI will explore alternative ways to remove fish from the iCage using techniques more similar to the way surface cages are operated. The first attempt will involve raising (floating) the iCage as high as possible, releasing the ties that fasten the net to the arch and running a cork-line beneath the main net, toward the harvest door. In this scenario, the main net acts as a seine net and there should be considerably less diving work required.

Conclusion

The iCage offers a viable strategy for avoiding risks associated with ice movement during spring break-up in freshwater lakes. However, the submergence process, at this point, is complicated and time consuming. Switching to a two point mooring system, from the current three-point system, has the potential to significantly improve operational efficiencies by reducing the time required for submergence and offering finer control over cage operating height. Additionally, this adaptation has the potential to improve the installation process by reducing both number of required components and the time involved.

The rotational ability of the iCage offers a very successful strategy for net cleaning. No significant fouling was observed on the nets and often wind activity alone was enough to rotate the cages. Manual net cleaning requirements are essentially eliminated. The self-cleaning tendency of the iCage coupled with the individual ‘pod’ type mooring scheme (ie. all sides of the iCage are exposed to ambient lake environment, as opposed to square cages which have ‘neighbors’ on at least one adjoining side) offers superior growing conditions to traditional square cages for trout at any stage of the production cycle. 

More operational challenges than anticipated were experienced throughout the project, however, practical solutions were developed to deal with most. The two most significant issues remain unresolved; that being improving the mooring system to simplify the installation and the submerging process and developing an efficient method for removing fish from the iCage. These challenges will be addressed in the coming months.