Farm Sub-surface Automated Feeding Delivery System

Table of contents

• Overview
• Results
• Transferable Technology from the SFC 2010 P007 AIMAP Project
• Information on Financing

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Overview

Sablefish Canada was awarded $200,000 in AIMAP funding to develop, build, install, and commission a farm sub-surface automated feeding delivery system for Sablefish aquaculture. The goal was to reduce the labour required for feeding and reduce the stress on sea pen grown Sablefish by replicating the natural environment where Sablefish feed.  The feed system was designed to ensure that feeding fish stay in stable temperatures, high salinity and low light levels.  To facilitate this, feed would have to be delivered to a depth below the established thermocline at our pen site.  The result of this new technology will increase fish quality and decrease farm production costs so that farmed Sablefish is profitable at wild Sablefish prices. A third benefit not anticipated when the project was conceived is that underwater feed dispersal and variable feed flow equipment that was incorporated into the design will increase overall feed use efficiency.

Sablefish Canada worked closely with Norcan Electrical Systems who were contracted to design, build, install and commission the farm sub-surface automated feeding delivery system. The feeding system is tailored to the unique biological requirements of Sablefish. This technology incorporates a precise, no-waste feeding regimen that aligns Sablefish farm-feeding labour costs, and feed delivery with the salmon industry standard. Development of the farm sub-surface automated feeding delivery system contributes value-added benefits to the Sablefish aquaculture industry by decreasing production costs and increasing ecological performance. The development of this project ensures that a developing Sablefish aquaculture industry can purchase specialized sub-surface automated feeding machines from Norcan Feeding Systems in the future.

Surface feeder description

One ton feed bags are unloaded into the Super Sac silo and the feed travels by conveyor to the cyclone tank where the feed is mixed with water for delivery to the sea pens. The central distribution pump pumps the feed to the sea pens and the version 6.1 control system computer controls the pumping equipment and rotary diverter valves that direct the feed to one of twelve possible sea pen locations. A three-inch high-density polyethylene pipe is attached to each of the twelve nipples on the rotary diverter valve line, which terminate ten meters below the surface in each of twelve sea pens. Rotary feed spreaders are installed at the end of each pipe to disperse the feed at ten meters in each pen. The system has the capacity for installing two rotary feed spreaders at two depths in each sea pen. SFC will experiment with one versus two feeders in each tank to determine the best option. Underwater monitoring cameras located forty feet below the feed spreader allow the operator to monitor and adjust the rate of feed delivery in order to minimize feed wastage.

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Specifications of subsurface feeder

1) The customized one-tonne super sac silo loads feed into 6 – 7 foot open silos.

2) Water is added to the feed in the cyclone mixing tank and then pumped to the sea pens.

3) The central distribution pump runs at 100 to 150 gallons per minute and can pump feed 600 ft through a three-inch pipe. When the feed reaches the discharge point ten meters below the surface in the sea pen the feed is discharged with an underwater rotary feed spreader the end of the pipe. The pump is a Hayward Gordon XCS Series – Screw Centrifugal Solids Handing Pump. This pump can be run slower than other models tested and was chosen because it has less chance of damaging the feed pellets and allows for approximately 30% farther pumping distance. The pump has a direct drive electric motor and is controlled by a variable frequency drive.

4) The pipe distribution system uses a modified Rotary Diverter Valve (12 x 3" Outlets) to deliver feed through three-inch high-density polyethylene pipes that connect to rotary feed spreaders installed approximately ten meters below the surface of each pen.

5) The Auto Feeder is controlled by a Version 6.1 Control System with Siemens Panel PC - 19" Touch Screen with a customized Human Machine Interface program. The program was customized for the Sablefish application. The control system enables the operator to remotely calibrate the feed delivery to the specific demands of different fish sizes.

Results

The measurable results of this AIMAP grant are:

• The sub-surface feeder was tested delivering feed to sea pens at rates from 0 to 200 kg of feed per minute. The machine easily meets this design specification. We are currently feeding most of our pens at an average of 700 to 1,000 kg per pen, which means that we can feed an entire pen in 5 to 10 minutes. The feed is transported from the a central feed shed building to the 30 meter by 30 meter sea pens via three-inch polyethylene pipes.

• The return on investment from the $200,000 AIMAP award is estimated at 52.8% or $105,000 for 2011. Feeding labour cost was reduced by 75% from $80 per ton of feed delivered to the pen to $20 per ton of feed delivered to the pen. Our total 2011 feeding labour saving will be $65,754 (1,093 tons X $60 ton = $65,574). We estimate our feed utilization will increase by 2% of the 2011 $2 million feed budget yielding a savings of $40,000 a year).

Outcome 1: Decreased labour costs

 Sablefish Canada estimated that the sub-surface automated feeding delivery system would decrease our feeding labour from four hours to one hour per ton of fish feed delivered to the pen. This objective was met with the feed machine consistently delivering one ton per hour. An additional benefit not anticipated is that the farm technicians feed the fish more effectively because they deliver feed by watching the fish on monitors from a feed shed as opposed to standing by the side of each sea pen often in inclement weather.

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Outcome 2: Lower crop stress

Adult Sablefish live at depths of 2,000 to 3,000 feet where temperatures are about 6C and are stressed by high light, warm surface water temperatures and low salinities.  When sablefish are fed at depths below of 10 meters or more the fish school into a tight ball and move as a coordinated unit while feeding. This feeding behavior is known as “vortex feeding”. When sablefish are surface fed they break out of the vortex feeding pattern and individuals dart into the warm brightly light water nearer the surface to grab a fish pellet and then immediately dive to the safety of deeper water.  The measure of fish stress during feeding is measured by the absence of vortex feeding behavior. Having studied the stressed non vortex feeding response in from 2005 to 2009 SFC decided to feed all the fish on the farm below 10 meters to obtain vertex feeding in 2010. This was accomplished before the farm sub-surface automated feeder was installed by using a Honda 5hp water pumps to deliver the feed to the fish in deeper water.

Outcome 3: Precise, no-waste feeding regimen

Precise no-waste feeding was achieved by installing feeding cameras at 20 meters of depth.  This is 10 m below the feeding spouts so the operator can stop the feeding as soon as he/she sees that pellets are getting below the fish vortex. The underwater feeder is designed to provide adjustable feed rates so the machine only delivers feed as fast as the fish population can consume it.

Outcome 4: Pellet integrity

When fish feed pellets are mixed with water in the cyclone tank and pumped to the individual sea pens we expected to see problems with pellet fracturing and thought we would experience feed loss to pellets dissolving in water. Neither of these loses occurred. A trial was conducted to determine the amount of time required to effect pellet integrity due to hydration from water. The pellets maintained their integrity for 30 to 60 minutes depending on the oil ratio (15% to 33%) in the pellet. The maximum time the pellets are exposed to water from entry into the cyclone tank to delivery to the sea pen is four minutes.  It was therefore determined that dwell time was not going to be a problem. Feed pellet breakage as they pass through the pump was not a problem nor was the sink rate of the standard feed pellet manufactured by Taplow Feeds of Skretting.

Transferable Technology from the SFC 2010 P007 AIMAP Project

Sub-surface feeding machine

The goal was to design, build and commissions a sub-surface feeding machine for Sablefish aquaculture that would provide a precise, no-waste feeding regimen, reduced labour costs and reduced Sablefish stress during feeding. The sub-surface feeding machine, which was designed by SFC and built by Canadian Feeding Systems, is performing to its designed specification. The equipment is expected to last ten years with a projected labour saving of over $650,000 over ten years and a feed savings of $600,000 over ten-year return on investment of about 6.3 times. This sub-surface feeding machine can now be purchased by other Sablefish aquaculture operations from Canadian Feeding Systems.

Information on Financing

This project was supported by the DFO AIMAP program. Sablefish Canada welcomes inquiries from industry and researchers working on related topics.

Bruce Morton
Sablefish Canada Inc.