Commercial Scale Cod Hatchery Production Technology

AIMAP 2009-N07
Newfoundland Aquaculture Industry Association

Table of contents

• OBJECTIVE
• INTRODUCTION
• SYSTEM MAINTENANCE AND IMPROVEMENTS
• CLEANING AND DISINFECTION
• Broodstock System
• Hatchery System
• Larval Systems
• Live Feed Systems
• JOE BROWN AQUATIC RESEARCH BUILDING IMPROVEMENTS
• Sand Filter Media
• Protein Skimmers and Ozonation
• Improved Environmental Monitoring and Control
• Plumbing Improvements
• Recirculating Aquaculture System
• WATER QUALITY

OBJECTIVE

The objective was to produce commercial quantities of juvenile fish to support industry needs. We achieved commercial production of 900,000 (0.1 gram) juveniles per single production run in 72 tonnes of rearing space. 12.5 larvae per litre at 10 grams is an outstanding benchmark or performance standard by industry guidelines.

INTRODUCTION

On September 23, 2009 the first batch of fertilized Atlantic cod eggs was collected from three month photoperiod advanced, communal spawning broodstock. These eggs were incubated at the Ocean Sciences Center in an attempt to produce 150,000 two gram juveniles as part of the Cod Demonstration Project. 72 tonnes or 18 larval rearing tanks were stocked from October 21- 27 with a total of 2.7 million larvae. All larvae looked good upon stocking and continued to thrive throughout the larval period. All larvae were feeding heavily by three to four days post stocking with swim bladder development progressing as normal. At first grade, the number of fish remaining in the tanks were counted and survival ranged from 15-60%. A number of trials were conducted involving different green water techniques, Artemia disinfection prior to feeding, early weaning and evaluating the success of stocking tanks with eggs versus larvae. At first grade (15mm/100mg size) there were approximately 900,000 + juvenile cod, but due to the limitations of tank holding capacity, fish had to be progressively culled through high grading processes. We are holding 250,000 juveniles between 4-6 grams. All fish are continuing to do exceptionally well with little to no deformities observed.

SYSTEM  MAINTENANCE AND IMPROVEMENTS

During the months leading up to the 2009-10 larval culture season extensive efforts were undertaken to improve rearing system performance and capability. Particular attention was given to the disinfection and remediation of areas within the water treatment and distribution system that had the potential to harbour fish pathogens. Improvements were subsequently carried out via plumbing modifications and new equipment installation to improve overall system dynamics and water quality.

CLEANING AND DISINFECTION

Efforts in this area were focused on the cleaning and sanitization of all larval rearing system components, including the internal surfaces of all pipe work, to remove accumulated fouling and biofilm from bacterial growth and to mitigate future contamination.

Broodstock System

This system was temporarily shut down to allow for thorough cleaning of the ultra violet (uv) sterilizer housing and quartz sleeves. All uv lamps were replaced with new lamps to ensure optimal performance and processing of the flow treatment to acceptable standards. The header tank was scrubbed and disinfected and the degasser was disassembled for complete cleaning and renovation. Degassing media was removed, soaked in a fresh water solution of oxalic acid for 24 hours, flushed with chemical free fresh water, and then further treated in sodium hypochlorite solution to disinfect and remove all deposits/biofilm before reinstallation. The Low Head Oxygenator (LHO) was cleaned and rebuilt to seal all inner plates and improve structural integrity. Upon recommissioning, a substantial improvement in efficiency was realized in that we are now using nearly half as much oxygen input at the LHO to achieve substantially higher header oxygen saturation.

Hatchery System

The hatchery uv was serviced, with housing and all quartz sleeves cleaned and lamps replaced with new lamps. The existing mechanical 10 micron cartridge filter bank was cleaned and minor repairs performed. The header tank and degasser were cleaned and disinfected, media treated as above, and the LHO cleaned and serviced. Utilizing newly purchased equipment, the supply pipeline from header to incubation tanks was pressure jetted with hot fresh water and acid washed to remove biofilm/deposits by completely filling all supply lines with a freshwater solution of oxalic acid (pH ~2.00) for a 12 hour+ static bath treatment. All pipes were flushed with hot fresh water, drained, and then treated similarly with a sodium hypochlorite solution at 100 ppm+ free chlorine. It is worthwhile to note that we installed ¼” valves in pipe work high points to bleed trapped air pockets and ensure a complete flooding with cleaning solution and to facilitate regular purging of air during operation. Once drained, the pipes were forcibly air dried using an axial fan blower for 24 hours to complete the disinfection process. This system remained out of service (fallow) until required for egg incubation in the fall.

Larval Systems

The “Low” and “High” systems were also shut down for complete renovation and maintenance. Both headers and degassers cleaned and disinfected with media treated as above.  LHOs were fully cleaned and repaired/renovated. All pipelines have been thoroughly cleaned and disinfected and purge valves installed as in hatchery system. The UV has been serviced and all quartz sleeves cleaned and lamps replaced with new lamps. These systems also remained fallow until returned to service.

Live Feed Systems

The uv units for both rotifer and Artemia production systems have been cleaned and all lamps replaced with new lamps. The system supply pipelines have been serviced and disinfected as above from the main A and B supply lines to the culture tanks. These systems also remained fallow until required.

JOE BROWN AQUATIC RESEARCH BUILDING IMPROVEMENTS

Sand Filter Media

The entire Joe Brown Aquatic Research Building (JBARB) water process stream is mechanically filtered through a bank of 16 Hayward high flow rate sand filters. These filters were installed with silica sand media, which was standard practice at the time; has been found to deteriorate with time and provide less than optimal performance value. Sand tends to become biofouled with autotrophic nitrifying bacterial which can increase the suspended solids as well as dissolved organic carbon (DOC) in the product water by converting inorganic carbon to organic carbon. Bacterial coagulation can lead to pressure drop and worm-hole channelling which can possibly allow dissolved components and fish pathogens to bypass the filter bed.

During the summer of 2009, the standard silica sand media was replaced with an amorphous aluminosilicate active filter media (AFM), imported from Dryden Aqua in the UK. This media is engineered to remove 30% more suspended solid load than sand and has catalytic properties which produce short lived oxygen free radicals that raise the surface redox potential, causing the media to be self sterilizing. The surface of AFM is hydrophilic with a high negative zeta potential which aids in the adsorption of small particles and dissolved organic molecules. The resulting reduction in DOC will decrease the overall bacterial load in the culture water, which is of particular importance during the early larval rearing stage when cod are most vulnerable to bacterial infection and intestinal enteritis. This media also has the important added benefit of non-degradation and should therefore last the lifetime of the sand filters.

Protein Skimmers and Ozonation

To further reduce dissolved organics and potential pathogens within the larval rearing areas, the JBARB has installed two 600 lpm protein skimmers, purchased from Water Management Technologies Inc. (WMT) in Baton Rouge, LA, USA. One unit has been installed on the “High” system and one on the “Low” system. The system headers have been re-plumbed and modified with a system of baffles to allow a side loop treatment process through the skimmers. New centrifugal pumps have been installed to draw water entering the headers (from degassers) through the side loop and return it for oxygenation in the LHOs before flowing down to the larval rearing tanks.

The protein skimmers function on the principle of foam fractionation, whereby air bubbles are introduced in a counter current direction to the process flow and collect organic material as they rise to the water surface. The bubbles are created via a secondary pump, venturi and air snorkel arrangement, and foam is collected and dewatered at the top of the skimmer unit where it is periodically washed to drain by automatically timed spray manifolds.

The efficacy of the fractionation has been improved through the installation of a Guardian Plasma Block ozone generator, also purchased from WMT. Ozone is delivered to the air intake snorkel on each of the protein skimmers where it is drawn into the air stream due to suction created by the venturi.

In addition to the effect of increasing foam production, ozone is an extremely reactive oxidant and a very effective bactericide and viricide. It can improve water quality by micro flocculating fine particulate matter and oxidizing nonbiodegradable organic molecules, nitrite, and refractory organic molecules. Ozone production and dosage is currently manually controlled by adjusting output percentage at the generator. Flow is controlled by way of a distribution manifold which is designed with four separate flow meters (zones), two in use for the protein skimmers and two for future expansion.

The JBARB is presently upgrading this system to provide for automatic ozone dosing based upon redox potential in the larval culture water. This is accomplished through use of a proportional-integral-derivative (PID) controller. This unit incorporates two oxidative reductive potential (ORP) meters placed in each of the two larval headers that have the skimmer side loop. The meters are part of a control loop feedback mechanism that will measure the ORP-based water chemistry and provide proportional dosing, thus ensuring consistent and accurate water quality control, even in variable supply water characteristics.

Improved Environmental Monitoring and Control

Prior to the 2009-10 production season, the existing environmental monitoring and control capability at the JBARB was improved by the addition of two new PT4 ION systems from Point Four Systems Inc., Coquitlam, BC.

The rotifer culture lab was installed with a stand alone multi channel temperature and oxygen monitor with automatic oxygen control. Temperature and oxygen sensors in each rearing unit transmit information on an input output network data bus system which is programmed with user defined set points allowing a target dissolved oxygen range for individual rearing units. A series of relay outputs and solenoids automatically control oxygen diffusers in each tank to maintain the programmed oxygen level.

During the rotifer production process, oxygen demand can change rapidly due to feeding and reproductive activity. This continuous automatic control system allows 24 hour optimal dissolved oxygen levels under varying culture tank conditions. Temperature and oxygen alarm set points are also programmed to alert staff (including facility custodians during off hours) when suboptimal conditions occur. This system has since been expanded with additional sensors and control apparatus to provide the same functionality in the Artemia culture room.

It should be noted that the ION monitoring system has computer connectivity, allowing the continuous logging of data and remote functionality via network connections including wireless and satellite.

The second PT4 ION system was installed to monitor temperature and oxygen in the larval rearing area. This unit continuously displays environmental data from the larval-juvenile tanks allowing manual control by staff to maintain optimal conditions. The system is also programmed with alarm set points to alert facility personnel when measured parameters exceed preset ranges.

Plumbing Improvements

In advance of the Cod Demonstration Project, several modifications were made to the general larval area infrastructure to improve performance and capability. Larval system degassers and low head oxygenators were serviced and repaired as required to provide maximum gas transfer/oxygenation efficiencies. Larval tank inlet piping and valves were upsized to allow for the higher flow rates required for anticipated elevated stocking densities. Air purge valves were installed at high points in the tank water gravity supply distribution system to ensure complete flooding and prevent any possibility of “air lock”.

Individual tank inlet and drain configurations were designed and reconfigured to provide improved hydrodynamic effects as conditions change due to fish growth and subsequent increased biomass, feed requirements, etc. Improvements were also made to various fish husbandry equipment including tank siphons and surface skimmers.

Recirculating Aquaculture System

The JBARB has purchased a portable skid-mounted 12 tonne (12 000L) recirculation system designed and manufactured by Water Management Technologies Ltd. This system was originally engineered to provide water treatment and high rate recirculation functionality for two 6000L larval tanks, but has the capability to perform various functions. The unit is equipped with a radial flow particulate separator, bag filter elements, ozone compatible protein skimmer, trickle degasser, moving bed biofilter, and uv sterilizer. This is truly a multiuse system with self contained recirculation pumps and control panel. It may be employed for various side loop treatment processes and, properly located, could provide the basis for a serviceable quarantine unit.

WATER QUALITY

Water quality parameters have been closely monitored during the 2009-10 production season. In addition to the new PT4 ION systems, the JBARB has purchased a new portable YSI Professional Series Optical Dissolved Oxygen meter, utilizing the latest in oxygen measurement technology. We have also acquired a new YSI 9500 photometer to improve accuracy and precision in the measurement of various water chemistry parameters. This equipment serves to complement the existing JBARB water quality instrumentation kit which includes portable ‘traditional’ oxygen meters, ORP and pH meters, tensionometer, and various test kits.

Dissolved gas levels and temperature are crucial to production success, especially during the early life stages. This season, these parameters have been maintained as close to optimal levels as possible and have remained within acceptable limits.

Other important water chemistry parameters are monitored on a regular basis and as culture conditions and observations dictate. System pH and metabolic by products including total ammonia-nitrogen, nitrite, nitrate and dissolved carbon dioxide have all remained within acceptable limits.