Last Updated on October 20, 2022 by Griselda M.
Raising salmon at home using aquaponics is possible given the proper climatic conditions and enough space for the salmon to grow. Salmon spend most of their natural life cycle out in the sea and return to freshwater to spawn. Farming salmon in a freshwater recirculating aquaculture system is a new trend that requires further research.
According to Scientific American, AquaSeed is farming salmon in closed freshwater aquaculture tanks from eggs to market size. Raising salmon in aquaponics is possible given some considerations which we will explore today.
Designing Your Aquaculture Operation
Consider The Developmental Stage Of Salmon When Designing Your Aquaculture Operation:
The early life cycle of a salmon begins from an egg, which hatches into alevins, develops into fish fry, and finally into parr. After 12 months, the salmon will begin smoltification depending on the conditions. Smolts travel into the estuaries to adapt to saline water for 2-3 years before moving into the ocean.
Most recirculating aquaculture systems that farm salmon in aquaculture tanks prefer to start with smolts or post-smolt around 14-16 months after hatching. Smolts adapt to the environment well and start growing rapidly.
For Ease Of Operations, It Is Best To Start With Smolts Or Post-smolt Salmon For The Aquaponics System:
Raising salmon at home using aquaponics requires a thorough understanding of the physiological response of salmon to its environment. Smolts are relatively more sturdy thus to reduce the risk of failing, start introducing salmon as smolts or post-smolt. The size and weight of smolts differ per species but range around 5-9 inches and weigh around half a pound.
According to research by Davidson et al., the 14-month-old smolts will grow up to 4kg or 8.8lbs in 9 months. The salmon were grown in a commercial setup with a high fish stocking density of 0.292 lbs per gallon. The research shows a high growth rate for the salmon, with an average of 0.875 lbs per month across three species of salmon.
This research shows a near-commercial setup with intensive practices which will be challenging for a home setup. Although the productivity and health of the salmon in the research show an opportunity for using salmon in a home aquaponics system.
Operating A Nursery Is Not Possible For Aquaponics Since It Requires Disinfection and UV Filtration To Avoid Diseases At the Early Stages Of Life:
During the early stages of the development of salmon, salmon are susceptible to high mortalities from diseases, pests, and water conditions. Most salmon nursery operations require intensive filtration and anti-bacterial UV light setups to increase survivability and turn a profit for their operation. It is possible to run a nursery operation with a small tank but it is not meant for aquaponics.
How To Setup Your Aquaponics System To Raise Salmon at Home – Tips
Raising salmon in aquaponics at home is similar to any other fish. It requires designing and programming your system based on the species you are growing. In this section, we will be going over system design specifically for salmon. We will take into consideration the space it needs to grow and water quality parameters for survival.
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1. Determine target weight and fish stocking density to compute how many salmons to put in your system
If you are new to aquaponics, start with a low fish stocking density of 0.125 lbs per gallon. Assuming that the maximum weight of your salmon is 8.8 lbs, this will mean your fish tank should have a water volume of 70 gallons per full-grown salmon. You can adjust your system depending on your target weight but always compute from the total fish biomass in the system.
2. Mechanical filtration, water flow, and aeration are crucial for ensuring low mortality of your salmon
Compute for your mechanical filtration and water flow from your fish stocking density and fish tank volume. Your mechanical filter should reach a water retention time of 1 hr of its fish tank volume. If you design your flow rate to be 1 fish tank volume per hour, your mechanical filter should be the same volume as your fish tank.
Regularly collect sediments that settle in your mechanical filter to ensure that the water stays clean and prevents bacterial bloom. Aeration is another crucial system design, if possible make sure dissolved oxygen is above 6.5 ppm. If there is no way to check dissolved oxygen concentration; design your system to have enough surface area exposed to the atmosphere by adding exposed water falling into your tanks, air stones, or venturi pumps.
3. Make sure your biofilter can accommodate the bacteria needed to convert the high-protein fish waste to avoid nitrite buildup
Since salmon are carnivorous fish, expect more nitrogen to be in your system from the high protein feeds. A buildup of unutilized nitrogen will lead to nitrite concentrations increasing and eventually fish kills. To avoid this, your biofilter and aeration must be able to house the necessary bacteria for nitrogen conversion into nitrate.
Biofilters are composed of a water tank filled with media with a high specific surface area where bacteria can be housed in. To set up your biofilter, purchase bio balls that have a specific surface area of at least 300 m2 / m3 or 91.44 ft2 / ft3. Your biofilter should be around 20% of your fish tank volume and filled up with bio balls up to 60% of its volume.
4. Water temperature should be kept between 59oF – 63oF for the salmon and 75oF for the plants
Temperature is the most challenging part of growing salmon in an aquaponics system but it is not impossible. Salmon and most plants differ in the temperature required for them to grow well. This will require introducing heating for your plants and cooling for your aquaculture tank.
For this issue, I combine shallow water culture or a deep water culture with the Kratky method for my hydroponics component. In the space between the water and plant cup, you can introduce 75oF air to simulate a warmer environment for your plants. Be sure to monitor the water temperature and your salmon’s eating habits to ensure the health of your salmon.
5. If you plan to harvest salmon cyclically it is best to put salmon of different ages in different tanks
Salmon will cannibalize smaller fishes so a tank should have fish of the same size and age. If you plan to harvest salmon regularly, have multiple tanks which will be harvested at certain target dates. If they are all of the smolt or post-smolt age, you can connect all these tanks. To avoid infections and diseases from spreading across your fish population, have a valve that could disconnect the infected tank from the rest of the system.
Salmon Are Carnivorous Fish Which Feed On Smaller Fishes
Salmon’s natural diet consists mostly of small fishes and in commercial aquaculture operations, they are fed fish meal. There are several choices for commercial fish meals like BioMar. Choose whatever is available and economically feasible for your fish as most of these fish meals are designed for your salmon.
How much should you feed your salmon?
Common aquaculture practice feeds salmon 1-2% of their body weight per day. You can choose to measure body weight monthly or to approximate body weight from the fish’s specific growth rate. The research by Davidson et al. shows that the salmon grows by 0.875 lbs per month per fish. Smolts generally weigh 0.5 lbs per fish at 14 months, thus feed your smolts starting with 0.005 to 0.01 lbs per fish, and add feed incrementally as they grow.
Raising salmon at home presents a challenge for aquaponics enthusiasts mostly because of the difference in requirements for salmon and plants. Salmon prefer cold water while plants grow well in a comfortable 75oF. As with any aquaponics system, set your goal whether you are focusing on the aquaculture or hydroponics component. This will help guide you with priorities on the design of your aquaponics system.
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