Salmon Aquaculture Beginner Guide
Salmon fish is amongst one of three most important fish species in aquaculture (the other species being the carp and tilapia fish).
They belong to the species of genus Salmon and Oncorhynchus as they are farmed in all marine locations with exclusion or exception of smolt (young salmon after the parr stage) produced or held in net pens.
Salmonids are usually farmed in two stages and in some places maybe more. First, the salmon are hatched from eggs and raised on land in freshwater tanks. An increase in the accumulated thermal units of water during incubation reduces time to hatching.
Then at 12 – 18 months, the juvenile salmon are transferred to sea floating cages or net pens anchored in sheltered bays along a coast; this process is called mariculture (farming in a marine environment).
They are given pelleted feed whilst in the cages or net pens for 12 – 24 months until when they reach the harvest period.
Modern salmonid farming systems are intensive and the ownership is often under the control of huge agribusiness where operations are mechanized in assembly lines on an industrial scale.
Considered production systems
Production systems vary depending on a person’s preference especially for a beginner aquatic farmer. This can be achieved by carefully assessing which method will work out best for the farmer and the production yield percentage when comparing each considered method.
- Offshore systems which involves open and closed containment systems.
- Hybrid systems which combine land recirculating aquaculture system (called RAS) production of post-smolts with marine grow-out to market size.
- Land-based recirculating aquaculture systems which focus on salmon market.
- Floating closed-containment systems which produce salmon for market.
Conventional hatchery systems operate on flow-through whereby spring water or other water sources flow into the hatchery.
How To Raise Salmon The eggs are then hatched in trays and the salmon smolts are produced in raceways; then the waste products from growing salmon fry and the feed are usually discharged into the local river.
This hatchery method requires 101,605 litres (100 tonnes) of water to produce a kilogram of smolts.
Another alternative method for hatching in freshwater tanks is to use spawning channels. These artificial streams are usually parallel to existing stream with concrete or rip-rap sides and gravel bottoms.
Spawning success is much better in channels than in adjacent streams due to the control of floods which can at some time later wash out the natural redds (red tide).
Escaped farmed salmon have the potential to disrupt ecosystems and alter the overall pool of genetic diversity through competition with wild fish and interbreeding with local wild stocks of the same population.
Interbreeding of farmed with wild salmon of the same species can result in reduced lifetime success, lowering individual fitness and decrease in production.
Escapes can occur in large events that are immediately noticeable at a farm, smaller events that are still noticeable, and through slower, lower levels of losses of fish that might go unnoticed. Move away from production of smolts in open systems to closed and semi-closed systems with lower risk of escapees.
The cages are placed side by side for form a sea-site or sea-farm which has a floating wharf and walkways along the net boundaries. Additional nets are placed to deter predatory marine mammals by surrounding the sea-farm. Farmed salmon in open net cages can escape to wild habitats (during storms).
Another cage used for salmonids is copper alloys as netting material because they are antimicrobial (they destroy bacteria, viruses, fungi, algae, and other microbes).
Different Salmon Types
Salmon is a diverse family of fish species found on the ocean (Atlantic and Pacific), which makes them migratory fish. During escapes, they interbreed hence the different species.
- Chum salmon – they are one of the larger variety species of Pacific salmon; have an average weight of 3.6 – 6.8 kg (8 – 15 pounds) and a growing potential weight of between 13.6 – 15.9 kg (30 – 35 pounds).
- Their length is 1.07 m (3 .5 feet); the young chum salmon migrate directly to marine water spending most of their life feeding and growing in the ocean though they do not stay in freshwater for prolonged periods.
- Sockeye salmon – is one of the smaller salmon fish which is commonly found in Alaska; having an average weight of between 1.8 – 6.8 kg (4 – 15 pounds) and an average length of 30.5 – 61 cm (1 – 2 feet). When they reach their largest potential they are half size of the Chinook salmon.
- This type of salmon is born in freshwater, migrate to the ocean to feed and grow then return to freshwater to spawn.
- Pink salmon – are the smallest salmon with a weight 2.27 kg (5 pounds) and not more than 61 cm (2 feet) long.
- They look very different from the other Pacific salmon species; with migratory habit moving from seawater to freshwater at different life stages. Juvenile pink salmon migrate to marine waters immediately after birth.
- Chinook salmon – also known as ‘King Salmon’ because they are the largest salmon species making them the most valuable commercial fish. It is about 91.4 cm (3 feet) long with a weight of 13.6 kg (30 pounds) and have a potential of growing even larger.
- Coho salmon – this is a smaller Pacific salmon that is widely popular for sport fish. They are sometimes called the ‘silver salmon’ as they are moderately sized; carrying an average weight of 3.6 – 5.4 kg (8 – 12 pounds) and have a potential of growing up to 13.6 kg (30 pounds) but they are mostly smaller. The best time to catch them is in saltwater from July through early September.
- Atlantic salmon – is a native species in the Atlantic Ocean but may also be called the sea-run salmon or black salmon, and largely overfished making their population to remain at risk.
- Though the female can lay an average of 7,500 eggs nearly twice as much as the other salmon species, the Atlantic waters coldness reduces heir viability with less than 20 percentages of those eggs surviving.