Farmed fish production
-Ocean based – salt water- mainly salmon (Chinook (pacific) and Coho (Atlantic) and shellfish
(Oysters, mussels, gooey duck clam) and shrimp
- Land based – fresh water (some new systems are trying to do salt water on land too
pacific salmon farming cycle
-slow process, 3 year cycle. we measure age as degree/days as cold blooded (tempxdays).
-first year in freshwater then smolt and move to sea. (artifically can do at 1.5 yr) mature at sea at 4 yr.
-females develop eggs released into abdomen.
-Eggs are expressed through the vent into gravel and
guarded by the female waiting for a male to come and deposit “milt” (seminal fluid). Females die after this.
pacific salmon breeding
-artifically females are raised in hatchery (best biosecurity) or matured at sea and brought back for breeding.
-mature around 4-5 years, males can mature early called jacking= small and they never go out to sea.
-eggs are stripped out of females into bowl and washed to minimize vertical transmission of disease. then females are euthanized.
-males are milked and milt is washed before mixing with eggs.
-seasonal breeders in fall based on photoperiod.
how female pacific salmon are euthizied and breed changed
- euthanized (anesthetic bucket of clove oil)- rendered used for pet food, fish oil.
-in industry all fish are female – salmon are weird 4N chromosome, treat some females with
methyl testosterone and they become male and produce milt. All offspring will be female)
how we manipulate pacific salmon breeding season
– can be manipulated by
photoperiod, temp, water chemistry and use of GnRH and Prostaglandins.
-Fertility rate typically 90-95% but drops off as you move out of season
egg hatching
-Eggs are placed in trays on a membrane over media. If fertile they become “eyed”. Trays are gently
shaken and infertile eggs become cloudy and are removed
-Eggs hatch and little fish swim through membrane into media. They have large Yolk sac that provides all
food for first stage of life.
fish right after hatching
- yolk sac is depleted, and the abdomen closes “buttoned up” – time of greatest loss but still
90% should survive.
-Fish start to swim to surface and look for food – start feeding.
-fish fed pellets
how fish are graded
-Fish are continually graded for size and any defects (sizing is automatic fish swim through a machine
with different sized grates, small ones drop through and are euthanized
-Expect approx. 20% loss due to culls etc pre molt
2 types of hatcheries
-Fresh water- continual flow of water and discharge
-Recirculating- use a biofilter to remove NH3, NO3 and CO2, needs very little water- v. complex
engineering. Cannot use antibiotics as kills the filter
smolting
-Massive physiological change as they move from fresh to salt water, huge impact on osmolality of body
systems. Fish still quite small approx. 100g
-Atlantic salmon – very tight window
-Pacific – you can control environment and push it back but risk skin fungus disease due to stress
-Fish are pumped out of tanks to trucks, then to barges and out to sea pens =12mths – 2 yrs in pen
-Management – feed daily and leave the fish alone! Keep the nets clean and remove any dead fish
harvest of fish
-Crowd fish in pens
-Use fish pump to suck fish up into harvester – dewatering table and percussive stunning and bleeding
(or use electricity) – much better than commercial fishing
Handling: fish
-Fish are anesthetized through compounds in water either: Clove oil or MS222/TMS. Both are very quick
and safe and recovery you just put the fish in clean water
important fish diseases in BC
-IHNV – controlled by effective vaccine
-VHS – no vaccine but managed by good husbandry – reduce fish stress – no disease – salmon v.
susceptible to stress. Once fish get sick – lots of disease shedding – outbreak
fish vaccines
In feed – experimental
Intra nasal – experimental
Immersion – used in small fish – need 2 treatments – short acting only – work in the hatchery
-Injectable – most vaccines – intra peritoneal -oil adjuvant vaccine – 4 vibrio spp, IHN and other viruses)
-Anesthetize fish and inject by hand – fish approx. 60g- v skilled (trying to develop machines)
treatment options for fish
-in hatchery use salt water, at sea use freshwater. great for patasites.
-can also put fish in chlorine tea to treat bacterial gill disease. (feedlot pneumonia)
-Antibiotics in feed – metaphylaxis – last resort, mainey florphenicol
diagnostic tequniques for fish
-gross necropsy
-routine bacteriology-blood agar, tsa
-virology: PCR routine screening
fish feed
-All pellets, 80% plant based 15-20% fish based (never salmon, never feed back due to disease)
-Salmon are carnivorous need marine fats esp omega 3s and 6s
-Fish meal is sourced from cut offs from commercial fishing (non salmon)
-Approved bait fish fisheries esp south America – fish with no human market
-Future – grow plankton and krill and make food!
Fresh water production – worldwide
-Much bigger industry than salt water (tilapia probably x10 salmon)
-Much much easier system! Simply put fish in a dug out!
-Warm water – faster growth, can even just feed of algae in the water)
