1 - Fish Flashcards
What are the ocean based (salt water) farmed fish?
-Salmon
>Chinook: pacific (BC’s biggest industry)
> Coho: ATlantic
-shellfish (oysters, mussels)
-shrimp
What are the land based (fresh water) farmed fish?
-Tilapia
-carp
-catfish
-trout
-arctic char
How long does the Pacific Salmon process/cycle take?
-3 years
>1st year (1.5years): fresh water, then ‘smolt’ and move to sea
>mature at sea for 4 years and then return to fresh water
How is fish age measured?
-degree days
>temperature x days
Ex. 10degrees C x 10 days = 100 degree days old
Where are the eggs developed in the female and released?
-released into abdomen and expressed through VENT into gravel
>guarded by female until male comes and deposits ‘milt’ (seminal fluid)
*females die after this
How are females raised? (2 ways)
- In hatchery (good biosecurity)
- Matured at sea and brought back for breeding (less good)
How is the ‘breeding’ done?
-eggs from females are stripped out into a bowl
>WASHED to minimize vertical transmission
>females are euthanized
-males are milked and ‘milt’ is washed before mixing with eggs
>can be collected several times
How are the fish euthanized?
-anesthetic bucket: clove oil
*rendered for pet food or fish oil
All fish in the industry are female, how do you ‘make’ them become male?
-treat them with methyl testosterone=become male=produce milt
*very restrictive gene pool
When do salmon usually breed? How can that be manipulated
*fall: based on photoperiod
-manipulate by
>photoperiod
>temperature
>water chemistry
>use of GnRH and prostaglandins
What is typically the fertility rate?
-90-95%
>will drops off as you move out of the season
*4 spawnings a year
How are eggs hatched?
-placed in trays on a membrane over media
-shake and infertile eggs will become cloudy=removed
-fertile eggs=’eyed’
-eggs hatch and swim through membrane into media
>have LARGE YOLK SAC that provides all food in first stage of life (don’t need to feed them)
When is the time of greatest loss? (eggs-hatching)
-once yolk sac is depleted, the abdomen closes ‘buttoned up’
-90% should still survive
*then swim to surface and start to look for food=start feeding them
What are fish feed?
-pellets
>80% plant based
>15-20% fish based (never feed fish back their type of fish)
Salmon are carnivorous, where do they get their marine fats from?
-can’t make omega 3 and omega 6=need to get it from their diet
1. Fish meal: ‘cut offs’ from commercial fishing (NOT as much anymore)
2. Approved bait fish fisheries where there is NO human market
3. Future: grow plankton and krill to make food
How much loss do you expect due to ‘culls’ pre-molt?
-20%
-continually graded for size and defects
>small ones fall through and are euthanized
What are the 2 types of hatcheries?
- Fresh water: continual flow of water and discharge
- Recirculating: use biofilter to remove NH3, NO3, CO2 (easier to manipulate)
>need less water, VERY COMPLEX ENGINEERING
>can’t use antibiotics=kills the filter
What is smolting?
-massive physiological change as they move from fresh water to salt water
-huge OSMOLALITY of body systems
-usually around 100g
Smolting window for Atlantic salmon vs. Pacific salmon
-Atlantic: very TIGHT window
-Pacific: can control environment and push it back
>downside=risk of skin disease due to stress (ex. fungus)
*waste from hatchery=great for fertilizer after composting
How are fish transferred to sea?
-pumped out of tanks into trucks, then barges out to the sea pens
*12 months to 2 years in pens
What are the pens at sea like?
-typical: 40x40m, with 50-80,000 fish
-15-20m deep
-walls tapering to a cone 30m deep
*typical fish farm=500,000 fish at sea
-floats at top that are tethered to sea floor
What does the management look like for fish at sea?
-feed daily
-leave them alone
-keep nets clean
-remove any dead fish
How do you harvest the fish at sea?
-crowd fish to one side
-suck up fish into harvester
>dewatering table
>percussive stunning and bleeding!
*do it right away
What does a fish vet do?
*purest form of population medicine
-lots of daily necropsy work
-visit sites: routine and disease outbreaks
>land or ocean
-paperwork and regulations
