Intensive Fish Production 1 Flashcards
UK Scottish Aquaculture industry ?
- Atlantic salmon (Salmo salar) dominates production almost exclusively in
Scotland. - Scottish salmon is UK’s largest fresh food export.
Gloabally norway just ahead, then chile then scotland
Feed conversion ratio in fish farming?
really sustainable this way because FCR <1.0 (resource efficient)
globally how many and which species farmed?
-600 species
- Dominated by carp and tilapia largely extensive systems
what happens with moving from extensive to intensive production?
- Stocking density increases
- Natural productivity (algae,
phytoplankton etc) decreases - Exogenous feeding increases
what do we see in europe’s intensive system?
predominance for cage
aquaculture, and an increasing
Recirculating Aquaculture System
(RAS) sector
what. considerations in intensive production?
- Diet that meets nutritional RQ
- Supp oxygen
- Removal of metabolic waste and uneaten food
- Pathogen control
- Bhvr & welfare
Salmon lifecycle?
explain the concept of degree days
- Since they are poikilothermic (cold-blooded) the rate of metabolism
in fish depends on the temperature of the environment in which they
are kept. - The higher the temperature, the faster the metabolism
example of these degree days?
25 days at 10° = 250°D
50 days at 5°C = 250°D
fundamentals of hatcheries?
- Year round production is key to profitable production
- Most systems need 2-3 egg inputs per year
- Varies hugely dependent on system type.
Key factors in hatching new stock?
- High quality genetics
- Exceptional biosecurity (Fungus is an issue, more later)
- High quality brood stock
- High quality, stable environment
- High quality management and husbandry
what is the earliest lifecycle stage we can manipulate?
Early sexual maturation of salmon ->
- Once fish mature, energy is directed towards gonadogenesis, rather than growth, & quality drops
- We WANT to DELAY maturation -> production of sterile fish, monosex cultures
What other tage can we manipulate?
Smoltification -> (metamorphosis from parr to smolt
Describe smoltification
- Initiated by decreasing day length (autumn) and completed on increasing day length
How do we modify smoltification?
most systems (RAS facilities) alter the pattern of daylight and temperature provided to the tanks. The result is an artificially short winter of 6-8 weeks.
Why does smoltification matter?
Becaue caues changes that make them ready to go to sea -
What changes happen?
- Chloride cell proliferation (Actively transport Na+, Cl- and K+ out of the tissue)
- Sodium-Potassium-ATPase pump reversed
- Endocrine changes
- Molecular isoform changes alpha to beta
- Become longer and more streamlines (K factor reduces)
- Changes of behaviour and swimming activity
ARE the smolts ready for sea?
BE SURE!
* Measure gill Na-K-ATPase activity – enzyme assay
* Measure plasma Chloride levels via blood sample
Describe the production of neo males ?
What is triploidy?
Triploid fish have 3 full sets of chromosomes
* They are entirely sterile
How/ why do we have triploidy?
- Achieved by heat or pressure shocking eggs that have been
fertilized as normal. - Advantageous higher growth rates, as no energy is channeled
into maturation - Although it has been seen that males can develop secondary
sexual characteristics and larger gonadal growth.
What are triploid fish more susceptible to ?
Disease (& therefore poorer welfare)
What is the most commonly used system currently?
- Freshwater RAS systems transfered to seawater systems at smoltification
- Although post smolt land based facilities are becoming more populat
What is a normal stocking density?
<15kg/m3, resulting in a 98.5:1.5 ratio
