1
Q
Comparison to terrestrial farming
A
- In some systems FCR ratio can be < 1.0, gaining kilo of meat for less than kilo of food; FCR 1.3 in Atlantic salmon in Scotland, lower carbon footprint
- Most resource-efficient animal protein
- Selective breeding only occurred for 14 generations
2
Q
Species of farmed fish
A
(In order of most popular, > 600 species)
- Carp
- Tilapia
- Catfishes
- Marine shrimps
- Salmons
- Marine fishes
- Freshwater crustaceans
- Trouts
- Milkfish
- Eels
3
Q
Production of fish
A
- Majority of world’s fish are extensively in Africa + Asia in freshwater ponds
- Transition from extensive to intensive -> inc stocking density, natural productivity dec (algae, phytoplankton) , exogenous feeding inc
- European intensive aquacultures - predominance for cage aquaculture + inc in recirculating aquaculture system (RAS)
- Norway, Chile, Scotland = world leaders in industry
4
Q
Extensive fish farming
A
- Natural food only - relying what is in the pond, algae, plankton
- African + Asian farming
- Possibly w/ fertilisation
- Low stocking density
5
Q
Semi intensive fish farming
A
- Natural food w/ fertilisation
- Possibly w/ supplementary feeding
6
Q
Intensive fish farming
A
- Usually dependent on complete artificial feeds
- High stocking density
7
Q
Intensive production considerations
A
- Complete diet - meets all nutritional requirements
- Additional supply of oxygen - inc water flow, inc aeration + oxygenation (most effective at high stocking densities) (mechanical failure can cause big problems)
- Removal of metabolic waste + uneaten feed
- Pathogen control
- Behaviour + welfare considerations
8
Q
Concept of ‘Degree days’
A
- Fish = poikilothermic (cold-blooded) - rate of metabolism depends on temp of environment
- Higher the temp, higher metabolism
- Used for estimating breakdown of drugs + fish developmental stages
- E.g. Statutory minimum withdrawal of AB = 500°D
- E.g. 2 Atlantic Salmon eggs take 250°D to reach ‘eyed’ stage (neural chord visible)
- 25 d at 10°C = 250°D / 50 d at 5°C = 250°D
9
Q
Salmon lifecycle
A
Egg -> Alevin -> Fry -> Parr -> Smolt -> Adult
- 1). Adult broodstock carefully selected
- 2). Females stripped of eggs, males stripped of milt (sperm-containing fluid). Usually based on strict genetics to maintain healthy stocks
- 3). Fertilisation
- 4). 250ºD to eyed eggs = neural chord visible
- 5). 250ºD to hatching
- 6). 300ºD to first feed (yolk sac runs out and alevins become fry)
- 7). Fry become parr at roughly 5 - 10cm long
- 8). Smoltification occurs (adapt from freshwater to seawater), depending on system. Can be achieved in 6 - 9 months by altering light and photoperiod. These stages are commonly in RAS facilities
- 9). Once fish are smolts, they need to be transferred to seawater. It is common at this stage to move fish from RAS facilities to sea or loch sites
- 10). By 2 years old salmon should be around 5 - 5.5kg and ready for harvest, or selection as brood stock.
- 11). If selected as broodstock, a series of genetic tests will happen, and only the best will be retained. Can reach as big as 15 kg by stripping
- 12). Whole cycle of egg to egg currently takes 3 - 4 years
10
Q
Hatcheries - key aspects + factors
A
- Year round production is key to profitable production
- Most systems need 2 - 3 egg inputs per year
- Varies hugely dependent on system type
- High quality genetics
- Exceptional biosecurity (Fungus is a huge issue)
- High quality brood stock
- High quality environment
- High quality management + husbandry
11
Q
Hatcheries
A
- Once selected, a 10 kg female can produce upwards of 20,000 eggs
- E.g. Hatchery in Iceland has the capacity to hold up to 400 million eggs at one time
- Eggs are disinfected in an iodine solution (0.01%) for 10 mins prior to being ‘laid down’ at 3 - 5 ºC
- Dead eggs should be removed to avoid fungus proliferation
- Hatch time varies hugely between species Eggs hatch around 500ºD later
12
Q
Where is the lifestyle of salmon manipulated?
A
- 1). Early sexual maturation of salmon
- 2). Smoltification
13
Q
Early sexual manipulation of salmon
A
- Once fish matures, energy is directed toward gondadogenesis (egg/sperm development), rather than growth, and the quality of the carcass drops dramatically
- To allow fish to continue growth to harvest weight, maturation must be delayed - by production of sterile fish, or monosex cultures
- Problem in aquaculture industry - quality of carcase drops as going to be smaller
14
Q
Smoltification
A
- Smolt = stage where anatomical changes occur to adapt to living in saltwater; metamorphosis in response to inc daylight following the winter (spring time)
15
Q
Changes seen in smoltification
A
- Chloride cell proliferation - actively transport Na+, Cl- + K+ out of the tissue - plasma chloride levels
- Na+-K+- ATPase pump reversed
- Endocrine changes
- Molecular isoform changes alpha to beta
16
Q
Testing if smolts are ready for sea
A
- Measure gill Na-K-ATPase activity via enzyme assay
- Measure plasma chloride levels via blood sample
- Test if live in saltwater
- Advanced testing - molecular testing, gene testing, ratio calculations
17
Q
Smoltification manipulation of salmon
A
- Conversion of Parr to Smolt occurs with some anatomical changes
- Smoltification is initiated by a decreasing day length (Autumn/Winter)
- Then completed on an increasing day length (Spring/Summer)
- Most systems (RAS facilities) alter daylight and temperature provided to the tanks, and give an artificially short winter of 6 - 8 weeks
- This can result in smolts being ready for sea transfer in 6 - 9 months, an advance of 3 - 6 months
18
Q
Why are only females selected?
A
- Male aggression
- Male anatomy changes + can cause more damage to self + others, e.g. hooked jaw
- Males must be harvested before maturation
19
Q
Production of sterile fish - ‘neo-males’
A
- Eggs hatch from XY x XX -> swim up frey fed 17a methyltestosterone for 75 d until 2 g
- Now all fish phenotypically male, converted males retrieved - have deformed gonads + hand-stripped of milt
- Converted male bred (XX) w/ normal female (XX) -> all offspring have XX -> heat/pressure shock => only produce females
20
Q
Production of sterile fish - triploidy
A
- = 3 full sets of chromosomes = entirely sterile
- Achieved by heat/pressure shocking eggs that have been fertilised as normal
Adv - Higher growth rates, no energy channelled into maturation, although males can develop 2y sexual characteristics + larger gonadal growth
- Salmon farms - if fish escape, no genetic introgression to wild salmon stocks
Disadv - More susceptible to disease
- Poorer welfare
21
Q
Grow out
A
- Freshwater RAS systems transferred to seawater systems at smoltification
- At any given site, there can be upwards of 30 - 50,000 fish per pen, and as many pens as 20 per site. (Sometimes upwards of 1 million fish per site!)
- Stocking densities typically < 15 kg/m^3, resulting in a 98.5 : 1.5 ratio
- A variety of cage/pen types, metal squares are typically used in sheltered sites, and polar circles are used in exposed sites
- Huge technological and engineering inputs – work boats, well boats, treatment boats, lighting, automated feeders, cameras, feed barges etc.
- Feeding can be either at the surface or at depth
- Fish are cropped, harvest of the largest fish, allowing smaller fish to grow quicker
- General harvest weight will be 5 - 5.5 kg
22
Q
Challenges to the industry
A
- Infectious disease/parasites - sea lice
- Predators - seals - how to control ethically, illegal to shoot/intervene + causes huge losses - use sonar deterrence
- Tx + environmental impacts - AB use, finding alternatives - not used at all
- Food sourcing - reliant on fish oil + fish meal, is it possible to produce pellets from other more sustainable protein sources - insects, veg protein
- Climate change - warming of seas
23
Q
Future of industry
A
- Offshore systems
- Closed containment systems
- Semi-closed containment systems
- RAS technology + completing entire lifecycle on land - allows control over disease + water quality, improved biosecurity, no lice, minimal environmental impact; but only can be small scale
24
Q
Sampling techniques
A
- 1) Observe behaviour - movements, history/records on farm, recent Tx?
- 2). Examine environment – size, densities
- 3). Select your fish - which ones - avoid all dead fish – autolysis is rapid. May help with investigation, but do not send off; avoid taking the biggest or picking favourites; pick moribund fish (appearing affected or nearly dead) AND apparently normal fish. ALWAYS live before sampling.
- 4). Examine fish macroscopically – gills, fins, scales, mucus, etc.
- 5) Examine microscopically – gills, organ samples, mucus, skin scrapes, PME
- Histopathology is the ONLY diagnostic tool in aquaculture.
- (Rest are pathogen ID tools)
- Will always get contaminants, due to the nature of water
25
Parasites
- Salmon lice - Caligus elongatus/
Lepeophtheirus salmonis*
- Whirling disease - myxobolus cerebralis
- Amoebic gill disease*
- Invisible killers - Ichthyophthirius multifilis – ‘ white spot*; Trichodina; Tetrahymena; Ichthyobodo (costia); Trypanosomes
- Gyrodactylus
- Glugea
- Diplostonum
26
Fungi
- Saprolegnia*
- Branchiomyces
- Exophila
- Aspergillus. Low dose = tumours, high dose = liver damage
27
Bacteria
- Aeromonas salmonicida*
- Yersinia
- Vibrio
- Pasteurella
- Pseudomonas
- Streptococcus
- Edwardsiella
28
Viruses
- Infectious Haemopoietic Necrosis Virus (IHNV)
- Cyprinid Herpesvirus 3
- Infectious Salmon Anaemia Virus (ISA)
- Mutate readily, therefore it is likely a whole range of uncharacterised viruses are present and cause disease
29
Sea lice
- Most economically sig to affect Atlantic salmon > £700 million globally per year
- Caligus elongatus - affects > 90 species of fish, less host-specific
- Lepeophtheirus salmonis - specific to salmonids, (salmon + trout) immunomodulate the host, inc susceptibility to 2y infection
- Feed on skin, mucus + blood if achievable
30
Sea lice - Tx + management
- 1). Vet med - Emamectin Benzoate in feed, organophosphates - v effective historically , act immediately but v expensive, poor environmental impact, widespread resistance, withdrawal periods, poor public image
- 2). Biological, cleaner fish - ballan wrasse + lumpfish, ratio 25 : 1, salmon to cleaner fish ratio, effective - predate on lice + remove from salmon
- 3). Mechanical, car wash - fish passed through system of water jets to remove lice, small mortalities seen if high burden
- 4). Thermal, thermolicer - fish moved through warm water where lice drop off + die
- 5). Chemical, hydrogen peroxide - tarpaulin Tx method, dilutes water + O2 so minimal environmental impacts
31
Sea lice - prevention
- Alteration of practices to reduce exposure of salmon to lice - single-year stocking (one age group, site fallowing/rotation (leave site empty for time period to disperse pathogens), improved site selection, genetic improvements, improved farm hygiene
- Some companies are keeping fish deeper, at a depth where sea lice are less abundant
- Some apply ‘skirts’ to the cages, which are permeable to water but not small copepods - lice won't penetrate upper layer
- Functional feeds are being developed that reduce sea lice burden
- Lighting strategies
- Lasers that ID lice and strike them
- Ultrasound and vacuum in research
32
Amoebic gill disease
- 2nd biggest issue
- Causal agent = Neoparamoeba peruans, amoeba that survives in sediment, net pens and the water column - hard to get rid of
- Causes gill damage - > epithelial thickening, reduced oxygen uptake, excessive mucus production. (Exacerbated by higher water
temperatures – hence warming oceans is a big problem for the salmon industry)
- Devastating disease, causing huge losses in Scottish industry
- In 2011 an outbreak caused loss of 13,600 tonnes of salmon, a loss of approximately £54 mil
33
Amoebic gill disease score monitoring
Gill scores recorded weekly
- 0 = No sign of infection, healthy colour
- 1 = white spot, light scarring or necrotic streaking, few white discolourations
- 2 = 2 - 3 spots, small mucus patch
- 3 = Established thickened mucus patch/spot groupings up to 20% of gull surface area, think of emergency harvest - cull stock + harvest what you can - will have compromised CVS if make it through lice Tx
- 4 = Established lesions covering up to 50% of gill SA
- 5 = Extensive lesions covering most of gill SA
34
Amoebic gill disease - histopathology
- Only true Dx
35
Amoebic gill disease - risks
- Severe CVS compromise - if environmental conditions unfavourable -> severe mortality events, > 50% of stock
- High salinity (> 32ppt)
- High temperatures
- Co-factors – jellyfish/algae blooms
- Biofouling of nets – reduces water turnover and Oxygen availability
- Smolt quality and size
36
Amoebic gill disease - Tx
- 1). Freshwater (8% of all Tx performed in Scotland)
- 2 - 3 hour baths in < 3ppt salinity to lyse amoeba
- Can see morts if oxygen in pens is low
- Bath every 35 - 40 days until parasites are gone
- Expensive but effective. Low environmental impact
- 2). Hydrogen peroxide (91% of all Tx performed in Scotland)
- 18 - 22 min at 1200 ppm, salinity, 8 - 15 C
* Can see high levels of morts if disease is severe
- 3). Emergency harvest
- If fish are of harvest size, producers may choose to harvest rather than treat, as when AGD infections are severe, fish may not survive the treatment process, leading to increased economic losses
- The goal is to create a vaccine
37
Ichthyophthirius multifilis - ‘ white spot’
- ‘Ich’ - endemic to almost every single water source, both fresh and sea
- Parasite stage - theront = Easiest stage to treat, covered in cilia + replicates in epithelium
- Encysted stage – tomont - leaves fish host, settles in substrate to encyst, hard to get rid of, in all water sources
- Replication – cysts undergo binary fission to produce tomites, which then differentiate into theronts
- Treatment = Formalin – up to 170 ppm for 1 hour, known carcinogen – PPE!, contradictory Tx
38
Saprolegnia
- Water mold – affects freshwater systems
- Huge problem in hatcheries
- Opportunistic + generally secondary pathogen
- Invades superficial tissue + secretes immunomodulatory compounds
- Number of spores directly proportional to the rate of infection
- Usually causes mortality through haemodilution
39
Saprolegnia - Tx
- Can prevent with malachite green, although this is banned in food fish, only koi, aquaria
- Formalin – 37%, although being phased out.
- Hydrogen peroxide - 500 - 1000 ppm for eggs
- Saltwater treatment
- Potassium permanganate
- Methylene blue
- Ozone – used as a disinfectant in hatcheries. Does significantly affect hatch rate.
40
Aeromonas Salmonicida - Furunculosis
- Ulcerative bacterial disease
- Causes sudden onset: depressed appetite, behaviour change, appearance change, H+, inc mortalities
- Dx - routine bacteriology + histopath
41
Aeromonas Salmonicida - Furunculosis
- Prevention - effective vacc, reduced pravalence
- Oxytetracycline in feed (only licensed AB in aquaculture, alongside Florenicol)
- Prevents spread rather than Tx those affected, reduce spread in stock
42
Non-infectious disease - nutritional
- Poor feed storage
- Contaminants
- Deficiences/toxicities/imbalances
43
Non-infectious disease - genetic
- Not common in wild - don't survive
- Common in farmed
44
Non-infectious disease - water quality
- Koi, aquaculture
- Not enough O2
- Too much ammonia, other toxins
- Nephrocalcinosis - > 12 ppm CO2
45
Non-infectious disease - trauma
- Handling/Tx/Vaccination
- Predators
- Aggression
- Bad weather
Idiopathic + iatrogenic - drug miscalculation
46
Aquatic public health - zoonoses
- Main zoonotic disease of concern is Fish TB
- Caused by Mycobacterium spp.
- People infected though open wounds if working w/ infected fish or water
- Treatment can be problematic - may need protracted chemotherapy
- Control in stocks based on exclusion and destruction of infected stocks
- Drugs not used - costly and resistance is high
Anisakis - worms usually killed by freezing or cooking. Mainly reported in Japan, where raw fish is consumed frequently
47
Vaccination
- First commercially available - Vibrio anguillarum; Vibrio ordalli; Yersinia ruckeri; Aeromonas Salmoncida
- 24 types available
- Mostly inactivated
48
Methods of vacc
- Immersion – a given time spent in a vaccine bath
- Injection (most common) – sedation, then hand or machine vaccinated. Via professional fish vaccinators on anaesthetised fish or recently developed vaccination machines (can admin vaccine to over 200,000 fish per day), on underside of fish to avoid expensive filler + easier to access coelomic cavity
- Orally – top-loading feed with vaccine
49
Antibiotics
- Not relied on heavily anymore
- Fewer than 1/10 farms use AB
50
Methods of slaughter
- 1). Electrical - achieved by running fish through electrified water
- 2). Mechanical (percussive stunning)
- Followed by bleeding out
51
Slaughter process
- 1). Fasting – reduces metabolic rate, lowers O2 demand before live transport, reduces water fouling (waste production) and improves hygiene of processing
- 2). Crowding – allows pumping or netting out of fish to move to place of slaughter. Need to be careful of oxygen levels, and exposure to high light intensity (location dependent). RSPCA suggest fish shouldn’t be crowded for > 2 hr before slaughter.
- 3). Moving – fish either slaughtered on farm or transported to a central plant.
- 4). Grading – Once dead fish are graded into superior, ordinary or rebate, dependent on carcass quality (shape, size, damage etc). As any other farm animal.
52
Role of vet in aquaculture
- Health testing + monitoring as part of veterinary health plans - consultancy role
- Disease outbreaks Dx
- Production monitoring + target setting
- Prescribing
- Streamlining genetics + selective breeding -> ultimately improve sustainability
AAA VMS4002
flashcards
Decks in class (15)
# Cards
-
Poultry Pathology15
-
Poultry Treatment + Procedures63
-
Poultry Therapeutics38
-
Poultry Common Diseases52
-
Poultry Images140
-
Poultry Common Diseases + Testing31
-
Poultry Production + Other26
-
Porcine Pathology162
-
Porcine Therapeutics24
-
Porcine Treament + Procedures111
-
Porcine Imaging67
-
Porcine Common Diseases32
-
Calculations4
-
Fish52
-
Gamebirds Common Diseases0
