Intensive Fish Production 2 Flashcards
How to we do health moniotring in fish?
- Observe behaviour - mov, history/records on farm
- Examine environemnt - fish size, quality etc
- Select your fish - avoid all dead fih autolysis rapid, avoid taking biggest, pick moribund fish and ‘normal’ ones
- Macroscopic analysis - gills, skin , eyes etc
- Gills, organ samples, mucus, skin scrapes
What is the only diagnostic tool in aquaculture?
HISTOPATHOLOGY
What main parasites in fish?
- Salmon Lice (Caligus elongatus/
Lepeophtheirus salmonis) - Amoebic gill disease
- Invisible dx -> Ichtyophtirius multifilis ‘white spot’
What important fungi?
Saprolegnia
Important bacteria?
- Aeromonas salmonicida
- Moritella viscosa
What two types of sea lice?
- Caligus elongatus – affects >80 species
of fish - Lepeophtheirus salmonis – specific to
salmonids, immunomodulate the host
increasing susceptibility to secondary
infection
What do sea lice do?
feed on skin, mucus, and blood if acheivable
What tx options for sealice?
What practices to reduce exposure of salmon to lice?
- Single year stocking
- Site fallowing/rotation
- Improved site selection
- Genetic improvements
- Improved farm hygiene
What other potential sea lice prevention?
- 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 - Functional feeds are being developed that reduce
sea lice burden - Lighting strategies
- Lasers that ID lice and strike them
- Ultrasound and vacuum in research
What causes Amoebic Gill dx ?
Causal agent - Neoparamoeba peruans
* Amoeba that survives in sediment, net
pens and the water column
What does Gill dx cause?
Causes, as name suggests, gill damage,
resulting in epithelial thickening, and reduced
oxygen uptake, excessive mucus production.
* This is exacerbated by higher water
temperatures – hence warming oceans is
a big problem for the salmon industry.
Gill scoring?
Histology on Gills?
- Top – Normal
- Bottom – extensive lamellae hyperplasia
and mucus cell proliferation - Arrows = Amoeba
AGD causes …?
severe CV compromise,
and if environmental conditions are
unfavorable, can cause severe
mortality events >50% of stock.
What factors/ risks of AGD?
- High salinity (>32ppt)
- High temperatures
- Co factors – jellyfish/algae blooms
- Biofouling of nets – reduces water
turnover and Oxygen availability. - Smolt quality and size
AGD tx optionS?
- Freshwater - 8% of all tx in scotland
- Hydrogen peroxide (biggest one)
- Emergency harvest
describe freshwater tx?
- 2-3 hour baths in <3ppt salinity to lyse amoebe
- Can see morts if oxygen in pens is low
- Bath every 35-40 days until parasites are gone
- Expensive but effective. Low environmental
impact
Describe hydrogen peroxide tx?
- 18-22 mins at 1200ppm, 8-15oC
- Can see high levels of morts if disease is severe
What is Ichthyophthirius multifilis?
‘WHITE SPOT’
- Enedemic to every waterr source
Stage of parasite lifecycle of’white spot’?
- Parasite stage – theront. Easiest stage to
treat - Covered in cilia and replicates in
epithelium - Encysted stage – tomont. Leaves fish host,
settles in substrate to encyst. - Replication – cysts undergo binary fission
to produce tomites, which then differentiate
into theronts.
Tx for ‘white spot’?
- Formalin – upto 170ppm for 1 hour.
- Known carcinogen – PPE!
Saprolegnia?
Water mold – affects freshwater systems
* Huge problem in hatcheries
* Opportunistic and always secondary pathogen
What does saprolegnia do?
Invades superficial tissue and secretes
immunomodulatory compounds
Number of spores is directly proportional to the rate
of infection.
Usually causes mortality through haemodilution