Fish Flashcards
What is aquaculture?
A form of farming- any type of aquatic animal, plant, seaweed, oysters or shrimps
Fish are cold-blooded?
What does this mean?
Require on external temperature for thermal regulation- everything is temperature dependent
Growth, immunity, reproduction, healing, feeding
Duration of any biological process time and temp dependent- degree days, temperature
What are the different types of aqua cultures and aquatic exploitation?
Extensive culture- ponds most common
Very basic enclosure, no feeding, no or little husbandry, may protect from poachers/predators, harvest slow, families/local markets
Intensive farms-
saltwater ponds- warm water
fresh water ponds- tropics
Temperate- salt water cages, sea water cages
Tanks- temperate
What are the human health issues associated with aquaculture?
Increased contact between people, pathogens and vectors
Terrestrial vectors- river blindness, malaria, mosquitoes
Aquatic vectors- cercarial dermatitis- swimmers itch
Survival of pathogens- cholera, fish can control vectors and eat larvae
What are the not true zoonotic hazards from eating aquatic products?
Most result from contamination of food with toxin-producing or food poisoning organisms- poor handling or storage
Infectious contaminants-
Hepatitis A- shellfish
Cholera- shellfish
Vibrio parahaemolyticus- undercooked shellfish
Contamination with biological toxins-
Clostridium botulinum- processed fish
Shellfish poisoning- amnesic, diarrhoea
Pufferfish- tetrodotoxin
Hazards-
Pollutants- heavy metals, herbicides
Chemotheraptutants
Parasites
What parasite can infect humans from fish?
Where does it live, and what size can it grow to?
Describe its life cycle?
Where is it found?
How is it controlled?
Diphylobothrium latum- broad tapeworm
Adult lives in SI of mammal- can be over 3m
Can cause chronic debilitation and pernicious anaemia in man
Life cycle- eggs hatch in water, larvae into corepod, eaten by fish-> muscle (plerocercoid), eaten by mammal, passes eggs in SI
Found- North Europe, Russia, Africa
Control- don’t eat raw, pickled, cook
What kind of bacteria can cause zoonosis from fish?
What specific bacteria can infect the superficial tissues?
What bacteria can cause zoonosis in immunosuppressed people?
Psychrophilic- can survive in cold and warm temps
Superficial- mycobacterium
Immunosuppressed- Aeromonas hydrophilia
How does zoonotic mycobacteriosis affect fish and humans?
Who is affected and how are they infected?
How is it controlled?
Why are drugs not used?
Fish- chronic conditions, fresh water and marine species- multiple internal granulomatous- low mortalities
Human- 3 species, M.marinum most common- swimming pool granuloma- superficial
People working with infected fish or water- through open wounds
Treatment in humans can be problematic and require protracted chemotherapy
Control is fish-based exclusion of the infection and destruction of infected
Drugs- resistance, cost
What other parasites can infect fish?
Trematoda- digenean flukes- eggs in heart and brain, flukes in liver or larynx
Anisakis- nematode-
Pseudoterranova spp- nematode
Anisakids- live worms, severe chronic inflammatory lesions, most reported in Japan and Netherlands
How can fish experience fear and pain from slaughter?
Nociceptors detect heat, toxins and pressure
Neurones convey nociceptive signals to the brain
Behavioural evidence-
trout learn to avoid adverse stimuli- nets
trout injected with acid rub in snouts their RR increased
Analgesic reduce pain-related behaviours
Why is animal welfare important for meat quality?
Carcase damage
External- eye damage, bruising, cuts, scale loss, net marks
Internal- early rigor, gaping, flesh texture/colour, haemorrhages
What are the different types of stunning used for fish and what influences selection?
Wet stunner- fish passed throug tube- electrodes either side
Dry stunner- removal from water (stressor)- electrodes and belt are two electrodes
Selection-
electricity flows through and around the fish
depends on species, size, stress level, temperature
water conductivity
What are the indicators of an effective stun?
Normal swimming before stun
After becomes rigid
Loss of balance, may turn upside down in water
No rhythmic movement of gill covers
Absence of eye-roll reflex
Small involuntary muscular twitches, tail may flutter
How are fish exsanguinated?
After checking stun- cut the animal immediately- 10-15 seconds after stun
Necessary to sever all gill arches on at least one side of the head
Turbot and halibut must always be bled
How should fish stunning be checked for an recovery prevented?
Employ a backup slaughterman to stun any mis-stunned
Transport fish to a processing plant in solid ice
Immediately after gill cutting immerse in ice or deoxygenated water
