Fish

Question 1

Why keep fish?

Answer 1

Pets
Restocking/restoration
Research
Angling
Biological control
Food

Question 2

What is the aim for aquaculture production in order to satisfy demand?

Answer 2

Must double by 2050.

Question 3

1. Examples of marine finfish?
2. Example of freshwater finfish?
3. Examples of molluscs?
4. Example of crustaceans?
5. Why are amphibians produced?

Answer 3

1. sea bass, bream.
2. carp
3. oysters, mussels and clams, cephalopods.
4. prawns
5. ornamental or research

Question 4

1. 2 categories of aquatic animal production?
   – which is more intensive?

Answer 4

1. Capture fishery (wild catch), aquaculture production (fish farm) – more intensive.

Question 5

2 types of capture fishery and types of finfish and others caught?

Answer 5

Marine – cod, halibut, plaice, sole, shark, ray (finfish).
mussels, clams, oysters, crab, lobster, shrimp etc. (others).
Freshwater – pike, bream, bass etc (finfish).
Some freshwater crustaceans e.g. crayfish.

Question 6

Systems of fish farming/aquaculture.

Answer 6

Recirculation systems (closed).
Open basins
Sea based seed systems
Rope cultivation
Open-pen sea cages
Combinations.

Question 7

Advantages of recirculation systems?

Answer 7

Full control over environment.
Very high biosecurity.
No predation.

Question 8

Disadvantages of open basin?
Disadvantages of sea based seed systems?
What is rope cultivation commonly used for?

Answer 8

Less control over the environment.
Lower biosecurity.

Less control over environment.
Lower biosecurity.
Increased predation.

Growing mussels.

Question 9

Disadvantages of open-pen sea cages?

Answer 9

Less control over environment.
Lower biosecurity.

Question 10

Main finfish and shellfish species farmed in the UK?

Answer 10

Salmon
Trout
Mussels
Oysters

Question 11

1. How many tonnes of salmon produced per year in UK?
2. Stages of production of salmon in the UK?

Answer 11

1. 190,000 t/yr.
2. 2 stages: Recirculation systems for 12-18 months.
   Then transferred to open-pen sea cages to fatten for another 12-24 months with feeding pellets to fatten them.

Question 12

1. Types of trout produced in UK?
2. How many tonnes of trout produced per year in the UK?
3. System for trout production?

Answer 12

1. Brown and rainbow
2. 16,400 t/yr.
3. Freshwater ponds on land.

Question 13

1. How many tonnes per year of mussels produced in UK?
2. What systems of production used to produce mussels in the UK?
3. How many tonnes per year of oysters produced in UK?
4. What system used to produce oysters in UK?

Answer 13

1. 10.000 t/yr.
2. Rope cultivation and mussel beds.
3. 600 t/yr.
4. Mesh bags.

Question 14

Make a table on the composition of fat fish, semi fat fish, lean fish, crustaceans, and molluscs in terms of water, protein and lipids.

Answer 14

Fat fish = 69% water, 20% protein, 10% lipids.
Semi-fat fish = 77% water, 19% protein, 2.5% lipids.
Lean fish = 82% water, 16% protein, 0.5% lipids.
Crustaceans = 76% water, 18% protein, 2% lipids.
Molluscs = 81% water, 13% protein, 1.5% lipids.

Question 15

1. Fat in fish is not all bad….how?
2. Why are carbs not mentioned? exception?
3. Mineral content?

Answer 15

1. It is highly unsaturated with lots of phospholipids.
2. They are negligible except molluscs with 3% glycogen.
3. Low but has full range.

Question 16

Processes of spoilage in fish.

Answer 16

Enzyme action.
Action of the bacteria.
Chemical action.

Question 17

Explain enzyme action causing spoilage.
How do we know that there is spoilage by this action?

Answer 17

Breakdown of ATP.
ATP > inosine > hypoxanthine.
Hypoxanthine produces a fishy odour, indicating spoilage.

Question 18

Explain the action of bacteria causing spoilage.

Answer 18

Bacteria reduce trimethylamine N-oxide (TMAO) to trimethylamine (TMA).
The breakdown of amino acids and formation of primary amines (e.g. histamine from histidine) – Can cause food poisoning in extreme cases.
Urea content may be high in flesh which some bacteria may turn into ammonia – smelly and nasty taste.

Question 19

Explain chemical action causing spoilage in fish.

Answer 19

In fatty fish, the oils oxidise and produce a rancid smell.
– levels of peroxide value and free fatty acid allow for us to measure the index of quality of the fish and the level of spoilage.

Question 20

We need to be able to tell when fish is turning or already off.
1. Describe the eyes just after catch.
2. Describe the gills just after catch.
3. Describe skin just after catch.
4. Describe odour of fish just after catch.

Answer 20

1. Convex, crystal-clear cornea.
2. Bright red or pink, clear mucus.
3. Well differentiated colours, glossy, transparent slime.
4. Sharp, sea-like/iodine-like, metallic.

Question 21

1. Describe the eyes at medium stage.
2. Gills
3. Skin
4. odour

Answer 21

1. Flat/slightly sunken, some loss of clarity of cornea.
2. Slight loss of red colour and brightness.
3. Slight fading of colours, slightly milky slime.
4. Slightly fishy, cut grass, shellfish-like, musty, garlic, lactic acid.

Question 22

Describe ____ when spoiled.
1. eyes
2. gills
3. skin
4. odour

Answer 22

1. Sunken, cloudy, discoloured cornea.
2. Bleached and/or discoloured, thick slime.
3. Loss of colour, yellow knotted slime.
4. Stale cabbage-water, sour drains, wet matches, ammoniacal, trimethylamine.

Question 23

1. Short term preservation of fish?
2. Long term preservation of fish?
   – effective for what?
3. Other preservation methods?

Answer 23

1. Chilling or icing.
2. Freezing.
   – retaining flavour, colour and nutritive value.
3. Drying/salting, canning, controlling autolytic enzymatic spoilage e.g. gutting, decapitation.

Question 24

1. In freezing, what initial temperature must the fish reach?
2. What temperature must the fish then be kept at?

Answer 24

1. -40C.
2. -18C.

Question 25

1. Where does bacteria tend to be on fish?
2. What is an important determining factor for the type of bacteria on fish?
3. What condition of eater helps bacteria to proliferate and grow?
4. Why are molluscs higher risk organisms for bacteria?

Answer 25

1. On skin, gill entrances and intestines.
2. Microflora of the water they live in.
3. Warmer and more contaminated water.
4. They are filter feeders.

Question 26

What are residues that must be tested for on/in fish?

Answer 26

Heavy metals – industrial dumping ground.
– Accumulation effect. e.g. mercury in tuna.
ABX
Malachite green (used for treatment of external fungal and protozoal diseases).
Organophosphorus pesticides – run off.
Organochlorine pesticides – run off.
Ivermectin (used for treatment of external and internal parasites).

Question 27

Vibrio parahaemolyticus/vulnificus…
1. Define halophilic.
2. In what fish types has this bacteria been isolated?
3. What fish type is the main culprit and why?
4. Symptoms in humans infected?
5. Antibiotic use?
6. Prevalence?

Answer 27

1. Can only grow when there is salt in the environment.
2. Finfish, shellfish, crustaceans.
3. Oysters as they live in warm waters.
4. V+D, fever/chills, self-limiting.
5. No evidence that use will help treat V. para, but V. vul can become systemic in immunocompromised people with 50% fatality so treatment highly indicated.
6. Rare in Europe.

Question 28

Leptospira ichterohaemorrhagiae….
1. Origin and mode of contamination in fish?

Answer 28

1. Rat urine contamination of fish farm feed sheds and then fish eat feed.

Question 29

Scombroid poisoning……
1. Cause.
2. Give examples of scombroid fish.
3. Who is most affected and why?

Answer 29

1. Meat of some scombroid fish contains high levels of histidine and spoilage bacteria convert it to histamine.
2. Mackerel, tuna, sardines.
3. Humans with deficiencies in diaminooxygenase (degrades histamine) due to congenic disorder, or being on DAO inhibitors (anti-depressants, TB drugs) can suffer histamine poisoning – like an allergic reaction.

Question 30

Symptoms of scombroid poisoning.

Answer 30

Typical of allergy, v rapid response.
Initially facial flushing and sweating, burning peppery taste sensations about the mouth and throat, dizziness, nausea, headache.
Progresses to facial rash, hives, oedema, short term diarrhoea and abdo cramps.
Severe (higher levels of ingestion): Blurred vision, respiratory stress, swollen tongue.

Question 31

1. What is the most frequently reported seafood-toxic illness in the world.
   – How many cases per year?
2. What is it caused by?
3. What area of the world are most affected?
4. What types of symptoms occur with this illness in humans?
5. Treatment types for this illness.
6. Why is this illness difficult to prevent?
7. How to avoid this illness?

Answer 31

1. Ciguatera fish poisoning
   – ~10,000-50,000 people per year.
2. Eating reef finfish containing ciguatoxins derived from dinoflagellates.
3. Areas with tropical and subtropical climates.
4. GI, neuro, CV symptoms.
5. Symptomatic and supportive.
6. Because the toxin is odourless and tasteless and are not removed by cooking or freezing (heat-stable).
7. Avoid large reef fish, large predatory reef fish and their viscera.

Question 32

1. What is another name for the parasite Anisakis simplex?
2. What is the disease called in humans?
3. What type of parasite is it?
4. Common spp of Anisakis simplex?
5. Cause.

Answer 32

1. Herring worm.
2. Anisakiasis.
3. Nematode.
4. Pseudoterranova decipens, Contracaecum, Hysterothylacium.
5. Eating raw or undercooked finfish or squid.

Question 33

Clinical signs of anisakiasis?

Answer 33

Tickly throat – worm coughed up, vomited or manually extracted.
Can burrow into gut wall and occasionally penetrate it, causing peritonitis.
Can attract eosinophils which form a granuloma around the worm, giving appendicitis-like pain in the area.
Normal host response eliminates worm, usually no more than 3 weeks post-ingestion.

Question 34

Which fish is Anisakis simplex most common in?

Answer 34

Cod, haddock, fluke, pacific salmon, herring. flounder, monkfish.

Question 35

1. What type of worm is diphyllobothrium latum?
2. What length can this worm grow up to and why?
3. Cause?
4. How could this parasite be killed at the level of the fish?
5. What illness can it cause?

Answer 35

1. Broad tapeworm
2. 1-15m long – mostly asymptomatic in people.
3. Improperly cooked freshwater finfish.
4. By adequately cooking or freezing the fish.
5. Megaloblastic anaemia.

Question 36

Shellfish poisoning….
1. Cause?
2. Can the toxin be eliminated from the shellfish?
3. Treatment?
4. What do PSP, NSP, ASP, and DSP all stand for respectively?

Answer 36

1. Harmful algal blooms with toxins that become concentrated in the tissues of shellfish when they eat the algae. The shellfish are ingested by people.
2. Ordinary cooking or freezing will not eliminate the toxin.
3. No specific treatment. So supportive ad symptomatic treatment need to be provided.
4. Paralytic shellfish poisoning, neurotoxic shellfish poisoning, amnesic shellfish poisoning, diarrheal shellfish poisoning.

Question 37

Give cause, toxin producing algae and symptoms for PSP.

Answer 37

PSP – cause – saxitoxin, neosaxiton and gonyautoxins I-IV
– Dinoflagellates
– Paraesthesia, coordination loss, speech defects, nausea, vomiting, muscle paralysis, death.

Question 38

Give cause, toxin producing algae and symptoms for NSP.

Answer 38

Cause – Brevetoxins.
– Dinoflagellates.
– Slurred speech, nausea, vomiting.

Question 39

Give cause, toxin producing algae and symptoms for ASP.

Answer 39

Cause – Domoic acid.
– Diatoms.
– Permanent short term memory loss, brain damage, death.

Question 40

Give cause, toxin producing algae and symptoms for DSP.

Answer 40

Cause – okadaic acid, azaspiracid.
– Dinoflagellates.
– Diarrhoea, nausea, vomiting.