Fish 1 + 2

What is aquaculture?

Farming of aquatic organisms, including fish, molluscs, crustaceans and aquatic plants in a controlled/semi-controlled environment.

What different water types can be used in aquaculture?

- Freshwater

- Marine

- Brackish - low salinity

Types of aquaculture systems: (lowest to highest intensity)

- Ponds

- Cages

- Raceways

- Recirculating aquaculture systems (RAS)

What are the 4 basic requirements in aquaculture production?

- Water: volume and quality.

- Oxygen:

- Food

- Waste Removal

waste removal for aquaculture

• generally falls through the bottom of cage/pond/tank, but depends on water movement,

• flow rate should occur at a rate that removes waste quickly enough so that waste doesn't build up and harm the fish.

• For ammonia production algae and bacteria can be used but if the system is intense then biofilters can be used. even low amounts of ammonia can cause stress

food sources for aquaculture

Natural sources (filter feeders)

Livefeeds

Formulated feeds

Others: whole fish, BIOFloc

Feeders: mechanical or demand

oxygen sources for aquaculture

• natural ( photosynthesis of green algae) or artificial (oxygen injectors and aerators/diffusers, for example in raceways, falling water causes splashes and diffusion of water from the air).

water sources for aquaculture and what does it need to be

• sea, wells, rainwater, watershed runoff, springs, streams, lakes locks

• have the adequate voluma

what is solid waste, what can it do and what needs to be done

• Solid waste: from uneaten feed, dead fish and faeces

• Need to be removed as they can be harmful to fish

• can Clog gills -> death

• if Left for long time -> inrcs in unsuspended and unsuspended solids, bact and ammonia in water

what normally happens to ammonia

• Is normally taken in by algae and bacteria and broken down

• Depending on intensity of the system, biofilters might be needed to help remove nitrogenous waste

what is the flow rate and what does it need to be

• rate at which the water is replaced by new water

• needs to be sufficient to not allow the waste products to build up

What is the first stage of the aquaculture production cycle?

Broodstock

What is the second stage of the aquaculture production cycle?

Hatchery

What is the third stage of the aquaculture production cycle?

Grow-out

What is the final stage of the aquaculture production cycle?

Slaughter

How are production plans for aquaculture companies generally calculated?

In degree days, considering temperature and number of days.

• number of days x temp

Why is temperature important in aquaculture production?

Fish are ectotherms and their growth is affected by temperature.

system of growing stock in aquaculture - basic atlantic salmon

broodstocked selected from farmed or wild pop.

induce spawining - light and temp manipulation

disease screening

ova are stripped

freshwater hatchery

incubated in troughs

fry - parr -

naturally or light manipulation turning into smolts

moved by boat or helicopter to where they will grow out

most vulnerable to environmental and disease pressure

why might you do disease screening in the cycle

• to make sure not

smoltification

body change shap and colour

upregulation

sodium potassium atpase pumps in gills and skin -

can now live at sea

What are the three stages of molluscan shellfish production?

1. production of seed (eggs).

2. Juvenile nursery culture.

3. Grow-out of sub-adults to harvest size.

What are the two methods for production of seed (eggs) in shellfish production?

Hatchery production from selected broodstock and seed collection from natural resources.

What are the locations for juvenile nursery culture in shellfish production?

Land-based flow through systems, floating/submerged nets or trays in intertidal ponds, and floating/submerged nets or trays in open water.

Where does the grow-out of sub-adults to harvest size occur in shellfish production?

In open waters, offshore, coastal ponds, or intertidal areas.

What are the methods used for grow-out of sub-adults to harvest size in shellfish production?

On-bottom/off-bottom poles or racks, floating rafts, longline systems, and cages or nets.

Summary of pond systems.

- Enclosed water areas

- Most commonly used

- Least intense

- Rely on natural processes to remove waste and supply oxygen

What species of fish are commonly kept in pond systems?

- Salmonids

- Tilapia

- Shrimp/Prawns

- Catfish

Summary of cage types

- Circular or squared

- Variable sizes

- Soft or hard materials

fixed to sea bed below

majority of atlantic salmon

Advantages of cages.

- Easy stocking

- Easy feeding

- Easy harvest

Disadvantages of cages.

- Little environmental control, meaning:

- Susceptible to predators

- Exposure to water-borne irritants (jellyfish, plankton blooms)

- Exposure to bad weather conditions

- Shared water body (quicker disease spread) - sea lice

- Limited water quality control.

What species of fish are commonly kept in cage systems?

- Salmonids

- Tilapia

- Seabass

- Seabream

- Tuna

Summary of sea cages.

- Much larger than normal cages

- More robust

-have a higher vol of water

- 'Movable' (as long as you have a licence to do so)

Summary of raceways.

- Rectangular structures

- Single pass system

- Built above or below ground

- Cement, fibreglass or wood

- Require large volumes of water that is high quality

- Gravity flow

Tend to be in mountainous regions (e.g. Idaho).

- more intense

Disadvantage of raceways.

- Water flows from one sub-unit to the next without treatment. Not ideal from a biosecurity perspective.

- To minimise disease risk, the fish getting the fresher water are the younger stages and theoretically, the largest and most robust fish will be located at the bottom of the farm.

- require a lot of water - needs to be high quality

What species of fish are commonly kept in raceways?

- Trout

- Tilapia

- Carp

- Prawns

Summary of recirculation aquaculture systems (RAS).

- Most intensive system

- Can be located almost anywhere

- Less water requirement

- Significant energy input

- Required expertise

- Expensive

- can be set up in most areas

Waste water is cleaned through a series of mechanical and biological filters and then put back into the system.

Disadvantage of RAS systems.

Recirculation of water can quickly magnify pathogen challenges - critically important to screen fish for disease before being brought into these facilities.

pathogens cause more acute illness

What do RAS systems require?

- culture tanks

- filter to remove solids

- biological filter - ammonia

- oxygenation equipment → o2 addition is v important

- co2 removal

- heating + cooling

- pH control

- pumping

What species of fish are commonly kept in RAS systems?

- Salmon

- Trout

- Eel

- Sturgeon

- Arctic char

- Yellowtail

What other less common aquaculture systems are there?

- Offshore aquaculture

- Semi-closed systems

systems which are being trialled

Why is fish welfare important?

Good welfare conditions --> less stress and disease susceptibility --> less dependence on medication/treatments --> better growth rates and food conversion --> better quality product

What looks after the welfare of fish in aquaculture?

-Major resource published 2018 by NOFIMA: 'Fishwell' report

-Operational Welfare Indicators (OWIs) proposed for fish

What is the definition of welfare?

The physical and mental state of an animal in relation to its environment. It requires:

- The animal's normal biological functioning

- Its emotional state

- Its ability to express certain normal behaviours

Do fish feel pain?

This is debated, however, the summary is that there are two main processes:

- Nociception

- Conscious recognition (unclear)

- Brain anatomy

Fish can show 'emotional fever' - this is stress-induced hyperthermia so indicates some form of emotional state.

How can we assess welfare in fish farms?

• Operational welfare indicators (OWIs).

• Would assume that if the fish look good, feeding , growing and behaving normally you expect their welfare is good

What are welfare indicators?

Measurable/observable parameters relating to the welfare needs of fish.

What are operational welfare indicators (OWIs)?

Welfare indicators that are judged to have practical application and value on-farm. OWIs can be individual or group-based.

what can OWIs be 

What does it mean for OWIs to be clearly defined?

OWIs should have a clear and specific definition.

How should OWIs relate to the welfare state of fish?

OWIs should correlate to the welfare state of the fish or at least one welfare need and be suitable for the life cycle stage and production system in question.

What does it mean for OWIs to be practicable?

OWIs should be feasible to implement.

What is the reliability requirement for OWIs?

OWIs should produce repeatable and comparable results with objective scores.

What types of scoring can OWIs use?

OWIs can be binary (positive/negative) or scalable depending on the indicator.

What is the validation requirement for OWIs?

OWIs should be validated for the species or be above reasonable criticism.

What does it mean for OWIs to be auditable?

OWIs should be capable of being audited.

What are some indirect OWIs?

- Water quality parameters: temp., salinity, oxygenation, total ammonia nitrogen, nitrites, ozone, turbidity, hardness/alkalinity, total gas pressure, suspended solids, water flow.

- Lighting

- Feed quality/load

- Stocking density

- Tank/filter microbiome

what can deviations of indirect OWI mean

• Deviations can indicate theres problems before they start to affect the fish

• but effects are often dependent on multiple factors and monitoring isnt always realistic

What are the indicators of group-based direct OWIs?

Mortality, Behaviour, Appetite, Growth, Presence of emaciated fish, Blood/scales in water, Discolouration, Presence of disease.

What are the indicators of individual-based direct OWIs?

Opercular movement, gill condition, body condition, sexual maturation, smoltification status, fin condition, skin condition, presence of haemorrhages/wounds, eye conditions, jaw or vertebral deformities.

how can OWIs be measured

• Scoring systems to help with this

1- Mild changes

3- Severe changes

• Do it routinely

What about crustaceans and molluscs, can they feel pain?

Although fish are protected under the Animal Welfare Act 2006, invertebrate decapods aren't.

Findings from several scientific studies suggest that it is highly likely that decapod crustaceans are 'capable of experiencing pain or suffering'.

What limitations are there to applying animal welfare to aquaculture?

-Fish welfare needs/concepts not yet clearly understood.

-Huge number of species cultured: limited understanding on welfare-related biology.

Regulatory bodies involved in welfare standards in aquaculture.

Globally:

- FAOs Code of Conduct for Responsible Fisheries

- Aquaculture Stewardship Council

- Organic certification schemes (Soil Association)

- Global GAP (Good Aquaculture Practice)

UK:

- RSPCA Assured (salmon, trout, cleaner fish)

- SSPO Code of Good Practice

How can farming in aquatic environments affect public health?

-Pollution of water bodies by increased organic load (through feeding/fertilisation) in the water can lead to survival of pathogens and multiplication of vectors.

-Water bodies represent unique opportunity for spread of anti-microbial resistance (AMR) through easy mixing of bacteria, overuse of antibiotics particularly in countries where veterinary controls are poor.

-In some places the water which fish are reared can be used for multiple things

•  Hygiene/ washing fascilities for people, disposing of waste ect

what are UK trout farms required to monitor

the amt of nitrogenous waste into streams or rivers

How can eating aquatic products affect public health via non-infectious contaminants?

-Contamination with veterinary residues

-Contamination with herbicides or pesticides (organochlorine pesticides, organotin compounds, phthalates, brominated flame retardants, polyflourinated compounds, PAHs, dioxins, PCBs, …)

-Contamination with heavy metals Cd, Hg (methylmercury) and Pb

-Biological toxins

how can toxins in wild species be passed to farm species

• if they are a food source

  • Can be monitored

  • Lots of wild fish is needed to make small vol of feed for farmed

Name some biological toxins produced by shellfish

-Amnesic (ASP)

-Diarrhoeic (DSP)

Paralytc (PSP

Name some biological toxins produced by fish

-Scombrotoxin (histamine poisoning - mackrel and tuna)

• due to consuming histadine -> is then coverted to histamine

• Is due to spoiling of fish

-Ciguatoxin (tropical sub tropical - barracuda, eels)

-Tetrodotoxin (puffer fish)

How can eating aquatic products affect public health via food and waterborne diseases?

Transmission of pathogenic organisms within water bodies and/or contaminated food.

pathogenic bacteria:

- Clostridium botulinum

- Vibrio parahaemolyticus

- Salmonella

- E.coli

- Listeria monocytogenes

Or pathogenic viruses:

- Norovirus - oysters particularly

Vibrio parahaemolyticus

• febrile gastroenteritis

• seasonal disease, temperate marine waters

• can come through wounds and ingestion of undercooked fish and shell fish

What zoonotic bacteria can humans contract from fish?

-Aeromonas spp.

-Vibrio spp.

-Mycobacterium spp.

-Streptococcus iniae

-Erysipelothrix rhusiopathiae

features of clostridium botulinum serotype 

where are you more likely to find salmonella spp with fish

High water temperaturas

Contaminated water effluents

theres Salmonella monitoring on some farms and processing plants in uk

what is e coli an indicator of in fish

caecal contamination (human handling)

what are features of listeria monocytogenes in fish

Frequently isolated from fish and fish products – of concern in vulnerable individuals

What zoonotic parasites can humans contract from fish?

-Trematodes: Opisthorchiidae and Heterophyidae

-Nematodes: Anisakidae and Gnathostomidae

-Cestodes: Diphyllobothridae

how would infections develop from contact with farmed fish

wounds when handling fish, contact with mucus and tissue of fish

what zoonotic diseases are there in fish, what clinical signs will be seen in fish and humans

• Aeromonas hydrophala most common in fish in uk

• Vibrio common in uk due to water temps

What is the most common 'true' bacterial zoonosis from fish?

Three major species (M. marinum, M. fortuitum, M. chelonae, amongst others)

mycobacteriosis

How do three major species (M. marinum, M. fortuitum, M. chelonae, amongst others) of bacteria that is zoonotic manifest in fish and in humans?

-In fish: multiple internal granulomas, low but persistent mortalities, chronic presentation (“fish tuberculosis”)

gram + bacteria colonies

-In humans: superficial skin lesions (“fish handlers disease” or “fish tank granuloma”) and systemic mycobacteriosis in immunocompromised individuals. respiratory symptoms

Describe the life cycle of Diphyllobothrium spp (cestode)

widespread

How can you see Diphyllobothrium spp in fish post mortem?

The cysts of Diphyllobothrium are white and clearly evident on the intestine of fish.

How can humans prevent contracting Diphyllobothrium spp. (cestode) from fish?

By properly cooking and freezing of fish.

describe the lifecycle of diphyllobothrium spp. (cestode)

what can cause anisakiasis

Anisakis (A. simplex),

Pseudoterranova (P. decipiens)

Contracaecum (C. osculatum)

Describe the lifecycle of this nematode Anisakis (A. simplex)

• dolphins are usually the final host -> become infected when they eat infected fish

• But if humans eat an infected fish (undercooked) -> burrow into lining of GIT -> inflam reaction

why is anisakiasis mainly a problem in wild fish

Bc farmed fish arent eating the intermediate host (shrimp ect) so don’t get the infection

how can you see if fish are infected with a.simplex

Shine light under the fillet and remove the worms if present

Describe Anisakis (A. simplex) effect and how it's spread it's controlled:

Causes: ingestion of larvae through the intermediate host

-Raw (sushi), rare (slightly cooked) or inadequately processed

Effects:

-Anisakiasis (gastrointestinal irritation of live larvae)

-Allergy to A. simplex larvae when they are ingested (like an allergic reaction to seafood in someone with no previous allergic reaction to seafood)

Control:

- Freezing and heat treatments (EFSA recommendations)

freezing and heat treatments for anisakis

freezing

• -20 degrees C maintained 24 hrs

• -35 degrees C for 15 hours

• -15 degrees C for 96 hours

heat treatment >60 degrees c no problems for fried fish

traditional processing treatments - cold smoking - not sufficient to kill larvae

Describe the distribution of A.simplex (nematode) in fish

-Worldwide in marine water fish (only occasional in freshwater fish)

-Aquaculture fish are not parasitized (rare exceptions)

-Between 40-80% of marine fish are infested with larvae

-There is a higher prevalence in fish from cold waters

what cold water fish can Anisakis be commonly found in

meditarranean - hake, blue whitling, mackeral

atlantic ocean - hake, blue whitling, mackeral, herring, cod redfish, halibut, turbot

Anisakis larvae location in the fish

- free in the peritoneal cavity

- forming very numerous tangles attached to the peritoneum

- larvae coiled in a flat spiral and encapsulated in peritoneum, mesentery, liver or muscles often hypoxial

What are the key challenges that vets in aquaculture work face in practice?

1.Endemic disease

2.Antimicrobial resistance (AMR)

3.Biosecurity

4.Water quality, carrying capacity and effect on fish health/welfare

5.Lack of fish health infrastructure (training, vets, regulation)W