Fish farming HANDOUT - Tennessee 2008thinking.freeshell.org/awesym/Fish farming.pdf · • Sustainable fish farming is essential to meet increasing consumer demand • Farming Atlantic

Fish farming

Catherine A. Hadfield

MA VetMB MRCVS

January 2008

Objectives

• Why farm fish?

• Sustainable fish farming

• The ideal fish species to farm

• Some examples• Atlantic salmon – FW then coastal sea pens

• Channel catfish – FW ponds

• Atlantic cod – offshore sea pens

• The roles of the vet

Why do we farm fish?

• Essential source of protein and EFAs

• High and increasing consumer demand– Cannot be obtained from capture fisheries

– 25-50% from culture fisheries • $1 billion, 0.5 million tons annually in US

• 80% in freshwater

– Dept of Commerce planning a 5-fold increase in aquaculture by 2025

• Can reduce imports + augment wild stocks

Why do we farm fish?

Sustainable fish-farming

• Production can be maintained in the long-term without adversely affecting ecosystems

• Economically sustainable– Highest costs are feed + initial capital investment

• Environmentally responsible– Smallest effect on water, land and other species

• Socially responsible– Traceable

What is the ideal fish to farm?

• Water/energy

– Freshwater species

– Species tolerant of:

• Wide temperature ranges

• Low dissolved oxygen (DO)

• Poor water quality (nitrogenous wastes)

• Mild salinity and pH changes

• High stocking densities


• Nutrition

– Herbivores/omnivores

• More economically, environmentally and socially sustainable

– Known nutritional requirements

– Complete foods readily available

• Suitable form, composition, cost

– Efficient food conversion ratio (FCR) + rapid growth rate to market size


• Health

– Genetics

• Limited inbreeding

• Bred for pathogen resistance

– Known disease issues, prophylaxis available

– Accessible pens that allow removal of morts

– Tolerant of handling/grading etc

– High reproductive potential in captivity


• Small footprint

– Low space requirements

– Low water discharge rates

• Extensive ponds or intensive recirculating/filtration

– Low energy costs

• Natural water flow

• Suitable water temperatures and light cycles

– Isolated from wild populations

• Limit disease or gene transfer


• High consumer demand

– Product – popular, consistent, safe

– Price – affordable

– Place – available

– Promotion – marketable

• There is no ideal fish species to farm

Salmon

• Atlantic salmon (Salmo salar) • >90% of the salmon market is farmed

Atlantic salmon

• Worldwide $4 billion, 1.2 million tons annually

– Chile, Sweden, Canada, Scotland, Norway

– US (Pacific northwest) $40 million

• Pacific salmon (Oncorhynchus)• Sockeye/red, chinook/king, coho, pink,

chum

• Some landlocked species

Atlantic salmon farming

• Roe and milt removed manually (stripping)

• Eggs are disinfected

• Alevin/sacfry hatch in low light in cold freshwater, feed off yolk sac


• Fry move up water column and start feeding to become parr

– Can put on pellets fairly early

– Carnivores - fish meal/fish oils

• Not sustainable

• Toxin accumulation

• High feed costs

– Pigments added


• Smolts develop at 1-2yrs → coastal sea pens– Sites are limited; need

– Good water flow, with DO >9 mg/L

– Adequate temp (14-18ºC, 57-64F)

– Protection from inclement weather

– Competition for land use – Capture and sport fisheries, recreation, shipping

– No environmental control

– Release of contaminants, eutrophication

– Infectious disease transfer

– Genetic transfer


O2

Feed

N2 waste

Waste feed

CO2

Predation

From direct/indirect contact or escapes• Infectious disease transfer• Genetic transfer• Competition for resources

Chemotherapeutics, antifouling agents etc

Unused chemotherapeutics, antifouling agents etc


• Harvested

– Takes 3-4yrs total, at 4-5kg

– Usually by cranial concussion or CO2 then bleeding


• Diseases

– Trauma/predation

– Nutritional issues

• Starvation

• Nutritional imbalances

– Environmental

• Hypoxia as temperatures or organic load increase

• Gas bubble disease (supersaturation of water under pressure)


• Diseases

– Bacteria causing mass acute morts • Listonella anguillarum (vibriosis), Aeromonas

salmonicida (furunculosis) – vaccines licensed

• Flavobacterium columnare and psychrophilum

(columnaris and cold water disease)

• Piscirickettsia salmonis (SRS)


• Diseases

– Bacteria and viruses that show latency and recrudescence

• Renibacterium salmoninarum (BKD, reportable to USDA)

• Infectious pancreatic necrosis (IPN, reportable to USDA)


• Diseases

– Viruses amplified between sea pens + wildstock

• Infectious hematopoietic necrosis (IHN) – shed by prespawning Pacific salmon = morts in farmed Atlantic salmon, reportable


• Diseases

– Parasites transmitted between sea pens + wildstock

• Sea lice e.g., Lepeophtheirus salmonis – increased salmon biomass (100x) = much higher infection rates

• Monogene trematode e.g., Gyrodactylus salaris –hatchery Baltic Atlantic salmon released in Norway for restocking = high morts in wild Atlantic salmon, reportable (absent)

Atlantic salmon - summary

• Farming Atlantic salmon is not environmentally or socially sustainable

• So, why are they farmed?

– Huge demand

– Whole process well calculated

– I.e., they are economically sustainable

Channel catfish farming

• Channel catfish (Ictalurus punctatus)

• Native to the Mississippi

• Most farming is in the SE USA

– $400 million, 300,000 tons annually

• High consumer demand

– Mild flavor, light texture, low fat

– Always available


• Spawn readily in ponds with ‘nests’, gelatinous egg masses collected

• Eggs incubated in race ways, water flow to simulate the male


• All stages (fry, fingerlings, adults) kept in shallow freshwater ponds

– Closed or semi-closed (i.e. isolated)

– Few environmental issues except eutrophication

– Natural diet supplementation

– Risk of low DO + high NH3

• But better able to control env

– Limited space available, competition for land

• Need warmer temperatures (28-32ºC, 82-90F)


• Hardy

– Tolerant of brackish water, usually kept at 6 ppt

– Tolerant of low DO (≥2.5 mg/L)

– Tolerant of handling/grading

• Omnivores

– Complete commercial diets

– Based on plant proteins/oils

– Very little fish meal used


• Harvested intermittently– From 18 mo, at 0.8-1 kg

– Usually by seining, not draining

• Checked for off-flavor– Due to overgrowth of some

bacteria and blue-green algae

– Limited by growing with carp or prawns, in brackish water, with few organics…


• Diseases:– Bacteria and viruses causing acute morts

1. Edwardsiella ictaluri (enteric septicemia of catfish, ESC) – licensed vaccine

2. Flavobacterium (Flexibacter or Cytophaga) columnare (columnaris disease) – licensed vaccine

3. Aeromonas hydrophila (motile aeromonad septicemia, MAS)

4. Channel catfish virus (CCV)


• Diseases:

– Parasites

• Ciliates e.g., Ichthyophthirius, Trichodina

Channel catfish - summary

• Channel catfish farming is sustainable

– Economically, environmentally and socially

• However, US production has recently decreased due to cheap production and import from Vietnam and China

Atlantic cod farming

• Atlantic cod Gadus morhua– (Pacific cod, Greenland cod)

• High consumer demand – White, flakey meat

– Low fat, high EFAs (liver)

• Atlantic wild stocks severely depleted– 1992 Grand Banks pop 1.1% that of 1960s

– 1992-present moratorium on northern Atlantic cod


• Eggs are spawned and collected in salt water pens

• Larvae kept in salt water ponds

• Yolk sac is resorbed

• Diet consists of zoo- and phyto-plankton e.g., rotifers + algae = ↑cost and complexity


• Fingerlings transferred to offshore sea pens

– Space available, less competition

– Water quality stable

– Greater dilution effect

– Increased technical requirements

• Feeding + monitoring needs to be unmanned

• Access + cage maintenance dependent on inclement weather


• Hardy

– Do well at high stocking levels

• Omnivores

– As adults

• Faster growth than in wild


• Harvested

– From 2-3yrs, at 2-3kg

– Labor intensive

– Risk of pressure changes


• Diseases

– Relatively disease resistant

• Especially compared to salmon

– More will probably be found

Atlantic cod - summary

• Capture fisheries mostly closed

• Culture fisheries may be sustainable

– Environmentally and socially sustainable

– Not yet economically sustainable

• Technical, regulatory and logistic issues to be resolved

The roles of the vet

• Biosecurity

• Selection of

– Water source/testing

– Site and design

– Stock

– Feed

• Monitoring and record keeping

• Health assessment


• Disease prevention, identification + management

– Optimize env parameters

– Minimize stress

– Minimize exposure to pathogen

– Consider biological control

– Responsible use of licensed

medicationsEnvironmentPathogen

Host


• Medication considerations

– Life support and waste water management

– Other species or biofilters

– True cost

– Re-evaluate constantly

– And…


• Medication considerations

– Must be approved by the relevant authority and must be used appropriately

• USDA for vaccines

• EPA for chemical applications and for discharges into surface waters

• FDA for therapeutics

1. Low regulatory priority e.g., salt, H2O2, CO2

2. High regulatory priority i.e., never use: malachite green, floroquinolones

3. Approved…


• Medications approved by the FDA1. Oxytetracycline (Terramycin)

• For MAS in catfish and salmonids

2. TMS (Romet-30) • For ESC in catfish and A. salmonicida in salmonids

3. Florfenicol (Aquaflor) • For ESC in catfish and columnaris in catfish and salmonids

4. Formalin (several products) • For fungi and external parasites in finfish

5. MS222 (Finquel, Tricaine) • For anesthesia

6. Chorionic gonadotropin (Chorulon) • To improve spawning in brood finfish

All other use is extra-label, under the Animal Medicine Drug Use Clarification Act 1994 and have no possible food residues

The wider roles of the vet

• Affect legislature

• Develop technologies and best management practices

– Breeding

– Growth and nutrition

– Handling

• Research and licensing of medicines

• Stock enhancement and conservation

Summary

• Sustainable fish farming is essential to meet increasing consumer demand

• Farming Atlantic salmon is a huge global industry, but is not sustainable

• Vets should be involved in all parts of the process, to safeguard animal welfare, food safety and conservation

For more info…

• Books– Aquaculture (Lucas)– Aquaculture biosecurity (Scarfe)– Aquaculture principles and practices (Pillay)– Ecological aquaculture (Costa-Pierce)– Fish disease (Noga)– Fish medicine (Stoskopf)– Fundamentals of Aquaculture (Avault)– Intensive fish culture (Weeks)

• Journals– Diseases of aquatic organisms– Fisheries bulletin– Journal of aquatic animal health– Journal of zoo and wildlife medicine– North America journal of aquaculture– North American journal of fisheries management– Vet clinics of north America

• Conferences– American fisheries society– Eastern fish health workshop– International association of aquatic animal medicine– World aquaculture society

• Courses– Aquavet and others (Cornell, Penn, Florida, Davis, N Carolina)

Documents

Fish farming HANDOUT - Tennessee 2008thinking.freeshell.org/awesym/Fish farming.pdf · • Sustainable fish farming is essential to meet increasing consumer demand • Farming Atlantic