Farmed Atlantic Salmon: Disease control and health management Flashcards
1
Q
Health management
- risks
- how to maximise
A
- Aquatic animal diseases are usually linked with changes to environment and husbandry
~ Individual animals living in close proximity to
~ Highly connected to their environment and husbandry
~ Highly vulnerable to environmental changes - Diagnosis and control depend on an understanding of the production system
- It is essential to adopt good husbandry and a pro-active approach to health management
~ Optimal use of first line defence through effective biosecurity
~ Robust health plan to minimise risk and spread
~ e.g. The Code of Good Practice for Scottish Finfish Aquaculture
2
Q
advances in disease control
A
- Modern gene technology, AI and vaccine gives better framework for health and welfare of salmon
- Integration of multiple disease control method to tackled complex diseases
~ sea lice infestation
~ Complex gill disease - Disease control through vaccine and feed technologies
~ viral disease
~ sea lice infestation - Molecular based surveillance programs:
to monitor and report ongoing and emerging disease
~ Viral diseases
~ Bacterial diseases
~ Complex gill diseases
3
Q
health management
- biggest threat to industry
A
- Aquatic animal diseases impose many constrains and devastating consequences
- Disease management, still disease remain as main threat for the industry’s sustainability
~ Loss of fish – mortalities; Loss of production; Loss of investor confidence; Loss of opportunity
~ Cost of control or prevention
Negative impact on :
Brood stock
Fisheries
Wild stocks
4
Q
Past sea lice control and treatment shifted to
A
- Sea lice control was heavily relied on chemotherapeutants in the past
(azamethiphos, cypermethrin, deltamethrin and hydrogen peroxide) - Antiparasitic drugs were administer via baths or in-feed methods.
- However;
~ Sea lice became resistant to many of these chemicals (Aaen, 2015)
~ Caused detrimental environmental effects - In the last few years treatment has shifted towards non-chemical procedures
5
Q
sea lice management - new approaches
why manage and not eliminate
A
- approved medicines
- technology (fresh water, hydrolicers, thermolicers)
- prevention (cleaner fish, lice skirts, clean nets, nutrition = immunomodulatory diets)
- stocking
~ larger smolts = used to be 200g but now 500g when reared in tanks, can withstand sea lice more than small fish
~ fallow periods,
~ stock coordination
manage rather than eliminate (cant be eliminated) reduce the burdan
6
Q
Barrier cages
A
- Technological innovations - Prophylactic depth-based rearing systems
- Avoid surface-dwelling salmon louse larvae
- Still provide surface air access for swim bladder reinflation
1. Skirt or snorkel tarpaulin wrapped around the upper depths
2. Submerged cages (repeatedly submerged or submerged with an air dome)
3. Semi-enclosed cages (with deep water pumped in)
4. Deep lighting and feeding (motivating salmon to swim deeper).
7
Q
Sea lice skirts
A
- skirt can act as a shield = prevent sea lice entering salmon cage
- located top third of cage
- important to manage oxygen level in upper part of cage
8
Q
Snorkel cage
A
- keeps salmon deeper in water column = away from sea lice larvae
- can still reinflate swim bladder without exposure to lice larvae (infective)
9
Q
Cleaner fish
- about
- 6 types used in salmon aquaculture
- advantages
- disadvantages
A
- Cleaner fish - small fish species that will eat salmon lice
- Cleaner fish are species of marine fish native to UK coastal waters.
- six species
~ lumpfish
~ five types of wrasse; Ballan, Goldsinney, Rock cook, Corkwing and Cuckoo. - All lumpfish used in Scottish salmon farming are farm reared in hatcharies. (dont need to be outsourced from wild)
- Effective form of biological delousing
- Can prevent chemicals entering the environment and saves a lot of money for the farmer.
- However cleaner fish act can transmit disease
- Can be predators for salmon feed
- Environment and various sustainability issues
10
Q
thermal treatments (ie. thermolicer/optilicer - process
A
- treatment system fitted onto boat and taken near to summit cage
- lice low tollerance to temp change = killed easily at high temp
- Fish enters the system
- Water separation
- Sea water is filtered and released
- Fish passes through warmer water
- Treatment loop
- Water surface
- Water separator for treatment water
- Fish exits the system
- Heated water is circulated to water tank for filtration, aeration and reheating
10Treatment water is pumped back into the system for re-use
11
Q
Flushers (i.e. Hydrolicer, Flatsetsund Flusher)
A
- sea lice can be dislodged by jets of water
- lice collected in tanks underneath
- fish released back into cages
- lice not completely killed, discard water before intoduce salmon to cages
12
Q
Anti-sea lice functional feed
A
- Formulated feeds which support optimum fish health.
1. Supporting fish natural defences
~ thicken protective mucus layers on the skin (sea lice can not attack)
~ Boosting fish immune and inflammatory responses
- Affecting the sea lice
~ Altering sea lice development/growth
~ Decreasing sea lice ability to attach to fish
~ Reducing immune suppression caused by sea lice
13
Q
Use of chemicals
- in feed treatment
- bath treatment
A
- There are a number of chemo- therapeutants are licensed
- They are prescription only drugs
- Use as;
1. in feed treatment
in-feed ( SLICE® )
~ contains avermectin
~ increase deficinecy chloride ions through cell mem of sea lice = impulse destruction, paralysis and death
~ affective agianst all stages
2. bath treatment
( Salmosan® = organophospate effect on nerve impulse transmission of lice and hydrogen peroxide)
~ antiparasitic drugs are administerd as a topical treatment and diluted in water
~ sea cages lifted to reduce volume of water and gate enclosed
~ prevents drug dissipating into water
~ medication added to cage and fish held for 1 hour
14
Q
Hydrogen peroxide treatment
A
- Used in aquaculture as a bath treatment (in well boats of in tarpaulin skirts)
- No wider adverse environmental impact
- H2O2is a registered medicine it has zero toxicity and zero persistence in the environment
- considered as a non-medicinal approach to sea lice management
- Mode of action:
~ the substance dissociates into oxygen and water
~ which causes disruption to internal structures,
~ resulting in the detachment and mortality of the sea lice
~ reducing their ability to re-attach - An increased gene expression and activity of catalase, an enzyme that breaks down H2O2, have been detected in resistant lice
15
Q
Intergrated pathogen management strategy
- aim
- develop process
- how it was first introduced
- current intergrated stratagy
A
- Not necessarily aim to eradicate pathogens
- Keep pathogen at levels at low
- Developed through step by step process;
1. gathering knowledge on pathogen, host, and environmental risk
2. development, evaluation of feasibility, and implementation of the best strategies.
3. monitoring of the disease crucial to review the effectiveness - The present strategy first introduced with sea lice developing resistance to antiparasitic drugs.
- The current IPM system that operate in farms are based on the fact thatsalmon licecopepodites are typically found near the surface during daylight.
- It is therefore hypothesized that decreasing the chances of contact between fish and sea lice in the sea cages will reduce lice infection rates on the farmed salmon.
