Aquaculture

Question 1

what does aquaculture include?

Question 2

basics

Answer 2

• globally, fisheries are declining and human population is growing
• seafood consumption is increasing
  
  • many rely on seafood for protein (20%)
• growing industry: accounts for more than half of seafood produced (growing at 4-5%)
• produces wide variety of products: oysters, mussels, seaweed, abalone etc.
• not just for food, animals can be raised for conservation, recreation, scientific, or regenerative purposes (like kelp)

Question 3

Types of systems

Question 4

recirculating aquaculture systems (RAS)

Answer 4

• water flushed throughout the tank and goes through mechanical filter then biological filter
• helps gain more O2 and inputs more water

Question 5

pond systems

Answer 5

• huge ponds in the ground
• fish like catfish, bass, sturgeon

Question 6

flow-through/raceway

Answer 6

• can siphon H2O from river
  
  • water flows in and flows out
• good for animals with high O2

Question 7

aquaponics

Answer 7

• beneficial O2 compound plants can use
• good if have limited H2O

ex: fish tank has water flowing to aquaponic (with plants) => water flows back to fish tank

Question 8

open water (fish)

Answer 8

• out at sea

Question 9

open water (shellfish/seaweed)

Answer 9

• have cages in the open water to catch shellfish & wait for seaweed to grow

Question 10

integrated multi-trophic aquaculture (IMTA)

Answer 10

• big tank, fish produce waste used to make system more environmental friendly
• waste acts as nutrients for algae and shellfish

Question 11

Major challenges

Answer 11

• intensive (high stocking density), semi-intensive (low stocking density), extensive production system (systems sitting out in the environment)
• disease outbreaks
  
  • sources of disease (ambient, environmental pathogens, contamination)
  • factors influencing disease outbreaks:
    
    • aquatic environment: transmission is easier relative to terrestial pathogens
    • stress from crowding, handling, diet, weather, etc.
• emergent pathogens
• resistant diseases, limited treatment solutions

Question 12

Major fish diseases

Question 13

Lactococcus

Answer 13

• pathogenic strain of bacteria
• highly infectious and deadly
• unknown source but likely came from birds
• first reported case in CA (2020)
• first case in North America was in Mexico (2016)
• in 2021: 3.2M thought culled
• resistant against every treatment

Host:
- rainbow trout, all life stages
- adaptive/innate immunity
- standardized diet

Environment:
- intensive system
- warm: facilitates spread
- high stocking density

Pathogen:
- bacteria
- resistant to antibiotics
- locally transmitted

Question 14

Sea Lice

Answer 14

• parasitic crustacean
• naturally present in marine environments
• attach onto any fish => problematic for salmon

Host:
- Atlantic salmon, all life stages
- adaptive/innate immunity
- standardized diet

Environment:
- semi intensive system
- high stocking density

Pathogen:
- crustacean
- known life cycle
- locally transmitted

• developed treatment that target life stages

Question 15

Disease Treatments

Answer 15

• environment manipulation
  
  • temperature, salinity: create environment not suitable for pathogen to spread
  • biological control: cleaner fish for parasite control
• antimicrobial products
  
  • broad spectrum: disinfection, sterilizing, external parasites
  • therapeutic: bacterial infections
• culling infected individuals if none of the above works

Question 16

AMR in aquaculture

Answer 16

• AMR around the world.
  
  • Chile, china, India: AMR detectable in the environment near aquaculture
• AMR and US aquaculture
  
  • strict regulations, AMR present in emerging pathogens
• policies and actions to slow development of AMR
  
  • required Rx for antibiotics
  • environmental/system monitoring
  • alternative strategies for disease treatment (use less AMR, products will slow it)

Question 17

Aquaculture and one health

Answer 17

• AMR & impacts on people/environment
  
  • not a major consumer of antibiotics
  • AMR reservoir

Animals:
- biosecurity, healthy stock, minimal chemical hazards, optimize systems, protected

Environment:
- optimize water usage, water quality, protect biodiversity, minimize energy use & spatial footprint

Humans:
- nutritious food, equitable income, gender equalization, quality employment, knowledge & skill generation

Question 18

Three levels of defense against disease

Question 19

Level 1: comprehensive protocols

Answer 19

• biosecurity: standardized cleaning and contamination protection
  
  • PPE, secure buildings (boot wash station, prevent people from moving freely)
  • frequent disinfection of tanks, equipment, tools (stop spread of disease)
  • quarantine procedure for sick or imported animals
  • personnel training on biosecurity principles
  • appropriate use of AM products (b/c can kill)
    
    • biocidal products (cleaning chemicals like bleach, alcohol, iodine etc.)
• disease-response: quick and appropriate response to clinical signs of disease
  
  • animals are frequently and thoroughly checked for distress
  • all personnel able to recognize clinical signs: provide sufficient info for personnel to have decent understanding of animal bio
  • outline response steps to follow when clinical signs are observed
  • quickly initiate treatment if disease is confirmed (consulting vet, initiating quarantine etc.)

Question 20

Level 2: good husbandry strategies

Answer 20

• stress management: precautions taken to mitigate stressful events
  
  • aspects that cause: size grading, transport, overstocking, bad weather etc.
  • stress can induce immune function & make fish susceptible to disease
  • important to identify sources of stress & minimize
    - ex: lower stocking density, protect tanks fr. elements, use animal sedatives & provide sufficient employee training prior to fish handling
• proper diet: meets species & age specific nutritional needs
  
  • aquafeed diet should contain all required nutrients: carbs, lipid, protein, micronutrients
  • nutritional requirements are species & age dependent: diets should be formulated w/ this in mind (current area of research)
  • research on sustainable ingredients
    
    • replace fisheries-derived ingredients w/ plant, insect, and other ingredients
    • impact on gut health and immune function (plants => toxins in unprocessed)
• optimal environment: appropriate species and age specific water conditions
  -monitor water conditions: temperature, O2, salinity, pH, nitrate/nitrite/ammonia, hardness
  
  • species specific optimization
    - animal requirements (suitable range of water quality parameters)
    - animal welfare (mental stimuli, suitable colors/textures/sound)
  • probiotics/prebiotics to regulate water quality
    - some bacteria can reduce high levels of nitrogenous compounds
    - compete w/ pathogens for space/nutrients

Question 21

level 3: effective antimicrobial products

Answer 21

• biocides: cleaning products for aquaculture system biosecurity
  
  • important for level 1
• therapeutics (antimicrobials): FDA approved for use as disease treatment
• therapeutics (antibiotics): classified as MIADs, FDA approved for use only as disease treatment and only under vet guidance
• not used for growth production => illegal & not effective, can even hurt fish
• new regs implemented in 2017 require vet prescription for antibiotics (MIADs)

Question 22

alternative methods to AMR

Question 23

stock selection

Answer 23

• genetic variations in fish lead to some being resistant to certain pathogens/stressors
• strains of fish can be bred to enhance these characteristics once identified
  
  • ex: hybrid catfish are crosses of Blue/Channel catfish that have been shown to be more resistant to common diseases
• advances in genetic technology helps identify regions in genome that correlate w/ disease resistance
  
  • individuals w/ these genes can be bred to produce populations w/ enhanced traits

Question 24

vaccines

Answer 24

types
- whole killed (inactivated)
- whole attenuated (live)

application methods
- oral: medicated feed
- difficult to maintain vaccine efficacy and to ensure appropriate dose, very easy to administer
- immersion: medicated bath
- difficult to maintain vacine efficacy, easy to administer
- injection: Intraperitoneal or intramuscular (belly or back)
- labor intensive but generally yields best immune response

Approved in US
- only 7 approved for commercial use
- 5 for salmonids, 2 for catfish
- 6 utilize a killed, weakened, or non-pathogenic antigen, mixed w/ an adjuvant (immunostimulant)
- one DNA vaccine approved for use in salmon against IHN virus

Question 25

novel antimicrobials

Answer 25

• antimicrobial peptides
  
  • already produced by most cells of most tissues in vertebrates
  • stimulate immune system and kill wide variety of pathogens
• antivirulence therapy
  
  • compounds that “disarm” pathogen
  • target specific virulence pathways that enable a pathogen to cause disease
    
    • ex: toxin and enzyme production/secretion, bacterial communication
• both categories have more specific mechanism of action and are less likely to lead to widespread AMR

Question 26

dietary supplements

Answer 26

• gastrointenstinal microbiome
  
  • collection of mutualistic bacteria inhabiting the GI tract
  • impacts many physiological processes like digestion, nutrient, absorption, growth, and immune response
  • protects against some indigested pathogens
• probiotic/prebiotic influence the collection of bacteria
  
  • probiotics: bacteria known to be beneficial to an organism
  • prebiotic: substances consumed/utilized by bacteria