Section 2 | Fish Health Management

Ontario Aquaculture
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Low-Stress Handling

Automated grader used for grading fish by size

At Cedar Crest, fish are graded 5 times prior to leaving the farm.


Ensuring homogenous-sized fish in a tank has many benefits, including:

  • Reducing size variability when fish are harvested/marketed
  • Minimizing cannibalism of smaller fish in the tank
  • Allows for an accurate estimate of tank stocking densities
  • Enables culling of weak fish and removal of nuisance fish that may have gained access to the tank
  • Feeding of appropriately sized pellets


RJ and Arlen note that any time a fish is moved is a stressful event. The number of necessary grading events should be carefully planned, with a focus on low-stress movement techniques. The old adage holds when re-grouping fish: “As little as possible, as much as necessary”.

For more information on the Key Aspects of Animal Husbandry, visit the Antimicrobial Stewardship FAAST Review. Merck has also developed a learning module containing videos for fish handling. Check those resources out here: Aqua Care 365.


A fish pump for low-stress handling of fish