Triploid Atlantic salmon are physiologically disadvantaged at larger body sizes

Area of Science:

• Aquaculture
• Fish Physiology
• Animal Welfare

Background:

• Triploid Atlantic salmon are sterile, preventing wild breeding but facing welfare issues in later growth stages.
• Previous studies on smaller fish showed subtle physiological differences between triploid and diploid salmon.
• Scaling constraints may magnify triploidy's disadvantages in larger fish due to cellular differences.

Purpose of the Study:

• To investigate physiological differences between large (≈3 kg) triploid and diploid Atlantic salmon.
• To test the hypothesis that triploidy becomes a disadvantage at larger body sizes.
• To identify mechanisms behind poor animal welfare in large triploid salmon.

Main Methods:

• Measured metabolic rates, stress responses, hypoxia tolerance, and critical thermal maximum in large triploid and diploid salmon.
• Assessed gill histology, including lamellar density.
• Compared physiological parameters between the two groups.

Main Results:

• Large triploid salmon exhibited higher standard metabolic rates and lower aerobic scopes.
• Triploids showed reduced tolerance to hypoxia and thermal stress.
• Lower oxygen extraction coefficients and lamellar densities in triploids indicated reduced gill oxygen uptake efficiency.

Conclusions:

• Large triploid Atlantic salmon are more vulnerable to environmental extremes due to limited oxygen supply and increased maintenance costs.
• Reduced gill surface area and oxygen uptake efficiency contribute to welfare issues.
• Findings provide a mechanistic explanation for poor animal welfare in the late marine growth phase of triploid salmon.