Whether depositing fat or losing weight, fish maintain a balance

Area of Science:

• Ichthyology
• Biomechanics
• Hydrostatics

Background:

• Fish tissue composition, including fat, muscle, and bone, varies with feeding and development.
• Changes in tissue density affect the body's center of gravity (COG) and center of buoyancy (COB).
• Gravitational and buoyant forces influence submerged animals, potentially impacting stability and locomotion.

Purpose of the Study:

• To investigate how changes in tissue density influence the center of gravity (COG) in fish.
• To determine if variations in feeding status and body composition affect fish hydrostatic stability.
• To understand the relationship between tissue distribution, COG, and swimming performance in fish species.

Main Methods:

• Analysis of computed tomography (CT) and magnetic resonance imaging (MRI) scans.
• Examination of Atlantic herring, Atlantic salmon, and Atlantic mackerel.
• Quantification of fat, muscle, and bone distribution along the body axis.

Main Results:

• The center of gravity (COG) was found to be relatively constant within each fish species studied.
• Significant interspecies differences in fat, muscle, and bone proportions were observed.
• Tissue distribution is closely adjusted to maintain a stable COG, irrespective of body fat content.

Conclusions:

• Fish maintain a consistent center of gravity (COG) through precise tissue distribution, ensuring hydrostatic stability.
• This COG constancy allows fish to manage significant variations in energy intake without compromising swimming performance.
• The findings highlight the adaptive strategies fish employ to maintain buoyancy and locomotion efficiency.