1.Any stress causes chemical changes in mucus which decrease its effectiveness as a chemical barrier against
invading organisms. Stress upsets the normal electrolyte (sodium, potassium, and chloride) balance which results
in excessive uptake of water by fresh water fish and dehydration in salt water fish. The need for effective
osmoregulatory support from mucus components is increased.
2.Handling stress physically removes mucus from the fish. This results in decreased chemical protection, decreased
osmoregulatory function (at a time when it is most needed), decreased lubrication thereby causing the fish to use
more energy to swim (at a time when its energy reserves are already being used up metabolically), and disruption
of the physical barrier against invading organisms.
3.Chemical stress (ie. disease treatment) often damages mucus resulting in loss of protective chemical barrier, loss
of osmoregulatory function, loss of lubrication, and damage to the physical barrier created by mucus.