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Transport, crowding, debugging and parasites can
quickly increase the secretion of mucus - and then change the barrier’s mucosal content for the long term. It takes more than two weeks for the gills to function normally again after an ordinary delousing. Frequent handling can weaken the fish. The weakening of the gills opens up for other pathogens that encounter less resistance, eg Amoebic Gill Disease (AGD). High density in the cages also challenges the mucus layer and delays the healing of wounds in the skin. Repeated debugging can dry out the skin so it has less than 2.5% mucus cells. The norm is between 15-30%. Healthy, wild chinook salmon has 30% of the skin filled with large mucus cells which means problems ”wash off”. Our observations and measurements give an objective view on the robustness of the fish, and is hence a hands-on tool for fishfarmers, fishhealth services and equipment suppliers. How much can YOUR fish take? |
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