Observations on the gall bladder of juvenile Atlantic salmon Salmo salar L., in relation to feeding

Measurements of gut contents and changes in the volume and colour of bile in the gall bladder of juvenile Atlantic salmon are described for a variety of feeding regimes. The gall bladders of actively feeding fish are virtually empty of bile. When deprived of food, the weight of the gall bladder increases within 6 h and reaches a value equivalent to approximately 20% of the liver weight within 36 h. Bile is pale straw, green and blue in colour after 1, 4 and 6 days of starvation respectively. Stored bile is released from the gall bladder in response to food entering the anterior hind gut.