Using condition factor as criterion of fatness, investigation confirms the report of those handling them that herring are characteristically fat in each locality of the Passamaquoddy region of southern New Brunswick. Herring feed by an act of capture, moving towards the source of light in doing so. They do not feed in darkness, requiring light about as strong as moonlight. Gastric digestion takes [Formula: see text] hours at 6° and 6 and 7 hours at 20 °C. in herring 14 to 16 cm. long. Where fattest, herring contain the most food and of the larger kinds. In some localities herring have more food and of special kinds after moonlight nights. Herring are mainly in upper layers of water in summer, and nearer surface when light intensity is low. Correlation between fatness of herring and either the total quantity of food present locally or the local degree of concentration of food in the water is quite imperfect. Good correlation exists between fatness and quantity of food present near the surface in the particular locality. In localities where herring have more food after moonlight nights, food organisms are much more abundant near the surface in moonlight than in sunlight. Food organisms are most concentrated in passages and near shoals where thorough mixing of the water occurs. In the passages at the mouth of Passamaquoddy bay, deepwater forms from the gulf of Maine are available at the surface at all times of the day, giving the fattest herring. To exhibit characteristic fatness herring must remain some weeks in the locality.