Gastrointestinal evacuation of particulate matter in polar cod Boreogadus saida

Gastrointestinal evacuation of inert particles was monitored in the polar c od Boreogadus saida (Lepechin), held at a temperature of 0.5 degrees C. Fis h (31.8 g +/- 0.8 SD) were fed a moist diet, based on natural prey items, c ontaining a particulate marker. Evacuation of marker from the gastrointesti nal tract started 48 h after ingestion of a meal. The average time needed t o evacuate 50% of the marker was estimated to be 132 h, whereas the total e vacuation time was approximately 400 h. This may indicate that the polar co d does not feed on a daily basis at temperatures close to zero because of t he prolonged time needed to evacuate meals. This work provides a methodolog ical basis for studies of feeding and growth in polar cod using X-radiograp hy.