Digestion and Food Consumption by Skipjack Tuna (Katsuwonus pelamis)

Abstract

Abstract Skipjack tuna, 39–50 cm fork length, were studied during their first month in captivity in tanks 7.3 m in diameter and 1.1 m deep. Water temperatures were 23.3° to 25.7° C. Passage of food through the alimentary canal was estimated from 54 fish that were fed as many thawed smelt as they would eat. At intervals from 2 min to 24 hrs later pairs of fish were removed and the wet and dry weights of the stomach and intestinal contents were measured. The fish ate the equivalent of about 8.6 per cent of the body weight. About 10 per cent of the original quantity eaten passed from the stomach each hour during the first 8 hrs and the stomach was essentially empty within 12 hrs after a meal. The content of the intestine reached a maximum after about 5 hrs. The intestine was empty within 14 hrs, but some of the food material moved into the digestive gland and apparently re-entered the intestine later. Blood glucose averaged 132 mg/100 ml blood from 0.5 to 7 hrs after a meal but 81 mg/100 ml blood 10 to 24 hr...