The Energetics of Feeding Territoriality in Juvenile Coho Salmon (Oncorhynchus Kisutch)

Abstract

1. A foraging time budget was developed for territorial, nonterritorial, and floater fish. Territorial fish spend 76% of total time at the station, 3% free swimming, 13% feeding, and 5 % in agonistic activity. Floaters spend 18% of their time stationary swimming, 54% free swimming, 10% feeding, and 10% in agonistic activity. Nonterritorial fish spend 50% of their time stationary swimming, 43% free swimming, 2% feeding, and 3% in agonistic activity. 2. Stationary swimming tailbeat frequency for the floater (4.3) is significantly higher than for the territorial fish (3.6). The floater flight tailbeat frequency (8.2) is significantly higher than the territorial chase tailbeat frequency (6.9). Normal feed tailbeat frequencies are similar for all fish groups. Nonterritorial fish tend to move slowly (tailbeat frequency = 3.3) for all activities except normal feed. 3. The total activity budgets for territorial, floater, and nonterritorial fish are 1199, 1318, and 910 cal/kg/hr, respectively. The territorial fish uses 91 % as many calories as the floater fish and the nonterritorial fish utilizes 76% of the territorial budget. 4. Total agonistic costs represent 12 and 14% of the territorial and floater fish activity budgets, respectively. 5. The costs per feeding motion for the territorial, floater, and nonterritorial fish are 4.03, 4.91, 10.1 cal/motion, respectively. 6. The territorial fish has a net energy intake advantage over the floater, and probably over the nonterritorial fish, due to 1) reduced search costs, 2) reduced prey pursuit costs, and 3) reduced agonistic activity costs.