Table 2. Estimated prey requirements of wild killer whales, based on two plausible values for calorie content of a typical, 4-year-old Chinook salmon.

Body Length	“Calorie-rich” Chinook Scenario			“Lean” Chinook Scenario
Scenario	“100%”	“100%”	“Summer”	“100%”	“100%”	“Summer”
(Source)	fish (per day)	fish ×103 (per year)	fish ×103 (per year)	fish (per day)	fish ×103 (per year)	fish ×103 (per year)
IWC NP Max	953	348	86	1640	599	147
IWC NP 99th	866	316	78	1489	544	134
IWC NP 95th	771	282	69	1327	484	119
IWC NP 80th	580	212	52	998	364	90
SeaWorld Max	559	204	50	963	351	86
SeaWorld 99th	545	199	49	938	342	84
SeaWorld 95th	493	180	44	848	309	76
SeaWorld 80th	410	150	37	705	257	63

Salmon of length 81 cm and mass 8.5 kg, the preferred size of Chinook prey of the resident killer whales [17]. Energy requirements predicted for southern resident killer whale (SRKW) population assume that activity levels are equal in captivity and in the wild. The “calorie-rich” scenario assumes an average energy density of 2,200 kcal/kg [44, p. 57)]; therefore each Chinook was estimated to represent 18,700 kcal. The “lean Chinook” scenario uses the mean of 5 Chinook of unknown size, collected in the Gulf of Alaska (mean = 5.35 kJ/g = 10,869 kcal/8.5 kg fish; [45]). Note that the row in bold type represents the most plausible estimate, based on observed body sizes from whaling records from the northeastern Pacific. The SRKW population in 2009 consisted of 87 individuals of the following age-sex classes (Center for Whale Research): females with calves (10); adult males (23); juveniles (15); calves (10); and adult females without calves (29).