THE SEA OTTER IN THE EASTERN PACIFIC OCEAN 127 



Relative Values of Sea Otter Foods 



Miss Neva L. Karrick, Assistant Laboratory Director, Food 

 Science Pioneer Research Laboratory of the Bureau of Commercial 

 Fisheries at Seattle, has furnished proximate analyses of certain 

 representative sea otter foods (table 18). From these data and 

 the knovm quantities of food consumed by captive otters and data 

 obtained from stomach examinations, it is evident that the sea 

 urchin is seldom as important a food item as previously supposed 

 and that the sea otter is primarily dependent for survival on 

 other foods v^ith more calories and higher protein content. 



A captive sea otter weighing about 40 pounds required an 

 average of about 8.4 lb. of food, primarily rockfish, per day (24- 

 hour period). This diet supplied about 3,400 calories (about 89 

 calories per 100 grams of fish). Sea urchins with gravid gonads 

 can supply roughly 58 calories per 100 grams of gonads and 16 

 calories per 100 grams of viscera. If large gravid sea urchins were 

 available, about 200 would be required to supply 3,000+ calories 

 to a sea otter in a 24-hour period. 



Most of the sea urchins now available at Amchitka are small. 

 The reason appears to be that a large sea otter population is over- 

 utilizing this food resource (see Depletion of Food Resources). 

 Mature gravid green sea urchins, weighing about 115 g. each, 

 were obtained for analysis from an area at Cold Bay, Alaska, 

 where there are no sea otters. At Amchitka, the size available in 

 greatest quantity weigh about 6 to 10 g. These are consumed in 

 large numbers, particularly by juvenile otters. The gonads in 

 these immature sea urchins are almost microscopic. The amount 

 of visceral material available in them is small and is a poor 



Table 18. — Proximate analysis of important sea otter food species 



[Averages. These data were furnished by Bureau of Commercial Fisheries Technological Lab- 

 oratory, Seattle, Wash.] 









Protein 





Calories 





Moisture 



Oil 



6.25 X % N. 



Ash 



per 100 



Species 



( percent ) 



(percent) 



( percent ) 



(percent) 



grams i 



Dungeness crab meat Cancer 













magister 



77.2 



0.90 



20.8 



1.61 



91 



Butter clam Saxidomus nuttaXli 



83.0 



1.30 



13.3 



1.9 



63 



Octopus 2 



85.7 



0.86 



12.1 



1.3 



56 



Sea urchin Strongylocentrotus 













drobachiensis: 













Gonads 



85.9 



2.70 



8.4 



2.51 



58 



Viscera 



92.2 



0.72 



2.3 



3.72 



16 



Rockfish Sebastodes sp 



79.0 



1.50 



19.0 



1.18 



89 



1 Calories per 100 grams = average percent oil X 9 plus average percent protein X 4. 



2 Sea otters usually discard most or all of the viscera of octopus; therefore only the flesh was 

 analyzed. 



