200 



T 1.00 



o 



uj 80 



60 



.40 



IE 



£ 20 



> 



UJ 



Q 



tr 

 O 



D 



z 

 < 



5 

 UJ 

 Q 



UJ 

 O 

 V 

 X 



o 



10 

 08 



06 



04 



02 



12 3 4 5 6 



SWIM SPEED (LENGTHS SEC" 1 ) 



FIGURE 3. — Respiratory demand (Gooding and Neill see foot- 

 note 2 1 versus respiratory supply ( Brown and Muir 1970; Stevens 

 1972) as a function of swimming speed in a 40-cm, 1.4-kg skip- 

 jack tuna. Respiratory demand increases geometrically while 

 respiratory supply increases arithmetically with increasing 

 swimming speed. When oxygen concentration decreases it is 

 more efficient to increase ram ventilation by increasing gape 

 rather than simply swimming faster. 



fairly rapid rise in the water column at a relatively 

 low energetic cost. Yellowfin tuna, in contrast, are 

 just not stressed at the levels of saturation 

 employed in our experiments. Yellowfin tuna 

 should be able to occur in the anoxic water in or 

 below the thermocline and since in the eastern 

 central Pacific Ocean anoxic, cool waters are as 

 inhospitable as the upper too warm waters, skip- 

 jack tuna may find no suitable habitat. 



Literature Cited 



BROWN, C. E., AND B. S. MUIR. 



1970. Analysis of ram ventilation offish gills with applica- 

 tion to skipjack tuna \Katsuwonus pelamis). J. Fish. 

 Res. Board Can. 27:1637-1652. 

 DIZON, A. E., W. H. NEILL, AND J. J. MAGNUSON. 



1977. Rapid temperature compensation of volitional 

 swimming speeds and lethal temperatures in tropical 

 tunas (Scombridae). Environ. Biol. Fish. 2:83-92. 

 MAGNUSON, J. J. 



1973. Comparative study of adaptations for continuous 

 swimming and hydrostatic equilibrium of scombroid and 

 xiphoid fishes. Fish. Bull., U.S. 71:337-356. 

 SHEPARD, M. P. 



1955. Resistance and tolerance of young speckled trout 

 iSalvelinus fontinalis) to oxygen lack, with special refer- 



ence to low oxygen acclimation. J. Fish. Res. Board Can. 

 12:387-446. 



Stevens, e. D. 



1972. Some aspects of gas exchange in tuna. J. Exp. Biol. 

 56:809-823. 



Whitmore, C. M., C. E. Warren, and p. Doudoroff. 



I960. Avoidance reactions of salmonid and centrarchid 

 fishes to low oxygen concentrations. Trans. Am. Fish. 

 Soc. 89:17-26. 



ANDREW E. DIZON 



Southwest Fisheries Center Honolulu Laboratory 

 National Marine Fisheries Service, NOAA 

 P.O. Box 3830. Honolulu, HI 96812 



A NONLETHAL LAVAGE DEVICE FOR 



SAMPLING STOMACH CONTENTS OF 



SMALL MARINE MAMMALS 



Historically, the only expedient and successful 

 method for determining the species upon which 

 marine mammals feed has been to kill the animal, 

 remove its stomach, and examine the contents in 

 the laboratory (e.g., Wilke and Nicholson 1958; 

 Tautsumi et al. 1961; Shomura and Hida 1965; 

 Fiscus and Baines 1966; Fitch and Brownell 1968; 

 Imler and Sarber 1947). This method, however, 

 does not always work. For example, when actively 

 feeding marine mammals are harpooned or shot, 

 they sometimes regurgitate most or all of their 

 food. While regurgitation by live captured marine 

 mammals is possible, it does not appear to be a 

 significant problem. Of the last 10 cetaceans that I 

 have captured alive and later released unharmed, 

 none has regurgitated during the capturing, hand- 

 ling, or releasing process. Although some re- 

 searchers have reported on stomach samples from 

 stranded marine mammals (e.g., Houck 1961; 

 Fitch and Brownell 1968), these samples may not 

 be representative of feeding habits of active 

 healthy organisms. 



Passage of the Marine Mammal Act in 1972 has 

 made it necessary to develop techniques beside 

 killing if we are to continue certain types of 

 marine mammal research. A useful tool for deter- 

 mining feeding habits of delphinids and certain 

 small pinnipeds would be a portable stomach 

 pump device capable of being used in the field. To 

 be effective, this device must be capable of remov- 

 ing small identifiable bits of food such as otoliths, 

 scales, preopercular bones, squid beaks, or other 



653 



