modification of it best describes the relation 

 between oxygen consumption and weight in 

 selected species of estuarine fish of the Beau- 

 fort, N.C. area. 



Methods and Materials 



Fish used in these experiments were col- 

 lected near Beaufort and maintained in tanks 

 in the laboratory before measurement of their 

 rates of respiration. The species were: pin- 

 fish, Lagodon rhomboides ; black sea bass, 

 Centropristes striatus ; Atlantic croaker, Mi- 

 cropogon undulatus ; oyster toadfish, Opsanus 

 tau ; and mummichog, Fundulus heteroclitus . 



Oxygen consumption was measured in a 

 recirculating water system which was a modi- 

 fication of those described in the literature 

 (fig. 19). Although this system was designed to 

 recirculate the water, it could easily be con- 

 verted to a single-pass system, depending on 



the needs of the investigator. The system con- 

 sisted of a reservoir, respirometer tank, con- 

 stant-level tank, and respiration chambers 

 constructed of Lucite. Water from the reser- 

 voir was pumped into the elevated constant- 

 level tank and then flowed by gravity to the 

 respiration chambers. The excess water from 

 the chamber returned through the overflow to 

 the reservoir. Water flowing from the respi- 

 ration chamber also returned to the reservoir. 

 The rate of flow of water through each respira- 

 tion chamber was regulated by adjusting the 

 height of the plastic tube leaving each respira- 

 tion chamber (fig. 19) and was measured by 

 diverting the flow of water fronn the chambers 

 into graduated cylinders for specific intervals 

 of time or by the use of flowmeters inserted on 

 the ends of the tubes leaving the chamber. 

 Rate of flow was measured just before water 

 samples were analyzed for oxygen content with 

 an oxygen meter. The water was maintained at 



CONSTANT LEVEL 

 TANK 



RESPIRATION 

 CHAMBER 



» » » » » f 

 RESPIROMETER 



jn 



RESERVOIR 



Figure 19. — Recirculating water system used to measure respiration in fish. The insert is a transverse section 



through 1 of the 10 respiration chambers. 



36 



