Pearcy: Movements of acoustically-tagged Sebastes flavidus 



727 



125"30' 



124'"30' 



-f- 



13" 

 30' 



IS" 



4- 



-f- 



h-- 



125"30- 



125"00' 



124''30 



Figure 1 



Location of Heceta Bank off Oregon. Hatched area of the bank encompasses the area of this study as shown in Figure 2 (depth 

 contours in meters). 



behavior. Homing is defined as returning to a site 

 formerly occupied instead of to equally probable loca- 

 tions. Homing does not imply a direct, straight-line 

 course back to the home site. 



Yellowtail rockfish are ideal for acoustical tracking 

 because they are common, large in size, and do not suf- 

 fer from the lethal embolisms of other rockfishes when 

 brought to the surface, but instead expel swimbladder 

 gases during decompression*. 



* Bubbles of gas were observed emanating from the region of the 

 opercle as yellowtail rockfish were reeled from about 2-3 m depth 

 to the surface. By immersing fish in tanks aboard ship, these 

 bubbles were seen forming and being expelled from under the thin 

 skin between the last gill and the cleithrum anterior to the base 

 of the pectoral fin. Samples of the gas were collected in syringes 

 and analyzed with a microgasometer using the methods of Scho- 

 lander et al. (1955). The gas was comprised of about 75% oxygen, 

 indicating that gases from the swimbladder were released without 

 causing lethal embolisms when yellowtail rockfish were rapidly 

 decompressed. 



