Davis and Stanley; Movements of Thunnus maccoyn in the Great Australian Bight 



455 



12 



13 14 15 16 



Local time (hours) 



17 



Local time (tiours) 



Figure 5 



(A) Track of southern bluefin tuna 5 on 13 March 1993. (B) Track of southern bluelin tuna 6 on 

 14—15 March 1993. The period when the tuna followed the chum line is shown. See Figure 3 for 

 legend details. 



Tuna 9 struck at a tag during calibration experiments 

 near Nuyts Reef at 09:05 on 15 January 1994 (Fig. 1). Conse- 

 quently, it was tagged without leaving the water. The tag was 

 either in the mouth or in the stomach. The tuna remained 

 with tuna schools in the vicinity of tagging until 09:50 h and 

 then moved away at considerable speed (2 m/s) for over an 

 hour before sounding and slowing (Fig. 6C). It returned to 

 the surface and remained there in association with a large 

 surface school. The tag detached from the tuna at 1410 h. 



Tuna 10 was released 11 km southeast of St Francis Is- 

 land at 11:40 h on 16 January 1994. It was tracked for 13 h 

 before it regurgitated the tag (Figs. 1 and 2D). The vertical 

 movements of this fish differed from other tracks in that 

 they were of relatively high amplitude (30-1- m), traversed 



the water column, and were of moderate frequency (Fig. 

 7A). It spent little time at a particular depth, except for 

 a short period at the bottom at the start of the track and 

 again around 21:00 h. The fish was associated with tuna 

 schools for most of the track. It made an extended dive just 

 after sunset. 



This was the first SBT to provide stomach-temperature 

 data. The stomach temperature dropped rapidly initially, 

 then increased to 25.4°C, which was about 6°C above wa- 

 ter temperature. Temperature then decreased gradually 

 for the rest of the track, but remained at least 4°C above 

 ambient temperature. 



Tuna 11 was released at The Lumps 41 km west of Sceale 

 Bay at 13:57 h on 17 January 1994 with a temperature-pres- 



