Determining feasibility of acoustic tag attachment and documenting ...

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Time (hh:mm)015:4816:5217:5719:01Sunset20:0621:1022:1523:190:241:282:333:374:427:556:515:46Sunrise9:0010:0411:0912:1313:1814:2215:2716:3117:36-0.5Depth (m)-1-1.5-2Figure 3: Data from the TDR recorded over 27 h, showing the depth profile over time.Activity budgetThe direction and position of the foraging pathway are presented in Figure 4. In totalthe sawfish travelled 28 714 m with an overall speed (distance/length of track) of 18.6m/min (Rate of movement = 0.31 m.s -1 ). The average speed (mean of distancetravelled between waypoints) was 28.4 (± 4.8 m.min -1 ). The minimum and maximumspeed recorded between 2 waypoints were 0.15 and 289 m.min -1 , respectively.The foraging area calculated over the 27 hours of continuous tracking was 8.032km 2(Figure 5)The tagged sawfish demonstrated rapid movement on two occasions, and both were inthe early morning corresponding with the ebbing tide. During these two events thesawfish travelled a distance of 1921 and 868 metres respectively (Figure 6). Thisrapid movement took place along the channel edge between waypoints 58 – 59 and 63– 64 (Figure 4).10
ObservationsSightings of the tag breaking the surface were observed on 6 separate occasionstotalling approximately 3.5 hours. During this time the water depth was less than 0.5m. The sawfish was observed on five separate occasions and its behaviour wasinterpreted to be that of feeding with the rostrum breaching the surface in a thrashingmovement. This behaviour was usually associated with baitfish breaking the surfacefollowed by a sudden burst of movement creating large swirls and waterdisplacement.Figure 4: Map of the track of a P. zijsron acoustically tagged on the 1/5/04. Tag released andrecovered after 27 hours11
Page 1: NORTHERN AUSTRALIAN SHARKS & RAYS:D
Page 4 and 5: Executive summaryA female Pristis z
Page 6 and 7: Figure 3: Data from the TDR recorde
Page 8 and 9: Failure to understand the life-hist
Page 10 and 11: Figure 1. Sawfish acoustic tracking
Page 12 and 13: Figure 2: Position and size of acou
Page 14 and 15: Activity budgetAn activity time bud
Page 18 and 19: Figure 5: Foraging area calculated
Page 20 and 21: DiscussionMovementA female P. zijsr
Page 22 and 23: 200mm net. Generally the nets are s
Page 24: ReferencesCavanagh, R.D., Kyne, P.M

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