Spatial Distribution and Habitat Utilisation of the Speartooth Shark Glyphis Sp

Home , Ducie River, Ganges shark, Northern river shark, Speartooth shark

Spatial distribution and habitat utilisation of the speartooth shark Glyphis sp. A in relation to fishing in Northern Australia

R. D. Pillans1, J.D. Stevens2, S. Peverell3, S. Edgar1

1 CSIRO Marine and Atmospheric Research, Cleveland 2 CSIRO Marine and Atmospheric Research, Hobart 3Queensland Department of Primary Industries and Fisheries

20 May 2008

A report to the Department of the Environment, Water, Heritage and the Arts

iii Enquiries should be addressed to:

Richard Pillans [email protected]

Distribution list Chief of Division Operations Manager Project Manager Client Authors Other CSIRO Staff National Library CMAR Libraries

Copyright © 2008 CSIRO To the extent permitted by law, all rights are reserved and no part of this publication covered by copyright may be reproduced or copied in any form or by any means except with the written permission of CSIRO.

CONTENTS

1. EXECUTIVE SUMMARY...... 1

2. INTRODUCTION ...... 2

2.1 Need ...... 3

2.2 Objectives...... 5

3. METHODS ...... 6

3.1 Capture and tagging...... 6

3.2 Telemetry...... 6

3.3 Data analysis...... 7

3.4 Long-term habitat utilisation ...... 8

4. RESULTS ...... 12

4.1 Distribution...... 12

4.2 Short term movement...... 14

4.3 Rate of movement...... 20

4.4 Archival tags ...... 31

5. DISCUSSION...... 31

5.1 Distribution...... 31

5.2 Short-term movement ...... 32

5.3 Long-term movement...... 34

6. CONCLUSIONS ...... 36

6.1 Management Recommendations ...... 37

ACKNOWLEDGEMENTS...... 39

REFERENCES...... 40

APPENDIX A - CSIRO ANIMAL ETHICS REPORT ...... 43

APPENDIX B - MEDIA RELEASE IN CAPE TIMES – OCTOBER 2007 ...... 45

1. EXECUTIVE SUMMARY

A three week field trip to deploy listening stations and capture and tag Glyphis sp. A in the Wenlock River was undertaken in July/August 2007. Eight listening stations were deployed in the Wenlock River and covered a range of habitats from the mouth of the river (salinity = 27 ‰) to the freshwater reaches approximately 40 km upstream

(salinity = 1.4 ‰). A total of 29 Glyphis sp. A were captured, however animals were only captured in salinities below 13 ‰ despite considerable fishing effort in salinities between 13 – 26 ‰. We only captured neonate and juvenile Glyphis sp. A below 80 cm total length (TL) during our survey. These data suggest that larger sub-adult sharks are occupying a different habitat to neonate and juvenile sharks which appear to be using the upper reaches of the river as a nursery area. The presence of larger sub-adult Glyphis sp. A in previous surveys downstream of the August 2007 capture sites indicates that these animals are utilising more saline habitats towards the mouth of the River. Although the current survey did sample these areas, no animals were captured, possibly due to seasonal shifts in the species habitat utilisation.

Three Glyphis sp. A were tracked continuously for periods of 24 – 27 hours and displayed similar movement patterns highlighted by limited movement and repeated use of the same habitat. All three sharks moved between 4 – 12 km up stream during the flood tide and similar distances downstream during the ebb tide.

We attached coded tags to 11 Glyphis sp. A within the listening station array between

27 July – 6 August 2007. Data downloaded from the acoustic receivers on the 31

August 2007 provided information on the habitat utilisation of five animals showing that Glyphis sp. A in the Wenlock have an extremely small critical habitat. All five animals spent more than 80 % of their time in a limited region of the river with a total area of less than 10km2.

In addition to their limited habitat utilisation, the narrow distribution of

Glyphis sp. A within the Wenlock River makes them highly vulnerable to over fishing and localised extinction. Data on their population size and trends in population size over time are urgently required. The limited habitat utilisation of neonate and juvenile sharks makes Marine Protected Areas (MPAs) a viable management tool to reduce fishing mortality; however more data are required on the movement patterns of sub- adult and adult sharks to inform on the management needs of these animals.

2. INTRODUCTION

The speartooth sharks, genus Glyphis, are a group of poorly known, cryptic sharks of the family Carcharhinidae with a patchy Indo-West Pacific distribution in tropical riverine and coastal habitats (Compagno, 1984; Last and Stevens, 1994). The systematics of Glyphis are currently under revision but the genus appears to comprise

5-6 species (Compagno et al., 2005). The Ganges shark Glyphis gangeticus (Müller

& Henle, 1839) is definitely known from the Ganges-Hooghly river system in India, while the speartooth shark Glyphis glyphis (Müller & Henle, 1839) was described from a single specimen, but without locality. The Irrawady River shark Glyphis siamensis (Steindachner, 1896 ) is known from a single specimen from the Irawaddy

River mouth, Burma (Compagno et al., 2005). The Bizant River shark Glyphis sp. A

(sensu Last & Stevens, 1994) is known from Queensland (Qld) and the Northern

Territory (NT) in northern Australia (Last and Stevens, 1994), but together with specimens from New Guinea, appears to be synonymous with G. glyphis (LJV

Compagno, South African Museum, Pers. Comm.). The Borneo river shark Glyphis sp. B (sensu Compagno et al., 2005) is recorded from the Kinabatangan River in

Sabah, Malaysian Borneo (Compagno, 1984; Manjaji, 2002). The northern river shark

Glyphis sp. C (sensu Compagno et al., 2005) has been recorded in Papua New Gunea

(Compagno et al., 2005) and northern Australia where it is found in the NT and

Western Australia (WA) (Taniuchi et al. 1991; Last and Stevens 1994; Thorburn and

Morgan 2004).

2.1 Need

Glyphis sp. A was originally reported from Australia in 1982 when two small

(70-75 cm total length (TL)) specimens were taken 17 km upstream in the Bizant

River, Qld (Last, 2002). No specimens have been recorded in the Bizant River since

1983 and this species appears to have become extinct on the east coast of Cape York

Peninsula. Peverell et al (2006) recently documented the occurrence of Glyphis sp. A in the Wenlock and Ducie River on the west coast of northern Cape York Peninsula, making these river systems the only known habitat for this species in Queensland.

The rarity of Glyphis spp in Australia is reflected in their conservation status. Glyphis sp. A is listed as Critically Endangered (CR) by both the IUCN (Cavanagh et al.,

2003) and the Australian Commonwealth Environmental Protection and Biodiversity

Conservation Act 1999 (EPBC Act) while Glyphis sp. C is listed as CR by the IUCN and Endangered by the EPBC Act.

3 The primary threat to Glyphis sp. A is their capture and resulting mortality in commercial gillnet fisheries operating in inshore rivers, estuaries and coastal foreshore areas of northern Australia. The current status and population trend of

Glyphis sp. A is unknown. However, the disappearance of this species from the Bizant

River (Pillans et al., 2008) indicates that population levels have declined and highlights the vulnerability of this species to extinction. Glyphis sp. A have been recorded in the catches of a commercial fishery operating in the Wenlock River by observers in the FRDC funded project “Northern Australian sharks and rays: the sustainability of target and bycatch species, Phase 2” and also by Peverell et al.

(2006).

Reducing capture rates of Glyphis sp. A in commercial fishing gear depends on knowing where and when they encounter nets. However, information about habitat requirements and movements is lacking. There is a need to obtain data on the long- term habitat utilisation and fine-scale movement patterns of Glyphis sp. A by employing a combination of active acoustic tracking and listening station arrays.

Accurate long-term positional information can be obtained if coded tags can be used successfully on Glyphis sp. A. Complementary data from manual acoustic tracking will provide data on fine-scale vertical and horizontal movements and habitat utilisation. Data on long-term movement patterns and habitat utilisation will allow for a better assessment of the interactions with coastal fishing gear and for the development of advice on mitigation methods, including the required spatial scale of management/conservation measures.

2.2 Objectives

1) Assess habitat utilisation of Glyphis sp. A in relation to fluctuations in environmental conditions. We will use archival DT tags on Glyphis sp. A to collect long-term and fine scale depth and temperature data.

2) Determine short-term and long-term movement patterns of Glyphis sp. A in areas where commercial fishing occurs. A combination of active tracking and listening station arrays will be deployed in the Port Musgrave system (Wenlock and Ducie

Rivers) providing abundance and distributional data within the commercially fished areas.

3) Recommend likely threat mitigation and management strategies and recovery policies that would reduce the impacts of commercial fishing on the populations of

Glyphis sp. A.

5 3. METHODS

3.1 Capture and tagging

The majority of specimens were captured using rod and line. This method was considered less damaging to the sharks than catching them in gill nets. Captured

Glyphis sp. A were measured (total length; TL), sexed and released if they were not to be tracked. Acoustic tags were attached with dissolving sutures, one end through the leading edge of the first dorsal fin and the other through the dorsal musculature.

Sutures were designed to dissolve within two weeks.

We had initially planned to surgically implant the acoustic tags in the peritoneal cavity. However, due to complications with the surgery on the initial animals we opted for external attachment. This will result in data only being collected for 4-6 months instead of at least 12 months because of probable tag shedding. A summary of this issue and an action plan for future work is provided in Appendix A.

Three animals had coded acoustic tags surgically implanted. However, as one animal died following release (determined through tracking data) we changed our method of attachment to external. This was achieved by making a small hole in the dorsal fin with a hole punch. A cable tie was passed through the hole and secured to the tag ensuring that it lay parallel to the shark’s fin.

3.2 Telemetry

Three sharks were tracked using acoustic telemetry equipment comprising a

Vemco VR-100 receiver, a hydrophone and either Vemco V16P-5HR transmitters

with a depth sensor, or a Vemco V16 – 5HR transmitter with no sensor. A fourth shark was also tagged but the acoustic tag failed to transmit. Tracking was carried out from a 4 m aluminium boat. The hydrophone was mounted on a pole and rotated manually to maximise signal strength. The tags had a range of about 1.0 km and a battery life of ~ 14 days. Depth from the tag together with position from a Garmin

GPS 12 was assumed to be the position of the shark and was recorded every 15 minutes. Bottom depth was recorded using a Hummingbird depth sounder.

Temperature and salinity was measured on the surface and on the bottom using a

WTW LF340 salinity/conductivity meter throughout the track at the position of the shark. There was no noticeable difference in surface and bottom salinity or temperature and all data presented are from the surface readings. Secchi depth (mm) was recorded using a secchi disk.

3.3 Data analysis

Recorded positions were plotted using ArcView GIS. Distance between successive positions was calculated following the contours of the river, using the measure distance tool in ArcView GIS. Rate of movement was calculated by dividing the distance between points by the sampling interval. Due to the highly directional

(either upstream or downstream) movement of sharks in this study, we assumed that point to point measures accurately reflected ROM. A t-test was used to test for differences in ROM between sharks. A Mann-Whitney U-test was used to test for diurnal differences in ROM. Depth of the shark and water depth were recorded at the same time as position. A Mann-Whitney U-test was used to test for differences in swimming depth in relation to bottom depth between time of day and tide. All data are presented as mean ± 1 S.D. Significance levels were set at p < 0.05.

3.4 Long-term habitat utilisation

Eight listening stations were deployed in the Wenlock River (Figure 1) and

covered a range of habitats from the mouth of the river to the freshwater reaches

approximately 45 km upstream. The distance upstream, salinity, temperature and

secchi depth were recorded at each receiver when they were deployed are shown in

Table 1. Receivers were placed in the middle of the river at locations that were chosen

based on distance from previous receiver and the known distribution of Glyphis sp. A

within the Wenlock River. No receivers were placed above the Island Group

(upstream of receiver 101056) as Glyphis sp. A have not been recorded upstream of

this location (Figure 1).

141°50' 142°00' 142°10' 142°20'

Gulf of Carpentaria Port

Musgrave

12°00' 12°00' Ducie River

101070 #Y

101055 #Y #Y Location of VR2 receivers

#Y 1868 12°10' 12°10' 1863 #Y Wenlock River Glyphis sp. A have not been recorded upstream of this location

101052 #Y #Y 101054 101063 #Y #Y 101056 Tentpole Creek

12°20' 60612Kilometres12°20'

141°50' 142°00' 142°10' 142°20'

Figure 1: Map of the Wenlock River showing the location of the VR2 receivers and serial number of each receiver.

Table 1. Distance upstream from the mouth of Wenlock River and salinity, temperature and secchi depth at the location of each receiver. Physical measurements were taken at the initial deployment (27 July 2007) and will be influenced by tidal and seasonal patterns.

VR2 serial Distance upstream from Salinity (‰) Temperature (ºC) Secchi depth (mm) number mouth of Wenlock River (km) 101070 7.4 27 26.5 1450 101055 10.7 25 26.6 1270 1868 15.2 23 26.5 900 1863 22.9 18.7 26.5 580 101052 31.6 18.5 26.4 280 101063 37.2 10.5 26.8 400 101054 39.9 5.9 26.9 200 101056 43.9 1.4 27 350

Data from the VR2 receivers were downloaded between the 31st August and

the 1st September 2007. Data were then imported into an Oracle database and

checked for false detections. Data were queried to obtain the time and date an

individual tag was within range of individual receivers. This provided a table of times

and dates that an individual was in range of a receiver and a time and date this

individual left the range of a receiver. The time between subsequent detections was

also included in this table. Analysis of the data in this table determined the total

number of minutes individual sharks spent around receivers and also between

receivers. Tags were assumed to be within the detection range (600 m) of a receiver if

they were detected periodically within a 10 min interval. If tags were not detected for

10 min then they were assigned to an area adjacent to the receiver. The river was

broken into 16 regions based on the location of the 8 receivers (Figure 2). For areas 2

and 6, that were upstream of the last receiver, the area was assumed to include all

habitable water upstream of the last receiver. However for area 0, we have data that

9 shows that Glyphis sp. A do not occur more than approximately 7 km upstream of receiver 101056. The area and length of each region was calculated from geo- referenced satellite imagery of the river at high tide using SigmaScan Pro and are shown in Table 2.

Tags that were detected by a receiver, followed by a period of no detections and subsequent detection/s on the same receiver, were considered to have spent equal time either upstream or downstream of the receiver. Since we could not tell with certainty if the animal was upstream or downstream of the receiver, assuming a 50:50 upstream/downstream distribution would lead to both under and over-estimation.

When animals moved from one receiver to another, the time between the last and first detection was assigned to the area between the two receivers.

Data on the percentage of time each individual spent within the 16 regions of the river was displayed using Arcmap. The total number of minutes an animal spent within a region of the river was divided by the sum of all minutes to give the percentage of time each animal spent within the 16 regions. The proportion of time animals spent within the 16 regions is a similar calculation to home range estimation and is based on fewer assumptions providing a more realistic overview of the animal’s movement over time.

Figure 2: Map showing schematic representation of the Wenlock River divided up into 16 regions (0 – 15) based on the position of the VR2 receivers and the area between receivers. A buffered polygon 600 m each side of the central line of the Wenlock River was used to create the regions. Similarly, each VR2 receiver (region 1, 3, 5, 7, 9, 11, 13 and 15) had a 600 m area based on detection range, around its position.

11 Table 2. Length and area of the 16 regions in the Wenlock River. Region ID corresponds to regions in Figure 2. Total river length and area of combined regions and the percentage area contribution of each region to total area are also shown.

Region Corresponding Distance km Area km2 Proportion of area ID receiver ID 0 6.5 1.9 7 1 101056 1.3 0.4 1 2 2.9 1.4 5 3 101054 1.3 0.3 1 4 7.2 3.0 11 5 101063 1.3 0.2 1 6 24.9 3.6 13 7 101052 1.2 0.7 2 8 7.6 3.7 13 9 1863 1.2 0.7 3 10 6.6 3.7 13 11 1868 1.2 0.7 2 12 3.3 2.1 7 13 101055 1.2 0.8 3 14 4.8 5.0 18 15 101070 1.3 0.4 1 TOTAL 73.8 28.5 100

4. RESULTS

4.1 Distribution

A three week field trip to deploy listening stations and capture and tag Glyphis sp. A in the Wenlock River was undertaken in July/August 2007. A total of 29

Glyphis sp. A were captured during the trip. Data on distribution of Glyphis sp. A in the Wenlock River was obtained from gillnetting and rod and line during this field trip and from previous surveys (Peverell et al., 2006) (Figure 3). In the current study,

Glyphis sp. A were only captured in salinities below 13 ‰ and in water that had a secchi depth of < 600 mm. Despite considerable fishing effort in salinities between 13

– 26 ‰, no Glyphis sp. A were captured. Only neonate and juvenile Glyphis sp. A below 80 cm TL were recorded during this survey (Figure 4).

141°52' 141°56' 142°00'

N Port Musgrave

12°4' 12°4'

e n

l o c k

R iv 12°8' e 12°8' r

# Recent captures of Glyphis sp. A

# Locations fished with zero catch 12°12' # $ Locations of captured Glyphis sp. A 12°12'

$ $ $ $$$$$$ $$ $

12°16' T $$ H $ $ $ 12°16' e u nt $$

po $ d $ $

le $ s $$ $ C o r e n e C k re ek 3036Kilometres

141°52' 141°56' 142°00'

Figure 3 . Map showing the locations of all Glyphis sp. A (n = 29) as well as locations where none were captured. Areas where Glyphis sp. A have been previously recorded are also shown.

13 16 14 12 10 8 6 4 2 Length frequency Length 0 Less 55 - 60 60 - 65 65 - 70 70 - 75 75 - 80 80 - 85 Greater than 55 than 85 Total length (cm)

Figure 4 . Length frequency of Glyphis sp. A captured between 27 July – 6 August 2007.

4.2 Short term movement

We attached continuously transmitting acoustic tags to four individual Glyphis sp. A. One of the tags malfunctioned and we were not able to track this individual.

The remaining three Glyphis sp. A were tracked continuously for periods of 24 – 27.8 h revealing important information about their short-term movement patterns.

Shark 1 was tracked continuously for 27.75 h and was never more than 5 km away from the tagging site (Figure 5). Following tagging, this shark spent approximately 8 h within a few hundred metres of the tagging location (Figure 5 and

6). During this time the shark was moving predominantly back and forth across the main river in a large eddy. After approximately 8 h, at the top of the tide, the shark began to move downstream. Subsequently, this shark displayed a tidally influenced up and downstream movement pattern moving approximately 4 km upstream and 4 km downstream over three successive tides.

Shark 1 experienced a significant increase in salinity from 1.7 – 11.8 ‰ during the first 8 h due to the flooding tide (Figure 6). Following this initial increase, environmental salinity fluctuated less (5.5 – 13.6 ‰) due to the shark moving up and downstream with the flood and ebb tides, respectively. Swimming depth of shark 1 showed no diurnal or tidally influenced patterns (Figure 7). The average swimming depth was 4.1 ± 1.7 m which translated to a swimming depth that was on average 2.7

± 1.5 m above the bottom.

Figure 5. Map showing the track of shark 1, a 73.5 cm TL Glyphis sp. A tracked continuously from 13:38 h on the 31/7/07 to 17:25 h on the 1/8/07 in the Wenlock River. Triangles represent the animal’s position approximately every 2 h during the 27.75 h track.

15 Position of shark Tidal height (m) Salinity (‰) 1 15 14 13 0 12 11 -1 10 9 8 -2 7 6 Salinity -3 5 4 3 -4 Distance from capture capture (km) from Distance 2 1 -5 0 0 6 12 18 24 30 Time elapsed (h)

Figure 6. Schematic representation of the track of shark 1 showing distance moved upstream (values > 0) and downstream (value < 0) since start of track. The salinity and tidal height are shown on the right hand Y- axis.

-2

-4

-6 Shark depth -8 Water depth Depth (m) Depth

-10

-12

-14 13:38 14:30 15:45 16:59 19:03 20:27 21:42 22:45 23:59 01:12 02:31 03:54 05:05 06:19 07:31 08:56 10:16 11:30 12:46 14:03 15:00 17:05 Time (hh:mm)

Figure 7. Swimming depth of shark 1 with respect to bottom depth throughout the duration of the track.

Shark 2 was tracked continuously for 26.6 h and spent the majority of its time in

Tent Pole Creek (Figure 8). The shark was never more than 6.2 km away from the tagging site (Figure 9). After being tagged this shark displayed a consistent down and upstream tidally influenced movement pattern, moving between 10 – 12 km on each flood and ebb tide (Figure 9).

Figure 8. Map showing the track of shark 2, a 71 cm TL Glyphis sp. A tracked continuously from 13:58 h on 3/8/07 to 16:39 h on 4/8/07 in the Wenlock River and Tent Pole Creek. Triangles represent the animal’s position approximately every 2 h during the 26.6 h track.

Shark 2 remained in water of similar salinity (8.8 – 10.9 ‰) due to its repeated up and downstream tidally influenced movements (Figure 9). Swimming depth of shark

2 showed no diurnal or tidally influenced patterns (Figure 10). The average swimming depth was 3.7 ± 2.1 m which translated to a swimming depth that was on average 3.9 ±

2.4 m above the bottom.

8 12 11 6 10 4 9 8 2 7 Position of shark 0 6 Tidal height (m) 5 Salinity -2 4 -4 3 2 -6 Distance from capture (km) capture from Distance 1 -8 0 0 6 12 18 24 30 Time (h)

Figure 9. Schematic representation of the track of shark 2 showing distance moved upstream (values > 0) and downstream (value < 0) since start of track. The salinity and tidal height are shown on the right hand Y- axis.

-2 -4

-6 Shark depth -8 Water depth Depth (m) Depth -10 -12

-14 13:58 15:01 16:15 17:33 18:30 19:45 21:00 22:18 23:30 00:43 02:03 03:11 04:37 05:44 07:07 08:02 09:18 10:45 13:02 14:15 15:45 Time (hh:mm)

Figure 10. Swimming depth of shark 2 with respect to bottom depth throughout the duration of the track.

Shark 3 was tracked continuously for 24.1 h and spent the entire time in Tent

Pole Creek (Figure 11). The shark was never more than 9 km away from the tagging site (Figure 12). After being tagged, this shark displayed a consistent down and upstream tidally influence movement pattern, moving about 8 km on each flood and ebb tide (Figure 12). Shark 3 remained in water of similar salinity (8.3 – 10.5 ‰) due to its repeated up and downstream tidally influenced movements (Figure 12). Swimming depth of shark 3 was not recorded.

Figure 11. Map showing the track of shark 3, a 70 cm TL Glyphis sp. A tracked continuously from 16:45 h on 5/8/07 to 16:50 h on 6/8/07 in Tentpole Creek. Triangles represent the animal’s position approximately every 2 h during the 24.1 h track.

10 12 11 8 10 9 6 8 7 Position of shark 4 6 Tidal height (m) 5 Salinity

Distance (km) Distance 2 4 3 0 2 1 -2 0 0 6 12 18 24 Time elapsed (h)

Figure 12. Schematic representation of the track of shark 3 showing distance moved upstream (values > 0) and downstream (values < 0) since start of track. The salinity (‰) and tidal height are shown on the right hand Y- axis.

4.3 Rate of movement

There was considerable variation in ROM between individuals (Table 3). Shark

1 had the slowest ROM (0.20 ± 0.27 m.s-1) and shark 3 the fastest (0.54 ± 0.38 m.s-1).

Overall ROM of all sharks were significantly different to each other (p<0.01). There was no change in individual ROM related to diurnal patterns (p > 0.4).

Table 3. Summary of average (± SD) rate of movement (ROM) (m.s-1) during tidal cycles and throughout the track for three sharks tracked continuously over 24 – 27.75 h. Letters denote significance for overall ROM.

Shark 1 Shark 2 Shark 3 1st ebb 0.12 ± 0.16 0.86 ± 0.57 - 1st flood 0.13 ± 0.17 0.54 ± 0.36 0.46 ± 0.27 2nd ebb 0.33 ± 0.30 0.48 ± 0.27 0.29 ± 0.22 2nd flood 0.32 ± 0.39 0.60 ± 0.46 0.51 ± 0.44 3rd ebb 0.15 ± 0.22 0.45 ± 0.30 0.35 ± 0.35 Overall 0.20 ± 0.27a 0.54 ± 0.38b 0.39 ± 0.33c

Coded acoustic tags were attached to 11 Glyphis sp. A within the listening station array. The location where individual animals were tagged is shown in Figure 13.

One shark (# 5433) was believed to have died as a result of surgery (the position of the tag did not change for 24 h). Up to the 7 August 2007, 9 of the 11 sharks fitted with coded tags were moving between the listening stations providing data on their long- term movements. Data from the listening stations were downloaded on the 7 August

2007 and again on the 31 August 2007 providing a full month of data from the tagged sharks.

A summary of detections of each on tag on the eight acoustic receivers is provided in Table 4. Unfortunately, the listening stations detached from their mooring between the 31 August and 10 September due to corrosion of the copper crimps securing the float to the mooring. This resulted in the listening stations being removed from the River. Additional moorings were constructed and re-deployed at the same locations in November 2007 resulting in a two month period where no movement data were collected.

Following the download on the 31 August it was apparent that tag # 5422 had not been detected by any of the listening stations. Three of the tags (5428, 5431and

5433) were detected continuously for periods of up to 24 h by receiver 101056 indicating that the tags were not moving. All of these tags were subsequently recorded downstream at receiver 101054 and then back upstream. These movements were inconsistent with Glyphis sp. A and more consistent with that of estuarine crocodiles

(Crocodylis porosus) (Kay, 2005; Craig Franklin, University of Queensland, Pers.

Comm. 2008). In particular, the diurnal detection patterns were consistent with animals

basking during the day and remaining in the water at night. It is likely that crocodiles preyed on the tagged Glyphis sp. A and consumed the animal and the tag. Crocodiles are known to retain small rocks and other inanimate objects in their gut for months at a time so it is not surprising that the tags have remained inside the crocodiles following consumption of the sharks.

Figure 13. Map showing the locations where 11 Glyphis sp. A were tagged with coded tags. The identification numbers of coded tags as well as the VR2 serial numbers are also shown.

Of the seven remaining tags, 5434 was detected by receiver 101063 on the 4

August 2007 but was not detected after this date. Tags 5430, 5421, 5420, 5432, 4839 and 5429 were detected by multiple receivers between 31 July – 31 August 2007 and

have provided data on the movement patterns of Glyphis sp. A during this period.

Information on habitat utilisation of these six animals is displayed in Figures 14 – 19.

Between 30 July – 31 August 2007, shark 5430 only occurred in regions 2 – 8

(Figure 14). It spent more than 87% of its time in regions 2, 3 and 4, with 33.3 % and

50.3 % of the time in region 2 and 4, respectively. The total area of habitable river in regions 2 – 8 is only 13 km2, while regions 2,3 and 4 comprise only 4.8 km2 of habitat.

Between 5 – 31 August 2007, shark 5421 only occurred in regions 2 – 6 (Figure

15). It spent 88% of its time in regions 2 - 4, with 34.5 % and 50.0 % of the time in region 2 and 4, respectively. The total area of habitable river in regions 2 – 6 is only 8.6 km2, while regions 2, 3 and 4 comprise only 4.8 km2 of habitat.

Between 27 July – 31 August 2007, shark 5432 only occurred in regions 0 – 8

(Figure 16). It spent 88% of its time in regions 4 - 6, with 51.4 % and 36.5 % of the time in region 4 and 6, respectively. The total area of habitable river in regions 0 - 8 is only 15.2 km2, while regions 4 - 6 comprise only 6.9 km2 of habitat.

Between 2 – 31 August 2007, shark 5420 only occurred in regions 0 - 10 (Figure

17). It spent 77% of its time in regions 2 - 4, with 41.8 % and 34 % of the time in region

2 and 4, respectively. The total area of habitable river in regions 0 - 10 is only 19.7 km2, while regions 2 - 4 comprise only 4.8 km2 of habitat.

Between 5 – 31 August 2007, shark 5421 only occurred in regions 4– 6 (Figure

18). It spent 100 % of its time in these regions. The total area of habitable river in

regions 4 – 6 is only 6.9 km2.

Between 30 July – 30 August shark 5429 only occurred in regions 0 – 4 and 6. It

spent more than 80% of the time in region 0 – 2. The total area of habitable river in

regions 0 – 4 and 6 was only 10.6 km, while regions 0 – 2 comprise only 3.7 km2.

Table 4. Summary of tagged animals showing the number of times each tag was recorded on each listening station between 27 July 2007 and 31 August 2007. VR2 serial numbers from left to right are in order of increasing distance from the Wenlock River mouth. * Animals that are providing data on the movement patterns ** Animals that are believed to have been preyed on by crocodiles and not providing data on the movement patterns of Glyphis sp. A.

Tag ID VR2 Serial numbers Total detections 101070 101055 1868 1863 101052 101063 101054 101056 5422** 0 5428** 185 13264 13449 5431** 6 17 338 18333 18694 5433** 86 286 37 74 7903 8386 5434** 124 124 5430* 245 291 2637 3173 5421* 508 2944 3452 5420* 91 195 58 754 820 1918 5432* 341 673 39 78 1131 4839* 219 219 5429* 186 271 13456 13913

Figure 14. Schematic representation of the habitat utilisation of shark 5430 showing the percentage of time this animal spent in each of the 16 regions of the Wenlock River. Data are comprised of 3173 detections between 30 July – 31 August 2007. Shark 5430 was tagged on 31 July 2007 in the location specified.

Figure 15. Schematic representation of the habitat utilisation of shark 5421 showing the percentage of time this animal spent in each of the 16 regions of the Wenlock River. Data are comprised of 3173 detections between 5 – 31 August 2007. Shark 5421 was tagged on 5 August 2007 in the location specified.

Figure 16. Schematic representation of the habitat utilisation of shark 5432 showing the percentage of time this animal spent in each of the 16 regions of the Wenlock River. Data are comprised of 1131 detections between 27 July – 31 August 2007. Shark 5432 was tagged on 27 July 2007 in the location specified.

Figure 17. Schematic representation of the habitat utilisation of shark 5420 showing the percentage of time this animal spent in each of the 16 regions of the Wenlock River. Data are comprised of 1918 detections between 2 – 31 August 2007. Shark 5420 was tagged on 2 August 2007 in the location specified.

Figure 18. Schematic representation of the habitat utilisation of shark 4839 showing the percentage of time this animal spent in each of the 16 regions of the Wenlock River. Data are comprised of 219 detections between 6 – 31 August 2007. Shark 4839 was tagged on 6 August 2007 in the location specified.

Figure 19. Schematic representation of the habitat utilisation of shark 5429 showing the percentage of time this animal spent in each of the 16 regions of the Wenlock River. Data are comprised of 13913 detections between 31 July – 30 August 2007. Shark 5429 was tagged on 31 July 2007 in the location specified.

4.4 Archival tags

Archival depth and temperature tags were not attached to any animals during this field trip due to the small size of specimens that were captured.

5. DISCUSSION

5.1 Distribution

The lack of larger sub-adult and adult sharks from our survey suggests that these sharks may occupy a different habitat to neonates and juveniles which appear to be using the upper reaches of the river as a nursery area similar to bull sharks

(Simpfendorfer et al., 2005; Pillans, 2006). The lack of sub-adults in the Wenlock River is in contrast to the Adelaide River, where sharks up to 1.5 m were captured together with neonates and juveniles (Pillans et al., 2008). Larger sub-adult Glyphis sp. A have been captured in the Wenlock River in previous surveys, however these animals were taken downstream of the August 2007 capture sites. This may indicate that larger animals are utilising more saline habitats towards the mouth of the River as shown in the Adelaide River (Stevens et al., 2005). Although the current survey sampled these areas, no animals were captured, possibly due to seasonal shifts in the species habitat utilisation. More detailed surveys of the Wenlock and Ducie Rivers are required to gain a better understanding of the species abundance and distribution within this system.

Glyphis sp. A have not been recorded outside of rivers and estuaries and data are required to determine whether this species occurs in marine environments outside of rivers and estuaries.

5.2 Short-term movement

All three sharks showed very limited short-term movements with animals moving an average of 7.8 ± 2.7 km during each ebb or flood tide. Shark 1, 2 and 3 moved no more than 4.8, 6.1 and 8.9 km from their capture site throughout their respective tracks. Movement up or downstream was strongly correlated with the tide, with animals only moving upstream with the flood tide and downstream with the ebb tides. The combination of the small distance moved each tide and animals moving back and forth with the tide results in animals repeatedly using a very small area of river. For the entire duration of the three tracks, the total area utilised by shark 1, 2 and 3 was

0.65, 3.1 and 1.4 km2, respectively.

Although there was significant variation in ROM between the three animals tracked, these differences have little biological meaning and the overall trend in movement was very similar for all three sharks. The individual differences in ROM are likely to be due to small changes in behaviour that influence the sharks decision to remain in an eddy, chase prey items or move up or downstream with the current.The

ROM of sharks 2 and 3 (0.54 and 0.39 m.s-1, respectively) tracked in the Wenlock River were very similar to ROM of three Glyphis sp. A tracked it the Adelaide River (0.45 –

0.52 m.s-1) (Pillans et al., 2008). The slower ROM of shark 1 tracked in the Wenlock

River was predominantly due to the fact that it spent the first 8 h of the track moving back and forth in a small area of river.

Swimming depth of shark 1 and 2 were similar and did not show any diurnal patterns. Both animals spent the majority of time swimming well above the river bed and appeared to vary their swimming depth independently of bottom depth. Secchi depths in this section of the Wenlock River were between 20 – 40 cm. Using the equation Id = I0*exp (-kd) where Id = irradiance at depth d, I0 = irradiance at depth 0, k

= 1.7/secchi depth (m), d = depth (m), a maximum secchi depth of 0.4 m would result in

99% of light being lost below 1 m. Therefore sharks swimming below 1m would be in constant darkness. Given the average swimming depth of shark 1 and 2 were 2.7 and 3.7 m, respectively, it is not surprising that no diurnal changes in swimming depth or ROM were observed.

The depth profile of the two animals in the Wenlock River was similar to that shown by a 1.5 m Glyphis sp. A tracked in the Adelaide River (Pillans et al., 2008). The

Adelaide River animal also showed no diurnal changes in swimming depth or ROM which was attributed to lack of light at the average swimming depth of 7.7 m. Although the swimming depth was deeper in the Adelaide River, this was probably due to a deeper river depth as the average swimming depth was 5.0 m above the bottom, compared to 2.7 and 4.0 m for sharks in the Wenlock River.

Given the highly turbid conditions, it is likely that Glyphis sp. A relies heavily on an elaborate ampullary electroreceptor system to detect low-frequency bioelectric fields from its prey (see Hueter et al., 2004). The swimming depth of these animals are consistent with a benthopelagic habitat, supported by gut contents such as bony bream

(Nematolosa come), king salmon (Polydactylus macrochir) and catfish (Ariidae)

(Thorburn and Morgan, 2004; Peverell et al., 2006).

The tidally influenced movement patterns of Glyphis sp. A in the Wenlock are very similar to those observed in this species in the Adelaide River, Northern Territory

(Pillans et al., 2008). Animals in the Adelaide River moved greater distances up and downstream. This is most likely due to the increased tidal currents, and possibly due to there being more preferred habitat in the Adelaide River. The Adelaide River has a large area of highly turbid water stretching from 100 km upstream to the mouth. In the

Wenlock River, turbidity decreases towards the mouth and upstream resulting in a narrow band of highly turbid water. During the dry season, approximately 55 km of the

Wenlock River was highly turbid water (secchi disk depth < 600 mm) with over half this length being attributed to Tent Pole Creek.

5.3 Long-term movement

One shark was believed to have died shortly after surgery to implant a coded tag

(the tag remained in the same location for thee days). After three days, the tag moved approximately 500 m upstream where it remained in range of receiver 101056 for extended periods throughout August 2007. This tag was subsequently recorded on listening stations downriver, before moving upstream in range of receiver 101056 suggesting that a crocodile had consumed the tagged animal. Of the remaining 10 sharks, we believe that three animals may have been eaten by crocodiles which have ingested the coded tags that are transmitting from within their stomachs. All three of these animals were being recorded by the receivers displaying movement consistent with Glyphis sp. A before suddenly switching to movement patterns more consistent with crocodiles (ie long periods around a single receiver). This is evidence for direct

predation of Glyphis sp. A by crocodiles. Two of the sharks were only detected briefly by acoustic receivers and have not been detected since, suggesting that the tags have either detached prematurely or that the animals have not moved within range of the receivers.

Data from the six sharks within the listening station array have provided valuable information on the movement of Glyphis sp. A over one month. Data show that neonate and juvenile Glyphis sp. A display extremely limited movement patterns. All five animals occurred primarily between region 0 – 7, with only one animal moving downstream of region 9 and three animals only spending less than 11 % of their time downstream of region 7. Over the duration of the study, all five animals spent more than

80 % of their time between regions 2 – 6, representing a core area of habitat utilisation of only 8.6 km2. The maximum area of habitat utilised was 19.7 and 15.2 km2 by shark

5420 and 5432, respectively. However, these two sharks spent 90% of their time in an area less than 8 km2. Apart from two animals moving further downstream for short periods, the distribution of all five animals overlapped and were remarkably similar.

Neonate Glyphis sp. A in the Wenlock River utilise a very small proportion of available habitat and appear to be restricted to a core area of river comprised of less than 10 km2 of habitat.

Reasons for the observed habitat utilisation are currently unknown although it appears that salinity and turbidity may play a role in habitat preference. Salinity appears to be less important upstream with animals occurring in freshwater below the Island Group but not occurring in freshwater above the Island Group. This suggests that turbidity may play a more important role in determining distribution above the Island Group as the

water upstream becomes less turbid as the river substrate changes from mud to sand

(Pillans, personal observation).

Salinity increases with decreasing distance from the mouth of the Wenlock River from

27 ‰ at the mouth (receiver 101070) to 1.4 ‰ at the most upstream receiver (101056).

Secchi depth ranges from 280 – 580 mm between receiver 101056 – 1863 (region 0 – 9) and increases rapidly downstream of region 9 (see Table 1). Although further data are required, it appears that turbidity is a critical factor determining the habitat utilisation of

Glyphis sp. A in the Wenlock River. This is consistent with of the observation of

Pillans et al., 2008 who suggested that turbidity was an important factor in determining the distribution of Glyphis sp. A within northern Australian Rivers.

6. CONCLUSIONS

Data on the short-term movement patterns of neonate and juvenile Glyphis sp. A in the Wenlock River show that animals have a tidally influenced movement pattern, moving up and downstream with the flood and ebb tides, respectively. Animals never moved more than 9km from the site of capture and repeatedly used the same habitat due to their tidally influenced movements. Data from the animals fitted with coded tags supported data from manual tracking and showed that during the month of August, animals occupied a very small area of habitat spending more than 80% of time in an area less than 8.6 km2. The influence of seasonal rainfall on the movement patterns of

Glyphis sp. A could not be determined due to floods in the Wenlock River preventing downloads of the receivers. These data will be presented once they become available.

It is well established that elasmobranchs living in rivers and estuaries are bound by physical constraints and are therefore less able to evade pollution, habitat destruction and fisheries (Compagno and Cook, 1995). For Glyphis sp. A, animals appear to have a very specific habitat requirement based on their limited movement within river systems.

These specific habitat requirements that limit them to certain areas within rivers may explain the species very limited geographic distribution, only being recorded in nine rivers and estuaries within Australia (Pillans et al., 2008).

While data on the habitat utilisation of neonate and juvenile Glyphis sp. A in the dry season were provided, data on the movement patterns, habitat utilisation and seasonal movement of sub-adult and adult Glyphis sp. A are urgently required to better understand the life history of this species in the Wenlock River System.

6.1 Management Recommendations

Additional data on the movement patterns and habitat utilisation of sub-adult and adult Glyphis sp. A are required. Data on the influence of seasonal rainfall events on the movement patterns and habitat utilisation of this shark are needed. The current study has provided the first data on the movement patterns of Glyphis sp. A in

Queensland and the first data on their habitat utilisation. Results show that this species has specific habitat requirements and only utilises a very small proportion of available habitat. These behavioural traits makes Glyphis sp. A highly vulnerable to localised over fishing and extinction.

Given the extremely small size of the critical habitat of Glyphis sp. A in the

Wenlock River, management initiatives need to ensure that this region is not overexploited by commercial and recreational fisheries. Although more data are required to determine the full extent of the critical habitat, current data suggest that small Marine Protected Areas would provide an effective management strategy for protecting neonate and juvenile Glyphis sp. A. Current commercial fishing effort in the

Wenlock River is concentrated around the mouth of the river and in Port Musgrave. The spatial separation of fishing effort, as well as the use of gill net mesh that is too large to capture neonates and juveniles of this shark would currently offer some protection to neonates and juveniles. Fisheries operating in the Wenlock River need to be carefully managed to reduce the overlap between fished areas and the habitat utilised by Glyphis sp. A. Once more data on the habitat utilisation of adult and sub-adult sharks is available, spatial management should prove effective in reducing fishing mortality.

Given the small area of habitat utilised by neonate and juveniles, any increase in fishing mortality within these area would have a significant impact on the population size. The status of Glyphis sp. A in the Wenlock River therefore needs to be closely monitored over time to ensure that their population size does not decline. Annual surveys need to be conducted to monitor population numbers and increase our understanding of this species. At the very least, numbers of neonate sharks could be easily assessed and used as a means of monitoring recruitment and levels of juvenile mortality.

Increased community awareness is also required to inform members of the public of the status of Glyphis sp. A in the Wenlock River. Signs regarding the status of

this species erected at public access points would raise public awareness and prevent recreational fishers from misidentifying animals as bull sharks. A collaborative study is already underway involving the local indigenous community at Mapoon, with this research already increasing awareness within the community (see Appendix B).

ACKNOWLEDGEMENTS

We would like to thank Peter Kyne, Dennis Round, John Salini, Stuart Hyland, Gareth

Spurling and Peter Tonan for their valuable assistance in the field. Bob Russell and

Owen Witt provided valuable knowledge of the river system and advice on the best places to camp. Thanks to Bob for the loan of the generator. Thanks to Toni Cannard who helped with formatting the report.

REFERENCES

Compagno LJV (1984) FAO species catalogue. Vol. 4, Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Part 2 –

Carcharhiniformes: 251–655. FAO Fisheries Synopsis 125: 4

Compagno LJV, Cook SF (1995) The exploitation and conservation of freshwater elasmobranchs: status of taxa and prospects for the future. In: Oetinger M, Zorzi GD

(eds) The biology of freshwater elasmobranchs. A symposium to honor Thomas B.

Thorson. Journal of Aquariculture & Aquatic Sciences, Volume 7

Compagno LJV, Dando M, Fowler S (2005). Sharks of the world. Princeton University

Press, Princeton. 368 pp.

Heuter RE, Mann DA, Maruska KP, Sisneros JA, Demski LS (2004) Sensory biology of elasmobranchs. In: Biology of sharks and their relatives. Carrier JC, Musick JA,

Heithaus MR (eds) CRC Press, New York, p 326 – 368

Kay WR (2004). Movements and home range of radio-tracked Crocodylus porosusin the Cambridge Gulf region of Western Australia. Wildlife Research 31: 495 - 508

Last PR, Stevens JD (1994). Sharks and rays of Australia. C.S.I.R.O. Australia, 513 pp

+ 84 colour plates.

Last PR (2002) Freshwater and estuarine elasmobranchs of Australia. In: Fowler SL,

Reed TM, Dipper FA (eds) Elasmobranch Biodiversity, Conservation and Management

Proceedings of the International Seminar and Workshop, Sabah, Malaysia, July 1997.

IUCN SSC Shark Specialist Group. IUCN, Gland, Switzerland and Cambridge, UK, P

185 – 193

Manjaji, BM (2002). New records of elasmobranch species from Sabah. In: Fowler SL,

Reed TM, Dipper FA (eds) Elasmobranch Biodiversity, Conservation and Management:

Proceedings of the International Seminar and Workshop, Sabah, Malaysia, July 1997.

IUCN SSC Shark Specialist Group. IUCN, Gland, Switzerland and Cambridge, UK, p

70-77

Peverell SC, McPherson GR, Garrett RN, Gribble NA (2006) New records of the river shark Glyphis (Carcarhinidae) reported from Cape York Peninsula, northern Australia.

Zootaxa 1233: 53 – 68

Pillans RD (2006) The physiological ecology of the bull shark Carcharhinus leucas in the Brisbane River. PhD Thesis, University of Queensland, Brisbane, Australia

Pillans RD, Stevens JD, Kyne PM, Salini JP (2008). Observations on the distribution, biology, short-term movements and habitat requirements of Glyphis species in northern

Australia. Endangered Species Research. In review.

Simpfendorfer CA, Freitas GA, Wiley TR, Heupel MR (2005) Distribution and habitat partitioning of immature bull sharks (Carcharhinus leucas) in a southwest Florida estuary. Estuaries 28: 78 - 85

Stevens JD, Pillans RD, Salini JP (2005). Conservation assessment of Glyphis sp. A

(speartooth shark), Glyphis sp. C (northern river shark), Pristis microdon (freshwater sawfish) and Pristis zijsron (green sawfish). Report to Department of Environment and

Heritage, Canberra, Australia.

Taniuchi, T., Shimizu, M., Sano, M., Baba, O. and Last, P. R. 1991. Descriptions of freshwater elasmobranchs collected from three rivers in northern Australia. In: Shimizu

M, Taniuchi T (eds) Studies on elasmobranchs collected from seven river systems in northern Australia and Papua New Guinea. The University Museum, The University of

Tokyo, Nature and Culture 3: 11–26.

Thorburn, D.C., and Morgan, D.L. 2004. The northern river shark Glyphis sp. C

(Carcharhinidae) discovered in Western Australia. Zootaxa 685: 1-8

APPENDIX A - CSIRO ANIMAL ETHICS REPORT

Project: Spatial distribution and habitat utilisation of the speartooth shark Glyphis sp. A in relation to fishing in Northern Australia

Richard Pillans

Between 23 July 2007 and 10 August 2007, a total of 12 Glyphis sp. A were tagged with acoustic tags.

Three sharks had coded acoustic tags internally implanted following a brief surgery. The first shark tagged was very slow to recover from the surgery which took approximately 4 minutes. The shark was revived alongside the vessel and swam off slowly but steadily. Tracking of the internal acoustic tag showed that after one hour the animal was not moving from a position approximately 100 m from the site of release. Our initial fear was that the animal had died. These fears were correct as the tag (and animal) remained in this location for the remainder of the trip.

There was nothing in particular that went wrong with the surgery. Each incision was closed with 3 sutures and the wound dressed with betadine antiseptic cream. Given that it was the first of this species to be internally tagged, the procedure took a bit longer than expected. In addition, this individual was captured in a gill net and although it was removed from the net almost immediately, the stress of being entangled may have added to the additional stress of handing and surgery.

The following day, two more sharks were captured and tagged internally; again, the surgery went smoothly. However, both sharks were again slow to recover from the surgery and handling. Both sharks swam off on their own after ~ 2 minutes of revival in the water (driving the boat slowly forward while supporting the shark’s head to irrigate the gills with water and ensure the blood became re-oxygenated). We were initially very nervous that both of these sharks would follow the same fate as the first shark. However, towards the end of the trip, both animals were recorded by the acoustic receivers and were swimming up and down the river. It was obvious that both of these animals survived the surgery and were still alive more than 2 weeks after being tagged.

Due to our initial fears that this particular species was simply very prone to stress and that individuals were not responding well to the surgery, we decided to forego internal tag attachment for external attachment. We decided on external attachment as this method was not as invasive and took about half the time of surgically implanting tags.

External attachment of acoustic tags was achieved by making a small hole in the dorsal fin with a hole punch. Following this, a cable tie was passed through the hole and secured to the tag. This method ensured that the tag was lying parallel to the shark’s fin. This method of attachment is virtually identical to using a cattle ear tag to secure the acoustic tag to the fin. All nine sharks tagged externally are still being recorded by the acoustic receivers more than 1 month after tagging. This indicates that all of these sharks are alive and well. Although the externally attached tags are providing us with data, in all likelihood, these tags will drop off after 3-6 months due to the superglue and cable ties breaking. Ideally, we require at least one year of data from each tagged shark and the only way to ensure this occurs is by internally implanting the tags.

We changed methods because we did not want any sharks to die as a result of surgery. Now that we know that the second two sharks survived the surgery; we would still be keen to use the internal implantation method with the following modifications.

Instead of removing sharks from the water, we would conduct the surgery in a large container onboard the vessel. This container would be filled with water from the site of capture and clove oil at a concentration of 30 ppm. The shark placed would be place upside down in the container and held with its head in the water and ventral surface above the surface. The water would have a slow trickle of 100% medical grade O2 bubbled through it. Having the animal in the water will reduce the risk of oxygen deprivation and having extra oxygen in the water would mean that the shark would obtain sufficient oxygen without having to swim. This method has been used by Heupel and Hueter, 2002; Heupel and Simpfendorfer, 2002 and Heupel et al., 2004. Heupel has tagged over 125 neonate (60 – 80 cm total length) black tip sharks (Carcharhinus limbatus) in Florida and only had 5 sharks die in the first week after tagging (mortality assumed to be related to surgery or predation shortly after release). In addition, over 70 bull sharks (between 80 – 150 cm total length) were tagged with no sharks dying as a result of surgery or predation (Michelle Heupel, Personal communication, August 2007). These results show that his is a viable method with both small and large sharks.

To replace the need for a local anaesthetic, we would administer clove oil to the water (in the large container the surgery will be conducted in). Clove oil acts as an anaesthetic by inhibiting prostaglandin H synthetase (PHS) by eugenol (Dewhirst and Goodson, 1974; Pongprayoon et al., 1991). Clove oil is widely used as an anaesthetic for fish as it rapidly induces anaesthesia with a short recovery time and no long-term adverse effects or mortality (Endo et al., 1972; Keen et al., 1998).

We are confident that by anaesthetising the shark using clove oil (not just the localised area), we will significantly reduce the stress associated with surgery. Following recovery from anaesthesia, we are confident that the sharks will survive given the long term survival of 2 out 3 sharks tagged internally as well the 100 % survival of sharks tagged externally.

References

Dewhirst FE, Goodson JM (1974). Prostaglandin Synthetase inhibition by eugenol, guaiacol and other dental medicaments. Journal of Dental Research. 53: 104

Endo T, Ogishima K, Tanaka H, Ohshima S (1972). Studies on the anaesthetic effects of eugenol in some freshwater fishes. Bulletin Japanese Society of Scientific Fisheries. 38: 761 - 767

Heupel MR, Hueter, RE (2002). The importance of prey density in relation to the movement patterns of juvenile sharks within a coastal nursery area. Marine and Freshwater Research 53:543–550

Heupel MR, Simpfendorfer CA (2002). Estimation of survival and mortality of juvenile blacktip sharks, Carcharhinus limbatus, within a nursery area using telemetry data. Canadian Journal of Fisheries and Aquaculture Sciences 59:624–632

Heupel MR, Simpfendorfer CA, Hueter RE (2004). Estimation of shark home ranges using passive monitoring techniques. Environmental Biology of Fishes 71:135–142

Keen JL, Noakes DLG, Moccia RD, Soto CG (1998). The efficacy of clove oil as an anaesthetic for rainbow trout, Oncorhynchus mykiss (Walbaum). Aquaculture Research. 29: 89 – 101.

Pongprayoon U, Baekstroom P, Jacobsson U, Lindstrom M (1991). Compounds inhibiting Prostaglandin synthesis isolated from Ipomoea pes-caprae. Planta Medica. 57: 515 – 518.

APPENDIX B - MEDIA RELEASE IN CAPE TIMES – OCTOBER 2007

DPI&F fisheries biologist Stirling Peverell with a rostrum from a 4m green sawfish

The Cape York community of Mapoon, including school students, have joined the quest to save the freshwater sawfish and spear-tooth shark, two critically endangered creatures of the deep native to their area.

Biologists from the Department of Primary Industries and Fisheries and CSIRO recently completed a three-week study trip to Mapoon with the aim of better understanding these creatures and their habitat.

Leader of DPI&F's sawfish acoustic tagging study, Stirling Peverell is working in collaboration with spear-tooth shark study leader, Dr Richard Pillans of CSIRO.

They have attached acoustic tags to the dorsal fins of 14 spear-tooth sharks and one 4.2m sawfish to track their movements. This was the largest sawfish to be acoustically- tagged in Australia.

Mr Peverell, a fisheries biologist based in Cairns, took time during his visit to explain the tagging research and engage the support of the local commercial fishers, community and especially the school children.

He said the research focused on short- and long-term relationships between the speartooth shark (Glyphis sp.A) and freshwater sawfish (Pristis microdon) and their shared habitat.

"The Mapoon region is the only area in Queensland where the spear-tooth shark occurs," he said.

"It is found in the Northern Territory and Western Australia, but presumed extinct on the east coast of Queensland.

"We are keen to know where they live and see how they use their habitat.

"When we have this information, we will be better able to advise commercial fishers on how to reduce their impact on this species.

"The spear-tooth shark is a docile creature that is a traditional food of the Aboriginal people on the Cape."

The acoustic tags emit an acoustic 'ping' to allow CSIRO and DPI&F researchers to track and map the movements of the fish in waterways and the sea. The tags also provide readings on temperatures, turbidity, salinity and tides.

"We have installed secured moorings for listening stations 7km apart along the crocodile-infested Wenlock River," Mr Peverell said.

"These listening posts will give us accurate information about the position of sawfish and spear tooth sharks.

"We believe the big sawfish we tagged in Wenlock River was a mature male seeking to catch up with females."

All four species of sawfish - freshwater sawfish, narrow sawfish, green sawfish and dwarf sawfish - will eventually be tagged in the area.

The Mapoon school students were advised of the program and encouraged to keep an eye out for sawfish and spear-tooth sharks in the area.

"They are studying marine animals in school, so the young people will actually be helpful to the program," Mr Peverell said.

Sawfish and spear-tooth shark numbers have declined dramatically around the world and have been listed under the International Union for Conservation of Nature as critically endangered.

Australia is a signatory to this treaty and the Commonwealth Department of Environment and Water Resources (DEWR) is overseeing Australia's responsibilities.

The joint project is funded by a DEWR Marine Species Recovery and Protection Grants program.