FINAL REpORT
NMFS contract number: WC133F-02-SE-0247
ABUNDANCE, MOVEMENT AND HABITAT USE OF THE
SMALLTOOTHSA~SH
Colin Simpfendorfer Senior Scientist Center for Shark Research
MOTE MARINE LABORATORY TECHNICAL REpORT NUMBER 929.
MARINE LABORATORY Background Sawfish are a group of distinct elasmobranchs (the sharks, skates and rays) characterized by their elongate, toothed "saw". Worldwide sawfish populations have been severely depleted by overfishing, entanglement in nets and habitat degradation. In the USA the smalltooth sawfish (Pristis pectinata) was once a very common inhabitant of estuarine and inshore waters of the Gulf of Mexico and southern Atlantic coast. Today, however, the population has been decimated and they regularly occur only in southwest Florida (Figure 1). The decline of smalltooth sawfish has led to their designation in the "Red List of Threatened Animal Species" published by the World Conservation Union (mCN) as Critically Endangered, and the National Marine Fisheries Service (NMFS) listed this species as Endangered under the US Endangered Species Acts in April 2003. Sawfish have been protected in Florida waters since 1992.
Figure 1: Sighting locations of small tooth sawfish in Florida waters. Data from the Mote Marine Laboratory's Sawfish Sightings Database.
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Conservation efforts for the smalltooth sawfish are being hampered by the lack of information on their current distribution, life history, critical habitats, movement patterns and genetic diversity. In response to the need for this information Mote Marine Laboratory's Center for Shark Research commenced an applied research program to collate historic data, undertake surveys of areas where sawfish are known to remain, conduct tracking studies to understand sawfish movement patterns and habitat utilization, collect information from the public on sawfish sightings, identify priority conservation areas, and determine genetic diversity of sawfish following the population decline. This information will be used to make recommendations about the most appropriate conservation strategies for smaIltooth sawfish.
Purpose The purpose of this research project was to begin to address the lack of scientific data available on smalltooth sawfish by:
• investigating their distribution and abundance in southwest Florida, and • studying their movement and habitat use patterns
Methods
Fishing surveys
Fishing surveys were used to investigate the relative abundance of sawfish, and to provide access to animals for telemetry studies (acoustic and satellite). Fishing was normally carried out with a longline, but at times a gill net, seine net or rod and reel were also used. The mainline of the longline was constructed of 800 m of 3/16th inch braided nylon rope. Gangions were constructed of 1 m of braided nylon, 1 m of stainless steel cable and a circle hook. Four sizes of hook were used (16/0, 14/0, 12/0 and 9/0 Mustad tuna circle hooks) depending on the size of the sawfish targeted. Gangions were clipped to the mainline at intervals of approximately 10 m, and floats attached every 200 m. The line was anchored at either end and marked with floats. Hooks were normally baited with frozen mullet unless fresh jacks, ladyfish or barracuda were available. The longline was set for periods from 1 to 2 hours (typically 1.5 hours).
A beach seine and gillnet were used to capture small sawfish « 1.2 m) that it was difficult to capture on longline. The seine net was 200 feet long and constructed of 2 inch stretched mesh multi-filament nylon. The seine was hauled on shallow banks and sandbars. The gillnet had a modular design, with each section 20 feet in length. Sections could be joined together to make a net up to 200 feet long. The net was constructed of monofilament nylon with a mesh size of 3 inches. It was weighted to be bottom set. The gillnet was set for short periods «1 hour) and regularly checked to avoid the mortality of any animals.
Rod and reel fishing was employed to capture sawfish of all sizes, although it was mo t successful at capturing mid-sized animals (140 to 200 cm). This type of fishing was often used while waiting for longlines to soak, or when working with fishing guides. Rods were normally rigged with 40lb monofilament, a steel leader and a 9/0 circle hook. Where possible fresh jack, ladyfish or barracuda were used as bait. For targeting very small sawfish, live or frozen shrimp were often used.
A series of physical and biological parameters were recorded at each sampling location. These parameters included, water temperature, salinity, oxygen level, secchi depth (turbidity) bottom type, depth, tidal flow and direction, adjacent habitat types (e.g. mangroves, seagrass, oyster reefs, etc), weather conditions, sea state, wind strength and direction, and cloud cover.
A series of four sites were fished using longlines for the section on relative abundance - Outer Keys (June 2003), banks of outer Florida Bay (March 2003), northeast Florida Bay (April/May 2003) and Highland Beach (July, 2003). Each location was fished for a week, with multiple longline sets each day. The locations of sets in each of these locations are shown in Figure 2. A combined total of 72 sets were undertaken in all four areas. In addition to the longline abundance surveys, a wide range of other locations were fished with a variety of gear types. A total of 306 sets (231 longline, 9 gillnet, 22 rod and reel and 4 seine net) were made during the grant period (Figure 3).
Figure 2: Sampling locations (gold triangles) for relative abundance of smalltooth sawfish at each of four sites in southern Florida.
Highland Beach
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1i } - ; .. Outer - .. Northeast Florida .., .' . Florida ,P Bay Figure 3: Locations of all smalltooth sawfish sampling events during the grant period, including those for relative abundance.
Sawfish measurement and tagging Captured sawfish were secured to the boat to avoid damage by the hook. Large sawfish had ropes tied around the saw, mid-section and tail. Smaller animals were scooped into a large landing net. Whenever possible, sawfish had five length measurements taken (Figure 4). Large sawfish were measured with a flexible fiberglass tape measure, while smaller animals were measured on a fish measuring board. Measurements were made to the nearest 0.5 cm. The weight of small individuals was determined by placing the sawfish in a mesh bag and suspended below a spring balance. Weight was determined?t:o the nearest 0.1 kg. The sex of sawfish was determined by examining all individuals for male intromittent organs (claspers) on the pelvic fins. Small individuals had to be carefully examined as the claspers are small and can be easily missed. Figure 4: Measurements taken on captured sawfish. An additional measurement (stretched total length, STL) was the measure from the tip of the saw to the tip of the tail, with the tail extended to its maximum amount.
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All sawfish were fitted with individually numbered external identification tags. Two types of tags were regularly used: nylon headed dart tags and rototags. Dart tags were inserted at the base of the first dorsal fin, making sure that the nylon barb passed between the cartilaginous rays supporting the fin. Rototags were attached to the first or seconds dorsal fin by first making a small hole in the fin with a leather hole punch and then clipping the two halves of the tag together through the hole in the fin. In addition to external identification tags, most sawfish were given an intra-muscular passive-integrated transponder (PIT) tag. These tags are very small (12 mm x 1.5 mm) and are uniquely coded. The tags were injected into the muscle at the base of the first dorsal fin using a syringe applicator. The tags send a code when they receive a signal at the correct frequency. The tags code is received and decoded using a PIT tag reader. These tags have the advantage of having an indefinite life and extremely low shedding rates, making the animal identifiable for its entire life.
Most sawfish were also fitted with an acoustic tag to allow their movements to be followed. The tags applied were Vemco V8 or V16 individually coded tags that emitted a pulse-stream at 50 kHz. The tags were attached to the dorsal fin of sawfish by first attaching the tag to a rototag, and then applying the tag to the sawfish's first or second dorsal fin. The acoustic signal was located using a receiver (Vemco VR60) with a directional hydrophone. The location of the animal, relative to the tracking vessel, was determined from the direction of the signal and the signal strength. The location of the animal was determined at 15 minute intervals unless it was moving, and then positionsR, were estimated every 5 minutes. Sawfish were tracked for as long as practical, and in most situations were re-acquired over several days to produce longer tracks and compare habitat use between days.
A small number (4) of larger sawfish were also fitted with pop-up archival transmitting (PAT) tags manufactured by Wildlife Computers. The tag is approximately seven inches long, one inch in diameter, and has six inch antenna. These tags store light level, depth and temperature data, and at a preprogrammed date and time release from the animal. After release the tag floats to the surface and transmits summaries of the stored data to the ARGOS system aboard polar-orbiting environmental satellites. The PAT tags were attached either to the dorsal fin using a rototag-type of system, or at the base of the dorsal fin with a nylon dart (similar, but larger than, the nylon headed dart tags).
Analysis of acoustic tracking data Acoustic tracking data were analyzed using the Animal Movement extension for ArcView 3.3. Sawfish tracks were plotted on satellite images rather than digitized maps as they produced more accurate and detailed information about the habitats in which these animals occur. Home ranges were calculated using minimum convex polygon (MCP) analysis. MCPs were calculated for individual animals for all tracking periods combined, and for individual days. Areas of the MCPs were calculated in ArcView.
Analysis of PA T tag data Data from PAT tags was delivered via email from ARGOS. The ARGOS data were initially analyzed using the PATDECODER program supplied by Wildlife Computers. This program produces position estimates using the light level data using standard light based geolocation algorithms. Movement plots based on geolocation were plotted in Arcview. Locational information produced from light-based methods is relatively inaccurate, with most estimates having error estimates from 0.5 to 1.0 degrees. Depth and temperature summary information was obtained in histogram form, and was analyzed by calculating daily weighted mean values. These mean values were then used to create time-series plots.
Sawfish reporting database To gather data on the distribution and abundance of sawfish throughout Florida a sawfish reporting database is maintained. Information is gathered from the public regarding sightings or captures of sawfish. The database is publicized via posters, a web site, reporting kits for fishing guides, press releases and articles in fishing and diving publications. Outreach trips funded by the Florida Fish and Wildlife Conservation - Commission are undertaken to all regions of the state every six months to ensure that an even coverage of publicity is achieved. The data gathered on each report includes location, date, time, size, habitat, activity at time of sighting, etc. The data are validated using a variety of methods (photographs, video, directed questions) to eliminate mis identified animals and then entered into an Access database. A variety of analyses are performed on the data, including calculating the density of sightings in 10 km square grids using ArcView Spatial Analyst.
Research results
Sawfish capture summary Seven juvenile and two adult small tooth sawfish were captured during the study period (Table 1). All of the sawfish were fitted with acoustic or satellite pop-up tags and tracked for periods from 1.5 hours to 3 months. Most animals were tracked on more than one occasion. The maximum time of continuous tracking was 24 hours. th Table 1: Details of smalltooth sawfish caught between July 1s r, 2002, and May 25 , 2003.
Date Location STL Weigh Sex ID tags Electronic Gear (cm) t (kg) tag 711712002 Caloosahatchee 153 F Rototag Acoustic Longline River 11111/2002 Ponce de Leon 355 F Rototag PAT Longline Bay 11123/2002 Mouth of Shark 81.5 1.1 M Rototag Acoustic Seine River 2/1712003 Coot Bay 148 7.1 M Rototag Acoustic Longline 311512003 Florida Bay 390 M Rototag PAT Longline 311712003 Coot Bay 153 F Rototag Acoustic Rod and Reel 4115/2003 Hurddles Creek 89 1.5 M Rototag Acoustic Gillnet 7/16/2003 Highland 121 F Rototag Acoustic Gillnet Beach 7118/2003 Mouth of 157 F Rototag PAT Rod and Lostmans River reel
Distribution and abundance of smalltooth sawfish in Florida
Reporting database The Mote Marine Laboratory Sawfish Reporting Database contains several hundred records collected over several years. The peak months for sawfish sightings are March through June (Figure 5). This is likely to represent, at least in part, seasonal effort in recreational fishing activity within the nearshore environment. However, it may also reflect the period when sawfish as a group are closest to shore.
The size frequency distribution of reported sawfish includes all size class within the population, with most being less than 300 cm in length (Figure 6). This broad range of sizes, and also the shape of the distribution - with the largest numbers at the smallest size - suggest that the sawfish population is successfully reproducing, and that there are n The sightings density of sawfish (Figure 7) shows five hotspots of sawfish sightings Marquesas Keys, the Cape Sable region of the Everglades coast, the central Everglades Coast (around Highland Beach), the Ten Thousand Islands and the mouth of the Caloosahatchee River. In addition, reports of sawfish occur continuously between Naples and Florida Bay, but are patchy beyond this central range. North of Naples reports are focused at the mouths of major rivers (Caloosahatchee, Peace, Myakka, Hillsborough and Suwannee). South of the central continuous range reports occur regularly along the Florida Keys, and appear to reach their peak abundance in the outer Keys. Along the east coast there are far fewer sightings than on the west coast, and these are mostly larger animals occurring along beaches and at offshore reefs. These observations are based on sightings densities that have not been corrected for sightings effort, and so may be biased by the amount of fishing effort. The most northerly sightings of sawfish that have been made recently (since 2000) represent the current known extremes of the population in US waters. On the east coast the most northerly sighting was made in 2002 by a Shark Longline Fishery Observer on a vessel offshore from northern Georgia in approximately 180 feet of water. In the Gulf of Mexico, the most northerly sighting was made by a researcher from Florida State University who observed a small animal at St. George Island on the Florida Panhandle. Figure 5: Number of sightings by month. Data from the Mote Marine Laboratory sawfish sightings database. Figure 6: Size frequency distribution of smalltooth sawfish reported to the Mote Marine Laboratory sawfish sightings database. 60 50 [ c~ 40 ~ 30 ~ 20 ~ 10 0 C:l C:lC:l r::P !:)C:l !:)C:l !:)C:l !:)C:l C:lC:l '" I't ~ l>l 'J co "\ Estimated length (em) Figure 7: Sightings density of smalltooth sawfish in Florida waters, January 1998 to October 2003. Data from the Mote Marine Laboratory Sawfish Reporting Database. 50 m 100 m Sig hting s de nSity (n umbe r pe r DO 00.001 - 0.04 0.041 - 0.09 0.091 - 0.1 0.101 - 0.14 0.141 - 0.19 0.191 - 0.22 _ 0.221 - 0.26 _ 0.261- 0.3 Abundance surveys Only one sawfish was caught during abundance surveys. This was mature male caught in Florida Bay in March 2003. Continued sampling of these four locations over time should build up a picture of sawfish relative abundance, however, a single year's data (2003) provides only limited information. Ongoing sampling of these areas will depend on continued funding. Conclusions Data from the Sawfish Reporting Database indicate that the current distribution of smalltooth sawfish extends from the central Florida Panhandle to northern Georgia. However, the main part of the range is from Naples to Florida Bay, with abundance reducing the further you move away from this central area. Along the west coast of Florida the sightings are concentrated around the mouths of rivers, consistent with observations of estuarine habitats being important, especially for juveniles. On the east coast of Florida, abundance appears to be lower than on the west coast, and is mainly larger animals spread along the beaches and offshore reefs. Movements and habitat use Acoustic telemetry Nine sawfish were captured during the grant period and five of these were tracked using acoustic tags for periods from a few hours to several days. The results of each of these tracks are given below in detail because each provides a unique insight into the movement and habitat use patterns. All were juvenile animals. Caloosahatchee River th A 153 cm STL smalltooth sawfish was captured on July 17 , 2002, at Palmetto Point on the Caloosahatchee River. It was fitted with an acoustic tag and released. It was not immediately tracked due to the presence of a severe thunderstorm. However, it was relocated two days later, 1.5 km downstream in the St Andrew's Marina, and tracked for 24 hours. This animal was subsequently relocated and tracked on three other occasions between July and September. This animal was always relocated within the same 1.5 km stretch of the southern shore of the Caloosahatchee River (Figure 8), indicating that it had a high level of site fidelity over this period. The home range size, based on all positions over the two months it was 2 tracked, was 1.2 km . Home range sizes for individual tracking days were much smaller, 2 2 ranging from 0.036 km to 0.35 km . This indicates that its daily activity space is relatively small, but that it moved within a larger, but still restricted, area over the longer period. The majority of the time that the animal was tracked it was located in a strip of shallower water « 1 m ) along the south shore of the river. In this habitat the sawfish spent most of its time lying motionless on the bottom, or swimming slowly for short distances (50 - 100 m). The only tracking event where it was outside ofthe shallow th nearshore habitat for any length of time was on September 20 , when it was tracked swimming in deeper water just north of the shallow habitat. During the time it was moving continually and covered a relatively large area. This change in behavior may have been a result of the sawfish hunting for food, or not wanting to lie on the bottom in an area where larger predators (e.g. bull sharks) may be a threat. ~ The Caloosahatchee River is a highly modified environment, with development (canals, marinas, docks, dredged channels, etc.) along most of the south bank where this sawfish occurred. During the tracking events, the sawfish spent much of its time closely associated with man-made features, including canal mouths, docks and inside a marina. Thus it appears that although the river habitat has been modified, sawfish are still able to occupy it. However, it is not known if the modifications change the carrying capacity of the river, and so present a limitation to the population. Figure 8: Track of a 153 cm STL smalltooth sawfish in the Caloosahatchee River. Different colored dots indicate tracks from separate days. Almost all of the time, except for September 20th (olive green dots), was spent in the shallow waters on the south side of the river (the pale blue strip). 200 0 200 400 Meters P""""'I Shark River A small smalltooth sawfish was sighted on November the 11 th, 2002, during a longline set on which a larger sawfish was captured. This small animal could not be captured at the time. The same location was visited two weeks later with a seine net, and the sawfish was still located on the same bank on which it was originally sighted. The sawfish was 81.5 cm STL and was fitted with an acoustic tag and released onto the same shallow bank (Figure 9). After release the animal was tracked for 3.5 hours (Figure 10). During thi& period it remained within 2 m of the waters edge along a shallow mud bank in depths less than 50 cm. The mud bank extended approximately 150 m along the edge of a mangrove island and the sawfish swam slowly along the bank, or lay motionless on the bottom. The sawfish could be visually observed at times, and this was used to confirm the tracking data. After 3.5 hours of tracking, with the tide rising, this sawfish swam up a narrow mangrove creek (Figure 9) that drained the mangrove forest on the island. The following day the animal was reacquired at low tide on the same mud bank and tracked until it again swam up the narrow mangrove creek. This time a canoe was employed to continue tracking the sawfish as it swam up the creek. It was relocated inside the creek and spent most if it's time as far up the creek as possible, resting for most of the high tide among mangrove roots. As the tide dropped it swam out of the creek and resumed its use of the margin of the mud bank. This pattern was observed over several more tidal cycles, and occurred both during the day and at night. It is hypothesized that the use of the mangrove creek at high tide reduced the risk of predation from larger sharks that are common in this area. Figure 9: Habitats used by an 81.5 cm STL smalltooth sawfish at the mouth of the Shark River. The shallow bank adjacent to the mangrove island (left) was used at lower tidal levels, while the mangrove drainage creek (right) was used at higher tidal levels. Figure 10: Track of 81.5 cm STL smalltooth sawfish at the mouth of the Shark River. The animal was tracked over several consecutive days and was always found on the shallow bank (yellow dots) or in the same mangrove drainage creek (green dots). The locations within the mangrove forest were based on visual navigation and not GPS fixes as the canopy obscured the signal from the satellites. 60 0 60 120 180 240 Meters M Coot Bay (2 animals) Two sawfish, both approximately 150 cm STL were captured and tracked in Coot Bay (near Flamingo in the Everglades National Park). The first was captured using a longline th on February 17 , 2003. This animal was tracked following release, and on the following two days. During this whole time the animal remained closely associated with the mangroves that line the entire bay (Figure 11). It also remained within a 1000 m stretch 2 of the shore (Figure 12). The home ran~e based on all tracking data was 0.081 km , but on individual days was 0.035 - 0.04 km . The close association between the sawfish and the mangroves may be to reduce the risk of predation from bull sharks that also occur in the Bay. Figure 9: Habitat in the area where the sawfish were tracked in Coot Bay (left). The sawfish normally remained within a ten meters of the mangroves which overhang several meters from the shore (right). Figure 10: Track of two juvenile smalltooth sawfish in Coot Bay, a 148 cm STL male (yellow points), and a 153 cm STL female (green points). The 148 cm STL animal was tracked over several consecutive days. The 153 cm STL individual was captured on one day, tracked the next for a short period before it was lost in thick weed that occurs in the section of the bay where it resided. {i'. 400 0 400 800 Meters ~iiiiiiiiiiil!!!!!!!!'!!!!!!!ll"llliiiiiiiiiiiiiiiiiiiiii th The second sawfish tracked in Coot Bay was caught on March 17 , 2003. This animal was captured by rod and reel, with a live shrimp bait. This animal was not tracked after release due to the presence of a severe thunderstorm. However, it was relocated and tracked for 1.5 hours the next day (Figure 12). The short track was the result of dense weed present in the section of the bay in which the sawfish was relocated. This weed prevented vessel access and also muted the acoustic signal. Further attempts to relocate this fish were not made. Hurddles Creek An 89 em STL sawfish was captured in a gillnet on a mud bank on Hurddles Creek on th April 15 , 2003. This animal was fitted with a small acoustic tag and tracked following release, and on the subsequent two days (Figure 11). This animal showed movements associated with the tide. At low tide the animal moved southeast along the mud bank away from a mangrove island; while at high tide the animal moved into the vicinity of the mangrove island. This pattern was repeated over the entire tracking period, with the same areas being used each day. By maintaining this rhythm the sawfish was able to remain in the shallowest water « 30 em). At times at low tide this animal could not be relocated, suggesting that the acoustic signal is attenuated rapidly by the muddy substrate and seagrass, or that it is refuging in the mangroves that fringe the creek. Figure 11: Habitats used by an 88 em STL smalltooth sawfish in Hurddles Creek. The animal was tracked on three days (different colored points indicate locations from separate days). .". 100 o 100 200 Mete rs ---- Home range analysis Home range size was variable between individual juvenile sawfish and also between days for the same sawfish (Table 2). For all daily tracking events there was no significant correlation between the length of tracking time and home range (Figure 14a.). However, two tracks can be excluded, one because it was based on a very short track (1.5 hours total time), and one because the behavior was very different (continuously swimming animal in Caloosahatchee River). Once these points are excluded, there is a significant curvilinear relationship between tracking duration and home range (Figure 14b.). However, there were two size classes of juveniles tracked. For the smallest juveniles « 90 cm STL) there was no correlation (R2 =0.02, Figure 14c), but for large juveniles (approximately 150 cm STL) there was a very strong correlation (R2 =0.93, Figure 14d.). These results indicate that small animals are re-using the same habitat on a short cycle (possibly tidal), and do not move far from their core areas. Larger juveniles, however, appear to be more mobile and have a larger overall home range that they move through over extended periods. Table 2: Homes range size (Minimum convex polygon) of juvenile smalltooth sawfish. Length Track time MCP Perimeter 2 Location (cm STL) Period (hours) (m ) (m) Caloosahatchee 153 All 1220717 5754 River 153 July 19th 24 107384 1327 153 July 28th 7 35939 919 153 July 29th 0.7 907 155 153 Aug 8th 6.75 6975 378 153 Sept 20th 4 353187 2940 Shark River 81 All 8198 423 81 Nov 23rd 3.5 1460 320 81 Nov 24th 12.5 6760 404 81 Nov 25th 533 177 Coot Bay 153 All 1.5 121773 1693 Coot Bay 148 All 81662 2119 148 Feb 17th 668 241 148 Feb 18th 9.5 39444 1233 R. 148 Feb 19th 8 35338 1746 Hurddles Creek 89 All 10175 421 89 April 15th 2 1233 185 89 April 16th 4 5998 318 89 April 17th 2.5 7671 386 Figure 14: Home range of juvenile smalltooth sawfish as a function of track duration. Pop-up satellite telemetry Only one of the four Pat tags deployed on sawfish during the grant period successfully transmitted data. This animal was a 157 cm juvenile sawfish that carried the tag for approximately a week before it prematurely released from the animal. The data returned for this time period showed that this animal remained in water less than 2 m deep for the entire week, and that it remained at about the same location that it was released in. The failure of the other tags to provide data represents a setback to this research. One of the tags did transmit a signal after popping up, but neither location or data were obtained. Reporting database To date the analysis of the reporting database for habitat use information has been limited to examining the relationship between depth and size of individuals (Figure 15). There was a significant relationship between sawfish length and the sightings depth. Small animals «200 cm) were almost exclusively found in water less than 5 m deep, and most often in water less than 1 m deep. Sawfish larger than 200 cm were sighted in a much greater range of water depths, including depths as great as 70 m. The data in Figure 15 suggests that there is a change in behavior of sawfish when they reach approximately 200 cm, moving out of very shallow habitats and ranging over a much broader depth range. Figure 15: Relationship between sawfish length and sighting depth for smalltooth sawfish based on data from the Mote Marine Laboratory Sawfish Reporting Database. 80 70 • • y = 0.0297x - 2.4076 60 R2 = 0.1345 50 • :§: • :: 40 • Co cQ) 30 • • • • 20 • • • •• • 10 • • • - • • - ... :• · .. ... ~ ~ • • ...... ,f f •• • :...... - .* 0 . ... . ~ . : • 0 100 200 300 400 500 600 Total length (em) Conclusions This research collected a substantial amount of information on the habitat use of juvenile smalltooth sawfish. A number of consistent observations were made in almost all of the animals that were acoustically tracked. Firstly, juvenile sawfish show a high level of site fidelity. This is particularly apparent in small juveniles that utilize the same habitats on a continuous basis, at least over several days and possibly over weeks at a time. Changes in distribution of small juveniles over time are driven by tidal fluctuation. In larger juveniles their home range appears larger, and they move within this range over a period of days or weeks, rather than having repeated movements over the same habitat on a daily basis. The second consistent observation is that juvenile sawfish have a strong preference for very shallow habitats. In almost all individuals tracked they remained in the shallowest habitat possible. Again, this was most apparent in the smaller juveniles that tended to stay associated with water less than 50 cm deep. In one situation this selection of very shallow habitat resulted in the repeated use of a small mangrove creek at high tide as the shallow bank used at low tide was covered by up to 1 m of water. In areas where very shallow habitats are not available juvenile sawfish remained very close to the mangrove root habitats. This preference for very shallow or mangrove root habitats is most likely a strategy to minimize predation risk. Juvenile sawfish are relatively weak swimmers, and occur in areas in which larger sharks (especially bull and lemon sharks) occur frequently. These sharks are very capable of consuming a small sawfish. In fact, one juvenile sawfish caught in Coot Bay had a relatively fresh shark bite on its back, indicating that although they may employ strategies for predator avoidance it is not a perfect solution. Limited data was collected on the winter habitat use patterns of adult sawfish. Although four sawfish were released with PAT tags attached, only one functioned correctly, and it was only attached to the sawfish for approximately one week. The failure of PAT tags to consistently provide data in studies on elasmobranchs is a common occurrence. There are many reasons for this potential failure, including fouling of the tag so that it could not surface or detach, tag failure, occurrence in low salinity areas at the time of programmed detachment and premature release. Further work to improve P AT tag performance on elasmobranchs is continuing. The data collected in this study have provided important information on the habitat use of juvenile sawfish. This information is of vital importance to the development of a spec'i:es recovery plan for this newly endangered species. The data will be used to start identifying critical habitat areas for smalltooth sawfish.