Sand tiger images were collected from multiple sources. SCUBA divers uploaded photos directly through the SAS website. The NCA routinely conducted outreach campaigns to local dive clubs, shops, and guides to raise awareness about this community science project. In peak visitor seasons (1–3 days per week depending on weather between Jun-Aug beginning in 2021), we engaged directly with divers to collect photos as they got off dive charter boats at two SCUBA diving charter operators near Morehead City, NC. Divers interacted with SAS technicians to download their photos. Technicians collected and uploaded all pertinent data and images to the SAS platform. Some divers also submitted images from their previous years of diving prior to SAS being launched. In addition to still photos, technicians downloaded video data with permission, typically from GoPro^® action cameras (GoPro, Inc., San Mateo, CA) from which still sand tiger images were extracted.

Sand tiger images for SAS were also extracted from video obtained from a remotely operated vehicle (ROV; Teledyne Benthos Stingray) footage collected from researchers conducting observations at shipwrecks Caribsea (16 Jul 2018), U-352 (07 Aug 2018), and W.E. Hutton (07 Aug 2018).

Finally, SAS images were retrieved from video recordings and still images taken at Frying Pan Tower ( Figure 1 ) as part of SharkCam, a live-streaming, publicly-viewable camera hosted and maintained by Explore.org (https://explore.org/livecams/frying-pan/shark-cam; visited 26 Feb 2024). The Frying Pan Tower structure (33°29′ N, 77°35′ W) is a privately-owned (https://fptower.org; visited 26 Feb 2024), decommissioned US Coast Guard Light Station located 51 km off Cape Fear, NC. Frying Pan Tower is situated above natural hard bottom habitat ( Figure 1 ; NC Division of Marine Fisheries, 2022) in approximately 17 m of water at the seaward edge of Frying Pan Shoals. Additional details about the camera and setting are found in Burge and Harris (2021) and Coleman and Burge (2021). Still images from SharkCam were collected from a gallery of snapshots submitted by viewers, by extracting them from recorded video files, and as screenshots taken in real-time while technicians watched the live feed.

All images were uploaded with metadata that included the submitter or SAS technician, image date of picture(s), and the location (typically at a known shipwreck). Each record of an individual shark on a given day at a specific location was considered an encounter. Each encounter submission received a unique alphanumeric identifier automatically generated by Wildbook^©, which remains with that encounter for its lifetime. Ancillary information about sex, relative size, environmental conditions, shark behavior, observed injuries, or other observations could also be entered for each encounter. Multiple images of a shark are included in a single encounter when images were taken from the same date and location. If multiple sharks were visible in a submitted photo, technicians copied the photo(s) and uploaded them as separate encounter(s), with notes added to each encounter to direct data managers to which shark is associated with each encounter.

Wildbook^© software was used by trained technicians to spot map the shark in each encounter. This software is used for photoidentification of terrestrial (Parham et al., 2018; Verschueren et al., 2023) and marine species (Blount et al., 2022, Weideman et al., 2020), including other elasmobranchs (Rohner et al., 2013; Norman et al., 2017). To spot map a shark’s photograph, the technician first rotated the photo to align the image horizontally ( Figure 2A ). Next, reference marks were placed on the image at the anterior insertion of the first and second dorsal fins, and the pelvic fin, as anatomical landmarks. Finally, between 3–30 additional marks were placed over discernable spots on the left or right flank of the shark. Images which did not contain the full body of the shark were usable if the three anatomical landmarks were visible. Once all spot marks were placed, the spot map was uploaded to Wildbook^© for comparison to all other spot maps in the SAS database. The spot map comparisons yielded a list of possible matches (typically between 5–50) from the existing database of all SAS encounters for the newly uploaded spot map ( Figure 2B ). Technicians then compared the new encounter to matching encounters to verify matches or establish a lack of match, in which case the encounter represented a new shark.

New encounters received a unique SAS alphanumeric identification sequence (SAS ID) following the convention of USA, plus L or R to designate side of the shark that was mapped, plus a sequential number; for example, USA-L0003 and USA-R0458. For encounters that returned matches with an existing shark in the database, a second technician confirmed that it was a match. Once confirmed, the new encounter was assigned the same SAS ID. Thus, a unique SAS ID may include multiple encounters with the same shark on different dates and possibly at different locations. These records are referred to as resighted sharks.

Some submitted images were not suitable for spot mapping due to a blurry or dark photo, spots being obscured by other fish, the shark having no discernable spots, or missing reference landmarks. For unusable images, the encounter was labeled as UNID and given a sequential numerical identifier (e.g., UNID-16). Data from these encounters were included in our analysis of temporal occupancy but were not useable to track movement of resighted individuals over time.

As each new encounter image was processed, technicians collected additional data and assigned a sex to the animal. Adult males were readily identifiable by the presence of fully calcified claspers extending from between the pelvic fins (Lucifora et al., 2002; Smale, 2002). Subadult males have smaller claspers ( Supplementary Figure 2 ) that do not project at all or only slightly beyond the pelvic fin, but, if visible, were also used for sex determination. A clear view of the cloacal area made assignment of female straightforward. If not, other features of the shark were used to assign a sex of female, including the absence of claspers on a shark that appeared to be above sub-adult size in length and girth. Younger, smaller sharks tend to be longer relative to body height (slimmer), while adults are stouter. In some photos, relative size could be estimated by comparison to other sharks or fishes present, human divers in the photo or shipwreck features. Using these clues about size, large sharks with no claspers visible were assigned as females. Additionally, presence of scars at the base of the pectoral fins consistent with wounds acquired during mating helped with assigning sharks as females ( Supplementary Figure 3 ). Finally, because females give live birth to young around 1 m in length, they become very rotund in late fall and winter months in later stages of gestation (Gilmore, 1993; Bansemer and Bennett, 2008; Wyffels et al., 2020). Sharks with prominently rounded abdomens consistent with pregnancy ( Supplementary Figure 4 ) were assigned as females. If there were no clear sex markers, then the sex of the shark was assigned as unknown.

Technicians also added informational keywords to encounters ( Table 1 ). An encounter may have no or several keywords. Primary keywords were used to maintain consistency in assignment, while secondary keywords further described what was observed. For example, a shark with a part of its caudal fin missing was assigned keywords of “fin damage” plus “caudal.” More detailed information about an encounter was sometimes recorded in a comment area by either the submitter or the technician. These comments were reviewed for keyword attribution as well.

The dataset was downloaded from the SAS website on 22 Jan 2022. We recognize the limitations of the Spot A Shark dataset with regards to statistical hypothesis testing because 1) as a community science project sampling was not standardized, 2) data were collected in multiple formats, and 3) sampling effort was not balanced spatially or temporally. Therefore, we limited our statistical analyses to descriptive metrics using SAS 9.4 or Microsoft Excel.

Counts and frequency tables were constructed for shark occurrence by site, region, month, year, and season and combinations thereof. Regional categories for sites and seasonal categories for dates were designated consistently with those reported by Marens (2021; Table 2 ; Supplementary Table 1 ). Seasons were set as Winter (Dec, Jan, Feb), Spring (Mar, Apr, May), Summer (Jun, Jul, Aug) and Fall (Sep, Oct, Nov), corresponding to the meteorological seasons for NC. We calculated counts and frequencies for the keywords listed in Table 1 .

For resighted sharks, we calculated the days at liberty (DAL) between all sightings. To calculate distances travelled between sites by resighted sharks, we compiled a matrix of coordinates for all sites (Comer and Love-Adrick, 2016; NOAA, 2022) and computed the distances in nautical miles (nm) between all possible combinations of sites using the formula:

where: Lat_place_1 = latitude of location 1, Lat_place_2 = Latitude of location 2, Lon_place_1 = longitude of location 1, Lon_place_2 = longitude of location 2 and PI() = pi

Distance calculations were converted to km using the formula:

Though sharks were photographed at 30 sites, 90% of images came from just 10 sites, with Frying Pan Tower accounting for 24% of all submissions ( Figures 3 , 4 ). The other most frequent locations were Spar (16%), Caribsea (15%), Aeolus (11%), W.E. Hutton (7%), and Atlas, Proteus, Dixie Arrow, Tarpon, and Hesperides (each 2–5%). The remainder of the sites had fewer than 25 shark encounters (range=1–24). For the shipwrecks where sand tigers were photographed, 14 were designated as northern, 10 central and 6 southern ( Table 3 ; Supplementary Table 1 ). Nearly 60% of encounters were from shipwrecks off the central coast, with 23% from southern and 17% from northern locations ( Figure 3 ).

Most sharks were encountered only once, but 101 sharks (5.5% resighted) were observed on more than one date. Of these, 74 were seen twice, 13 were seen 3 times, 8 were seen 4 times, 3 were seen 5 times, 1 was seen 8 times, and 2 were seen 14 times. DAL between sightings ranged from 1–2176 days (mean=171.5 ± 356.4 days; median=16 days). Typically, sharks were observed at the same location during a relatively short window for all encounters, but 28 were resighted at a different location from the previous encounter. The distance between sightings ranged from 0 (i.e., seen at the same location on different dates) to 213.2 km. For sharks observed at a different location in the subsequent encounter, the distance between sightings averaged 21.1 ± 48.2 km. Below, we detail resightings of selected sharks arranged by location where they were first encountered.

Over 1900 keywords were assigned to sharks during image processing ( Table 1 ). We observed 19 sharks (12 female, 7 unknown sex) with attached fishing gear. Of these, six were at Aeolus, three at Frying Pan Tower, two at Hyde and the rest distributed among eight other sites. Sharks with attached fishing gear were mostly photographed in summer and early fall months. For 17 of these sharks, fishing hooks and sometimes trailing line were visible. Hooks were in the jaw for all but one shark, which had the hook embedded in its head. One shark had a section of gillnet tangled in its teeth and one had a length of rope (estimated 1.5 m long) around its caudal peduncle.

External tags were observed on 28 females, seven males, and five unknown sex sharks. Most were photographed at Frying Pan Tower, Aeolus, Caribsea and W.E. Hutton. Most tag numbers could not be discerned because the tags were fouled, numbers were not visible, or the resolution was too poor. However, we were able to confirm USA-R0756 carried a tag numbered #399299 when encountered on 30 March 2021 at Aeolus. The tag was reported to the NOAA Cooperative Tagging Project, which confirmed this male shark measuring 155 cm fork length had been tagged in Delaware Bay on 12 August 2019. It was visually estimated by the SAS contributing diver to be 170 cm long.

Parasitic copepods ( Supplementary Figure 8 ) were observed attached to 25 female, 12 male and 9 unknown sex sharks, with most of those encounters submitted in Jun and Jul. Copepods were generally attached on the sharks’ heads, often around the nostrils and mouth. Most sharks with copepods attached were photographed at Caribsea (n=25), Spar (n=8) and Aeolus (n=4). It was not possible to determine the species of copepod from any images. We observed 30 sharks with hydroids on their teeth ( Supplementary Figure 9 ), of which 18 were female, 2 male and 10 unknown sex. Most of these were photographed at Caribsea (n=9), Spar (n=8) and Aeolus (n=6) in summer months.

Small claspers were noted for 41 male sharks. These were observed in encounters from all months except Feb, with the most reported in May (n=6) and Jun (n=8). Most of these sub-adult males were photographed at Frying Pan Tower (n=12), Spar (n=9) and Caribsea (n=9) with the remainder at the wrecks of Aeolus, Hyde, Atlas, W.E. Hutton and British Splendor.

Wounds or scars consistent with mating injuries ( Supplementary Figure 3 ) were observed on 121 female and 17 unknown sex sharks. Of these, 41% were photographed on Caribsea, 14% on Hesperides, and 9% on British Splendor. These wounds were most often reported in Jun (30%) and Jul (44%), though scars were visible on sharks in various stages of healing throughout the year.

We found 202 female sharks at 18 sites displaying morphology consistent with pregnancy ( Figure 7 ; Supplementary Figure 4 ). While 87% of these encounters were submissions from Jun–Dec, this keyword was assigned to sharks throughout the year. The two sites with the most females appearing pregnant are Frying Pan Tower and Spar, each with 41 encounters and collectively accounting for 41% of these observations. Other sites with possible pregnant females reported include Caribsea and Dixie Arrow, each with 20; Proteus and Aeolus, each with 18; Tarpon with 11; and the remaining sites, including all those from the northern region, which each had 1–6 reported.

Fin damage was observed on 119 females, 16 males and 24 unknown sharks ( Supplementary Figure 10 ). Of these, 25 were missing all or a portion of the fin. Most often damage was to pectoral (n=55), caudal (n=52) and dorsal (n=46) fins, with less damage to pelvic (n=16) or anal (n=2) fins. It was not possible to discern the etiologies of these injuries. More severe injuries were observed ranging from fresh wounds to healing injuries. Injuries included puncture wounds, and deeper cuts or gashes with incomplete healing or scarring ( Supplementary Figure 11 ). Such wounds were observed on 29 females (not assigned as mating injuries), 6 males and 6 unknown sex sharks. For these wounds, the location(s) of the injuries were recorded. Three of these injuries appeared to be consistent with rope damage. We found an additional 7 sharks with significant bite wounds ( Supplementary Figure 12 ). Two of these were females that also had some mating wounds at the base of the pectoral fin. Because scars and scratches could not always be differentiated, they were grouped. We observed 258 sharks (n=163 female, 36 male and 59 unknown sex) with scars or scratches visible. For these, the body location was assigned as head, body, caudal or any combination of these three areas ( Supplementary Figure 13 ). Many sharks (n=81) had scars or scratches only on their bodies, often on dorsal or lateral areas. Scratches on the head (n=45) were typically on the snout and top of the head. The most common combination of scratch or scar locations was the head and body (n=62), and 20 sharks had scars or sctatches present on all three body locations.

The SAS database of 1837 sand tigers reflects what has previously been reported for sand tiger distribution in NC waters. Since STS are federally protected from harvest (NMFS, 2009, 2017) anecdotal reports of captures in recreational and commercial fisheries are rare (Mcclellan Press et al., 2016; Kilfoil et al., 2017). A 27-year systematic longline survey in Virginia suggest sand tigers are a minor constituent of the total abundance of sharks with only 135 sand tigers caught among 4830 total individuals during 577 longline sets (Latour and Gartland, 2020). Similarly, sand tigers were rarely reported in a decades-old scientific survey of South Carolina waters with 2 of 297 sharks captured on bottom longlines during 74 sets (Low and Ulrich, 1984). The most comprehensive and recent information available on sand tiger populations in the NWA (Carlson et al., 2009) synthesized scientific catch data from 1974–2004, concluding that trends in abundance of sand tigers showed only modest declines between 0.2% and 6.2% and that there was not growth overfishing as would be expected for such a long-lived and very low productivity species. Despite these encouraging signs for abundance and demographics in this species the authors note that “exceptionally low productivity of sand tigers and the relatively low sample sizes on which we based our trend analyses” argued for a continued listing by NMFS as a species of special concern (Carlson et al., 2009).

We received submissions from locations coastwide in NC and throughout the year. Some sites are more heavily represented, such as the complex of wrecks in the central region that includes Aeolus, Spar, Caribsea and Atlas (n=958 of 2028 encounters), as these are frequently visited SCUBA destinations (Gerken, 2013). Because of the live camera at Frying Pan Tower, we have a high proportion of observations from that location as well. Collectively, our observations are consistent with Paxton et al. (2020a) who found up to four times as many sand tigers at artificial habitats compared to natural hard bottom or natural ledge habitats. Others also document sand tigers at artificial reef habitats in the northern and central NC coasts (Whitfield et al., 2011; Brown et al., 2020). Using acoustic telemetry, Marens (2021) reported extended sand tiger residency at Frying Pan Tower; multiple shipwreck sites including Caribsea, Proteus, Tarpon, Atlas, Papoose, Schurz; and multiple artificial reef sites (e.g., AR-285, 275, 255) that are not popular dive sites (Dottie Benjamin, pers. comm.).

Valuable information about the occurrence of sand tigers comes from anecdotal and photographic evidence from the dive community about the sites frequented by SCUBA divers where sand tigers are most consistently observed. Conducting field research on sharks often requires labor-intensive and expensive methods to deploy divers, angle specimens and launch telemetry equipment, resulting in relatively fewer locations surveyed, fewer sampling days and lower numbers of sharks documented overall compared to the nearly 1900 sharks in SAS. Thus, because of its crowd-sourcing approach, SAS provided a cost-effective and non-invasive research tool. Resighting sharks within and between years will continue to illuminate finer-scale patterns of behavior.

Despite the non-random sampling inherent to SAS, we can draw conclusions about which sites seem to be especially important. In the southern region, Frying Pan Tower has sand tigers year-round ( Figure 4 ), and it is the potential role it may be playing for females during winter that is of particular interest as detailed below. The complex of shipwrecks in the central region is occupied by sand tigers year-round. Likely due to accessibility for dive operators and consistently good visibility, shipwrecks in this region are highly represented in the SAS database. Unbalanced sampling makes it difficult to draw rigorous conclusions about which sites may be most important for sand tigers, but the resighting data from 101 sharks indicate sand tigers display site fidelity within and between years and residency to shipwrecks in this region. Most sharks were resighted at the same or a nearby location, typically within a relatively short time span, indicating some sand tigers may be residential at certain sites for days to weeks in a given year. However, a few sand tigers were observed at the same location with months or even years between sightings. Given the high proportion of sand tigers in the SAS database recorded at Frying Pan Tower (24%), it is noteworthy that, of the 37 resighted sharks first recorded there, none were ever photographed at any other NC locations. In contrast, 28 of the resighted sharks were observed at more than one location, averaging more than 20 km away and up to 2176 DAL, indicating that individuals move between sites within and across years.

We have the least data from the northern shipwrecks (n=329 of 2028), perhaps due to the many days when marine conditions preclude diving. While this makes it difficult to ascribe more importance to any one site in this region, Dixie Arrow, Tarpon and Proteus, are noteworthy as possibly being important seasonally as aggregation sites for females. Marens (2021) found overall lower average residency times for sand tigers in the northern region (2 days) compared to southern (4 days) and central (6 days) sites. Though no explanation for this is evident, it is possible that environmental, physiological, or social drivers of occupancy and movement patterns may differ between these coastal regions in NC.

Our data showed most resightings occurred at the same or nearby locations, confirming previous findings that sand tiger sharks show high levels of residency and site fidelity to specific NC artificial reef sites (Paxton et al., 2019; Marens, 2021). This was especially evident at Frying Pan Tower where all the sharks first encountered there were resighted only there, including female USA-0272 who was seen there on 14 dates in 3 years. At several other locations, sharks were often resighted at the same site on sequential days or weeks and were also shown to return to the same site after presumably migrating out of NC waters for months or even years. Given the proximity of Aeolus and Spar and the high number of sharks resighted between those two sites, this area could be functionally perceived by the sharks as a single site as illustrated by many resighted sharks moving frequently between these two locations.

Our findings are consistent with telemetry data from Marens (2021) showing Atlas, Caribsea, Aeolus, and Papoose in the central region had the longest residency of male as well as immature and pregnant female sand tiger sharks (ranging from hours to 75+ days) compared to the other two regions. Coleman and Burge (2021) quantified frequency of sand tiger shark occurrence at Frying Pan Tower in more than 1000 video clips from Nov 2014–Jan 2019, reliably finding them every year fall through winter.

SAS data suggest sand tiger occupancy patterns show differential use of sites based upon season. This was true of Dixie Arrow and Tarpon where female occupancy was highest in summer, while at Proteus it was highest in fall. Interestingly, the occupancy patterns of sharks at Frying Pan Tower appear to be shifting. Prior to 2020, high numbers of sand tigers appeared in Oct, remained abundant through the winter, and left in April, with summer months having few or no records. In the last three years, live camera data suggest sand tigers are increasingly abundant year-round, though winter residency remains the time of peak abundance (E. Burge and A. McClanahan, unpublished data).

SAS has the most shark encounters in summer months. Consistent with generalized migratory patterns for this species driven by reproductive cycles, we begin to see higher numbers of shark encounters in spring and through summer. This is also the time of year when mixed groups of sand tigers are known to be migrating to and inhabiting summer grounds further north (Haulsee et al., 2018). Marens (2021) noted variability in movement of females in summer with some going north, while 7 were never observed outside of NC during her 3-year study. It is unknown if the sharks observed in NC in summer months are migratory, residential or a combination of these, and more research into their movement ecology during this period is needed. Because SCUBA divers who are SAS submitters are more active in summer months, our data cannot be relied upon to provide unbiased detection, and a more rigorous sampling protocol to investigate this is required.

Overall, we see about four times as many females as males in the SAS dataset, with nearly a third of the sharks’ sex not assignable. There is not a clear explanation for the unbalanced sex ratio, as we can find no published accounts that the population as a whole demonstrates a skewed sex ratio. Except for the two locations noted previously, sharks of both sexes were encountered at all locations. However, there is some indication that males and females may be utilizing habitats differently and at times may be sexually segregated. For example, at Atlas, Proteus, Tarpon and Dixie Arrow, females far outnumbered males. In contrast, other sites had male to female ratios more consistent with that of the SAS database, including Spar, Aeolus and W.E. Hutton. Studies in other populations have also found skewed sex ratios for this species during portions of the year, attributing this to sexual differences in movement patterns and differences in habitat requirements between juveniles and adults (Parker and Bucher, 2000; Lucifora et al., 2002; Smale, 2002; Lynch et al., 2013; Klein et al., 2019). Frying Pan Tower was one site were a higher proportion of males, including sub-adult males, were present contemporaneously with females, including in winter months. This was a different dynamic from any other location both in terms of timing of peak abundances in winter and sex ratios closer to parity.

Differences in female and male SAS encounter numbers could be attributed to males, especially adults, being more transient once mating season has passed. This is supported by most male encounters being in spring and summer months. If this is the case, then males may be more likely to be moving between shipwrecks and artificial reef sites and may display shorter residency times, thus having overall lower probability of being encountered by divers. Similar disparity in male versus female residency times, though not occupancy, which was similar, was found by Marens (2021) particularly in the central region. Those data also demonstrated that males that had migrated to NC waters after being fitted with acoustic telemetry tags in Delaware were absent in summer, unlike females that showed greater variability in summer residency patterns (Marens, 2021).

The number of female sharks exhibiting mating scars indicate mating takes place in NC after males and females arrived following winter migrations. Given that females with healed mating scars continued to be observed through summer and fall, it appears at least a portion of pregnant females are remaining in NC waters for all or part of gestation. Some female sharks overwintered at Frying Pan Tower and many females observed there and elsewhere in winter appeared to be pregnant. Two videos from Frying Pan Tower (Erin Burge/Explore.org; 9 Sep 2021 https://www.youtube.com/watch?v=sZr3Jk45hF0, 11 Mar 2021 https://www.youtube.com/watch?v=tg6i79iZVgI) and one from Aeolus (12 Oct 2021; Ethan Simmons; https://youtu.be/E2_KmZb256I) show seemingly pregnant females with distinctive movement inside their abdomens likely to be live gestating pups. While this cannot be confirmed with photographic data alone, it is consistent with ultrasonography that confirmed 21 ovulatory and gravid females in NC between Jun-Jan (Marens, 2021; Wyffels et al., 2022; James Sulikowski, pers. comm.). Two of these sharks were part of Marens (2021) telemetry study and displayed extended winter residency at Frying Pan Tower before moving north in spring, presumably after parturition. SAS data suggest other locations that possibly serve as gestation aggregation sites in winter months included Spar, Aeolus, Schurz, and Tarpon, in the central region, and Proteus in the northern region. Marens (2021) similarly found pregnant tagged females off all regions of NC during winter months. This reproductive philopatry and aggregatory behavior of pregnant females is consistent with observations for this species in Australia (Bansemer and Bennett, 2009; Barker and Williamson, 2010; Lynch et al., 2013), South Africa (Smale, 2002; Dicken et al., 2007) and South America (Lucifora et al., 2002, 2009).

Mating and birth have not been observed in situ for this species in NC, and exact timing and location of these events remains unknown. SAS encounters of females both with mating scars and appearing pregnant are reported over spans of several months. Marens (2021) reported fresh mating scars were evident on females as late as early Aug. An extended mating timespan from Mar-Jun was described (Gilmore et al., 1983; Gilmore, 1993) as it may be occurring over a wide geographic range from NC to Florida. Although sand tigers are not thought to store sperm (Gilmore et al., 1983; Gilmore, 1993; Wyffels et al., 2022), one study did find they exhibit both behavioral and genetic polyandry in South Africa (Chapman et al., 2013). Females are investing significant energetic resources to produce only one or two offspring each reproductive cycle. If females in NWA are copulating with multiple males to enhance offspring fitness, they may be extending individual mating windows to increase the likelihood of encountering fit males. Gestation lasts between 9-12 months and may be determined by water temperature for this species (Bennett and Bansemer, 2004; Tokunaga et al., 2022). Dispersal of pregnant females along the NC coast in varying depths likely means they may be experiencing a range of winter temperature regimes. Thus, mating, gestation and parturition may be occurring over protracted and overlapping periods of time, rather than in tight synchrony. While these reproductive life history events may not all be taking place in NC for all sand tigers in the NWA population, SAS data reflects the importance of this area of the SEUS for this shark, particularly for mature females.

Based upon their size at encounter, USA-0128 and USA-L0817 were likely young of year (YOY) sharks, suggesting parturition may be occurring in NC waters. We have additional photographs not useable for SAS and anecdotes from divers of very small sand tigers, less than 1.2 m in length (the maximum size at birth for sand tigers (Gilmore, 1993; Gilmore et al., 2005) that support this possibility (C. Price, unpublished data). The exact locations of NWA pupping grounds have not been established for sand tigers. Our data contain no records of possible YOY sand tigers at Frying Pan Tower (E. Burge, unpublished data), nor have we observed small sharks there to suggest pupping is occurring at or near this location, despite its importance for overwintering pregnant females. One possibility is that females give birth closer inshore at natural hard bottom sites. This habitat type is widespread, but highly patchy, in NC (NCDEQ, 2016; Steward et al., 2022), not often frequented by dive charter operators, and often exhibits highly turbid conditions not conducive to underwater photography. In Australia, females do not give birth in estuaries, but are believed to prefer rocky reef habitats on the coast (Bennett and Bansemer, 2004). In South Africa, pupping grounds are also thought to be nearshore (Smale, 2002; Dicken et al., 2007).