Estimating population parameters of broadnose sevengill sharks (Notorynchus cepedianus) using photo identification capture-recapture

The broadnose sevengill shark (Notorynchus cepedianus) is a common high trophic-level predator around coastal New Zealand. Data on the ecology of the species in New Zealand are severely lacking, and anthropogenic impacts are unquantified. To partially address this, the authors undertook a study of the demographics of a population at Stewart Island. Sampling trips were carried out seasonally from winter 2016 to spring 2017. A baited underwater video system (BUV) was deployed on 133 occasions (mean = 22.2 deployments per season) in a shallow coastal embayment to capture underwater video of N. cepedianus for photo identification of individuals. N. cepedianus was detected on all but one deployment. Images extracted from video recorded the presence of 149 different individuals. Capture-recapture analysis of these data using robust design methods indicated a seasonal trend in abundance of the population using the study area, ranging from 34 (95% C.I. = 21–55) during winter 2016, to 94 (95% C.I. = 44–199) during spring 2017. This study presents the first data on demographic parameters of N. cepedianus in New Zealand.     

Habitat use,seasonality and demography of the broadnose sevengill shark Notorynchus cepedianus in central Patagonia: Another piece of the puzzle

The habitat use, seasonality and demography of the broadnose sevengill shark Notorynchus cepedianus were investigated in central Patagonia, where a data gap exists for the species. Catch and effort and video‐derived indices indicated high relative abundance of sharks during warm months. Video stations revealed differences in the spatial use by sharks, being more frequently observed in the inner section of the bay. Complementary tagging efforts evidenced both a seasonal residence pattern and site fidelity between consecutive warm seasons. Juveniles outnumbered adults, which suggests that they may use the study area as a secondary nursing ground. Evidence from spontaneous regurgitation further suggests that prey abundance may be driving the seasonal occurrence of sharks in the region. This study allows for a more comprehensive understanding of the population structure and dynamics of sevengill sharks in the Southwest Atlantic. Abstract in Spanish is available with online material.     

Occurrence and biological characteristics of broadnose sevengill sharks (Notorynchus cepedianus) in Pacific Northwest coastal estuaries

The broadnose sevengill shark (Notorynchus cepedianus) is a high-order marine predator distributed worldwide in shallow coastal waters of temperate seas. Recent reports have suggested it may be a prevalent component of Pacific Northwest coastal estuarine communities, although biological characteristics of the shark population remain undocumented despite growing interest in recreational harvest of the species. Longline sampling was conducted in Willapa Bay and Grays Harbor, Washington, USA seasonally during 2003–2006 to collect sevengill shark size, maturity, and sex ratio data, and establish some baseline catch rate information. Sevengill sharks were collected on 65% of longline sets and catches were composed of subadult and mature individuals (122–283 cm TL) of both sexes. Most male sevengill sharks were large sexually mature adults, based on external clasper calcification levels, whereas most comparably sized females were considered subadults, based on literature-based size-at–maturity estimates. Neonates and young sharks <120 cm were not collected, nor have they been reported in other historic estuary sampling efforts. Sex ratios were skewed toward males in Willapa Bay and suggest some degree of sexual segregation for the species, as has been shown for populations elsewhere. We suggest sevengill sharks are a largely ignored but potentially important predator in Pacific Northwest estuaries. This study therefore provides some of the first, basic information for guiding management decisions associated with a late-maturing, slow-growing shark species in these coastal habitats.     

Bioenergetics of free-ranging juvenile scalloped hammerhead sharks (Sphyrna lewini) in Kāne'ohe Bay, ō'ahu, HI

Metabolic and activity rates determined from free-ranging juvenile scalloped hammerhead shark pups (Sphyrna lewini) in Kāne'ohe Bay, ō'ahu, HI, were used to develop a simplified energy budget for this population. Five shark pups were tracked using a specially designed acoustic tail beat transmitter. Previous laboratory experiments determined that tail beat frequency (TBF) and water temperature could be used as predictors of instantaneous swimming speed (U) and oxygen consumption rates (V?o₂). Sharks carrying transmitters had higher cost of transport than uninstrumented sharks, but because the difference was quantifiable, appropriate corrections could be made for transmitter effects on energy consumption of instrumented sharks. Sharks tracked in Kāne'ohe Bay had an overall average TBF of 70±10 beats min⁻¹ and a U of 0.81±0.1 body lengths s⁻¹, but swam significantly faster at night than during the day. These sharks also exhibited high average metabolic rates (MR) (96±15 kJ kg⁻¹ day⁻¹) compared with other species of sharks previously studied. Sharks tracked during warmer summer months swam slightly faster and exhibited higher MR than one tracked in December. The high MR measured for sharks in the bay indicate that these sharks require a high daily ration. The relatively low caloric value of the most common prey (snapping shrimp, Alpheus malabaricus) suggests that high numbers must be consumed to meet the sharks' daily requirements. Low and/or negative growth rates of shark pups in the field and declining population size over the summer season suggests that a significant percentage of pups in Kāne'ohe Bay may starve as the result of their high MR requirements. Although availability of A. malabaricus may not be limiting in Kāne'ohe Bay, foraging skills of some neonates may be inadequate to enable them to meet their daily energetic needs. However, sharks that are successful in surviving through the winter may actually grow faster in the colder months due to the temperature dependent decrease of their MR and a reduction in conspecific competition as the result of high summer seasonal attrition due to starvation and emigration.     

Diet of tuatara (Sphenodon punctatus) translocated to Ōrokonui Ecosanctuary in southern New Zealand

ABSTRACT

Scats from tuatara (Sphenodon punctatus) were investigated in autumn at ōrokonui Ecosanctuary on South Island, New Zealand. Eighty-seven tuatara had been translocated there 5–7 months previously, either directly from Stephens Island/Takapourewa or via captivity. Tuatara at ōrokonui fed on diverse invertebrates, including beetles, millipedes, spiders, dipteran flies and cave wētā. Prey occurrence in large scats (presumed to come from adults) was similar in frequency to that in small scats (presumed to be from medium–large juveniles), apart from a higher incidence of spiders in those from adults. Tuatara scats contained scarabaeid and large carabid beetles more frequently, and tenebrionid beetles less frequently, than reported on Stephens Island. Unlike tuatara on Stephens Island, those at ōrokonui do not have access to seabirds or tree wētā, and showed no certain predation on passerines or reptiles. Some differences in diet composition may reflect differences in prey availability resulting from the past presence of rodents at ōrokonui.     

Ultrasound examination and behavior scoring of captive broadnose sevengill sharks,Notorynchus cepedianus (Peron, 1807)

Serial ultrasound examination of four mature female sevengill sharks (Notorynchus cepedianus) was carried out over 18 months. Monitoring the reproductive cycle and development of follicles and fetuses in sharks in a noninvasive manner using this technique has not been reported previously. Sharks were caught out of the “Oceanarium” tank by divers using a specially made catch‐out bag, and brought to a holding area for examination. A behavior scoring system was used to monitor the impact of regular handling on the well‐being of the animals. Ultrasound showed the growth and regression of follicles in sevengill ovaries, and allowed an approximation of the reproductive stage of these sharks. Monitoring behavior at five time points during the procedure showed that regular handling of sharks for clinical studies could be done with minimal impact on animal welfare. The ability to follow reproductive events in elasmobranches using ultrasonography is an important step in the application of assisted reproductive technology in these species. Assisted reproductive technology, such as monitoring female reproductive cycles and artificial insemination, could potentially be used to maintain genetic diversity and compliment aquaria‐based breeding programs for endangered species such as the gray nurse shark (Carcharias taurus). Zoo Biol 26:383–395, 2007. © 2007 Wiley‐Liss, Inc.     

Molecular phylogeny of the prickly shark, Echinorhinus cookei, based on a nuclear (18S rRNA) and a mitochondrial (cytochrome b) gene.

The classification of the sharks is unclear. This is particularly true for the superorder Squalomorphii. The relationships between the squalomorphs and other superorders of sharks and the relationships between the different orders within the squalomorphs are a matter of debate. Here, we report a molecular phylogeny for a little known member of this superorder, the genus Echinorhinus. Echinorhinus is most commonly classified in either the family Echinorhinidae (Squaliformes) or the family Squalidae (Squaliformes). However, some authors have suggested a closer relationship to the order Hexanchiformes. In an attempt to shed light on this controversy, we have cloned, sequenced, and compared two genes widely used in molecular phylogeny studies, the cytochrome b and the 18S rRNA from the rare prickly shark, Echinorhinus cookei, and two potential relatives, the spiny dogfish Squalus acanthias (Squaliformes), and the sevengill shark, Notorynchus cepedianus (Hexanchiformes). The sequences of these genes for the prickly shark, the dogfish, and the sevengill shark were found to be equally divergent, suggesting that the prickly shark is no closer to the order Squaliformes than to the order Hexanchiformes.     

Residency,Habitat Use and Sexual Segregation of White Sharks,Carcharodon carcharias in False Bay,South Africa

White sharks (Carcharodon carcharias) are threatened apex predators and identification of their critical habitats and how these are used are essential to ensuring improved local and ultimately global white shark protection. In this study we investigated habitat use by white sharks in False Bay, South Africa, using acoustic telemetry. 56 sharks (39 female, 17 male), ranging in size from 1.7–5 m TL, were tagged with acoustic transmitters and monitored on an array of 30 receivers for 975 days. To investigate the effects of season, sex and size on habitat use we used a generalized linear mixed effects model. Tagged sharks were detected in the Bay in all months and across all years, but their use of the Bay varied significantly with the season and the sex of the shark. In autumn and winter males and females aggregated around the Cape fur seal colony at Seal Island, where they fed predominantly on young of the year seals. In spring and summer there was marked sexual segregation, with females frequenting the Inshore areas and males seldom being detected. The shift from the Island in autumn and winter to the Inshore region in spring and summer by females mirrors the seasonal peak in abundance of juvenile seals and of migratory teleost and elasmobranch species respectively. This study provides the first evidence of sexual segregation at a fine spatial scale and demonstrates that sexual segregation in white sharks is not restricted to adults, but is apparent for juveniles and sub-adults too. Overall, the results confirm False Bay as a critical area for white shark conservation as both sexes, across a range of sizes, frequent the Bay on an annual basis. The finding that female sharks aggregate in the Inshore regions when recreational use peaks highlights the need for ongoing shark-human conflict mitigation strategies.     

Potential expansion in the spatial distribution of subtropical and temperate west Australian sharks

Fishery-dependent and -independent data collected since 1975 were examined to explore the spatial distribution of 30 shark and ray species in the west coast of Australia. Bigeye sixgill (Hexanchus nakamurai), tiger (Galeocerdo cuvier) and spinner (Carcarhinus brevipinna) sharks, and scalloped hammerhead (Sphyrna lewini) were observed >1000 and 300 km to the east of the edge of their reported distributions. Broadnose sevengill sharks (Notorhyncus cepedianus) and southern sawsharks (Pristiophorus nudipinnis) were observed >1000 km to the west of the edge of their reported distributions. Our study highlights the value of collecting and examining long time-series of data for understanding the spatial distribution of large marine predators.     

Environmental Influences on the Abundance and Sexual Composition of White Sharks Carcharodon carcharias in Gansbaai,South Africa

The seasonal occurrence of white sharks visiting Gansbaai, South Africa was investigated from 2007 to 2011 using sightings from white shark cage diving boats. Generalized linear models were used to investigate the number of great white sharks sighted per trip in relation to sex, month, sea surface temperature and Multivariate El Niño/Southern Oscillation (ENSO) Indices (MEI). Water conditions are more variable in summer than winter due to wind-driven cold water upwelling and thermocline displacement, culminating in colder water temperatures, and shark sightings of both sexes were higher during the autumn and winter months (March–August). MEI, an index to quantify the strength of Southern Oscillation, differed in its effect on the recorded numbers of male and female white sharks, with highly significant interannual trends. This data suggests that water temperature and climatic phenomena influence the abundance of white sharks at this coastal site. In this study, more females were seen in Gansbaai overall in warmer water/positive MEI years. Conversely, the opposite trend was observed for males. In cool water years (2010 to 2011) sightings of male sharks were significantly higher than in previous years. The influence of environmental factors on the physiology of sharks in terms of their size and sex is discussed. The findings of this study could contribute to bather safety programmes because the incorporation of environmental parameters into predictive models may help identify times and localities of higher risk to bathers and help mitigate human-white shark interactions.     

Reproductive biology,multiple paternity and polyandry of the bull shark Carcharhinus leucas

To improve understanding of bull shark Carcharhinus leucas reproductive biology, we analysed reproductive traits from 118 bull sharks caught along Reunion Island coasts (Western Indian Ocean), including 16 gravid females. Specific microsatellite loci were used to investigate the frequency of multiple paternity. Males and females reached maturity at c. 234 cm and 257 cm total length (L_T), respectively, and litter sizes ranged from 5 to 14 embryos. Analysis of the 16 litters collected in various months of the year indicated that parturition occurs between October and December, with a size at birth c. 60–80 cm L_T and that the gestation period is probably c. 12 months. Assuming a 1 year resting period and a period of sperm storage (4–5 months) between mating (in June–September) and fertilisation, the reproductive cycle of bull sharks at Reunion Island would be biennial. At least 56.25% of the litters investigated were polyandrous, sired by 2–5 males. Several males that each sired several litters conceived during the same or distinct mating seasons were detected, suggesting both a seasonal aggregation of sharks to mate and some male fidelity to mating site. Altogether, these findings provide valuable information for both shark risk management and conservation of the species in the Western Indian Ocean.     

Seasonal occurrence and population structure of the broadnose sevengill shark Notorynchus cepedianus in coastal habitats of south-east Tasmania

Research longline sampling was conducted seasonally from December 2006 to February 2009 to investigate the occurrence and population structure of the broadnose sevengill shark Notorynchus cepedianus in coastal areas of south-east Tasmania. Notorynchus cepedianus showed a consistent temporal trend in seasonal occurrence in Norfolk Bay characterized by high abundances in summer to near absence in winter. This pattern was less pronounced in the Derwent Estuary, where fish were still caught during winter. The absence of smaller total length (L(T) ) classes (<80 cm) from the catches suggests that N. cepedianus are not using these coastal habitats as nursery areas. Of the 457 individuals tagged, 68 (15%) were recaptured. Time at liberty ranged from 6 days to almost 4 years and all but one of the recaptures were caught in its original tagging location, suggesting site fidelity. The large number of N. cepedianus in these coastal systems over summer indicates that these areas are important habitats for this species and that N. cepedianus may have a significant influence on community dynamics through both direct and indirect predator-prey interactions.     

‘I Have Māori in Me’: Shades of Commitment and Negotiation of Subjectivity in an Aotearoa/New Zealand School

ABSTRACT

Based on ethnographic fieldwork (1997–1998) at a secondary school with a Māori?English bilingual unit in Aotearoa/New Zealand, this article examines two different ways students with Māori ancestry identified themselves contextually: those in the bilingual unit identified themselves mostly as being Māori, while those in mainstream classes identified themselves mostly as Pākehā (white New Zealander) but occasionally as being Pākehā but having Māori in them. Existing analytical frameworks, such as symbolic ethnicity (Gans 1999) or citizenship (Ong 2003), fail to capture the contextual and dialogic display of these different shades of identification practices. Applying the notion of commitment and its disavowal proposed by Doerr for this special issue (2013), this article analyses these two identification practices as a proactive commitment and a hedging commitment linked to institutional belonging to the bilingual unit and mainstream classes, respectively, and to the wider cultural politics of the official yet tokenistic biculturalism of Aotearoa/New Zealand.     

Distribution and reproduction of the southern lantern shark from New Zealand

Distribution, population structure and reproduction are described for the southern lantern shark Etmopterus granulosus at the Chatham Rise, New Zealand. Depth of capture for E. granulosus ranged from 744 to 1420 m, with highest catch rates between 800–1200 m. More than twice as many females as males were captured, and the majority of sharks caught were mature, indicating that there may be segregation according to sex and size class. Only 10 of 492 female sharks captured contained ova in uteri, and none contained embryos. The absence of pregnant females suggests that they move to another area or depth prior to pupping. Size of sharks captured ranged from 20·0 to 78·8 cm total length. Females began to mature at 62 cm total length, and males at 52 cm. There was no evidence of a seasonal reproductive cycle. Ovulation appeared to occur when ova reached a diameter of 40–45 mm. The average number of ova in mature females was 12·7. This information is crucial for assessing the impact of fisheries on E. granulosus populations.     

Essential waters: Young bull sharks in Fiji's largest riverine system

Coastal and estuarine systems provide critical shark habitats due to their relatively high productivity and shallow, protected waters. The young (neonates, young‐of‐the‐year, and juveniles) of many coastal shark species occupy a diverse range of habitats and areas where they experience environmental variability, including acute and seasonal shifts in local salinities and temperatures. Although the location and functioning of essential shark habitats has been a focus in recent shark research, there is a paucity of data from the South Pacific. In this study, we document the temporal and spatial distribution, age class composition, and environmental parameters of young bull sharks (Carcharhinus leucas) in the Rewa, Sigatoka, and Navua Rivers, Fiji's three largest riverine systems. One hundred and seventy‐two young bull sharks were captured in fisheries‐independent surveys from January 2016 to April 2018. The vast majority of the captures were neonates. Seasonality in patterns of occurrence of neonate individuals suggests a defined parturition period during summer. Environmental parameters between the Rewa and the Sigatoka River differed significantly, as did the recorded young bull sharks abundance. According to the surveys, young bull sharks occur in all three rivers with the Rewa River likely representing essential habitat for newly born bull sharks. These results enhance the understanding of bull shark ecology in Fiji and provide a scientific basis for the implementation of local conservation strategies that contribute to the protection of critical habitats.     

Occurrence of the whitetip reef shark Triaenodon obesus at the Kermadec Islands,Southwest Pacific Ocean

ABSTRACT

Four observations of what was probably a single vagrant adult female whitetip reef shark Triaenodon obesus were made at Raoul and Meyer Islands, Kermadec Islands, New Zealand, over a 12 month period in 2014/15. This is the most southerly occurrence of the whitetip reef shark and ambient winter temperatures were close to the assumed thermal minimum for the species. The closest potential source population occurs at Minerva Reefs, about 598?km northwest of Raoul Island.     

Post-mortem examinations of New Zealand birds. 2. Long-tailed cuckoos (Eudynamys taitensis,Aves: Cuculinae)*

Little is known about the biology of long-tailed cuckoos (Eudynamys taitensis). In this study, 79 dead cuckoos, mostly from the wider Auckland region, New Zealand, were examined and dissected to shed light on the sex ratio, morphology, breeding season and diet. There were no statistically significant sexual differences in the means for weight or body measurements. However, immature birds had significantly shorter bill, wing and tail lengths than adults. In adults, gonads were enlarged (for breeding) from October to January, while all cuckoos identified (from plumage) as immatures had small gonads. Of 888 food items identified from 62 gizzards, 94% were insects. The main foods were cicadas and shield-bugs (Hemiptera, 48% of food items), stick-insects (Phasmatodea, 19%) and wētās and katydids (Orthoptera, 13%). Small vertebrates (lizards and birds’ eggs and nestlings) were a minor dietary element (1% of food items; 13% of stomachs). Cicadas, stick-insects and praying mantids (large insects abundant in late summer) made up 57% of the immature diet; in adults these three categories made up just 13% of food items. Immatures leave New Zealand on migration several months after adults, and this delay in late summer and autumn coincides with an opportunity to exploit a seasonal abundance of large insects.     

Multi-Year Impacts of Ecotourism on Whale Shark (Rhincodon typus) Visitation at Ningaloo Reef,Western Australia

In-water viewing of sharks by tourists has become a popular and lucrative industry. There is some concern that interactions with tourists with ecotourism operations might harm sharks through disruption of behaviours. Here, we analysed five years of whale shark (Rhincodon typus) encounter data by an ecotourism industry at Ningaloo Reef, Western Australia, to assess the impact of ecotourism interactions on shark visitation, within the context of the biological and physical oceanography of the region. Our data base consisted of 2823 encounter records for 951 individual whale sharks collected by ecotourism operators between 2007 and 2011. We found that total encounters per whale shark and encounters per boat trip increased through time. On average, whale sharks re-encountered in subsequent years were encountered earlier, stayed longer and tended to be encountered more often within a season than sharks that were only encountered in a single year. Sequential comparisons between years did not show any patterns consistent with disturbance and the rate of departure of whale sharks from the aggregation was negatively correlated to the number of operator trips. Overall, our analysis of this multi-year data base found no evidence that interactions with tourists affected the likelihood of whale shark re-encounters and that instead, physical and biological environmental factors had a far greater influence on whale shark visitation rates. Our approach provides a template for assessing the effects of ecotourism interactions and environmental factors on the visitation patterns of marine megafauna over multiple years.     

Quantification of Massive Seasonal Aggregations of Blacktip Sharks (Carcharhinus limbatus) in Southeast Florida

Southeast Florida witnesses an enormous seasonal influx of upper trophic level marine predators each year as massive aggregations of migrating blacktip sharks (Carcharhinus limbatus) overwinter in nearshore waters. The narrow shelf and close proximity of the Gulf Stream current to the Palm Beach County shoreline drive tens of thousands of sharks to the shallow, coastal environment. This natural bottleneck provides a unique opportunity to estimate relative abundance. Over a four year period from 2011–2014, an aerial survey was flown approximately biweekly along the length of Palm Beach County. A high definition video camera and digital still camera mounted out of the airplane window provided a continuous record of the belt transect which extended 200 m seaward from the shoreline between Boca Raton Inlet and Jupiter Inlet. The number of sharks within the survey transect was directly counted from the video. Shark abundance peaked in the winter (January-March) with a maximum in 2011 of 12,128 individuals counted within the 75.6 km^-2 belt transect. This resulted in a maximum density of 803.2 sharks km^-2. By the late spring (April-May), shark abundance had sharply declined to 1.1% of its peak, where it remained until spiking again in January of the following year. Shark abundance was inversely correlated with water temperature and large numbers of sharks were found only when water temperatures were less than 25°C. Shark abundance was also correlated with day of the year but not with barometric pressure. Although shark abundance was not correlated with photoperiod, the departure of the sharks from southeast Florida occurred around the vernal equinox. The shark migration along the United States eastern seaboard corresponds spatially and temporally with the spawning aggregations of various baitfish species. These baseline abundance data can be compared to future studies to determine if shark population size is changing and if sharks are restricting their southward migration as global water temperatures increase.