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Shipboard power systems that service large-scale dynamic loads and electric propulsion can significantly improve their performance by adding controllable energy storage. These systems require power management controls that consider dynamics like generator ramp rates, along with energy storage capacity and location. In the early-stage design process, many alternative designs are considered, and each requires a unique controller. This article describes a numerical optimization technique that establishes an upper bound performance criteria without manually designing controllers for each system. The solution is a best case performance that assumes perfect future knowledge of the time-varying load. While unrealistic in real-time, this technique yields a fair comparison between competing architectures without the variability of different control methods. To demonstrate the concept, a notional multi-bus power system architecture is evaluated on a representative set of operational duties to illustrate comparisons between system attributes like energy storage power and efficiency ratings. A design trade study shows that the success rate for a baseline ship can improve from under 60% to nearly 100% by increasing generator power by 10% and energy storage capacity by 100%. These automated architecture benchmarks fit into a broader total ship optimization process, or can be used in human-driven trade studies.

This paper describes extending a real-time 4-zone Medium Voltage DC Shipboard Power System (MVDC SPS) simulation with an operational load model. Prior efforts have resulted in two separate simulation platforms 1) 4-zone MVDC SPS and 2) vBOLDPower, a non-real-time operational load modeling tool. This paper focuses on combining these two tools into a single multi-domain real-time simulation. This will allow the power system and associated controllers to interact with a realistic load model and further development of a system-relevant environment for evaluating system-level SPS controls. This paper's primary contribution is the interface design and cosimulation approach for an integrated electrical and operational load real-time simulation testbed. Demonstrations of this work are given highlighting the importance and relevance for control evaluation.

Practical laboratory exercises improve student understanding and motivation for learning abstract engineering concepts. The Department of Electrical and Computer Engineering at the United States Naval Academy (USNA), a four-year undergraduate institution, is tasked with teaching all students a course in electrical circuits and power. The course aimed at non-STEM majors includes a weekly two hour laboratory period to assist in drawing out these abstract concepts. The instructors for an Electrical Engineering circuits and power course for non-STEM majors jointly developed and troubleshot a series of five real-world, laboratory experiments. These experiments are intended to demonstrate real world skills and applications of the abstract concepts covered during the class.

Small power systems are often used in support of broader systems like factories, climate control, and electric warships. Aggressive operation of the power systems often creates power shortfalls, which can be studied and controlled by assigning a value of lost load. However, this formulation is typically not sufficient to cover the potential interactions between the power system and the “process controller” that supervises the overall system and creates the load demand. For example, if a load demand for a device is not met, it will re-occur rather than just disappear. This paper formulates a general partition of the system control into a process controller which proposes actions, and a power manager which provides feedback on the feasibility of those actions. The two modules communicate via a defined interface to agree on a set of feasible actions that best accomplish the tasks within the limits of a power system. An electric warship is used as an example to demonstrate this setup, which can be used to operate power systems and to generate representative load profiles for use in evaluating candidate designs.

With the advent of high energy pulse mission loads and distributed power and energy on all-electric ship platforms, a new total ship control system capability is emerging that could significantly impact overall mission success. No longer are loads limited to an all-or-nothing power per use approach. Rather, energy applied to advanced mission loads can be scaled—even regulated—to achieve a desired outcome. Within this new framework, the effectiveness of unique missions can be quantified as a function of the amount and allocation of power to service each mission load. Power elasticity enables a new frontier of how decisions are made during intense operational scenarios where limited power and energy resources are applied to competing load demands. Herein, a power allocation strategy that addresses this challenge is proposed. The general approach is to use state-space models to represent the evolution of both the mission and the engineering system that is supporting the mission. An optimal control problem is performed to maximize some functional over the mission state and actions. By doing so, it indicates the capability of the engineering system to support such missions. The uniqueness of this approach is that solutions become far more mission specific. Results based on a simple two-function platform—each competing for the same limited power resources—show that this approach can be used to assess the probability of success given a certain initial allocation of power.

Effective ocean management and the conservation of highly migratory species depend on resolving the overlap between animal movements and distributions, and fishing effort. However, this information is lacking at a global scale. Here we show, using a big-data approach that combines satellite-tracked movements of pelagic sharks and global fishing fleets, that 24% of the mean monthly space used by sharks falls under the footprint of pelagic longline fisheries. Space-use hotspots of commercially valuable sharks and of internationally protected species had the highest overlap with longlines (up to 76% and 64%, respectively), and were also associated with significant increases in fishing effort. We conclude that pelagic sharks have limited spatial refuge from current levels of fishing effort in marine areas beyond national jurisdictions (the high seas). Our results demonstrate an urgent need for conservation and management measures at high-seas hotspots of shark space use, and highlight the potential of simultaneous satellite surveillance of megafauna and fishers as a tool for near-real-time, dynamic management., Data analysis was funded in part by the Marine Biological Association (MBA) and the UK Natural Environment Research Council (NERC) (NE/R00997X/1) (to D.W.S.) with additional research support from the Save Our Seas Foundation and the NERC Oceans 2025 Strategic Research Programme, in which D.W.S. was a principal investigator. D.W.S. was supported by an MBA Senior Research Fellowship, N.Q. by European Regional Development Fund (FEDER) via the Programa Operacional Competitividade e Internacionalização (COMPETE), National Funds via Fundação para a Ciência e a Tecnologia (FCT) under PTDC/MAR/100345/2008 and COMPETE FCOMP-01-0124-FEDER-010580 (to N.Q. and D.W.S.), and Norte Portugal Regional Operational Programme (NORTE 2020) under the PORTUGAL 2020 Partnership Agreement through the European Regional Development Fund (ERDF) in project MarInfo (NORTE-01-0145-FEDER-000031). Additional support was provided by an FCT Investigator Fellowship IF/01611/2013 (N.Q.), FCT Doctoral Fellowship PD/BD/52603/2014 (M.V.), PTDC/MAR-BIO/4458/2012, Xunta de Galicia - Isabel Barreto Program 2009-2012 (G.M.), Australian Research Council (ARC) grant DE170100841 and operational funds from the Australian Institute for Marine Science (AIMS) (both to A.M.M.S.).

The ability of predators to switch between hunting and scavenging (facultative scavenging) carries both short-term survival and long-term fitness advantages. However, the mechanistic basis for facultative scavenging remains poorly understood. The co-occurrence of tiger sharks (Galeocerdo cuvier) and green turtles (Chelonia mydas) at Raine Island (Australia), provides an opportunity to examine a top marine predator’s feeding mode in response to seasonal pulses in nesting turtles that offer both hunting and scavenging opportunities. Using satellite telemetry, we evaluated home range overlap between sharks and turtles and quantified their surfacing behavior around Raine Island during the turtle nesting season. We found core home range overlap to be highest during the nesting season. Both sharks and turtles spent significantly more time at the surface in areas of greatest range overlap closest to shore, where turtle density was highest. Both sharks and turtles showed decreased surfacing with increasing distance from Raine Island. Combined with published data on turtle demography at Raine Island, we propose the following: (1) sharks patrol the surface to increase scavenging opportunities on turtle carcasses and intercept weakened individuals after nesting; (2) healthy turtles may not perceive sharks as a major threat and/or other biological factors override anti-predatory responses; and (3) sharks during the nesting season may primarily scavenge on dead turtles individuals rather than actively hunt. Our study results and approach may be applicable to other situations in which direct observations of predator-prey interactions are limited. Every animal encounters dead or dying resources, yet the role of facultative scavenging has been difficult to study, and thus largely overlooked in marine behavioral ecological research. Movement analyses of tiger shark and green turtle movement and surfacing behavior at Raine Island (Australia) suggest that facultative scavenging may be a prevalent, yet underappreciated, feeding strategy in tiger sharks. Our integration of behavioral ecology theory with multi-species electronic tagging provided a valuable approach for investigating predator-prey interactions in situations where direct observations are limited or not possible.

Marine protected areas (MPA) are one management tool that can potentially reduce declining shark populations. Protected-area design should be based on detailed movements of target animals; however, such data are lacking for most species. To address this, 25 sharks from three species were tagged with acoustic transmitters and monitored with a network of 103 receivers to determine the use of a protected area at Mangrove Bay, Western Australia. Movements of a subset of 12 individuals ( Carcharhinus melanopterus [ n = 7 ]), C. amblyrhynchos [ n = 2 ], and Negaprion acutidens [ n = 3 ]) were analysed over two years. Residency for all species ranged between 12 and 96%. Carcharhinus amblyrhynchos had C. melanopterus adults that ranged between 0 and 99%. Juvenile sharks had high percentages of position estimates in the MPA (84–99%). Kernel density activity centres for C. melanopterus and C. amblyrhynchos were largely outside the MPA and mean activity space estimates for adults were 12.8 km 2 (±3.12 SE) and 19.6 km 2 (±2.26), respectively. Juveniles had smaller activity spaces: C. melanopterus , 7.2 ±1.33 km 2 ; N. acutidens , 0.6 km 2 (±0.04). Both C. melanopterus and C. amblyrhynchos had peaks in detections during daylight hours (1200 and 0900 h, respectively), whereas N. acutidens had a peak in detections at 0200 h. Long-distance movements were observed for adult C. melanopterus and C. amblyrhynchos , the longest being approximately 275 km. These migrations of C. melanopterus might be related to reproductive behaviours, because they were all observed in adult females during the summer months and provide links between known in-shore aggregation and possible nursery areas. The MPA at Mangrove Bay provided some protection for juvenile and adult reef sharks, although protection is likely greater for juveniles due to their more restricted movements.

Both naval and commercial ships are incorporating new power and energy system technologies to improve fuel economy and performance while servicing high power pulsed loads. These assets can be best utilized with load demand forecasting and/or prediction, especially when considering limits on generator ramp rates, distribution lines, and energy storage capacity. Obtaining future load demand data and designing a controller to accommodate it can be challenging, but with potentially large payoff. However, this information is not useful in all cases. This paper develops a method to quantify the potential value of future information depending on the specific power system characteristics. This quantitative approach aids designers in deciding how and when to deploy future forecasting in controller design, and provides insight into the potential benefits of these more complex controllers. To quantify this trade off, two optimization-based control methods are developed. One uses only current information, while the other has an exact forecast of the future. As examples, the method is applied to a notional naval ship and drill platform service vessel with representative power and energy system architectures under indicative operational load demands.

Future shipboard power system architectures are designed to service high-power pulsed loads through a combination of generators and energy storage for volume and weight considerations. Optimal control solutions therefore depend on both past and future events. This complicates evaluation of the relative performance of different architectures due to dependence on controller strategies and algorithms. Herein, we introduce a technique for early stage evaluation of the relative performance of various ship power system designs by assuming a known future and calculating the best-case performance of any possible controller design. We demonstrate this technique using 6 mission scenarios on a representative multi-bus power system architecture. The controller has perfect future knowledge of the loads on each 10 minute mission, which provides an upper bound on performance for a given architecture. While not usually achievable in practice, this technique allows a fair early stage comparison of multiple architectures regardless of controller type.

High energy pulse load weapons and sensors on smaller, more affordable platforms are the driving factors behind future all-electric warship power and energy systems. For design space exploration, legacy design tools based on ideal steady-state conditions are not sufficient. Design studies must factor in the significant impact that these dynamic loads have on the stability of the warship's power and energy system, especially under critical operational demands. This paper continues to improve the fidelity of a shipboard load demand model by introducing exogenous features that trigger load responses. This operational vignette-based model contains a set of shipboard asset and rival characteristic features in a virtual battlespace. With pre-defined rules that model human-in-the-loop decision-making, a representative time-domain battle scenario is simulated and ship-wide load demands are recorded. By modifying ship and opponent features along with the rules that define engagement, a set of realistic test cases designed specifically for Monte Carlo simulation can accurately predict the load demand over a wide range of notional operational vignettes. In addition, since representative rival data is now added to the model, tactical mission effectiveness can be assessed as a function of power demand.

Little information is available on the movements and behaviour of tropical rays despite their potential ecological roles and economic value as a fishery and a tourism resource. A description of the movement patterns and site fidelity of juvenile rays within a coral reef environment is provided in this study. Acoustic telemetry was used to focus on the use of potential nursery areas and describe movement patterns of 16 individuals of four species monitored for 1–21 months within an array of 51 listening stations deployed across a lagoon, reef crest, and reef slope at Mangrove Bay, Ningaloo Reef, Western Australia. Juveniles used a small (< 1 km2), shallow (1–2 m depth) embayment where three receivers recorded 60–80 % of total detections of tagged animals, although individuals of all species moved throughout the array and beyond the lagoon to the open reef slope. Detections at these primary sites were more frequent during winter and when water temperatures were highest during the day. Long-term use of coastal lagoons by juvenile rays suggests that they provide an important habitat for this life stage. Current marine park zoning appears to provide an effective protection for juveniles within this area.

Long-term vital rate and life-history data essential for sustainable harvest management are rare in tropical fisheries. Two commercially important shark species, Australian blacktip ( Carcharhinus tilstoni ) and spot-tail ( C. sorrah ) sharks in northern Australia have changed in size and population status over the last 25 years. These populations were exploited heavily from the early 1970s to the mid-1980s by foreign fishers, and since then have been harvested by a relatively small domestic fishery. We examined the differences in fork length of these species caught in 1983–1985 and 2002–2006 using Bayesian forms of generalised linear and mixed-effects models. We found clear regional differences and changes in size over time. For blacktips, sharks from the Gulf of Carpentaria have become smaller, and those from the western Northern Territory, larger over time. For spot-tail sharks, average size increased from the 1980s in the Gulf of Carpentaria, but not in the western Northern Territory. On average, sharks from the Gulf of Carpentaria were larger than those on the west coast of the Northern Territory, and females were larger than males. We suggest that changes over time and between regions in the size of spot-tail sharks are most likely due to over-exploitation in the past and subsequent recovery of populations. We discuss the uncertainty in trends for blacktip sharks in relation to fishing effort, availability of resources and species identification errors.

Life-history parameters of Deania calcea and Deania quadrispinosa suggested that their productivity was very low. Maturity (L(T50) ) occurs at c. 80% of maximum observed total lengths (L(T) ) for both species and sexes. A large proportion of mature females were neither pre-ovulatory nor pregnant, and the reproductive cycle included a distinct resting phase after pregnancy. For D. calcea, mean ovarian fecundity was 12 and maximum observed litter size was 10 (average of six); D. quadrispinosa averaged 17 pups per litter. Birth L(T) was 28-33 cm for D. calcea and 23-25 cm for D. quadrispinosa. The male and female reproductive cycles were aseasonal, and consequently, the length of the reproductive cycle could not be determined. Preliminary ageing data from dorsal-spine growth bands suggested that female D. calcea lived to 31-36 years and males to 24-32 years. The L(T) -at-age data using external bands on the spines showed maturity occurring at 15·5 years (males) and 21·5 years (females), whereas banding on the internal dentine indicated maturity at 10·5 and 17·5 years for males and females. Thus, a female lifetime of 31-36 years allowed for a maximum of 7 litters if a 2 year cycle is assumed or only five litters with a 3 year cycle, resulting in a lifetime fecundity of only 42 pups (2 year cycle) or even lower (3 year cycle).

The quantification of spatial and temporal movement patterns of coral reef sharks is im- portant to understand their role in reef communities and to aid the design of conservation strategies for this predatory guild. We observed 4 species of reef sharks aggregating in an inshore bay in the north of Western Australia for over 2 yr, using acoustic telemetry and visual censuses to examine how they par- titioned this site in space and time. We fitted 58 sharks with acoustic transmitters: Carcharhinus melanopterus (36), C. amblyrhynchos (11), Negaprion acutidens (7) and Triaenodon obesus (4). Aggre- gations consisted primarily of C. melanopterus, although C. amblyrhynchos and N. acu tidens were of- ten present. We observed aggregations by visual census in summer (maximum of 44 sharks). Detec- tions were highest during warmer months (Sep to Mar) for all species, although some individuals showed year-round residency. C. melanopterus, C. amblyrhynchos and N. acutidens had strong diel patterns of attendance at the aggregation site. Peak daily detections occurred from 13:00 to 14:00 h local time for C. melanopterus and C. amblyrhynchos; juvenile C. melanopterus and N. acutidens peaked at 05:00 and 10:00 h, respectively. There was considerable spatial overlap of core areas of use (50% kernel density estimates) at the northern end of the bay by all species; the southern end was used primarily by C. melanopterus and N. acutidens. Aggregations of C. mela nop terus and C. am- blyrhynchos consisted mainly of adult females, some of them pregnant. Courtship behaviour in C. melanopterus and T. obesus suggests that these aggregations are related to reproduction. All species displayed inter-annual site fidelity. The long-term presence of juvenile C. melanopterus and N. acuti- dens also suggests that this bay provides suitable conditions for younger age classes.

Combining movement behaviour with other ecological information of predators and their prey is essential for an adequate understanding of ecosystem dynamics. The movement patterns of broadnose sevengill sharks, Notorynchus cepedianus, were monitored with acoustic and satellite technology in coastal areas of southeast Tasmania, Australia. Individuals were tagged in two habitats (Norfolk Bay and the Derwent Estuary) for which we had ecological information such as diet, population structure and abundance. Notorynchus cepedianus showed seasonal site fidelity in the use of the coastal habitats. The general pattern was for sharks to exit coastal areas over winter and females to return the following spring and males in summer. Their movement into these coastal areas coincided with high seasonal abundance of their known prey species during summer, suggesting feeding site fidelity. Individuals tagged in two coastal areas showed low spatial and dietary overlap, suggesting localized site fidelity and fine spatial scale resource partitioning. This has rarely been reported for large mobile predators. Both satellite and acoustic methods showed that males make northerly migrations during winter to distances of at least 1000 km. The combined use of tracking, diet and abundance information demonstrated that N. cepedianus are likely to exert significant predation pressure on prey inhabiting these areas during summer. Overall, this study highlights the benefit of complementing movement data with other ecological information to understand the habitat use of large mobile predators and their potential influences on ecosystem structure and function.

The diet of the broadnose sevengill shark Notorynchus cepedianus was investigated over 3 years from 2 coastal locations in south-east Tasmania: the Derwent Estuary and Norfolk Bay. In general, individuals from both locations consumed the same broad dietary categories (sharks, batoids, teleosts and mammals). However, within these categories, species composition differed. Variations in chondrichthyan prey consumed matched estimations of prey abundance: Mustelus antarcticus was the primary prey in Norfolk Bay, where it was also the most abundant prey species; similarly, Squalus acanthias was an important prey and the most abundant in the Derwent Estuary. A decline in the catch rates of N. cepedianus and elasmobranch prey, in particular M. antarcticus over 3 years coincided with declines in dietary occurrence of M. antarcticus. Also, N. cepedianus and M. antarcticus abundances were both higher in Norfolk Bay than the Derwent Estuary. The correla- tion with diet and estimations of predator and prey relative abundance suggests N. cepedianus may move into coastal areas to exploit regular seasonal abundant resources, but they can also be versatile opportunistic predators that exploit a temporarily abundant resource.

Dietary information of apex predators is crucial to understanding community dynamics and ecosystem processes. However, as dietary studies traditionally involve lethal sampling, obtaining this essential information can have repercussions on predator populations and the structure and functioning of marine ecosystems. With stronger emphasis being placed on conservation of species that are vulnerable to overexploitation, the need for non-destructive methods of sampling is imperative, as is the requirement to maximize the information obtained from each sample. Stomach flushing (gastric lavage) and DNA analysis of stomach contents methods were tested on the broadnose sevengill shark Notorynchus cepedianus Peron 1807. Acoustic tracking and recaptures of sharks implied high survivorship post-fishing and stomach flushing. From 85 prey items collected, 36 (43%) could be identified to species level using morphological analysis. After DNA analysis, a further 35 items were identified to species level, doubling the information obtained from these stomachs. The number of N. cepedianus that were confirmed to have eaten gummy sharks Mustelus antarcticus Gunther 1870 also doubled after DNA analysis. Without DNA analysis (of stomach contents) the importance of M. antarcticus in the diets of N. cepedianus would have been substantially underestimated. In addition, the non-lethal approach provides an opportunity to obtain meaningful information from non-harvested, endangered or rare species or sampling of species within protected areas.

Seven whale sharks were tracked using satellite-linked tags from Ningaloo Reef, off northern Western Australia, following tagging in April and June 2002 and April–May 2005. We investigated how the movements of those whale shark tracks were influenced by geostrophic surface currents during sequential one-week periods by using a passive diffusion model parameterised with observed starting locations of the sharks and weekly maps of surface current velocity and direction (derived from altimetry). We compared the outputs from the passive diffusion model and maps of chlorophyll-a concentration (SeaWiFs/MODIS) and with the actual tracks of the sharks using GIS and generalized linear mixed-effects models (GLMM). The GLMM indicated very little support for passive diffusion with sea-surface ocean currents influencing whale shark distributions in the north eastern Indian Ocean. Moreover, the sharks' movements correlated only weakly with the spatial distribution of sea-surface chlorophyll-a concentrations. The seven whale sharks had average swimming speeds comparable with those recorded in other satellite tracking studies of this species. Swimming speeds of the seven sharks were similar to those reported in previous studies and up to three times greater than the maximum sea-surface current velocities that the sharks encountered while traversing into lower southerly latitudes (moving northward towards the equator). Our results indicate that whale sharks departing from Ningaloo travel actively and independently of near-surface currents where they spend most of their time despite additional metabolic costs of this behaviour.

Satellite telemetry was used to study the movements and behaviour of ten blue sharks and one individual each of shortfin mako, thresher and bigeye thresher off eastern Australia. The tracks showed latitudinal movements of up to 1,900 km, but none of the sharks travelled away from the eastern Australian region. Tracking periods did not exceed 177 days. All species showed oscillatory dive behaviour between the surface layers to as deep as 560–1,000 m. Blue sharks spent 35–58% of their time in 300 m. Of these four species, the bigeye thresher spent the least time in the surface layers and the most time at >300 m depth. All four species showed clear diel behaviour generally occupying shallower depths at night than during the day. Blue sharks were mainly in 17.5–20.0°C water, while the thresher sharks showed a more bimodal temperature distribution.

The genus Glyphis comprises a group of rare and poorly known species. G. glyphis and G. garricki are found in northern Australia, and both species are listed as Critically Endangered C2a(i) on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. We collated all available records of G. glyphis and G. garricki in Australia to gain an understanding of the species’ distribution and biology. All records of G. glyphis (n = 106) were confined to 9 tropical rivers and estuaries north of 15°S. G. garricki (n = 32) were captured in 4 rivers and estuaries as well as in marine environments north of 18°S. Both species can be classified as euryhaline elasmobranchs. Parturition is thought to occur in October to December, and size at birth for both species is around 50 to 65 cm total length (TL). Two male G. garricki were mature at 142 and 144 cm TL, 2 females of 177 and 251 cm TL were mature, with the smaller animal having 9 early-stage embryos in utero. No mature G. glyphis have been recorded to date. Short-term movement patterns of 3 G. glyphis were investigated in the Adelaide River (Northern Territory) using acoustic tags. Animals were tracked for 27.8, 27.0 and 50.2 h respectively and displayed up- and downstream tidally assisted movement, moving on average 10 to 12 km per tide. The limited distribution, specific habitat requirements and repeated use of available habitat make Glyphis species particularly vulnerable to localised overfishing and habitat degradation. These findings highlight the need for additional research and the implementation of national recovery plans for both species

1. Fishing spans all oceans and the impact on ocean predators such as sharks and rays is largely unknown. A lack of data and complicated jurisdictional issues present particular challenges for assessing and conserving high seas biodiversity. It is clear, however, that pelagic sharks and rays of the open ocean are subject to high and often unrestricted levels of mortality from bycatch and targeted fisheries for their meat and valuable fins. 2. These species exhibit a wide range of life-history characteristics, but many have relatively low productivity and consequently relatively high intrinsic vulnerability to over-exploitation. The IUCN-World Conservation Union Red List criteria were used to assess the global status of 21 oceanic pelagic shark and ray species. 3. Three-quarters (16) of these species are classified as Threatened or Near Threatened. Eleven species are globally threatened with higher risk of extinction: the giant devilray is Endangered, ten sharks are Vulnerable and a further five species are Near Threatened. Threat status depends on the interaction between the demographic resilience of the species and intensity of fisheries exploitation. 4. Most threatened species, like the shortfin mako shark, have low population increase rates and suffer high fishing mortality throughout their range. Species with a lower risk of extinction have either fast, resilient life histories (e.g. pelagic stingray) or are species with slow, less resilient life histories but subject to fisheries management (e.g. salmon shark). 5. Recommendations, including implementing and enforcing firming bans and catch limits, are made to guide effective conservation and management of these sharks and rays. Copyright (c) 2008 John Wiley & Sons, Ltd.

Chondrichthyans are one of the most vulnerable groups of marine species, with increasing numbers being listed as endangered or threatened. Fundamental to the conservation and management of any animal is an understanding of their reproduction and particularly, the size at which individuals enter the reproductive population. Size at maturity in sharks is typically obtained by macroscopic examination of the gonads after sacrificing the fish. Using the draughtboard shark Cephaloscyllium laticeps as a case study, we found that equivalent information can be obtained nondestructively using steroid hormone levels measured from a blood sample. This technique allowed us to release the shark after only 1 to 2 min of handling. A combination of plasma steroid hormone concentrations and an external measurement (total length for females and clasper length for males) was used to determine that over 90% of female and 95% of male sharks were either juveniles or adults. The estimates of size at maturity from the hormone analysis were within 3% of equivalent values of dissected sharks. Once validated, hormone levels can also be used to determine seasonal reproductive patterns for the adult population. Our results demonstrated how measurement of plasma levels of steroid hormones can provide a non-destructive method for obtaining reproductive data necessary for managing vulnerable and endangered shark species. The development of a non-destructive sampling tool also allows for improved ethical investigation into this vulnerable group of marine fishes.

This study examined the endocrine and reproductive correlates of reproduction in 636 female and 468 male draughtboard sharks (Cephaloscyllium laticeps) captured from southeastern Australia. Females were oviparous and displayed a single external-type ovary with a maximum follicle diameter of 35 mm. Vitellogenesis commenced at a follicle diameter of 10 mm. Females showed a constant overlap between follicular recruitment, ovarian growth, and egg laying. The male reproductive tract consisted of paired testes with spermatocysts undergoing diametric development. Plasma levels of the presumptive gonadal steroids, testosterone (T), 17β-estradiol (E2), progesterone (P4), and 11-ketotestosterone (11-KT; males only) were correlated with morphological developmental stages of the gonads. In females, E2 increased as the follicle developed before declining as the follicle reached maturity. T remained low during the first stages of ovarian growth and increased as the follicle reached maturity. P4 showed a peak just before ovulation. In males, T was the only hormone that varied with maturity, increasing in adults; E2 and P4 were present at low plasma concentrations in males and did not change with stage of gonadal development. 11-KT was undetectable at all times. Endocrine changes in draughtboard sharks were consistent with hormonal correlates reported for other species and suggest roles for E2( in females) and T (in both sexes) in gametogenesis and P4 in maturational events in females. J. Exp. Zool. 309A:184–197, 2008. © 2008 Wiley-Liss, Inc.

Sleeper sharks are a poorly studied group of deep-sea sharks. The subgenus, Somniosus, contains three morphologically similar species: S. microcephalus found in the Arctic and North Atlantic; S. pacificus in the North Pacific; and S. antarcticus in the Southern Ocean. These sharks have been reported mainly in temperate to polar waters and occasionally in subtropical locations. They have not been recorded in tropical waters. This study investigates the relationships among the accepted species of Somniosus through analysis of mitochondrial cytochrome b sequence variation. Seventy-five samples were examined from four sampling locations in the North Pacific, Southern Ocean and North Atlantic. Twenty-one haplotypes were found. A minimum spanning parsimony network separated these haplotypes into two divergent clades, an S. microcephalus and an S. pacificus/antarcticus clade, strongly supporting the distinction of S. microcephalus as a separate species from the Pacific sleeper shark species. Analysis of genetic structure within the S. pacificus/antarcticus clade (analysis of molecular variance, allele frequency comparisons, and a nested clade analysis) showed limited or no differences amongst three populations. Further examination of genetic variation at more variable mtDNA and nuclear markers is needed to examine the species status of S. pacificus and S. antarcticus. © 2007 Springer-Verlag.

Two scyliorhinid catsharks of the genus Halaelurus, H. sellus n. sp. and H. maculosus n. sp., are described from northwestern Australia and eastern Indonesia, respectively. The new species, which have been confused with H. boesemani (western North Pacific) and H. buergeri (northwestern Indian Ocean), have a colour pattern consisting of dark bars and dark spots but differ from these species by a combination of coloration, morphometrics, and meristics. These species differ from southern African endemics, H. lineatus and H. natalensis, in having a snout tip that is rounded rather than upturned. A related catshark Halaelurus quagga, from the northwestern Indian Ocean, has a colour pattern consisting of more numerous dark bars without spots.

Pop-up satellite archival tags (PSATs) are now widely used to document the geographic and vertical movements of large pelagic fishes. These instruments record measurements of ambient light, depth and temperature at regular intervals and the light data are used to compute daily estimates of latitude and longitude. Several methods have been developed to improve those estimates, including the application of Kalman filter models and matching sea surface temperatures (SST) from tags with remotely sensed SSTs. Despite their widespread use, few studies have evaluated the accuracy of raw estimates of location from PSATs or quantified the improvements that may result from refinement techniques. To assess the accuracy of raw and refined estimates of locations from PSATs, we attached two PSATs and one Argos satellite-linked transmitter (SAT tag) to one whale shark (Rhincodon typus) at Ningaloo Reef, Western Australia. The root mean square error (RMSE) in raw estimates of location provided by the PSATs was 5.16� latitude and 2.00� longitude. Estimates were more accurate after processing the data with a Kalman filter (RMSE = 2.97� latitude and 0.78� longitude) and most accurate after processing with a Kalman filter model that integrates SST measurements (RMSE = 1.84� latitude and 0.78� longitude). We also assessed the precision of the PSAT-derived locations, and depth and temperature measurements by comparing the data from the two PSATs. Our findings support the use of archival tag data to reconstruct the large-scale movements of marine animals and demonstrate the significant improvements that may result from two refinement techniques.

The diet of six skate species caught as bycatch in south-eastern Australian waters was examined over a 2-year period. The skates were segregated into two regions (continental shelf and continental slope) based on prey species and depth of capture. The shelf group consisted of four species, Dipturus sp. A, D. cerva, D. lemprieri and D. whitleyi, while the slope group comprised two species, Dipturus sp. B and D. gudgeri. The two groups varied in feeding strategies with the shelf species generally occupying a broader feeding niche and preying on a larger diversity of prey including a variety of crustaceans (brachyurans, anomurans, achelates, carideans and dendobranchiates), cephalopods, elasmobranchs and teleosts. Within the slope group, Dipturus sp. B and D. gudgeri were more specialised. Dipturus sp. B preyed primarily on anomurans (galatheids) and bachyurans (homolids), whereas D. gudgeri preyed primarily on teleosts. A size related change in diet was evident for all species with the exception of D. gudgeri in which all sizes preyed predominantly on teleosts. Smaller representatives of the four shelf species all preyed on numerous amounts of caridean shrimps, in particular Leptochela sydniensis. In contrast, the continental slope species, Dipturus sp. B consumed anomurans when small, shifting to brachyurans with increasing size. Of the six skate species examined in this study, three were secondary consumers (trophic level 4). Although ANOSIM found significant differences in dietary composition between species within groups, there was some overlap in prey species amongst co-existing skates, which suggests that there is some degree of resource partitioning amongst them.

In the 160 years since Andrew Smith described the whale shark in 1828, two people devoted much of their scientific lives to whale sharks. This period of research mainly comprised documenting the known sightings, captures and strandings of this species. Dr Eugene Gudger collected reports of whale sharks from all over the world and published 47 papers on these sharks in 40 years. Dr Fay Wolfson also documented whale shark records from all over the world and published a bibliography on the species as well as a paper summarising all the known (320) occurrences from published records and verified reports up to 1985. However, life history information during this period was scant. In the succeeding 20 years from 1986, there has been a huge increase in recreational diving and boating activity around the world that has led to discoveries of whale shark aggregations in various places. Together with increased demand and prices for whale shark products this has led to considerable conservation and marine ecotourism interest in the species that has provided the impetus for a number of studies. However, while some further understanding of whale shark reproduction and age and growth has resulted, our knowledge of the species biology and ecology is still poor. Over the last 10 years several tagging and tracking studies have been initiated on whale sharks in various parts of the world. Despite the relatively recent increases in demand for whale shark meat driven by the Taiwan market, there are still few good data in the primary literature from existing fisheries.

Between 1995 and 1997, 360 observations of whale sharks at Ningaloo Reef revealed that approximately 85% were males (4-12 m TL). Based on the external morphology of claspers, all males 9 m were considered mature. A logistic equation fitted to the percentage of mature males in each size class predicted a length at first maturity (L50) of ∼8.0 m TL, while 95% (L95) of males were mature by ∼9.0 m TL. Female whale sharks at Ningaloo Reef during this study were generally smaller and ranged in length from 4 to 8 m TL. The small size and general absence of female whale sharks from Ningaloo Reef suggest that the region may be important for feeding rather than breeding.

The size and depth distribution, stomach contents and reproductive status of Somniosus (Somniosus) microcephalus, Somniosus (Somniosus) pacificus and Somniosus (Somniosus) antarcticus were examined from specimens collected from the North and South Atlantic, North and South Pacific, and the Southern Ocean. Specimens ranged in size from 42 to 480 cm total length, LT, and were taken from depths of 35–1280 m. Stomach contents included coelenterates, gastropods, cephalopods, echinoderms, crustaceans, elasmobranchs, teleosts, penguins, marine mammals and human waste. Female S. (S.) microcephalus mature at c. 450 cm and S. (S.) antarcticus at c. 435 cm LT; a female S. (S.) pacificus of 430 cm was mature. Male S. (S.) microcephalus mature at c. 300 cm, but male S. (S.) antarcticus may not mature until c. 400 cm LT. The size at birth in these three species of Somniosus is c. 40 cm LT.

The design and control of electric warship power systems is a complex, challenging problem and numerous power system architectures, technologies, algorithms, and control schemes have been proposed. Instead of a quantitative assessment of these ideas based on ideal, steady-state conditions, a set of representative operational vignettes that span the entire electric warship mission package is introduced in order to obtain true results. This paper describes a set of realistic test cases that provide load demand dynamics based on a variety of unique scenarios, mission load characteristics, and human-in-the-loop decision-making. Stochastic and deterministic power profiles are established for individual ship systems and mission loads, which are then combined together for a particular scenario. These test cases can be applied to early-stage design trade studies as well as design tool development. For example, various control methods can be benchmarked against the same test cases. In addition to the established test cases, the method used here enables operators to communicate to design engineers how they intend to use the ship (not the other way around).

A principle motivation for the development of early-stage shipboard power system simulation techniques is the need to perform time-domain simulation during the early design stage. In particular, there is a need to understand the performance of a candidate system during challenging situations involving dynamic load profiles and disruptive conditions in order to assess the system dependability. An early-stage simulation technique is applied to simulate the performance of a candidate system for given operational vignettes. Using this early-stage approach allows simulations to be performed very quickly, allowing many vignettes to be considered and the overall system dependability to be assessed.

The giant lantern shark, Etmopterus baxteri, is taken as bycatch of commercial fisheries that operate in deepwater off southeastern Australia. Bands on the second dorsal spine were used to obtain age estimates. The number of bands on the external surface of the spine and within the inner dentine layer increased with animal length. Most spines had more bands on the external surface, and the rate of band formation was significantly different between the external surface and the inner dentine layer. Females had a maximum of 57 external bands and 26 internal bands, while males had up to 48 external bands and 22 internal bands. Age estimates from external bands suggest maturity (A 50) at 20 years for males and 30 years for females. Internal band age estimates suggest maturity at 10.5 years for males and 11.5 years for females. Although there is a large discrepancy between these two preliminary (i.e., unvalidated) age estimates, they both suggest that E. baxteri is a long-lived and late maturing species that is likely to be susceptible to over fishing.

We used a combination of satellite telemetry, archival and conventional tags to show that white sharks made broad-scale movements consistent with mixing of the population across their entire Australasian range. The capture of one of these sharks in New Zealand, some 3,550 km from the point of tagging in South Australia, provides further confirmation that white sharks sometimes move into open ocean waters and cross deep ocean basins. However, most movements were confined to shelf waters, generally in areas of less than 100 m depth and in some cases into waters of less than 5 m depth. Sharks showed considerable plasticity in swimming patterns, which included many of the behaviours reported for other species. One of the archival-tagged sharks showed separate periods of distinct swimming behaviour as it moved into different habitats and travelled between them. The changes in swimming behaviour were abrupt and suggested rapid switching of hunting strategies for different prey types in these habitats. All tracked sharks showed both prolonged periods of directional swimming in coastal waters at swimming speeds of 2–3 km h−1 as well as temporary residency in particular regions. Movements of tagged white sharks, together with data from shark control programs and bycatch records, suggest a seasonal movement northward along the east coast of Australia during the autumn–winter months and south in spring–early summer. The consistency of paths taken by white sharks in Australian waters suggests that they may follow common routes or “highways” in some areas. If so, identifying such areas may assist in reducing interactions with fishing operations and thus reduce bycatch.

Bands on the external surface of the second dorsal-fin spine proved to be a novel method of estimating the age and growth of Centroselachus crepidater. Bands that followed the shape of the spine base were enhanced with an alizarin red derivative. Internal bands in spine cross sections were also examined. The number of both external and internal bands increased with animal size, although most spines had more external than internal bands. External bands were more reliable and were assumed to be annuli. The rate of band formation differed after five bands had been formed, and internal bands ceased forming after 30 years. Females to 54 years old and males to 34 years old were examined. Maturity occurred over a wide age range, with estimates of 20 years for females and 9 years for males. The youngest pregnant female was 27 years old. The Francis reparameterized von Bertalanffy growth model found similar growth for males and females, and the von Bertalanffy equations were Lt = 96.12(1 – e(–0.072(t+6.13))) for females and Lt = 73.22(1 – e(–0.141(t+2.99))) for males.

Past treatments of the sleeper shark genus Somniosus generally recognize three species: S. microcephalus, S. pacificus, and S. rostratus. Based on morphometrics and meristics, we conclude that this genus includes two subgenera (Somniosus and Rhinoscymnus) and five species. Subgenus Somniosus differs from Rhinoscymnus by being much larger when adult and in having more numerous tooth rows in the lower jaw, hooklike rather than leaf-shaped dermal denticles, more numerous spiral valve and vertebral counts, and a poorly calcified vertebral column. Subgenus Somniosus includes S. (Somniosus) microcephalus and S. (S.) pacificus of the Northern Hemisphere and S. (S.) antarcticus of the Southern Hemisphere. Although Somniosus antarcticus has been synonymized with S. microcephalus and identified as S. pacificus in past literature, it differs from S. microcephalus in having a shorter interdorsal space, a more posterior first dorsal fin, lower dorsal fins, more numerous tooth rows in the lower jaw, more numerous spiral valve counts, and fewer precaudal vertebrae. Somniosus antarcticus also differs from S. pacificus by having a shorter prebranchial length, lower dorsal fins, more numerous spiral valve counts, and slightly more precaudal vertebrae. Subgenus Rhinoscymnus includes S. (Rhinoscymnus) rostratus from the eastern North Atlantic and Mediterranean Sea (senior synonym of S. bauchotae) and S. (R.) longus from the western Pacific Ocean. Somniosus longus has been synonymized with S. rostratus, but differs in having a relatively longer second dorsal fin, a slightly larger eye, more lower tooth rows, and slightly higher spiral valve counts. Both Somniosus (Somniosus) antarcticus and S. (Rhinoscymnus) longus from the Pacific Ocean were redescribed. A key to the species and the geographical distribution of all species are provided.

Tiger sharks (Galeocerdo cuvier) are apex predators occurring in most tropical and warm temperate marine ecosystems, but we know relatively little of their patterns of residency and movement over large spatial and temporal scales. We deployed satellite tags on eleven tiger sharks off the north-western coast of Western Australia and used the Brownian Bridge kernel method to calculate home ranges and analyse movement behaviour. One individual recorded one of the largest geographical ranges of movement ever reported for the species, travelling over 4000 km during 517 days of monitoring. Tags on the remainder of the sharks reported for shorter periods (7-191 days). Most of these sharks had restricted movements and long-term (30-188 days) residency in coastal waters in the vicinity of the area where they were tagged. Core home range areas of sharks varied greatly from 1166.9 to 634,944 km2. Tiger sharks spent most of their time in water temperatures between 23°-26°C but experienced temperatures ranging from 6°C to 33°C. One shark displayed seasonal movements among three distinct home range cores spread along most of the coast of Western Australia and generalized linear models showed that this individual had different patterns of temperature and depth occupancy in each region of the coast, with the highest probability of residency occurring in the shallowest areas of the coast with water temperatures above 23°C. These results suggest that tiger sharks can migrate over very large distances and across latitudes ranging from tropical to the cool temperate waters. Such extensive long-term movements may be a key element influencing the connectivity of populations within and among ocean basins.

The rapid expansion of human activities threatens ocean-wide biodiversity. Numerous marine animal populations have declined, yet it remains unclear whether these trends are symptomatic of a chronic accumulation of global marine extinction risk. We present the first systematic analysis of threat for a globally distributed lineage of 1,041 chondrichthyan fishes—sharks, rays, and chimaeras. We estimate that one-quarter are threatened according to IUCN Red List criteria due to overfishing (targeted and incidental). Large-bodied, shallow-water species are at greatest risk and five out of the seven most threatened families are rays. Overall chondrichthyan extinction risk is substantially higher than for most other vertebrates, and only one-third of species are considered safe. Population depletion has occurred throughout the world’s ice-free waters, but is particularly prevalent in the Indo-Pacific Biodiversity Triangle and Mediterranean Sea. Improved management of fisheries and trade is urgently needed to avoid extinctions and promote population recovery. DOI: http://dx.doi.org/10.7554/eLife.00590.001, eLife digest Ocean ecosystems are under pressure from overfishing, climate change, habitat destruction and pollution. These pressures have led to documented declines of some fishes in some places, such as those living in coral reefs and on the high seas. However, it is not clear whether these population declines are isolated one-off examples or, instead, if they are sufficiently widespread to risk the extinction of large numbers of species. Most fishes have a skeleton that is made of bone, but sharks and rays have a skeleton that is made of cartilage. A total of 1,041 species has such a skeleton and they are collectively known as the Chondrichthyes. To find out how well these fish are faring, Dulvy et al. worked with more than 300 scientists around the world to assess the conservation status of all 1,041 species. Based on this, Dulvy et al. estimate that one in four of these species are threatened with extinction, mainly as a result of overfishing. Moreover, just 389 species (37.4% of the total) are considered to be safe, which is the lowest fraction of safe species among all vertebrate groups studied to date. The largest sharks and rays are in the most peril, especially those living in shallow waters that are accessible to fisheries. A particular problem is the ‘fin trade’: the fins of sharks and shark-like rays are a delicacy in some Asian countries, and more than half of the chondrichthyans that enter the fin trade are under threat. Whether targeted or caught by boats fishing for other species, sharks and rays are used to supply a market that is largely unmonitored and unregulated. Habitat degradation and loss also pose considerable threats, particularly for freshwater sharks and rays. Dulvy et al. identified three main hotspots where the biodiversity of sharks and rays was particularly seriously threatened—the Indo-Pacific Biodiversity Triangle, Red Sea, and the Mediterranean Sea—and argue that national and international action is needed to protect them from overfishing. DOI: http://dx.doi.org/10.7554/eLife.00590.002

Stevens, J. D., Bonfil, R., Dulvy, N. K., and Walker, P. A. 2000. The effects of fishing on sharks, rays, and chimaeras (chondrichthyans), and the implications for marine ecosystems. – ICES Journal of Marine Science, 57: 476–494. The impact of fishing on chondrichthyan stocks around the world is currently the focus of considerable international concern. Most chondrichthyan populations are of low productivity relative to teleost fishes, a consequence of their different life-history strategies. This is reflected in the poor record of sustainability of target shark fisheries. Most sharks and some batoids are predators at, or near, the top of marine food webs. The effects of fishing are examined at the single-species level and through trophic interactions. We summarize the status of chondrichthyan fisheries from around the world. Some 50% of the estimated global catch of chondrichthyans is taken as by-catch, does not appear in official fishery statistics, and is almost totally unmanaged. When taken as by-catch, they are often subjected to high fishing mortality directed at teleost target species. Consequently, some skates, sawfish, and deep-water dogfish have been virtually extirpated from large regions. Some chondrichthyans are more resilient to fishing and we examine predictions on the vulnerability of different species based on their life-history and population parameters. At the species level, fishing may alter size structure and population parameters in response to changes in species abundance. We review the evidence for such density-dependent change. Fishing can affect trophic interactions and we examine cases of apparent species replacement and shifts in community composition. Sharks and rays learn to associate trawlers with food and feeding on discards may increase their populations. Using ECOSIM, we make some predictions about the long-term response of ecosystems to fishing on sharks. Three different environments are analysed: a tropical shelf ecosystem in Venezuela, a Hawaiian coral reef ecosystem, and a North Pacific oceanic ecosystem. 2000 International Council for the Exploration of the Sea

The short-term movements and behaviour of whale sharks (Rhincodon typus Smith, 1828) during March 1994 and April 1997 are reported from data collected by acoustic tracking and archival tags at Ningaloo Reef on the north west coast of Western Australia. Sharks were tracked for up to 26 h and generally swam slowly at ≃0.7 m s -1 parallel to the reef edge; occasionally they swam in a wide arc adjacent to passes in the reef. All tracked sharks made regular dives through the water column, mostly from the surface to near the bottom. These dives did not appear to be related to hydrographic features, and the sharks were probably searching the water column for food. Most sharks were accompanied by other fishes, usually the golden trevally Gnathanodon speciosus.

A simple probabilistic model that incorporates fishing mortality, natural mortality, tag shedding, and differing reporting rates is developed, a likelihood function for estimating its parameters is derived, and a set of tagging data on newborn school shark, Galeorhinus galeus, is analysed to estimate their instantaneous natural and fishing mortalities. For a truncated tagging experimental period of 92 days, the instantaneous rate of natural mortality of newborn school sharks was estimated at 9.0427 × 10-3 (±2.4553 × 10-2)·day-1 or 3.3028 (±8.9680)·year-1 and is equal to a survival rate (from natural death only) of e-0.0090427 = 99.10%·day-1 or e-3.3028 = 3.68%·year-1. From this estimate and its corresponding estimates of catchability coefficients, we also calculated their instantaneous rate of fishing mortality in the study area from longlines, gill-nets, or both, and their survival rate, all as a function of time. This work extends previous work by incorporating fish tag shedding rates and reporting rates and by giving a detailed derivation of the likelihood function.