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"CRAB"
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Lobster vs. crab
Contains facts about lobsters and crabs, comparing such aspects as their sizes and abilities, and what the outcome would be if they were to fight each other.
Book
Gamma-Ray Flares from the Crab Nebula
A young and energetic pulsar powers the well-known Crab Nebula. Here, we describe two separate gamma-ray (photon energy greater than 100 mega-electron volts) flares from this source detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The first flare occurred in February 2009 and lasted approximately 16 days. The second flare was detected in September 2010 and lasted approximately 4 days. During these outbursts, the gamma-ray flux from the nebula increased by factors of four and six, respectively. The brevity of the flares implies that the gamma rays were emitted via synchrotron radiation from peta-electron-volt (10¹⁵ electron volts) electrons in a region smaller than 1.4 x 10⁻² parsecs. These are the highest-energy particles that can be associated with a discrete astronomical source, and they pose challenges to particle acceleration theory.
Journal Article
Captain Phil Harris : the legendary crab fisherman, our hero, our dad
Presents a portrait of the late star of Discovery Channel's \"Deadliest Catch,\" revealing his high-risk private life of tempestuous affairs, drug-fueled parties, and motorcycle riding, as well as his virtues as a devoted friend, loving father, and steadfast captain.
Book
Walking Sideways
The world's nearly 7,000 species of crabs are immediately recognizable by their claws, sideways movement, stalked eyes, and thick outer shells. These common crustaceans are found internationally, thriving in various habitats from the edge of the sea to the depths of the ocean, in fresh water or on land. Despite having the same basic body type as decapod crustaceans-true crabs have heavy exoskeletons and ten limbs with front pincer claws-crabs come in an enormous variety of shapes and sizes, from the near microscopic to the giant Japanese spider crab.
InWalking Sideways, Judith S. Weis provides an engaging and informative tour of the remarkable world of crabs, highlighting their unique biology and natural history. She introduces us to recently discovered crabs such as the Yeti crab found in deep sea vents, explains what scientists are learning about blue and hermit crabs commonly found at the shore, and gives us insight into the lifecycles of the king and Dungeness crabs typically seen only on dinner plates. Among the topics Weis covers are the evolution and classification of crabs, their habitats, unique adaptations to water and land, reproduction and development, behavior, ecology, and threats, including up-to-date research.
Crabs are of special interest to biologists for their communication behaviors, sexual dimorphism, and use of chemical stimuli and touch receptors, and Weis explains the importance of new scientific discoveries. In addition to the traditional ten-legged crabs, the book also treats those that appear eight-legged, including hermit crabs, king crabs, and sand crabs. Sidebars address topics of special interest, such as the relationship of lobsters to crabs and medical uses of compounds derived from horseshoe crabs (which aren't really crabs).
While Weis emphasizes conservation and the threats that crabs face, she also addresses the use of crabs as food (detailing how crabs are caught and cooked) and their commercial value from fisheries and aquaculture. She highlights other interactions between crabs and people, including keeping hermit crabs as pets or studying marine species in the laboratory and field. Reminding us of characters such asThe Little Mermaid's Sebastian and Sherman Lagoon's Hawthorne, she also surveys the role of crabs in literature (for both children and adults), film, and television, as well in mythology and astrology. With illustrations that offer delightful visual evidence of crab diversity and their unique behaviors,Walking Sidewayswill appeal to anyone who has encountered these fascinating animals on the beach, at an aquarium, or in the kitchen.
eBook
A star explodes : the story of Supernova 1054
\"About 7,500 years ago, a star exploded in our galaxy, burning bright as billions of suns. It took thousands of years for the light of this explosion to reach Earth, but in the year 1054, people of the Chinese court recorded a new star in the night sky that shone brighter than all the other stars. A guest star, they called it, and they marvelled as its light shone even through the bright of day.\"-- Front jacket flap.
BOOK
Mud crab fishery in climate vulnerable coastal Bangladesh: an analysis towards sustainable development
Developing countries are far more vulnerable to climate change impacts than industrialised countries. Most of the world’s poor live in South Asia where they have limited livelihood options that have become even narrower in recent years, indicating a need for alternative income-generating options. Mud crabs (Scylla spp.) are considered to have promising prospects in different parts of the world including Bangladesh, a well-known region for its vulnerability to climate change. At present, this fishery has become a growing venture in coastal Bangladesh, primarily due to the potential of the export market and availability of seed locally. This study included a calculation of the Human Development Index linked to mud crab fishery (HDIMCF) and a strengths, weaknesses, opportunities and threats (SWOT) analysis to clarify the present status of and strategic directions for the mud crab fishery, for the first time. Results revealed an intermediate level of development of mud crab aquaculture, indicating potential alternative livelihood opportunities for vulnerable coastal communities. The SWOT analysis revealed that positive factors, both internal (strengths) and external (opportunities), predominate over negative factors (weaknesses and threats) and that the fishery can be an alternative livelihood option for vulnerable coastal communities. Despite noticeable diversification of the mud crab fishery, dependence on wild seedstock and possible over-exploitation in the wild appear to constrain sustainable development of the fishery. This study’s findings suggest undertaking immediate wild crab stock assessment for determining current status of wild populations. Moreover, modification of the Government of Bangladesh’s existing mud crab policy is needed to better meet growing demand and sustainability of the fishery. Recommendations of this study may be of help in guiding responsible integrated coastal fisheries management and policy.
Journal Article
A critical review of cast-off crab shell recycling from the perspective of functional and versatile biomaterials
Shellfish cultivation is an expanding economic activity worldwide. However, the rapid development of crab farming and processing result in a large number of crab shells (CS). Utilizing CS could not only benefit the environment and economy but also promote the sustainable development of aquaculture. In this work, it reviews and analyzes recent attempts in CS recycling, including extracting chitin and its derivatives, for use as adsorbent and flocculant and for preparing polymer composites and catalysts, as well as medical applications. The challenges in these utilizations are discussed, and future research directions are proposed as well. Extracting chitin and its derivates, for use as adsorbent and flocculant, are recent major recycling approaches. Preparing polymer composites and carbon materials has gained more and more attentions. Biotechnology is an alternative method for extracting chitin and its derivates from CS, and high-efficiency desalted and deproteinized bacteria need to be screened. Immobilizing the CS-based adsorbents is the key of treating wastewater in continuous systems. Using CS as a biofiller to prepare polymer composites is promising, and surface modification to improve the interfacial compatibility between CS-based fillers and matrix needs to be further studied.
Journal Article
Ultrahigh-energy photons up to 1.4 petaelectronvolts from 12 γ-ray Galactic sources
The extension of the cosmic-ray spectrum beyond 1 petaelectronvolt (PeV; 10
15
electronvolts) indicates the existence of the so-called PeVatrons—cosmic-ray factories that accelerate particles to PeV energies. We need to locate and identify such objects to find the origin of Galactic cosmic rays
1
. The principal signature of both electron and proton PeVatrons is ultrahigh-energy (exceeding 100 TeV) γ radiation. Evidence of the presence of a proton PeVatron has been found in the Galactic Centre, according to the detection of a hard-spectrum radiation extending to 0.04 PeV (ref.
2
). Although γ-rays with energies slightly higher than 0.1 PeV have been reported from a few objects in the Galactic plane
3
–
6
, unbiased identification and in-depth exploration of PeVatrons requires detection of γ-rays with energies well above 0.1 PeV. Here we report the detection of more than 530 photons at energies above 100 teraelectronvolts and up to 1.4 PeV from 12 ultrahigh-energy γ-ray sources with a statistical significance greater than seven standard deviations. Despite having several potential counterparts in their proximity, including pulsar wind nebulae, supernova remnants and star-forming regions, the PeVatrons responsible for the ultrahigh-energy γ-rays have not yet been firmly localized and identified (except for the Crab Nebula), leaving open the origin of these extreme accelerators.
Observations of γ-rays with energies up to 1.4 PeV find that 12 sources in the Galaxy are PeVatrons, one of which is the Crab Nebula.
Journal Article
Factors Affecting the Recovery of Invertebrate Stocks From the 2011 Western Australian Extreme Marine Heatwave
The extreme Western Australia 2011 marine heatwave had a lasting effect on the marine ecosystem and after seven years, only parts of the ecosystem have showed good signs of recovery. After the heatwave, scallop fisheries in the Abrolhos Is. and Shark Bay were closed for 3-5 years, while the Shark Bay crab fishery was closed for 18 months; these fisheries at the centre of the heatwave have shown some improvement due to better protection of spawning stock and improved environmental conditions. Also at the centre of the heatwave, Roe’s abalone suffered a catastrophic mortality and has not recovered as spawning stock remains very low. The Perth abalone stock which was outside the peak heatwave area had a major stock reduction but remained opened with reduced catches. The heatwave had a marked indirect effect on brown tiger prawns in Exmouth Gulf due to loss of seagrass habitat. The heatwave also resulted in a decline in western king prawn recruitment in Exmouth Gulf, to the north of heatwave centre, but an improved recruitment in the cooler waters of Shark Bay. Western rock lobsters near the heatwave peak also appear to have been indirectly affected and have not recovered. Factors influencing the recovery rate from the heatwave appeared to be: species near their upper temperature range and/or sensitive to warming temperatures; spatial overlap between the warming event and species distribution; whether spawning stock was affected to the point of recruitment impairment; life-cycle duration of invertebrate (or habitat) species affected; and management intervention. This study provides a framework for managing the consequences of heatwaves on fisheries by highlighting the value of early identification of the event and its effect on fisheries and having flexible harvest strategies for early management intervention. This is particularly important as long-term increases in water temperatures will increase the frequency of marine heatwave events and the fisheries stocks would have less time for recovery
Journal Article
Feeding Behavior and Bait Selection Characteristics for the Portunidae Crabs Portunus sanguinolentus and Charybdis natator
Understanding the feeding behavior of Portunidae crabs with different baits can improve bait selection and is crucial for improving the effectiveness of crab fishing gear. This study, conducted in indoor experimental tanks, used trajectory tracking software and two types of natural baits (mackerel (Scomber australasicus) and squid (Uroteuthis chinensis)) to understand the behavior of Portunus sanguinolentus and Charybdis natator. Spatial distribution results showed that P. sanguinolentus was frequently present in the starting area (S1) and bait area (S3) in the control and treatment groups. However, C. natator was frequently present and concentrated in the S1 area compared to the middle areas S2 and S3, and only in the mackerel treatments were they observed to move to the S3 areas. The spatial distribution results indicate that P. sanguinolentus shows a stronger willingness to explore its surroundings, while C. natator is generally in a stationary, wait-and-see state. The swimming speeds of P. sanguinolentus and C. natator showed different trends. P. sanguinolentus showed continuous movement with no fixed speed when no bait was present in the control groups. However, when treated with mackerel and squid, the average swimming speed of P. sanguinolentus was faster (>5 cm/s) in the first 10 min and showed a more stable movement speed when searching for the baits. C. natator showed a stationary or low movement speed when no bait was present in the control groups. However, when C. natator perceived the presence of the baits in the treatment groups, their movement speed increased in the first 10 min. In addition, there was no significant difference between male and female crabs of P. sanguinolentus and C. natator in movement speed in the control and treatment groups. Compared to C. natator, P. sanguinolentus might be more sensitive to natural baits, as shown by its movement from S1 to S3. The results indicate that the species of Portunidae crabs show different bait selections. Natural baits (mackerel and squid) are recommended for catching P. sanguinolentus in crab fisheries.
Journal Article