نتایج جستجو برای: sharks

تعداد نتایج: 2511  

2011
Rafael de la Parra Venegas Robert Hueter Jaime González Cano John Tyminski José Gregorio Remolina Mike Maslanka Andrea Ormos Lee Weigt Bruce Carlson Alistair Dove

Whale sharks, Rhincodon typus, are often perceived as solitary behemoths that live and feed in the open ocean. To the contrary, evidence is accumulating that they are gregarious and form seasonal aggregations in some coastal waters. One such aggregation occurs annually north of Cabo Catoche, off Isla Holbox on the Yucatán Peninsula of Mexico. Here we report a second, much denser aggregation of ...

2001
William D. Heyman Rachel T. Graham Björn Kjerfve Robert E. Johannes

This study confirms reports by fishermen of a large and predictable aggregation of whale sharks Rhincodon typus along the Belize Barrier Reef. Although whale sharks are rarely sighted at this location during most of the year, we counted as many as 25 whale sharks in a 50 m diameter area on 1 occasion and tagged 6 sharks during a 22 min period on another. The whale shark aggregation coincides se...

2009
Carl G. Meyer Timothy B. Clark Yannis P. Papastamatiou Nicholas M. Whitney Kim N. Holland

Little is known about the long-term movement patterns of most marine apex predators. A network of acoustic receivers was used to quantify the long-term movements of transmitterequipped tiger sharks Galeocerdo cuvier Péron & Lesueur, 1822 in the Main Hawaiian Islands. Tiger sharks were wide-ranging, swam between islands and patrolled up to 109 km of contiguous coastline. Visits to specific acous...

2013
Alison Kock M. Justin O’Riain Katya Mauff Michael Meÿer Deon Kotze Charles Griffiths

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 ...

2012
Nuno Queiroz Nicolas E. Humphries Leslie R. Noble António M. Santos David W. Sims

Dramatic population declines among species of pelagic shark as a result of overfishing have been reported, with some species now at a fraction of their historical biomass. Advanced telemetry techniques enable tracking of spatial dynamics and behaviour, providing fundamental information on habitat preferences of threatened species to aid conservation. We tracked movements of the highest pelagic ...

2009
Nicole Nasby-Lucas Heidi Dewar Chi H. Lam Kenneth J. Goldman Michael L. Domeier

BACKGROUND Although much is known about the behavior of white sharks in coastal regions, very little is known about their vertical movements offshore in the eastern Pacific where they spend up to five months. We provide the first detailed description of the offshore habitat use of white sharks in the eastern North Pacific. METHODOLOGY/PRINCIPAL FINDINGS This study uses 2-min data from four re...

Journal: :Current Biology 2009
Gregory B. Skomal Stephen I. Zeeman John H. Chisholm Erin L. Summers Harvey J. Walsh Kelton W. McMahon Simon R. Thorrold

The world's second largest fish, the basking shark (Cetorhinus maximus), is broadly distributed in boreal to warm temperate latitudes of the Atlantic and Pacific oceans from shallow coastal waters to the open ocean. Previous satellite archival tagging in the North Atlantic has shown that basking sharks move seasonally, are often associated with productive frontal zones, and may make occasional ...

2008
Julia K. Baum

Julia K. Baum* and Ransom A. Myers Department of Biology, Dalhousie University, Halifax, Nova Scotia, B3H 4J1, Canada *Correspondence: E-mail: [email protected] Abstract Historical abundances of many large marine vertebrates were tremendously greater than today. However, while pelagic sharks are known to have declined rapidly in the northwest Atlantic in recent years, there, as elsewhere, li...

2012
Martin A. Becker

Chipped and broken functional teeth are common in modern sharks with serrated tooth shape. Tooth damage consists of splintering, cracking, and flaking near the cusp apex where the enameloid is broken and exposes the osteodentine and orthodentine. Such damage is generally viewed as the result of forces applied during feeding as the cusp apex impacts the skeletal anatomy of prey. Damage seen in s...

2016
Kwok Ho Tsoi Sau Ying Chan Yeung Chung Lee Brian Ho Yeung Ip Chi Chiu Cheang

Shark conservation has become a focus of current international conservation efforts. However, the misunderstanding of sharks and their negative public portrayal may hinder their conservation. More importantly, the consumption of shark fin, which is very common in Chinese cultures, poses a significant threat to sharks. Hong Kong has long been the world's largest shark fin trading center. Shark c...

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