نتایج جستجو برای: sharks

تعداد نتایج: 2511  

Journal: :Advances in marine biology 2017
Peter A Mieras Chris Harvey-Clark Michael Bear Gina Hodgin Boone Hodgin

Historically sharks have been seen either as a source of income through harvesting, or as a nuisance and danger. The economic value of sharks has traditionally been measured as the total value of sharks caught for liver oil, fins, or meat for consumption. Sharks have also been killed to near extinction in cases where they were seen as a threat to fisheries on other species. This is illustrated ...

2015
Kerstin B. J. Glaus Irene Adrian-Kalchhauser Patricia Burkhardt-Holm William T. White Juerg M. Brunnschweiler

Limited information is available on artisanal and subsistence shark fisheries across the Pacific. The aim of this study was to investigate Fiji's inshore fisheries which catch sharks. In January and February 2013, 253 semi-directive interviews were conducted in 117 villages and at local harbours on Viti Levu, Vanua Levu, Taveuni, Ovalau and a number of islands of the Mamanuca and Yasawa archipe...

Journal: :Molecular phylogenetics and evolution 2004
Christopher J Winchell Andrew P Martin Jon Mallatt

The dominant view of the phylogeny of living elasmobranchs, based on morphological characters, is that batoids (skates and rays) are derived sharks, joined with saw sharks, and angel sharks in the clade Hypnosqualea [S. Shirai, Squalean Phylogeny: A New Framework of 'Squaloid' Sharks and Related Taxa, Hokkaido University Press, Sapporo, 1992]. By contrast, a recent molecular-phylogenetic study ...

Journal: :progress in biological sciences 2015
mona goharimanesh fereshteh ghassemzadeh masoud goharimanesh

the mouths of some bony and cartilaginous fishes are located in the anterior part of theirbodies, with a slight variation in sharks, which have theirs located in the abdominal part. thisvariation is evolutionary over time. the force exerted by the jaws of sharks in order todismember their prey can be examined from two origins: .the determined force exerted by teethand muscles and the force as a...

2016
David P. Robinson Mohammed Y. Jaidah Steffen Bach Katie Lee Rima W. Jabado Christoph A. Rohner Abi March Simone Caprodossi Aaron C. Henderson James M. Mair Rupert Ormond Simon J. Pierce

Data on the occurrence of whale sharks, Rhincodon typus, in the Arabian Gulf and Gulf of Oman were collected by dedicated boat surveys and via a public-sightings scheme during the period from 2011 to 2014. A total of 422 individual whale sharks were photo-identified from the Arabian Gulf and the northern Gulf of Oman during that period. The majority of sharks (81%, n = 341) were encountered at ...

Journal: :Archives of environmental contamination and toxicology 2014
Darren Rumbold Robert Wasno Neil Hammerschlag Aswani Volety

As large long-lived predators, sharks are particularly vulnerable to exposure to methylmercury biomagnified through the marine food web. Accordingly, nonlethal means were used to collect tissues for determining mercury (Hg) concentrations and stable isotopes of carbon (δ(13)C) and nitrogen (δ(15)N) from a total of 69 sharks, comprising 7 species, caught off Southwest Florida from May 2010 throu...

2014
Jonathan M. Werry Serge Planes Michael L. Berumen Kate A. Lee Camrin D. Braun Eric Clua

Knowledge of the habitat use and migration patterns of large sharks is important for assessing the effectiveness of large predator Marine Protected Areas (MPAs), vulnerability to fisheries and environmental influences, and management of shark-human interactions. Here we compare movement, reef-fidelity, and ocean migration for tiger sharks, Galeocerdo cuvier, across the Coral Sea, with an emphas...

2011
Jonathan J. Dale Austin M. Stankus Michael S. Burns Carl G. Meyer

Empirical data on the abundance and habitat preferences of coral reef top predators are needed to evaluate their ecological impacts and guide management decisions. We used longline surveys to quantify the shark assemblage at French Frigate Shoals (FFS) atoll from May to August 2009. Fishing effort consisted of 189 longline sets totaling 6,862 hook hours of soak time. A total of 221 sharks from ...

2015
Christoph A. Rohner Amelia J. Armstrong Simon J. Pierce Clare E. M. Prebble E. Fernando Cagua Jesse E. M. Cochran Michael L. Berumen Anthony J. Richardson

Large planktivores require high-density prey patches to make feeding energetically viable. This is a major challenge for species living in tropical and subtropical seas, such as whale sharks Rhincodon typus. Here, we characterize zooplankton biomass, size structure and taxonomic composition from whale shark feeding events and background samples at Mafia Island, Tanzania. The majority of whale s...

1999
Edward J. Heist John R. Gold

The U.S. Atlantic large coastal shark fishery grew rapidly during the 1980s when commercial landings increased from 135 metric tons (t) in 1979 to a high of 7122 t in 1989 (NMFS, 1993). In 1993, a quota of 2750 t was established; in 1997 this quota was halved to 1375 t in order to rebuild depleted shark stocks. This fishery targets several species of sharks that are valued for fins (exported to...

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