scholarly journals Intraspecific demography of the silky shark (Carcharhinus falciformis): implications for fisheries management

2019 ◽  
Author(s):  
Michael I Grant ◽  
Jonathan J Smart ◽  
Cassandra L Rigby ◽  
William T White ◽  
Andrew Chin ◽  
...  
Keyword(s):  
Life History ◽  
Fisheries Management ◽  
Life Stage ◽  
Leslie Matrix ◽  
Parameter Estimates ◽  
Shark Species ◽  
Life History Parameter ◽  
Silky Shark ◽  
Carcharhinus Falciformis ◽  
Management Approaches

Abstract The silky shark (Carcharhinus falciformis) is one of the most heavily fished tropical shark species globally, and currently there is increasing concern for its conservation status. However, large differences and ambiguity in life history parameter estimates among regions complicates its conservation and fisheries management. Using a Leslie matrix model that incorporated stochastic effects, we analysed the intraspecific demography of C. falciformis using available life history data from seven regions. Among regions, large differences were observed in generation time and age-specific reproductive contributions. Carcharhinus falciformis generally had low resilience to fishing mortality (F) throughout its distribution. Age-at-first-capture and age-at-last-capture management approaches resulted in substantial differences among regions. This was largely influenced by age-at-maturity. However, in scrutinizing some regional life history studies, it is likely that sampling design and methodological differences among regions have resulted in inaccuracies in life history parameter estimates and subsequent demographic attributes. This implies that age and life-stage-dependent management approaches using these possibly inaccurate life history parameters may be inappropriate. We suggest that a greater emphasis needs to be placed on eliminating human sources of error in elasmobranch life history studies to ensure management for wide-ranging species, such as C. falciformis, is most effective.

Life history characteristics of the silky shark Carcharhinus falciformis from the central west Pacific

2018 ◽  
Vol 69 (4) ◽  
pp. 562 ◽  
Author(s):  
Michael I. Grant ◽  
Jonathan J. Smart ◽  
William T. White ◽  
Andrew Chin ◽  
Leontine Baje ◽  
...  
Keyword(s):  
Life History ◽  
Growth Parameters ◽  
Growth Models ◽  
Significant Risk ◽  
Growth Parameter ◽  
Parameter Estimates ◽  
West Pacific ◽  
Average Litter Size ◽  
Silky Shark ◽  
Carcharhinus Falciformis

In the central west Pacific region, silky sharks (Carcharhinus falciformis) are commonly taken in fisheries, forming up to 95% of incidental elasmobranch bycatch. The present study examined the life history of silky sharks (n=553) from Papua New Guinean waters. Age was analysed using sectioned vertebrae, and a multimodel approach was applied to the length-at-age data to fit growth models. Females ranged in length from 65.0- to 253.0-cm total length (TL), with the oldest estimated at 28 years. Males ranged in length from 68.4 to 271.3cm TL and were aged to a maximum of 23 years. The logistic model provided the best fitting growth parameter estimates of length at birth L0=82.7cm TL, growth coefficient g=0.14year–1 and asymptotic length L∞=261.3cm TL for the sexes combined. Females reached sexual maturity at 204cm TL and 14.0 years, whereas males reached maturity at 183cm TL and 11.6 years. The average litter size from 28 pregnant females was 8 (range of 3–13). The growth parameters and late ages of sexual maturation for silky sharks in the central west Pacific suggest a significant risk from fisheries exploitation without careful population management.

scholarly journals Availability of vulnerable elasmobranches in the marine water of Bangladesh

2013 ◽  
Vol 40 (2) ◽  
pp. 221-229 ◽  
Author(s):  
Roy Bikram Jit ◽  
Nripendra Kumar Singha ◽  
SM Hasan Ali ◽  
Md Gaziur Rhaman
Keyword(s):  
Marine Water ◽  
Shark Species ◽  
Total Catch ◽  
Percentage Contribution ◽  
Percentage Composition ◽  
Average Percentage ◽  
Silky Shark ◽  
Carcharhinus Falciformis

A study was conducted about vulnerable shark and ray species availability and their percentage composition in two fish landing centers at Fishery ghat, Chittagong and BFDC fish harbor, Cox’s Bazar district during April 2006 through March 2012. A total of 35 species (11 shark and 24 ray species) was identified within these six years. Out of 35 species, only one vulnerable shark species, the silky shark Carcharhinus falciformis (Muller and Henle, 1839), was not abundant all the year round and three were vulnerable ray species, Javanese cow ray Rhinoptera javanica (Muller and Henle, 1841), banded eagle ray Aetomylaeus nichofii (Bloch and Schneider, 1801) and white spotted shovelnose ray Rhynchobatus laevis (Bloch and Schneider 1801) were found throughout the year during the study period. The average percentage composition by weight of C. falciformis was 1.38 and the availability of average number was 3202. The average percentage contribution and the landed average number of vulnerable R. javanica, A. nichofii and R. laevis species were 1.46% (948 numbers), 0.61% (554 numbers) and 0.54% (298 numbers), respectively of the total catch. DOI: http://dx.doi.org/10.3329/bjz.v40i2.14316 Bangladesh J. Zool. 40(2): 221-229, 2012

scholarly journals SIZE, SEX AND LENGTH AT MATURITY OF FOUR COMMON SHARKS CAUGHT FROM WESTERN INDONESIA

2007 ◽  
Vol 32 (1) ◽  
pp. 7-19 ◽  
Author(s):  
Fahmi ◽  
Kurnaen Sumadhiharga
Keyword(s):  
Conservation Status ◽  
Shark Species ◽  
Sex Composition ◽  
Sphyrna Lewini ◽  
Scalloped Hammerhead ◽  
Landing Sites ◽  
Silky Shark ◽  
Carcharhinus Falciformis

A study on four common shark species in Indonesia, the spinner shark Carcharhinus brevipinna (Muller and Henle, 1839), silky shark Carcharhinus falciformis (Bibron, 1839), spot-tail shark Carcharhinus sorrah (Valenciennes, 1839) and scalloped hammerhead Sphyrna lewini (Griffith and Smith, 1834) was conducted at several shark landing sites in western Indonesia from March 2002 to December 2004. Data were collected from the surveyed areas including the length of frequency, sex composition and length at maturity. In general, they were caught at size smaller than their maturity size. The proportion of immature C. brevipinna, C. falciformis, C. sorrah and S. lewini to their total number recorded at the surveyed area during the study were about 87%, 50%, 80% and 65%, respectively. According to the length at maturity, females generally attained their maturity in larger size than males. Some factors contributing the catches in immature size and conservation status of those four species were also discussed.

Isotopic niches of the blue shark Prionace glauca and the silky shark Carcharhinus falciformis in the southwestern Indian Ocean

2012 ◽  
Vol 17 (1) ◽  
pp. 83-92 ◽  
Author(s):  
N Rabehagasoa ◽  
A Lorrain ◽  
P Bach ◽  
M Potier ◽  
S Jaquemet ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Blue Shark ◽  
Prionace Glauca ◽  
Silky Shark ◽  
Carcharhinus Falciformis ◽  
Southwestern Indian Ocean

scholarly journals Diet of three shark species in the Ecuadorian Pacific, Carcharhinus falciformis, Carcharhinus limbatus and Nasolamia velox

2017 ◽  
Vol 98 (4) ◽  
pp. 927-935 ◽  
Author(s):  
Colombo Estupiñán-Montaño ◽  
Fabian Pacheco-Triviño ◽  
Luis G. Cedeño-Figueroa ◽  
Felipe Galván-Magaña ◽  
Jose F. Estupiñán-Ortiz
Keyword(s):  
Stomach Contents ◽  
Thunnus Albacares ◽  
Shark Species ◽  
Dosidicus Gigas ◽  
Katsuwonus Pelamis ◽  
Carcharhinus Limbatus ◽  
Lack Of Information ◽  
Bony Fishes ◽  
Carcharhinus Falciformis ◽  
Conservation Plans

We analysed the stomach contents of 69 silky sharks Carcharhinus falciformis, 44 blacktip sharks Carcharhinus limbatus and 24 whitenose sharks Nasolamia velox caught in the Ecuadorian Pacific from August 2003 to December 2004. Prey included bony fishes, elasmobranchs, molluscs, crustaceans and turtles, with bony fishes being the most important to the diets of all three sharks, suggesting they are piscivorous predators. Based on the index of relative importance, the C. falciformis diet includes Thunnus albacares, Thunnus sp. and Auxis thazard, as well as some squid, fish and turtles. Similarly, the C. limbatus diet was dominated by T. albacares, Exocoetus monocirrhus, A. thazard, Katsuwonus pelamis, members of the Ophichthidae family and other elasmobranchs. Meanwhile, N. velox consumed mainly Dosidicus gigas, Larimus argenteus, Cynoscion sp. and Lophiodes spilurus. There is little competition for food between these tertiary carnivores: C. limbatus prefers prey from coastal-oceanic habitats; C. falciformis consumes mostly oceanic prey and N. velox focuses on prey from coastal habitats. The lack of information on the biology of sharks in Ecuador hinders the development of appropriate management and conservation plans to protect shark resources. This study increases our knowledge and understanding of sharks in Ecuador, thus contributing to their conservation.

scholarly journals Population structure and reproductive characteristics of the silky shark Carcharhinus falciformis (Müller & Henle, 1839) (Carcharhiniformes: Carcharhinidae) off the coast of Oaxaca, Mexico

2017 ◽  
Vol 44 (3) ◽  
pp. 513-524
Author(s):  
María del Carmen Alejo-Plata ◽  
Miguel Ángel Ahumada-Sempoal ◽  
José Luis Gómez-Márquez ◽  
Adrián González-Acosta
Keyword(s):  
Population Structure ◽  
Sex Ratio ◽  
Seasonal Changes ◽  
Sexual Maturity ◽  
Size Structure ◽  
Landing Sites ◽  
Silky Shark ◽  
Oceanic Species ◽  
Carcharhinus Falciformis ◽  
Gravid Females

Carcharhinus falciformis is an abundant oceanic species, which occurs in equatorial and tropical zones, with an important catch in the Atlantic and Pacific coasts of Mexico. Samples were taken from December 2000 to December 2007 in four landing sites of the artisanal fleet on the coast of Oaxaca. During the period of study 1236 specimens (602 females and 634 males) of C. falciformis were registered. Total length (TL) ranged from 49 to 217 cm for females (mean = 111.3 cm) and from 59 to 265 cm for males (mean = 111.7 cm). The sex ratio of females to males was 1:1 ( 2 0.05 = 0.78, P > 0.05). The present data suggest a size at first sexual maturity of about 184.8 cm TL for females and 178.5 cm TL for males. The catches were composed mainly of young. In the 52 gravid females examined, the average number of embryos per female was seven; with a range of 3-14 embryos. Mean TL of embryos ranged from 10 to 66 cm with evidence of seasonal changes in the size structure. Results obtained showed that C. falciformis gives birth most of the year, with the highest proportion of births during the rainy season (May to October).

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