Age, growth and reproductive biology of the silky shark, Carcharhinus falciformis, and the scalloped hammerhead, Sphyrna lewini, from the northwestern Gulf of Mexico

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.

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Population structure and reproductive biology of the scalloped hammerhead Sphyrna lewini (Carcharhiniformes: Sphyrnidae) caught in artisanal fisheries of Oaxaca, Mexico

Hidrobiológica ◽

10.24275/uam/izt/dcbs/hidro/2018v28n3/alejo ◽

2018 ◽

Vol 28 (3) ◽

pp. 265-275 ◽

Cited By ~ 1

Author(s):

María Del Carmen Alejo Plata ◽

Keyword(s):

Population Structure ◽

Reproductive Biology ◽

Artisanal Fisheries ◽

Sphyrna Lewini ◽

Scalloped Hammerhead

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Monitoring of the status of eleven bony and cartilaginous fish populations in the Malpelo Sanctuary of Fauna and Flora, Colombian Pacific

Bulletin of Marine and Coastal Research ◽

10.25268/bimc.invemar.2021.50.1.1084 ◽

2021 ◽

Vol 50 (1) ◽

pp. 105-120

Author(s):

Felipe Ladino ◽

Sandra Martínez ◽

María Duarte ◽

Natalia Vélez ◽

Sandra Bessudo

Keyword(s):

Management Plan ◽

Cartilaginous Fish ◽

Tropical Eastern Pacific ◽

Sphyrna Lewini ◽

Hammerhead Shark ◽

Scalloped Hammerhead ◽

The Status ◽

Silky Shark ◽

Spotted Eagle Ray ◽

Over Time

To determine trends over time in the relative abundance of species prioritized in the Malpelo Fauna and Flroa Sanctuary Management Plan, underwater visual censuses were done from April 2009 to August 2019. Data were collected for five species of bonefish: bluefin trevally (Caranx melampygus), longfin yellowtail (Seriola rivoliana), yellowfin tuna (Thunnus albacares), leather bass (Dermatolepis dermatolepis) and sailfin grouper (Mycteroperca olfax), and six cartilaginous fish: spotted eagle ray (Aetobatus laticeps), silky shark (Carcharhinus falciformis), Galapagos shark (Carcharhinus galapagensis), whitetip reef shark (Triaenodon obesus), whale shark (Rhincodon typus) and scalloped hammerhead shark (Sphyrna lewini). A negative non-significant trend in abundance through time was observed for most of the evaluated species, except A. laticeps and T. obesus, which showed positive non-significant trends. The hammerhead shark (S. lewini) was the only species that showed a statistically significant decrease in abundance over time. The results of this study highlight the urgent need to establish more effective fisheries management and regulation measures that promote the conservation of important fish species, not just inside the sanctuary but also within the Tropical Eastern Pacific.

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SHARK LONGLINE FISHERY IN TANJUNGLUAR-EAST LOMBOK

Indonesian Fisheries Research Journal ◽

10.15578/ifrj.19.1.2013.39-46 ◽

2013 ◽

Vol 19 (1) ◽

pp. 39

Author(s):

Dharmadi Dharmadi ◽

Ria Faizah ◽

Lilis Sadiyah

Keyword(s):

Size Range ◽

Weather Conditions ◽

Biological Data ◽

Fishing Ground ◽

Survey Method ◽

Sphyrna Lewini ◽

Catch Data ◽

Scalloped Hammerhead ◽

Fishing Vessels ◽

Silky Shark

Studies on artisanal shark fisheries in Tanjungluar - East Lombok were conducted during the year 2001-2011 (except in 2003 and 2007). A sampling method called “rapid market survey” method was employed to collect catch data from surface and bottom longlines fishing, rapidly. Biological data and fisheries data were collected during survey. Catch data for shark were also obtained from daily records filled by TPI officers in Tanjungluar between 2009 and 2010. The results showed that shark longline fishing was conducted every month. The trend of shark catches relates to the number of fishing vessels, fishing ground, and weather conditions at sea. The period between July and September is a transitional season from East to West seasons. During this season, the wind strength is weakened and a good fishing season for the fishers. The lowest catch occurs in January (1.06 tonnes) and the highest catch in September with the total catch of 24.6 tonnes. Sharks caught by surface longline were dominated by Silky shark, Carcharhinus falciformis (40-90%) with the size range of 100-125 cm. The catch of bottom longline was mostly consisting of fish in mature condition that dominated by Grey reef shark (Carcharhinus amblyrhynchos), Common black tip shark (C. limbatus), Spot tail shark (C. sorrah), and Scalloped hammerhead shark (Sphyrna lewini), with the size range of 125-200 cm, 170- 250 cm, 100-150 cm, and 170-300 cm, respectively. Surface longline fishing occurs in the offshore waters in depth more than 200 m to 3000 m, whereas bottom longline fishing is operated at a depth of 50-100 m around islands.

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Reproductive biology of the silky shark Carcharhinus falciformis in the southern Mexican Pacific

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315414001970 ◽

2014 ◽

Vol 95 (3) ◽

pp. 561-567 ◽

Cited By ~ 7

Author(s):

C. Galván-Tirado ◽

F. Galván-Magaña ◽

R.I. Ochoa-Báez

Keyword(s):

Reproductive Biology ◽

Reproductive Organ ◽

Seminal Vesicles ◽

Birth Size ◽

Mexican Pacific ◽

Female Reproductive Organ ◽

Gulf Of Tehuantepec ◽

Silky Shark ◽

Carcharhinus Falciformis ◽

First Maturity

Despite being one of the most abundant and highly exploited species in the Mexican Pacific Ocean, information on the biology of the silky shark, Carcharhinus falciformis is limited. The objective of the present study was to describe the reproductive biology of this species, based on 262 sharks (117 females and 145 males) caught from September 2004 to May 2006 in the Gulf of Tehuantepec, Mexico. The size of females ranged from 70 to 229 cm total length (TL); males measured from 69 to 220 cm TL. Female reproductive organ measurements showed that between 175 and 190 cm TL there was an increase in oviducal gland width (19–45 mm), as well as in uterus size (20–220 mm width). Mature males over 180 cm had calcified claspers, well-developed testes (184–282 mm) and presence of sperm in the seminal vesicles. The estimated length of males at first maturity was 180 cm, and that of females was 190 cm. Ovarian fecundity varied from 4 to 11 oocytes, and uterine fecundity varied from 2 to 14 embryos. We infer that mating occurs between May and June. We did not find sperm storage in the oviducal glands. Birth size was observed to be between 60 and 69 cm TL. No defined gestation period was observed.

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Reproductive biology of the scalloped hammerhead (Sphyrna lewini) in the central-eastern Pacific Ocean

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315421000138 ◽

2021 ◽

pp. 1-6

Author(s):

Colombo Estupiñán-Montaño ◽

Maribel Carrera-Fernández ◽

Felipe Galván-Magaña

Keyword(s):

Pacific Ocean ◽

Reproductive Biology ◽

Eastern Pacific ◽

Eastern Pacific Ocean ◽

Fishing Activity ◽

Sphyrna Lewini ◽

Additional Information ◽

Scalloped Hammerhead ◽

Central Eastern ◽

June July

Abstract There are limited data regarding the reproductive biology of the scalloped hammerhead (Sphyrna lewini) in Ecuadorian waters, which limits the development of appropriate management measures of its populations. A total of 1664 S. lewini specimens were recorded in Manta, Ecuador in 2003–2009. Specimens were caught by local commercial fisheries and measured between 50–310 cm total length (TL). Females were more frequently caught, with a sex ratio of 1M:1.8F. The median size at maturity was 178.1 cm TL for males and 219.4 cm TL for females, which was larger compared with other localities. Gravid females, which measured 246–298 cm TL, contained 16–22 embryos. Embryos, which were observed from October–July, measured between 11.1–54.6 cm TL and the available data agreed with a gestation period of 10–11 months that starts in September and ends in June/July. Size at birth was 47–55 cm TL. Sampling data indicated that most fishing activity occurred in nearshore and around seamounts in the central-eastern Pacific Ocean, with much of the landed catch comprising immature individuals. This study documents the reproductive biology of S. lewini in the central-eastern Pacific Ocean and provides additional information to improve management and conservation measures for this species.

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Diet comparison between silky sharks (Carcharhinus falciformis) and scalloped hammerhead sharks (Sphyrna lewini) off the south-west coast of Mexico

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315416000424 ◽

2016 ◽

Vol 97 (2) ◽

pp. 337-345 ◽

Cited By ~ 6

Author(s):

Isaac Antonio Flores-Martínez ◽

Yassir Edén Torres-Rojas ◽

Felipe Galván-Magaña ◽

Julia Ramos-Miranda

Keyword(s):

West Coast ◽

Trophic Levels ◽

Ecological Network ◽

The South ◽

Sphyrna Lewini ◽

Scalloped Hammerhead ◽

South West ◽

South West Coast ◽

Carcharhinus Falciformis ◽

Hammerhead Sharks

Ecologists examine diet composition in order to assess the spatial and temporal variations in interactions between species, the impact of different species traits on the ecological network structure, and the long-term effects of the removal of different species by small-scale fisheries. In this study, our goal was to compare the diets of silky sharks (Carcharhinus falciformis) and scalloped hammerhead sharks (Sphyrna lewini) off the south-west coast of Mexico in order to infer their diet preferences and spatial distributions. We sampled 164 S. lewini (96 stomachs had food, 68 were empty) and 183 C. falciformis (30 stomachs had food, 153 were empty) in Puerto Madero, Chiapas in 2011. The large number of empty stomachs may be the result of using longline fishing gear, which causes high stress resulting in regurgitation. Based on the index of relative importance (%IRI), the fish Chloroscombrus orqueta (IIR = 27.7%) was the most important species in the diet of S. lewini, while the squid Dosidicus gigas (IIR = 34%) was the primary prey of C. falciformis. Levin's index (Bi) and Shannon's index (H′) confirm that both sharks are generalists, as in other regions. The trophic levels of S. lewini (TL = 4.1) and C. falciformis (TL = 4.2) are characteristic of tertiary consumers; meanwhile, the Morisita–Horn index indicates low interspecific overlap between all categories. These results confirm that these two sharks have different foraging preferences or movement patterns; thus, there is no trophic overlap between species as they play unique roles in the ecological network off the south-west coast of Mexico.

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