First detection of critically endangered scalloped hammerhead sharks (Sphyrna lewini) in Guam, Micronesia, in five decades using environmental DNA

Hybridization between closely related species has been documented across a wide range of taxa but has not been well studied in elasmobranchs. Hammerhead sharks have drawn global conservation concern because they experience some of the highest mortality rates among sharks when interacting with fisheries. Here we report on the detection of hybrids between the globally distributed scalloped hammerhead ( Sphyrna lewini ) and recently described Carolina hammerhead ( S. gilberti ) which are only known from the western Atlantic Ocean. Using a genomics approach, 10 first-generation hybrids and 15–17 backcrosses were detected from 554 individuals. The identification of backcrosses demonstrates hybrids are viable, and all backcrosses but one involved a scalloped hammerhead. All hybrids but one possessed Carolina hammerhead mtDNA, indicating sex-biased gene flow between species. Repeated hybridization and backcrossing with scalloped hammerheads could lead to the loss of endemic Carolina hammerheads.

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Inter-island movements of scalloped hammerhead sharks (Sphyrna lewini) and seasonal connectivity in a marine protected area of the eastern tropical Pacific

Marine Biology ◽

10.1007/s00227-014-2393-y ◽

2014 ◽

Vol 161 (4) ◽

pp. 939-951 ◽

Cited By ~ 38

Author(s):

James T. Ketchum ◽

Alex Hearn ◽

A. Peter Klimley ◽

César Peñaherrera ◽

Eduardo Espinoza ◽

...

Keyword(s):

Protected Area ◽

Marine Protected Area ◽

Tropical Pacific ◽

Eastern Tropical Pacific ◽

Sphyrna Lewini ◽

Scalloped Hammerhead ◽

Hammerhead Sharks

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VERTICAL AND HORIZONTAL MOVEMENTS OF THE SCALLOPED HAMMERHEAD SHARK (SPHYRNA LEWINI) AROUND MALPELO AND COCOS ISLANDS (TROPICAL EASTERN PACIFIC) USING SATELLITE TELEMETRY

Bulletin of Marine and Coastal Research ◽

10.25268/bimc.invemar.2011.40.0.133 ◽

2016 ◽

Vol 40 ◽

Author(s):

Sandra Bessudo ◽

Germán A. Soler ◽

Peter A. Klimley ◽

James Ketchum ◽

Randall Arauz ◽

...

Keyword(s):

Satellite Telemetry ◽

Movement Patterns ◽

Eastern Pacific ◽

Depth Range ◽

Tropical Eastern Pacific ◽

Sphyrna Lewini ◽

Scalloped Hammerhead ◽

Distribution Ranges ◽

Cocos Island ◽

Hammerhead Sharks

Understanding distribution ranges and the daily movement patterns of pelagic fishes are key aspects for the establishment and planning of protected areas for their conservation. In this study the vertical and horizontal movements of scalloped hammerhead sharks, Sphyrna lewini, were recorded in Malpelo and Cocos Island using satellite telemetry. Nine sharks were tagged with satellite transmitters during March 2006, 2007 and 2008 at Malpelo Island, and three hammerhead sharks were tagged at Cocos Island in June 2008. The sharks moved between islands in the Tropical Eastern Pacific and made regional movements from Malpelo to the south of Cocos and around the Malpelo ridge. When away from the island, sharks made infrequent nocturnal short dives down to 1000 m where temperatures were as low as 4 °C. For a shark that was tracked for five months, results indicated significant differences between the time spent at different depth ranges, as well as an interaction between depth, water layers, and the time of the day. The shark swam mostly at surface waters (0-10 m) during the cold water season, and spent more time at the deepest depth range (>100 m) during nigh time. Further long-term studies on shark movement patterns are required for a better management of this highly mobile and vulnerable species.

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Short Communication: Genetic diversity of scalloped hammerhead sharks (Sphyrna lewini) landed in Muncar Fishing Port, Banyuwangi

Biodiversitas Journal of Biological Diversity ◽

10.13057/biodiv/d200430 ◽

2019 ◽

Vol 20 (4) ◽

pp. 1154-1159 ◽

Cited By ~ 1

Author(s):

FAQIH AKBAR ALGHOZALI ◽

DIAH PERMATA WIJAYANTI ◽

AGUS SABDONO

Keyword(s):

Genetic Diversity ◽

Short Communication ◽

Polymerase Chain Reaction Amplification ◽

Haplotype Diversity ◽

Population Expansion ◽

Fishing Ground ◽

Sphyrna Lewini ◽

Scalloped Hammerhead ◽

Hammerhead Sharks ◽

Longline Fisheries

Abstract. Alghozali FA, Wijayanti DP, Sabdono A. 2019. Short Communication: Genetic diversity of scalloped hammerhead sharks (Sphyrna lewini) landed in Muncar Fishing Port, Banyuwangi. Biodiversitas 20: 1154-1159. The majority of sharks caught in Indonesian fisheries were bycatch products from the tuna longline fisheries, but some regions in Indonesia fish the sharks as their main target. One of these regions is located in Muncar, Banyuwangi, which fishes the endangered Scalloped Hammerhead sharks (Sphyrna lewini) as target species. This research aimed to study the genetic diversity of the endangered Scalloped Hammerhead sharks landed in Muncar Fishing Port, Banyuwangi. Genetic analysis was done through PCR (Polymerase Chain Reaction) amplification and sequencing of the mitochondrial DNA COI (Cytochrome Oxidase subunit I) gene. Out of the 37 samples collected, 30 were successfully amplified and sequenced.The results showed moderate haplotype diversity (Hd: 0,582 ± 0,079) and low nucleotide diversity (π: 0,00392± 0,0024) with five haplotypes (h) and 26 polymorphic sites (S). Tajima’s D neutrality model values indicated a population expansion event. Two different clades were determined through phylogenetic analysis and by GenBank sequences comparison. These results provided basic information and present status of the Scalloped Hammerhead sharks population genetically within the fishing ground (Makassar Strait-Kangean Islands).

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Bioenergetics of free-ranging juvenile scalloped hammerhead sharks (Sphyrna lewini) in Kāne'ohe Bay, Ō'ahu, HI

Journal of Experimental Marine Biology and Ecology ◽

10.1016/s0022-0981(02)00331-3 ◽

2002 ◽

Vol 278 (2) ◽

pp. 141-156 ◽

Cited By ~ 81

Author(s):

Christopher G Lowe

Keyword(s):

Sphyrna Lewini ◽

Scalloped Hammerhead ◽

Hammerhead Sharks ◽

Free Ranging

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THE FEEDING HABITS OF JUVENILE SCALLOPED HAMMERHEAD SHARKS (SPHYRNA LEWINI) CAUGHT IN THE GULF OF NICOYA, COSTA RICA

Bulletin of Marine and Coastal Research ◽

10.25268/bimc.invemar.2010.39.2.337 ◽

2016 ◽

Vol 39 (2) ◽

Author(s):

Ilena Zanella Cesarotto ◽

Andrés López Garro ◽

Randall Arauz Vargas

Keyword(s):

Teleost Fish ◽

Feeding Habits ◽

Stomach Contents ◽

Geographic Location ◽

Niche Separation ◽

Sphyrna Lewini ◽

Scalloped Hammerhead ◽

Importance Index ◽

Hammerhead Sharks ◽

Gulf Of Nicoya

Sharks present strong intraspecific changes in feeding habits, which may vary according to size, geographic location and season. This study analyzed the stomach contents of 52 juvenile scalloped hammerhead sharks (25 females and 27 males) caught by artisanal vessels in the Gulf of Nicoya. Regarding the organisms found in the stomachs, 41.07 % were teleost fish, 30.36 % mollusks and 28.57 % crustaceans. Mollusks presented the highest Relative Importance Index (RII) (43.05 %), followed by teleost fish (41.37 %) and crustaceans (15.58 %). Squids (Loliginidae) were the items with the greatest RII (32.57 %). By means of the Pianka index, a relatively low overlap between sexes was identified, suggesting a spatial sexual segregation and, in consequence, an ecological niche separation between male and female hammerhead sharks.

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Corrigendum to: Evidence of site fidelity and deep diving behaviour of scalloped hammerhead shark (Sphyrna lewini) around the Saint Peter and Saint Paul Archipelago, in the equatorial Mid-Atlantic ridge

Marine and Freshwater Research ◽

10.1071/mf19029_co ◽

2020 ◽

Vol 71 (6) ◽

pp. 719

Author(s):

Natalia P. A. Bezerra ◽

Bruno C. L. Macena ◽

Paulo Travassos ◽

Pedro Afonso ◽

Fábio H. V. Hazin

Keyword(s):

Site Fidelity ◽

Saint Paul ◽

Sphyrna Lewini ◽

Hammerhead Shark ◽

Deep Diving ◽

Scalloped Hammerhead ◽

Mesopelagic Zone ◽

Mid Atlantic Ridge ◽

Hammerhead Sharks ◽

Saint Peter

Seven scalloped hammerhead sharks (Sphyrna lewini) were satellite tagged around the Saint Peter and Saint Paul Archipelago (SPSPA), located at the equatorial Mid-Atlantic ridge, to investigate their vertical and horizontal movements. All sharks remained in the surroundings of the SPSPA over the course of the 120-day monitoring period, suggesting a high degree of medium-term site fidelity. During this period, scalloped hammerhead sharks covered a wide extension of the water column, ranging from the mixed layer to the mesopelagic zone. All sharks remained in warm (>22°C) shallow layers most of the time, but also dove to depths greater than 150m, mostly at night, eventually reaching 728m (5.6°C) on two occasions. This study contributes important, novel information on the habitat use and movement patterns of scalloped hammerhead shark in Atlantic equatorial oceanic waters. It also highlights the potential of protecting key, large oceanic areas as a useful tool for the conservation of this endangered species.

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