Pacific nurse shark

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Pacific nurse shark
Ginglymostoma unami.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Division: Selachii
Order: Orectolobiformes
Family: Ginglymostomatidae
Genus: Ginglymostoma
Species:
G. unami
Binomial name
Ginglymostoma unami
Pacific Nurse Shark Range.png
Range of the Pacific nurse shark

The Pacific nurse shark (Ginglymostoma unami) is a medium sized shark from the family Ginglymostomatidae. The species is endemic to the Tropical Eastern Pacific, and is not to be confused with Ginglymostoma cirratum , which is restricted to the Atlantic Ocean. [2] G. unami has the characteristic round, elongated body and fin shape of nurse sharks, which can be useful when identifying them in aerial image data. [3] The species has a wide habitat range, including the Gulf of California, Costa Rica, Peru, and Panama. However, Pacific nurse sharks are considered endangered, and they are threatened by fishing practices like many other shark species. They have also been observed to disperse over long distances away from their home ranges, though they also exhibit high site fidelity. [4] [5] Therefore, researchers focus on the importance of better studying and tracking the sharks, often using aerial imaging data, in order to improve policies and protections regarding them. [3] [5]

Contents

Etymology

The species name unami comes from the acronym of la Universidad Nacional Autónoma de México (UNAM), or the National Autonomous University of Mexico. [2]

Species Description

Adult Pacific nurse shark specimen, showing lateral, dorsal, and ventral views Lateral, dorsal, and ventral views of Pacific nurse shark adult.jpg
Adult Pacific nurse shark specimen, showing lateral, dorsal, and ventral views

The Pacific nurse shark was first described in 2015 based on a holotype caught near Puerto Angel in Mexico, as previously, the species had been considered the same as Ginglymostoma cirratum. Pacific nurse sharks can generally be recognized by the characteristics of their family. [2] Ginglymostomotidae are considered to be medium sized sharks, ranging around 200 cm in length in adulthood , with the maximum size being cited as 280 cm long. [2] [6] They have elongated, slightly depressed bodies that are widest towards the anterior, and they have rounded fins. [7] Their iconic body shape with a broad head, short pectoral fins, long tail, and two dorsal fins is valued in conservation research, since it makes the Pacific nurse shark easy to identify from aerial surveys. [3] Their broad, round snouts, which are shorter than the interorbital distance, are characterized by a small inferior mouth and long barbels around their nose. [2] Their eyes, gills, and spiracles sit on the dorsal side of their body, likely due to their benthic lifestyle. [7] As for coloration, they appear in varying shades of brown with yellow undertones and a light belly, and juveniles have a spotted pattern along their dorsal region. [2]

Juvenile Pacific nurse shark specimen, showing lateral, dorsal, and ventral views Lateral, dorsal, and ventral views of Pacific nurse shark juvenile.jpg
Juvenile Pacific nurse shark specimen, showing lateral, dorsal, and ventral views

Furthermore, G. unami can be distinguished from their close relatives due to their unique habitats and a few defining characteristics. Notably, G. unami has a shorter distance between the prebranchial and interdorsal region, as well as a shorter space between the second dorsal fin and caudal lobe than its Atlantic counterpart. G. unami also uniquely has the ends of its pelvic fins reach the origin of the second dorsal fin when pressed against the body. Their teeth are another trait which help differentiate them from G. cirratum. They have a high central cusp, with more secondary cusps placed symmetrically to the central one. Their dermal denticles are also distinct, with a rhombus shape and 5 to 6 keels (G. cirratum has longer dermal denticles with fewer keels). [2]

Distribution and Habitat

G. unami is endemic to the Tropical Eastern Pacific, from the Southern coast of Baja California, Mexico and the Gulf of California to Peru. [2] The species has been observed and tracked in Mexico, Panama, Costa Rica, and Peru. [3] [5] [8] [9] The species is also known to be highly mobile, traveling up to 390 km from their home-range. They can swim back and forth between different sites in response to ecological drivers, making full ecological use of their habitat. [4] They spend almost all their time at the bottom of the water. They live in shallow waters, with sandy and rocky bottoms, and can often be found near rocky or coral reefs, and mangrove forests. [7] They are often sighted in warm, calm embayments like the Santa Elena Bay in Costa Rica. [4]

Biology

As benthic predators, nurse sharks feed on small bony fishes and invertebrates like squids, octopuses, crabs, sea urchins, lobsters, and shrimps. [7] With their ventrally-located mouth, nurse sharks are observed to perform suction feeding to capture their prey, similar to bony fishes. With modified structures of their skull and mouth, they can generate one of the greatest suction pressures of any aquatic-feeding vertebrate. However, the suction is only effective within a close distance, so sharks must forage close to reefs or substrate, likely using on ambush or stalking predation. [10] Family Ginglymostomatidae also use these suction structures to facilitate buccal pumping respiration, which allows them to rest on the bottom of the seafloor without needing to swim to breathe. [11]

Group of Pacific nurse sharks huddling together A group of Pacific nurse sharks displaying aggregation behaviors.png
Group of Pacific nurse sharks huddling together

This sedentary behavior can be observed when Pacific nurse sharks aggregate in small numbers around their feeding grounds. Aggregation is the event where two or more individuals appear in the same place at the same time, usually seeking beneficial environmental conditions. G. cirratum is known to aggregate for reproductive reasons, but the behavior is understudied in G. unami. One explanation is that Pacific nurse sharks gather together as a response to changing water temperatures, since upwelling is common in their Pacific habitats. Upwelling can cause water temperatures to drop to 16℃ from the normal 28℃. The sharks aggregate together more during upwelling seasons in groups of up to 52 individuals in warm, shallow waters. Pacific nurse sharks specifically practice huddling behavior, where they will physically touch bodies, further suggesting they aggregate for thermoregulation or social reasons. Other possible reasons that influence aggregation may be conspecific attraction, mating, prey availability, or predator avoidance. [12]

Despite this sedentary behavior, studies on Pacific nurse shark lifestyle also describe their ability to travel much larger distances than previously thought. Some studies report the sharks making up to 390 km journeys, and traveling back and forth between a few different sites over the course of 46 days near the coast of Costa Rica. Seasonal upwelling may be the driver of their movement as well, as the sharks will migrate to warmer waters for refuge. This creates a pattern of site fidelity to the Santa Elena Bay in Costa Rica, which is known as an important conservational area for many species of elasmobranchs. They travel to the bay during the upwelling season, and even move between different parts of the bay based on the time of day and temperature, demonstrating a thermoregulatory behavior. [4]

Nurse sharks are known to be ovoviviparous, with the embryos gestating within egg capsules, then hatching within the female. [13] However not much is known about the courtship or breeding behaviors of Pacific nurse sharks. The species is highly understudied, and much of their biology remains unclear. [4]

Conservation Status

The Pacific nurse shark has most recently been assessed in 2019 and is currently labeled as endangered under the IUCN red list of endangered species. This is due to continuing declining populations, human impacts through fisheries, and habitat destruction. [4] Fisheries pose a particular concern for chondrichthyans in many countries within the species’ distribution, and G. unami has been known to be caught as bycatch or get fatally tangled in nets. [4] [8] [9] [14] In Peru, for example, elasmobranch products are regularly traded within the country, and although there are no known commercial uses of Pacific nurse sharks, fisheries can lack proper identification on bycatch, leading to the exploitation of many shark species. [9] Unfortunately, little research has been done on G. unami due to its recent species description. [4] Its sister species, G. cirratum, has more extensive literature on it, but this often excludes G. unami. [15] Thus, current conservationists are particularly worried about improving the available data for the species, including using improved aerial imagery technology or passive acoustic telemetry to monitor their movement and appearance. [4] [16] Tracking the sharks’ movement and behavior can help improve conservation and management efforts in the regions where they live. [12] Certain regions of their habitat are classified as protected areas, but since they often travel outside of these areas, they may be left vulnerable. Additional research can improve their conservation. [4]

References

  1. ↑ Pollom, R.; Avalos, C.; Bizzarro, J.; Burgos-Vázquez, M.I.; Cevallos, A.; Espinoza, M.; González, A.; Herman, K.; Mejía-Falla, P.A.; Navia, A.F.; Pérez Jiménez, J.C.; Sosa-Nishizaki, O.; Velez-Zuazo, X. (2021). "Ginglymostoma unami". IUCN Red List of Threatened Species . 2021 e.T144151831A144151864. doi: 10.2305/IUCN.UK.2021-1.RLTS.T144151831A144151864.en . Retrieved 10 February 2022.
  2. 1 2 3 4 5 6 7 8 Del Moral-Flores, L. F., Ramírez-Antonio, E., Angulo, A., Pérez-Ponce De León, G. (22 May 2015). "Ginglymostoma unami sp. nov. (Chondrichthyes: Orectolobiformes: Ginglymostomatidae): una especie nueva de tiburón gata del Pacífico oriental tropical". Revista Mexicana de Biodiversidad. 86 (1). doi:10.7550/rmb.46192. eISSN   1870-3453. ISSN   2007-8706 . Retrieved 12 October 2025.
  3. 1 2 3 4 Ayres, K. A., Ketchum, J. T., González‐Armas, R., Galván‐Magaña, F., Hearn, A., Elorriaga‐Verplancken, F. R., Hoyos‐Padilla, E. M., Kajiura, S. M. (November 2021). "The use of an unoccupied aerial vehicle to survey shark species over sand and rocky-reef habitats in a marine protected area". Journal of Fish Biology. 99 (5): 1735–1740. Bibcode:2021JFBio..99.1735A. doi:10.1111/jfb.14838. eISSN   1095-8649. ISSN   0022-1112. PMID   34180053.
  4. 1 2 3 4 5 6 7 8 9 10 Madrigal-Mora, S., Lowe, C., Clark, C., Espinoza, M. (5 December 2024). "Pacific nurse sharks Ginglymostoma unami exhibit yearly patterns of site fidelity to a tropical embayment subjected to seasonal upwelling". Marine Ecology Progress Series. 750: 89–104. Bibcode:2024MEPS..750...89M. doi:10.3354/meps14733. eISSN   1616-1599. ISSN   0171-8630.
  5. 1 2 3 Madrigal-Mora, S., Chávez, E. J., Arauz, R., Lowe, C. G., Espinoza, M. (24 January 2024). Dudgeon, C. (ed.). "Long-distance dispersal of the endangered Pacific nurse shark (Ginglymostoma unami, Orectolobiformes) in Costa Rica revealed through acoustic telemetry". Marine and Freshwater Research. 75 (2) MF23162. Bibcode:2024MFRes..7523162M. doi:10.1071/MF23162. eISSN   1448-6059. ISSN   1323-1650 . Retrieved 30 September 2025.
  6. ↑ Weigmann, S. (March 2016). "Annotated checklist of the living sharks, batoids and chimaeras (Chondrichthyes) of the world, with a focus on biogeographical diversity". Journal of Fish Biology. 88 (3): 837–1037. Bibcode:2016JFBio..88..837W. doi:10.1111/jfb.12874. eISSN   1095-8649. ISSN   0022-1112. PMID   26860638.
  7. 1 2 3 4 McEachran, J. (1998). Fishes of the Gulf of Mexico, Vol. 1: Myxiniformes to Gasterosteiformes. University of Texas Press. ISBN   978-0-292-75206-1.
  8. 1 2 Morales‐Saldaña, J. M., Guzmán, H. M., Vega, A. J., Robles, Y. A., Montes, L. A., Kyne, P. M. (April 2025). "A Review of the Status of Sharks, Rays and Chimaeras of Panama to Guide Research and Conservation". Aquatic Conservation: Marine and Freshwater Ecosystems. 35 (4) e70122. Bibcode:2025ACMFE..3511.R2M. doi:10.1002/aqc.70122. eISSN   1099-0755. ISSN   1052-7613.
  9. 1 2 3 Campos‐León, S., Hernández‐Muñoz, S., Huerta‐Beltrán, B. L., Zavalaga, F., Cevallos‐Garcias, A., Ehemann, N. (29 September 2025). "Peruvian Chondrichthyes biodiversity, marketing and conservation: a synthesis of current knowledge". Journal of Fish Biology jfb.70227. doi:10.1111/jfb.70227. eISSN   1095-8649. ISSN   0022-1112. PMID   41022569.
  10. ↑ Motta, P. J., Hueter, R. E., Tricas, T. C., Summers, A. P., Huber, D. R., Lowry, D., Mara, K. R., Matott, M. P., Whitenack, L. B., Wintzer, A. P. (September 2008). "Functional morphology of the feeding apparatus, feeding constraints, and suction performance in the nurse shark Ginglymostoma cirratum". Journal of Morphology. 269 (9): 1041–1055. Bibcode:2008JMorp.269.1041M. doi:10.1002/jmor.10626. eISSN   1097-4687. ISSN   0362-2525. PMID   18473370.
  11. ↑ Whitney, N. M., Lear, K. O., Gaskins, L. C., Gleiss, A. C. (April 2016). "The effects of temperature and swimming speed on the metabolic rate of the nurse shark (Ginglymostoma cirratum, Bonaterre)". Journal of Experimental Marine Biology and Ecology. 477: 40–46. Bibcode:2016JEMBE.477...40W. doi:10.1016/j.jembe.2015.12.009. ISSN   0022-0981.
  12. 1 2 Madrigal-Mora, S., Lowe, C. G., Clark, C., Espinoza, M. (December 2025). "Aggregation behavior of pacific nurse sharks (Ginglymostoma unami) associated with seasonal water temperature changes in a tropical upwelling bay". Journal of Experimental Marine Biology and Ecology. 593 152138. Bibcode:2025JEMBE.59352138M. doi:10.1016/j.jembe.2025.152138. ISSN   0022-0981.
  13. ↑ Castro, J. I. (May 2000). "The Biology of the Nurse Shark, Ginglymostoma cirratum, Off the Florida East Coast and the Bahama Islands". Environmental Biology of Fishes. 58 (1): 1–22. Bibcode:2000EnvBF..58....1C. doi:10.1023/A:1007698017645. eISSN   1573-5133. ISSN   0378-1909.
  14. ↑ González-Acosta, A. F., Monsalvo-Flores, A. E., Tovar-Ávila, J., Jiménez-Castañeda, M. F., Alejo-Plata, M. D. C., De La Cruz-Agüero, G. (June 2021). "Diversity and conservation of Chondrichthyes in the Gulf of California". Marine Biodiversity. 51 (3) 46. Bibcode:2021MarBd..51...46G. doi:10.1007/s12526-021-01186-9. eISSN   1867-1624. ISSN   1867-1616.
  15. ↑ Cardoso, M. N. M., Faria, V. V., Da Silva, G. B. (9 May 2025). "A Review of Fisheries and Conservation of the Atlantic Nurse Shark, Ginglymostoma cirratum (Bonnaterre, 1788), (Orectolobiformes: Ginglymostomatidae) in the Atlantic Ocean". Fisheries Management and Ecology e12818. doi:10.1111/fme.12818. eISSN   1365-2400. ISSN   0969-997X.
  16. ↑ Lalgudi, C. K., Leone, M. E., Clark, J. V., Madrigal‐Mora, S., Espinoza, M. (September 2025). "Zero-shot shark tracking and biometrics from aerial imagery". Methods in Ecology and Evolution. 16 (9): 2023–2035. Bibcode:2025MEcEv..16.2023L. doi:10.1111/2041-210X.70116. ISSN   2041-210X.
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