A team of marine scientists led by the Wildlife Conservation Society (WCS) has confirmed that the Critically Endangered shorttail nurse shark (Pseudoginglymostoma brevicaudatum; formerly Ginglymostoma brevicaudatum) has been found to occur in Mozambique – extending their home range more than 1,367 miles (2,200 kilometers).
Known as southern Africa’s most threatened endemic shark, it is one of the smallest members of the family Ginglymostomatidae (nurse sharks) measuring no more than 30 inches (76.2 centimeters). A tropical reef species found in the Western Indian Ocean along the coast of Tanzania, Kenya, and Madagascar, their biology and ecology remain largely unknown. The new study, which is published in the journal Marine Biodiversity, shows the discovery was based on underwater video surveys collected in 2019, recent photos of shore-based sport anglers’ catches, and the identification of a specimen collected all the way back in 1967.
The researchers declared that these latest findings expand the range of the shorttail nurse shark southward by some 1,367 miles (2,200 kilometers) and 683 mi (1,100 km) westward from Madagascar across the Mozambique Channel. “Owing to its strong association with coral reefs, it is under particular threat from overexploitation by coastal fisheries and habitat degradation, and is suspected to have declined by more than 80 percent over the last 30 years,” the authors said in a statement, stressing that this shark was in urgent need of management due to their ‘Critically Endangered’ standing on the International Union for the Conservation of Nature (IUCN) Red List of Threatened Species.
It is unclear as to why the sharks have suddenly been spotted here- were they always here and undetected or is there more to these new sightings? The authors believe climate change might be the answer: “Predicted responses for coastal marine fish species as a result of climate change include theoretical range expansions and poleward shifts in distribution ranges driven by broadening thermal gradients and shifting biogeographic boundaries, as recorded for several invertebrate and fish species along South Africa’s east coast.” Whatever the reason as to why this species has been showing up here, scientists are worried. And for good reason, since there are “no species recovery plans in place for the species and no specific regulations pertaining to its harvest, other than a listing on the Kenyan threatened and protected species list,” as explained by Rhett Bennett, WCS Shark and Ray Conservation Program Manager, Madagascar & Western Indian Ocean.
However, there is hope for the shorttail nurse shark as one of the records was from Mozambique’s Ponta do Ouro Partial Marine Reserve, suggesting that these sharks may have some degree of protection within the large coastal marine protected area (MPA). The first marine transfrontier conservation area in Africa, it stretches from Ponta do Ouro in the south of Mozambique, to the Maputo River Mouth in Maputo Bay in the north, and includes the waters around Inhaca and Portuguese islands.
The authors recommend that the species should be considered for legal protection in Mozambique and throughout their confined African range. In addition, they suggest that the appropriate entities better monitor the shorttail nurse shark and discuss improved management measures to reduce their targeted and incidental catch in artisanal and small-scale fisheries.