Fact file: Brazilian guitarfish (Pseudobatos horkelii; Previously Rhinobatus horkelii)

Image: “Brazilian guitarfish” by www.worldlifeexpectancy.com

IUCN statusCritically endangered
Population sizeUnknown
Population trendDeclining
Unique evolutionary history42 million years

Why is the Brazilian guitarfish so special?

The Brazilian guitarfish is a shark-like ray that has a unique reproductive cycle. Their flat body and strange shovel tipped head allow them to bury themselves in mud and sand up to 150m depth off the coast of Brazil. It is one of the most endangered species in the south Atlantic with a population decline of over 80% in the last decades.

The female of this strange-looking Rhinobatid (i.e. from the guitarfish family) can live up to 30 years and have a year-long reproductive cycle, whereby the young develop inside the candle (a shared egg) within the mother, but are birthed live. The fascinating part of this ovoviparity is that after being fertilised, the embryos of the young remain dormant while the mother retreats to the greater depths from March until November, and when she returns to the warmer shallow waters, the embryos begin to develop rapidly. The presumed function of this embryonic diapause is to uncouple mating from birthing, to ensure that both occur at the most favourable moment for survival of the species.

What are the threats facing the Brazilian guitarfish?

The biggest threat to the Brazilian guitarfish comes from the overfishing at poorly regulated Brazilian fisheries from both commercial and artisanal fishers. They are often hauled up in great numbers as bycatch in trawling practices, but they are also targeted by beach seines and fixed nets.

This is made all the worst as the fish is often targeted at the nursery grounds in the summer and due to the reproductive cycle of these fish, the fishing of the females is doubly devastating to the populations as they are invariably pregnant with 4-12 pups. In other words, each female that is removed from the population could be the equivalent of removing 13!

This unregulated fishing has resulted in a decline from 1,804 tonnes being caught in 1975, to only 157 tonnes in 200, which is equivalent to a reduction of >99% scaled over three generations (55.5 years). Fishing pressures have not ceased and it is widely recorded that the protections in place for this fish are largely ignored as it remains publicly commercially available.

Rhinobatos horkelii Müller & Henle, 1841

What is being done to help save the Brazilian Guitarfish from extinction?

The Brazilian Guitarfish is listed as Critically Endangered on the Brazilian National Red List and the Brazilian Ordinance of Ministry of the Environment, which restricts all harvest and trade of the species. However, there is intense opposition to these laws from the fishing industry and even governmental departments within Brazil. Regardless of the status of this legislation, this species is still landed and traded in Brazil.

The Brazilian guitarfish does occur in Anchieta Island State Park, which is a relatively well-enforced no-take zone in São Paulo state. However, there are no species-specific protections or conservation measures in place in the edge of its range in Uruguay or Argentina.

What can I do to help?

The IUCN red list make it clear that to conserve the population and permit recovery, a suite of measures will be required which will need to include species protection, spatial management, bycatch mitigation, and harvest management, all of which will be dependent on effective enforcement. Further research is needed on life history and population size and trends, and species-specific monitoring should be undertaken in commercial and artisanal fisheries.

If you love weird animals of all shapes and sizes and you want to see how you can help with WAWA’s conservation support, then please see how you can get involved here.

Further information