University Of São Paulo Researchers Show The Suffering Of Endangered Porpoises In Fishing Nets
“The porpoise is a small dolphin that occurs exclusively in coastal waters in the Southeast and South of Brazil, Uruguay, and northern Argentina. The biggest factor of porpoise mortality is an operational accident when fishing nets seek to capture fish in order to bring marine protein for human consumption. Even equipped with an efficient echolocation system, the porpoise has been getting tangled in fishing nets and, because it is unable to rise to the surface of the water to breathe oxygen from the air through its lungs, it drowns”, warn the authors of the e-book Porpoise, a small endangered cetacean , available for free on the website of the Laboratory of Biology for the Conservation of Aquatic Mammals (LABCMA) of the Oceanographic Institute (IO) of USP. It is possible to download the publicationin this link .
The book is the result of the study Assessment on the state of the art of knowledge with a view to the conservation of the porpoise, Pontoporia blainvillei , a small cetacean threatened with extinction , linked to the Program of Scientific Initiation and Initiation in Technological Development and Innovation of USP, with authorship by Isabela Rugitsky Domingues, from the USP Institute of Biosciences, under the guidance of Professor Marcos César de Oliveira Santos, from the USP Oceanographic Institute.
The authors’ goal is that the material, produced in Portuguese and freely accessible, has a greater and more effective reach to members of the South American non-academic society. “If it depends only on scientists, the porpoise will not be saved from extinction”, they warn. The professor reiterates, in an interview with Jornal da USP , that the reversal of the process of extinction of the porpoise passes, firstly, through the process of piercing a bubble that encompasses only scientists and environmental agents.
“This remarkable group of enthusiasts will not save the porpoise from extinction without support from other actors. Achieving the goal must necessarily include the federal governments of Brazil, Uruguay and Argentina through the establishment of clear public policies aimed at the mission of removing the porpoise from the list of endangered cetaceans”, he hopes.
river dolphin
The porpoise, also known as “franciscana” and “La Plata dolphin”, is a small cetacean endemic to the coast of South America. Despite being considered one of the five existing species of “river dolphins”, the porpoise preferentially inhabits the marine coast, with two populations described for estuarine waters. The species is characterized by a relatively small size when compared to other members of the order Cetacea . Its length in adulthood can vary between 113 cm and 136 cm for males, and 129 cm and 180 cm for females, and its coloration is brownish on the back, with grayish tones.
They usually live in small groups, composed of two to five individuals, but larger groups have been sighted on the coast of Rio de Janeiro, reaching 15 individuals, and in the estuarine complex of Paranaguá, with 12 individuals. Its diet consists preferably of fish and squid, and its predation occurs by species such as tiger sharks and killer whales. The life expectancy for the species is around 20 years.
Due to its restricted distribution, small population stocks, habit of living close to the coast and threats it suffers throughout its distribution, the porpoise is the small cetacean most threatened with extinction in the Southwest Atlantic, according to information in the book. It is currently classified as “threatened and vulnerable to extinction” on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. In Brazil, until 2018, the species was in the “critically endangered” category, in the Red Book of Brazilian Fauna Threatened with Extinction , according to the Chico Mendes Institute for Biodiversity Conservation (ICMBio), as the authors inform in the introduction.
ecological concern
There is no data on the actual number of porpoises. “Most records made so far only take into account animals found stranded and, therefore, when compared with monitoring the fishing fleet and sightings of porpoises caught in nets, accidental mortality ends up being underestimated”, point out the researchers. Bycatch occurs throughout the year on the Brazilian coast and mainly in summer and spring in Uruguay and Argentina. The context of the intense threat suffered by the porpoise for years throughout the distribution brought concerns about maintaining the size of population stocks.
Due to this scenario, in 2000 a workshop was held with scientists from Brazil, Uruguay and Argentina who had experience with investigations and actions aimed at the conservation of porpoises. The meeting focused on the compilation of information published up to that year, referring to the biology and ecology of the species, and the discussion on effective strategies for its conservation. The study was carried out based on a bibliographic review of scientific articles published on the biology and conservation of porpoises, before and after the publication of the results obtained from the workshop, bringing an updated version on the current state of knowledge about the species.
How to save them from extinction?
According to Marcos, it is necessary to structure policiespublic, with the participation of scientists and environmental agents, as well as state government representatives on the coast of the States, regions, municipalities and provinces where the porpoise occurs, agencies and fishing colonies that use nets to capture fish, educators , and teachers of all levels of basic, secondary and higher education who work in the coastal strip where the porpoise occurs. “In a joint action, the numbers of accidental captures in time and space should be evaluated more precisely through integrated monitoring for at least two years, the fishing production with the use of nets generated in this coastal strip by the three countries and the economic impact they generate,
In addition, Marcos points out that this entire process must be accompanied by a basic and standardized educational program so that the three nations in question adopt the porpoise as a symbol of protection for the ocean. “Since it is a top predator in the food web, it maintains the biological diversity of all components below it, and therefore it must remain in that system to keep it in balance, he informs and adds: “This whole process can take between six and ten years so that, from this effort, the sequence of management of this species and the fish stock is based on a robust database collected in a tripartite manner, and which will guide the regionalized adjustments”.