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Ecology

Vulnerable predators

A plan proposes strategies to save the rays and sharks of the Brazilian coastline

NOAAManta ray: in spite of prohibition, exploration still continues in Santa Catarina StateNOAA

Predators in the seas and rivers, the sharks and rays that inhabit the Brazilian ecosystems are living their day of being the hunted ones. Over the last two decades, overfishing has placed on the list of endangered animals various elasmobranchs – the class that covers sharks and rays and the dogfish, which, in common, have their skeleton formed only by cartilage. Research carried out in Brazil put the endangered list that were very prevalent on the national coastline such as the Rhinobatos horkelii guitarfish, the daggernose shark (Isogomphodon oxyrhynchus), the stripped smoothhound shark (Mustelus fasciatus), the  smalltooth sawfish (Pristis spp.), the grey nurse shark (Carcharias taurus) or the angel shark (Squatina spp).

These animals have a relatively slow rate of growth, are late in entering into adulthood and reproduce only rarely. There is no economic justification for the misfortune of the elasmobranch. This is because the species that have economic value are rare, as is the case of the Dasyatis marianae stingray, sold for ornamental use in aquariums, or the night shark (Carcharhinus signatus), whose meat and fins are appreciated. In truth, the immense majority of sharks and rays are captured by fishermen who are looking for other targets, such as shoals of tuna. Dead, they end up being discarded. Or else, in order not to lose the opportunity, the fishermen pull out products of some value, such as teeth (used for ornaments) and shark’s fin (an ingredient of soups in Asian countries) and then throw the carcass back into the sea.

For some years now a group of oceanographers and icthiologists have been calling attention to the extermination of the elasmobranch, but now they have the chance of presenting a strategy to guarantee the survival of these species. One is talking about the National Action Plan for the Conservation and Management of Elasmobranch Fish in Brazil, which is suggesting a series of measures, such as a moratorium on the exploration of some species, an increase in the control of fishing boats and the banning of fishing techniques harmful to sharks and rays.

The diagnosis is based on almost 200 scientific papers. Sent on to the Ministry of the Environment, this is the result of two years of work of 12 researchers, members of the Brazilian Society for the Study of Elasmobranches (Sbeel in the Portuguese acronym), who work in different regions of Brazil. The plan recommends a research effort to better understand the biology of these fish and their population dynamics. Along the Brazilian coast 85 species of sharks and 55 of rays are known. The number, considered modest, would be the reflex of the, as yet, unknown vast void of scientific knowledge concerning sharks and rays in Brazil. “As the elasmobranches are not the fishermen’s direct targets, their research is not considered a priority by funding organs”, says the oceanographer Rosangela Lessa, a professor at the Federal Rural University of Pernambuco (UFRPE) and the organizer of the document.

The researchers admit that it is difficult to make the development agencies and lay public fully aware of the need to preserve species that make up part of thrillers and horror movies. But, they recall, sharks and rays are important for the biodiversity of seas and rivers. “They make up part of the food chain, and, if they get eliminated, may produce a cascading ecologically unbalanced situation whose configurations not even we could imagine”, says Ricardo Rosa, a researcher with the Federal University of Paraiba (UFPB). “Furthermore, the stigma is unfounded. Of the 400 species of sharks, no more than a dozen are really dangerous.”

Among the species most at risk, a variety of ray named the Brazilian Guitarfish or Rhinobatos horkelii stands out, which, known by its larger size, can reach 1,3 meters in diameter. Up until the start of 1980s it was abundant along the coast of the state of Rio Grande do Sul. Today it is critically threatened. Between 1985 and 1997 there was a decline of 85% in its population throughout the southern Brazil continental shelf, because of the overfishing of other species. The management plan is drastic in relation to this ray. A fishing ban is proposed, with the prohibition of its commercialization in Brazil for an undetermined period, until scientific data attests to the recovery of its populations.

The coasts of the Southeast and South of Brazil are those most affected, according to the diagnosis of the action plan. In the South, the expansion of Brazilian fishing activity began in 1947, with the development of a technique capable of capturing fish at as deep as 50 meters depth. The fishing of oceanic species began in 1959, with the use of a trotline for fishing tuna. The trotline is fishing equipment widely used, which consists of a main line linked to other secondary ones dotted with fishhooks to hook the fish. In 1998, the fleet that carried out this type of fishing targeted some types of sharks, due to the value of their fins on the international market. But the carcass was not normally of commercial value. For this reason the fishermen would cut off the fins and throw the animals back into the sea, at times still alive. As the control of exploration is normally done when the fishing boats are unloading, this practice escaped inspectors.

A study carried out in 2000 by the researcher Carolus Maria Vooren, from the Foundation of the Federal University of Rio Grande (Furg), evaluated that the fleet of boats that fished with the trotline in the Southeast and South was responsible for the capture of 186,000 sharks in 1997 – of which 156,000 were thrown back into the sea, after any lucrative product had been removed. The data suggests that 83% of the captured sharks never arrive at disembarkation. Among the large sized sharks, one of the major victims is the gray nurse shark (Carcharias taurus), which has disappeared from the Southeast and South regions. Two factors have determined its decline. With its distribution restricted to coastal waters, the species made itself vulnerable to fishing in shallow waters. In the second place, its reproduction rate is low, with only two offspring per hatching, which hurts its restocking within a hostile environment. Another abuse is the exploration of the manta rays (Manta birostris) along the coast of the state of Santa Catarina State, which is prohibited.

In the central region of the Brazilian coast line, which covers the states of Bahia, Espirito Santo and Rio de Janeiro, fishing for sharks and rays is of economic, social and cultural importance. The meat of the ray is very welcome in the preparation of fish stews (moquecas) and there are divers who capture the animals alive to sell them as stuffed fish ornaments. Statistics point to a fall in the population of these fish in Bahia between 1998 and 2002. In the case of the rays, their volume fell from 6% to 2% of the total tonnage of fish. Among the dogfish, the drop was from 4.7% to 0.8%. Close to urban regions the problem is pollution. In the Todos os Santos bay, Bahia, there has been the registration of rays of the species Rhinobatos percellens captured with congenital deformities.

Rented fleet
In the Northeast, the greatest worry is the opening up of tuna exploration to boats rented by other countries. Of the total of fish captured by this fleet, up to 25%, in the majority of times accidentally, are elasmobranches. During 1998 two national tuna boats and 16 rented boats from countries such as Belize, Spain, Portugal, Taiwan and Equatorial Guinea were in activity. This number increased to 29 national boats and 69 rented boats in 2002. The growth of the fleet was not accompanied by a structure of fish monitoring. “We’ve information that the prohibited practice of cutting off sharks fins and throwing the carcass back into the sea is still common”, advised researcher Rosa, from UFPB. Among the sharks studied, the oceanic white-tip shark (C. longimanus) is one of the most vulnerable. On the other hand, the blue shark (Prionace glauca), a species high fertility, with a population increase of 5% a year, runs less of a risk

Curiously enough, one of the main fishing efforts in the Northeast does not reach any animal under threat of disappearing. One is dealing with the Carcharhinus leucas, a flathead shark, the object of a project directed by the Federal Rural University of Pernambuco. It has come to be the species that attacked around 50 surfers in Recife over the last twelve years. The project’s objective is to study its biological cycles and to analyze environmental factors related to the attacks. It is stated as certain that the aggressions have something to do with the construction of the Suape port, which change the estuary’s configuration and could have pushed the sharks in the direction of Recife city. Also on the North cost, the lack of knowledge concerning the marine fauna and that of fresh water calls one’s attention.

“The most urgent goals are to collect biological data at disembarkations and the implementation of a program of observers aboard the region’s fleet”, says the biologist Patricia Charvet Almeida, a doctorate degree student at UFPB and one of the few elasmobranch researchers in activity in the North of Brazil.”Up until this moment, only information concerning the exploration, feeding and reproduction of twelve species has been surveyed.”, she says. “The North coast will as yet bring new information as to the species diversity of the elasmobranches.”

Ecotourism, which is seen as an environmentally sustainable development solution, is a major enemy of fresh water rays in some parts of the Amazon region. They are the target of the so-called “negative fishing”. One is dealing with a mild form of classifying the killing. Hotel owners or have therays that inhabit shallow areas of fresh water beaches killed. It so happens that when the tourists step on them, they get pricked. The wound is extremely painful and very often difficult to heal. The management plan is in the hands of the Ministry of the Environment, which will decide what is to be done with the suggestions. The expectation is that at least a part of the suggestions will be incorporated into the legislation of environmental conservation.

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