The IUCN/SSC Shark Specialist Group
Shark News 14: March 2002
|
Projeto Cação: a study of sharks caught by artisanal fisheries in Sao Paulo, Southern Brazil
Otto B. F. Gadig1, Fábio S. Motta2 and Rafael C. Namora3
1Universidade Santa Cecília, Santos, São Paulo, Brazil
2Unesp, Campus de São Vicente, São Paulo, Brazil
3Unesp, Instituto de Biociências, Rio Claro, São Paulo, Brazil
There have been few long-term studies on Brazilian coastal sharks
(Lessa 1987, Stride et al. 1992, Hazin 1995). None has been undertaken
in São Paulo State since Sadowsky (1967) examined sharks from
Cananéia.
Studies on the biology and fisheries of coastal sharks caught by the
artisanal fleet in São Paulo, Brazil, commenced in July 1996. This work,
known as Projeto Cação (Cação is a Portuguese name for shark, widely
utilised in Brazil, mainly by fishermen), aims to understand the biological
and ecological aspects of the species occurring in the study area. The study
is underway in Praia dos Pescadores (fishermen's beach), Itanhaém
County, where weekly samples are taken. The fishing fleet comprises
about ten motorised small boats (5-6 m long), which utilise gill nets
within 5-19 nautical miles from the shore.
Sharks landed are examined and dissected by the researchers on
the beach, before processing takes place. Biological material obtained
is taken to the laboratory for later analysis. To date, up to 11,000 sharks
belonging to 14 species have been studied.
Summarised species composition data
Rhizoprionodon lalandei - Brazilian sharpnose
Probably the most abundant coastal shark in Southern Brazil (Figueiredo
1977). This is the most heavily commercially exploited shark in the
present study, representing more than 50% of total shark catches. The
species is present year-round in the area, in different sizes classes.
Adult females give birth between June-August.
Rhizoprionodon porosus - Atlantic sharpnose
Observations from this study indicate that it is caught all year round.
Birth apparently occurs during the Southern Brazil spring (September-
November). Individuals from all size classes have been examined.
Sphyrna lewini - scalloped hammerhead
One of the most common shark species caught by artisanal fisheries during the
summer months in São Paulo State, when adult females arrive to give birth. The
catches are composed almost exclusively of newborns and juveniles.
Sphyrna zygaena - smooth hammerhead
This species appears to be more common in coastal waters during the
winter period. Only juveniles (70-140 cm) were studied.
Carcharhinus species - requiem sharks
Six species have been examined. Carcharhinus brevipinna (spinner shark)
is the most frequently caught, occurring in summer. C. limbatus (blacktip
shark) shows a similar distribution pattern to C. brevipinna, regarding the
seasonal occurrence of newborns, but is less abundant than the former.
Juvenile C. obscurus (dusky shark) occur in winter. C. plumbeus (sandbar
shark) and C. porosus (smalltail shark) are uncommon, and juveniles
occur during spring-summer periods. Only one specimen of C. acronotus
(blacknose shark) was caught. This was a juvenile male and the
southernmost known record of this species, which is most common in
Northern Brazil (Gadig 1994, Hazin 1995).
Squatina guggenheim - angel shark
A few samples of adults were obtained in winter. Some juveniles were
collected in spring. This species is more frequently caught by bigger vessels
in the deeper waters of South Brazil (Vooren and da Silva 1991).
Other Sharks
Three juvenile Galeocerdo cuvier (tiger shark) were caught in summer.
Three adult male sandtiger sharks, Carcharias taurus, were observed in
the same season, showing developed and haemorragic claspers,
suggesting mating activity. A juvenile specimen of Alopias vulpinus
(thresher shark) measuring about 135cm TL was caught during winter.
The former is more abundant in Northern Brazil (Gadig 1994, Hazin
1995), while the thresher is usually associated with oceanic areas
(Amorim and Arfelli 1992).
Future strategies and goals
Having now gained adequate information on the biology and fisheries of
shark species inhabiting this area, future strategies to be undertaken will
consider the following topics:
- the establishment of educational programmes to inform the fishermen
about sharks;
- the development of a document presenting the results of the project
for submission to scientific and government authorities;
- the implementation of measures to reduce fishing pressures on small
coastal sharks.
The importance of researcher - fishermen interactions
Two Masters theses are in development, utilising data from this
project. The Projeto Cação does not receive any direct financial
support from government or private agencies. The monthly costs of
travelling, sampling and other expenses, (about US $300), are obtained
through sales of Project T-Shirts.
This sum would not be enough if it were not for the collaboration
and friendship of the local fishermen who have been helping the
Project staff. These fishermen frequently donate whole specimens for
research and allow all sharks to be made available for study before
processing, as well as putting their boats at the disposal of the Project.
Without such help this work would not be possible.
References
Amorim, A. F. and C.A. Arfelli. 1992. The shark fishery in south and southern
Brazil. Chondros 3(3):1-2.
Figueiredo, J. L. 1977. Manual de Peixes Marinhos do Sudeste do Brasil.
Introdução. Cações, Raias e Quimeras. Museu de Zoologia, Universidade
de São Paulo. 104 pp.
Gadig, O. B. F. 1994. Fauna de Tubarões da Costa Norte/Nordeste do Brasil
(Chondrichthyes, Elasmobranchii). Master Thesis, Universidade Federal
da Paraíba. 309 pp.
Hazin, F. H. V. (Coord) Projeto Etepe - Eecologia de Tubarões do Litoral de
Pernambucano.
Lessa, R. P. T. 1987. Levantamento faunístico dos elasmobrânquios (Pisces,
Chondrichthyes)dolitoralocidentaldoMaranhão,Brasil. Bol.Lab.Hidrobiol.,
São Luis, 7:27-41.
Sadowsky, V. 1967. Selachier aus dem litoral von São Paulo. Bresilien. Beit.
Neotrop. Fauna 5(2):71-88.
Stride, R. K., V. S. Batista and A. A. B. Raposo. 1992. Pesca experimental de
tubarão com redes de emalhar no litoral maranhense. Projeto Pesca
Artesanal. CORSUP/EDUFMA, São Luis. 160 pp.
Vooren, C. M. and K. G. da Silva. 1991. On the taxonomy of the angel sharks
from southern Brazil, with description of Squatina occulta sp. n. Rev. Brasil.
Biol. 51(3):589-602.
Otto Bismarck Fazzano Gadig
Universidade Santa Cecília
Santos - São Paulo, Brazil
Email: gadig@bignet.com.br
|
|
|
|
|
