The IUCN/SSC Shark Specialist Group
Shark News 14: March 2002
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Coastal shark fishery off Pernambuco - Brazil: is there any possibility of management?
Sérgio Macedo Gomes de Mattos,
SUDENE - Renewable Resources Group, Brazil
Since the 1970's it has been questioned if a sustainable fishery for
elasmobranchs is possible. It is now generally accepted that economic
and biological sustainability can be reached through the exploitation
of relatively more fecund species, under careful management.
The intention of this article is to highlight the importance of small
coastal sharks stocks in poor regions with social, economic and
technological difficulties, making it extremely difficult to implement
conservation and management measures. However, there are no
conclusive studies on the subject, and many questions still concern
researchers and policy and decision makers.
The first problem that we face when considering shark fisheries is
with the term itself. Can we say that there is a small coastal shark fishery
in Pernambuco, Brazil? Not as such, although the pressures on this
resource as highlighted throughout this article, lead us to believe that
these resources are in serious danger.
Small sharks play an important role in the economy of developing
countries, because they form part of the diet of the poorest communities.
Studies aimed at improved exploitation, which take into account
conservation of the resource, are thus of great importance.
In the past, high value commercial fish species occurring off
Pernambuco, Brazil, such as snappers, groupers, and mackerel, were
targeted in preference to less valuable fish, such as small coastal sharks.
However, the sharp decline of many valuable commercial stocks has
resulted in an increased and directed fishing effort to make use of less
valuable species such as sharks.
The contribution of sharks to the fishing production of the State of
Pernambuco has always been very low. In the late 1970's the average
contribution was 1.38% (SUDENE 1983), during the 1980's the average
was 1%, (SUDEPE 1988), reaching the lowest contribution in 1995,
with 0.12% (4.6t) (IBAMA 1996) and fluctuating around 0.25% since
then. In 2000 the total catch of sharks was 13.91t (0.24%) (IBAMA
2001). The catch of coastal sharks around Pernambuco comprises 4
species: Rhizoprionodon porosus, the most abundant species (60%),
Rhizoprionodon lalandii, Carcharhinus porosus and Carcharhinus
acronotus.
In 2000, motor boats caught 91.6% of the total shark production
(12.74t), rafts 6.8% (0.95t) , and canoes 1.6% (0.21t). Gillnets are the
most common fishing gear used for the capture of coastal sharks,
although gillnets were second in the State total production responsible
for 19% (1,046.77t), being surpassed by fish traps (covos), which were
responsible for 20%. Handlines were responsible for 17% of the catch.
The relative contribution of sharks to the total catch (by gillnets only),
was 1.33% (IBAMA 2001).
Management difficulties
Some of the difficulties for the management of small coastal sharks off
Pernambuco are as follows:
- Non-target species.
Small coastal sharks are considered of low value and importance
commercially, thus few studies have been conducted, and historical
data are scarce. Generally, these species are important among lowincome
communities, due to low prices, ease of processing and
the comparatively low size/volume of the catches.
- High fishing effort and low abundance index;
The relative abundance was estimated through the catch per
unit effort (CPUE) in terms of total weight and number of individuals
caught per 1000m2 of net per day of fishing. This allowed the
estimation of a fishing effort of approximately 320,000m2, with a CPUE
of 0.12-kg/1000m2 of net/day or 0.09 ind./1000m2 of net/day.
- Lack of trustworthy baseline data;
The lack of baseline data hinders an in-depth analysis on the
occurrence and frequency of sharks off Pernambuco coast.
- Restricted area fishing
The fishing fleet operates near shore in depths between 10- 30m due
to unsophisticated equipment. Wooden hull man-made boats of 6-10
m length are used, usually with 30-hp engine. It is therefore highly
likely that shark nursery areas are under heavy fishing pressure.
- Low selectivity of fishing gears
Amongst the variety of fishing gears used for the artisanal fishery off
Pernambuco State coast, fixed gillnets are one of the most abundant,
as stated above, and catch small sharks as bycatch. Average mesh
size is 50 mm from knot to knot, nylon monofilament of 0.6 mm,
an enrolment coefficient between 50%-60%, 24 meshes in height
and 100 m in length.
- No options of diversification of fishing activities
Attempts to diversify traditional fishing activities is always
considered when development plans for the artisanal fishery sector
are discussed, but resistance to this is common among fishermen
who generally oppose changes to their way of fishing, and among
official government agencies considering economic aspects and
not the social and ecological aspects.
- Social and economic conditions of fishing communities
Generally very poor social and economic conditions of coastal
fishing communities impede the introduction of new technologies,
and, sometimes prevent their development. Local sustainable
development is necessary to change this situation.
- Vocation strengthening
The local fishing sector is known for intra- and interregional
inequalities. Fishing is the natural vocation for these communities,
supplying immediate necessities, consolidating societies and
developing other local advantages.
- High divergence and competition among fishermen and low
associative organisation
Much needs to be done to reach an adequate level of organisation
in the fishing communities of Pernambuco in order for them to
participate in the planning to achieve the desired sustainable
development. In fact, the social structure of these communities
currently hinders awareness and faith in the planning and
development process.
- Migration, distribution and abundance of stocks
There is little information on the stocks, and currently no seasonal
or spatial pattern can be drawn.
- Environmental impacts
Coastal and estuarine areas off Pernambuco State are suffering
intense habitat degradation, due to high levels of anthropogenic
activities. It is these nearshore habitats most under threat that
provide nursery grounds for many shark species.
Plan of Action
The environmental impacts, unsustainable fishery, and poor socioeconomic
conditions of these fishing communities all seem to be
contributing to the reduction of the coastal shark stocks. These
conditions, together with the slow growth, high longevity, late
maturation and low fecundity of these sharks, mean that any
management measures introduced for the artisanal fishing sector
are likely to face problems. Following the guidelines developed by
FAO (FAO 2000), a specific plan of action for small coastal sharks
stocks off Pernambuco should include and prioritise studies on:
Fisheries: fishing technique evaluation, gathering of fisheries data,
and fisheries-independent abundance information;
Ecology: temporal and spatial distribution and abundance, habitats
characteristics, oceanographic conditions, and location of nursery
grounds;
Demography: incorporating biological data on reproduction, age
at maturity, fecundity, maximum age, sex ratio, and natural mortality
at specific ages (Márquez-Farias and Castillo-Geniz 1998);
Anthropogenic impacts: aquatic sports, bathers, industrial and
domestic waste, and harbour developments; and
Socio-economics: technological and economic dependencies of
fishing communities on production variability, strategy of harvest,
processing and commercialisation. Emphasis must be give to the
management credibility and the integration between management and
evaluation.
Acknowledgements
Thank you to Rachel Cavanagh for her useful suggestions and English
review.
References
FAO. Fisheries Management 1. Conservation and Management of
Sharks. FAO Technical Guidelines for Responsible Fisheries 4.
Suppl. 1. Rome, 2000. 37 pp.
Holden, M. J. 1974. Problems in the rational exploitation of
elasmobranch populations and some suggested solutions in Sea
Fisheries Research. F. R. Harden Jones (ed.). p. 117- 137.
Holden, M. J. 1977. Are long term for sustainable fisheries for
elasmobranch possible? Sustainable fisheries for elasmobranchs.
p360-367.
IBAMA. 2001. Boletim Estatístico da Pesca Marítima do Estado de
Pernambuco no ano de 2000. SUPES-PE.
Márquez-Farias, J. F. and Castillo-Geniz, J. L. 1998. Fisheries biology
and demography of the Atlantic sharpnose shark, Rhizoprionodon
terraenovae, in the southern Gulf of Mexico. Fisheries Research
39:183-198.
Mattos, S. M. G., M. K. Broadhurst, F. H. V. Hazin and D. M. Jonnes.
2001. Reproductive Biology of the Caribbean sharpnose shark,
Rhizoprionodon porosus, from northern Brazil. Australian Journal
of Marine and Freshwater Research 52:745-52.
SUDENE. 1983. Avaliação do potencial de tubarões da costa nordeste
do Brasil. Recife. il. Brasil. SUDENE. Estudos de Pesca. no. 10.
31pp.
SUDEPE. 1988. Diagnóstico da Pesca do Estado de Pernambuco.
Sérgio Macedo Gomes de Mattos
Instituto de Ciências do Mar - ICM/CMIMA
Paseig Maritím de la Barceloneta, 37-49
08003 - Barcelona, Spain
Fax: 34 93 230 9555
Email: smattos@icm.csic.es
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