Marine mammal species in an area of charge/discharge of oil and its by-products
in Rio Grande do Sul, southern Brazil.
SUCUNZA, F.1-7*; DANILEWICZ, D.1-2-3; TAVARES, M.1-4; MORENO, I.B.1-5; OLIVEIRA, L.R.1-6 &OTT, P.H.1-7
1Grupo
de Estudos de Mamíferos Aquáticos do Rio Grande do Sul (GEMARS). ²Laboratório de Ecologia e Conservação de Mamíferos Marinhos - ECOMMAR
Universidade Estadual de Santa Cruz (UESC) 3InstitutoAqualie. 4Centro de Estudos Costeiros, Limnológicos e Marinhos, Instituto de Biociências, Universidade Federal do Rio Grande do Sul (CECLIMAR/IB/UFRGS).
5Laboratório de Sistemática e Ecologia de Aves e Mamíferos Marinhos, Departamento de Zoologia/IB – UFRGS. 6Laboratório de Ecologia de Mamíferos da Universidade do Vale do Rio dos Sinos (UNISINOS).
7Laboratório de Biologia da Conservação de Aves e Mamíferos Aquáticos, Universidade Estadual do Rio Grande do Sul (UERGS).
*E-mail: [email protected]
INTRODUCTION
The knowledge about marine mammals that occur in areas potentially threatened by oil spill is one of the first steps
in the development of a risk assessment plan (GERACI and St. AUBIN, 1988). In this study, we investigated the
marine mammals occurrence near the petroleum ocean terminal “Almirante Soares Dutra” (30º01’S/50º05’W) in Rio
Grande do Sul state, southern Brazil.
The most frequent species (Pb, Tt, Ea, Aa and Of) are also probably the most susceptible species to oil impact in this
area, exhibiting the following patterns of use: Pb and Tt are year-round residents, Ea occurs on winter and spring and
Aa and Of on autumn and winter.
MATERIALS AND METHODS
Study area and data colection
The terminal is composed by two monobuoys, utilized to anchor ships that load and discharge oil and its byproducts, placed at 2 and 4 nm from de coast, at depths of 22 and 25 m, respectively. The occurrence of marine
mammal species in this area was accessed primarily from onboard opportunistic surveys (n=193) and systematic
beach surveys (n=116), between 1991 and 2011. The area considered in these analyses included one fishery
community (Tramandaí/Imbé) and 41 km of sandy coast (Figure 1).
B
A
C
D
Fig. 1. Map of the study area and pictures of the beach surveys (A, B), tanker ship discharging oil (C), and the onboard
oportunistic surveys (D)
RESULTS
From the onboard surveys, a total of six species were recorded: south american fur seal (Arctocephalus australis –
Aa) (n=14), south american sea lion (Otaria flavescens – Of) (n=11), southern right whale (Eubalaena australis –
Ea) (n=40), common bottlenose dolphin (Tursiops truncatus – Tt) (n=21), rough-toothed dolphin (Steno
bredanensis – Sb) (n=2) and killer whale (Orcinus orca – Oo) (n=1). Two other species were recorded from bycatch
in coastal gillnets: franciscana (Pontoporia blainvillei – Pb) (n=30) and striped dolphin (Stenella coeruleoalba – Sc)
(n=2). From the stranding records (n=146), the most common species were Pb (36%), Aa (18%) and Tt (12%)
(Figure 2, Table 1).
Table 1. Total sightings and strandings data for the five most marine mammal species recorded in the study area.
Species
Sightings
groups
South american fur
seal
South american sea
lion
Southern right whale
Common bottlenose
dolphin
Franciscana*
* Data provided from bycatch
SUPPORT
14
Group size
individual
14
mean
1
range
1
Strandings
SD
0
individual
27
Fig. 2.. Maps showing the habitat-use for the entire monitoring period based on kernel density estimator of the marine mammals
sightings (A – pinnipeds; B – southern right whale; C – delphinids) and bycatch (D – franciscana).
DISCUSSION
Although we know that is needed a fine scale data analyses, the kernel results indicate a high degree of the habitatuse by marine mammal species.
An interdisciplinary research will be made to combine oceanographic data and marine mammal habitat modeling in
order to assess the exposure risk. Improving the knowledge needed to indentify critical habitats and then elaborate
maps to guide management plans to the area.
It is known that in the transportation phase exist the risk to oil spill (cronic and acute) noise and ship strikes
(GERACI and St. AUBIN, 1980), in this sense, the species richness and the occurrence of two endangered species
(franciscana and southern right whale) pointed out the importance of the preventive protection of this area.
% of total
strandings (n=146)
18
12
15
1,25
1–3
0,62
8
5
40
71
1,78
1–5
0,95
1
1
23
53
2,3
1–5
1,33
17
12
25
30
1,2
1–3
0,5
53
36
ACKNOWLEDGEMENTS
We are very grateful to all the peoples that gave invaluable field support, especially: Márcio Borges Martins, Rodrigo
Machado, Janaína Carrion Wickert, Sue Bridi Nakashima, Cariane Campos Trigo, Lucas Milmann de Carvalho,
Martin Sucunza Perez and Jonathas da Silva Barreto.
This study was possible tanks to finnancial support of The Conselho Nacional de Desenvolvimento Científico e
Tecnológico of the Brazilian Government (CNPq), Cetacean Society Intenational and Petrobras Transporte S.A.
(Transpetro). Cetacean Society Intenational, Society for Marine Mammalogy and Pró-Reitoria de Pesquisas
(UFRGS) provided financial support to my upcoming Biennial Conference.
REFERENCES
GERACI, J.R. AND AUBIN, St. D. J. 1980. Offshore petroleum resource development and marine mammals: a
review and research recomendations. Marine Fisheries Review, 42 (11): 1 – 12.
GERACI, J.R. AND AUBIN, St. D. J. 1988. Synthesis of Effects of Oil on Marine Mammals. Department of
Interior Mineral Management Service Atalntic OCS Region. 298p.