Babitonga Bay Research Articles

CARACTERIZAÇÃO MORFOSEDIMENTAR E SETORIZAÇÃO DO COMPLEXO ESTUARINO DA BAÍA DA BABITONGA/SC

A presente pesquisa tem como objetivo analisar a distribuição espacial dos sedimentos de fundo do complexoestuarino da baía da Babitonga, situado no nordeste do Estado de Santa Catarina, através de técnicasestatísticas multivariadas. Foram utilizadas duas técnicas de estatística multivariada: a análise de agrupamento(Cluster) e a análise de componentes principais (PCA) para 140 pontos de coleta de sedimentos, contendo oitovariáveis, o que resulta em total de 1.120 casos analisados. A análise de agrupamento indicou a presença detrês ambientes distintos de sedimentação no interior da baía. Através da análise de componentes principais,foi possível explicar 88,79 % da variância da nuvem de pontos de coleta e identificar as principais variáveis noagrupamento dos pontos. Desta maneira foi possível reconhecer, no complexo estuarino da baía da Babitonga,três grandes ambientes deposicionais, com dois ambientes contrastantes.

Distribution, abundance and density estimates of franciscanas, Pontoporia blainvillei (Cetacea: Pontoporiidae), in Babitonga bay, southern Brazil

Pontoporia blainvillei (Gervais & d'Orbigny, 1844) is threatened throughout its distribution. The species can be found year-round in the Babitonga bay estuary (26º 02'-26º 28'S and 48º28'-48º50'W), in the north coast of the state of Santa Catarina, Brazil. Boat surveys were conducted in order to evaluate its abundance and density between 2000 and 2003. Sampling was random and stratified, with 46 transects in five sub-areas, comprising a total area of 160 km². Data collection was conducted following the linear transect method with distance sampling. A total of 1174.7 km was scanned and 38 groups were observed. Franciscanas were not uniformly distributed in Babitonga bay. Group size ranged from one to 13 animals (mean ± SD = 5.02 ± 3.62). Model 1 (Half-Normal) showed the best fit to the data. The estimated population size was 50 animals and the density was 0.32 individuals km-2. Density estimates evaluated in the sub-areas where franciscanas occurred resulted in a density of 0.46 individuals km-2. Monitoring this population is of considerable importance due to the constant threats that this species faces in this bay.

Hydrological mixing and geochemical processes characterization in an estuarine/mangrove system using environmental tracers in Babitonga Bay (Santa Catarina, Brazil)

The hydrologic complex of Babitonga Bay (Brazil) forms a vast environmental complex where agriculture, shellfish farming, and industries coexist with a unique natural area of Atlantic rain forest and mangrove systems. The origin of different continental hydrological components, the environmental transition between saline and freshwaters, and the influence of the seasonality on Babitonga Bay waters are evaluated using isotopes and chemistry. End-member mixing analysis is used to explore hydrological processes in the bay. We show that a mixing of waters from different origins takes place in the bay modifying its chemical characteristics. Furthermore, biogeochemical processes related to well-developed mangrove systems are responsible for an efficient bromide uptake, which limit its use as a tracer as commonly used in non-biologically active environments. Seasonal behaviours are also distinguished from our datasets. The rainy season (April) provides a homogenization of the hydrological processes that is not seen after the dry season (October), when larger spatial differences appear and when the effects of biological processes on the bay hydrochemistry are more dynamic, or can be better recognized. Moreover, Cl/Br and stable isotopes of water molecule allow a neat definition of the hydrological and biogeochemical processes that control chemical composition in coastal and transition areas.

Conhecimento ecológico local de pescadores da Baía Babitonga, Santa Catarina, Brasil: peixes da família Serranidae e alterações no ambiente marinho

General aspects of the Local Ecological Knowledge (LEK) of long-line and spear fishermen on seven fish species of the Serranidae family (habitat use, maximum size and popular names) and on the main marine environmental changes were investigated in Babitonga Bay, Santa Catarina State, Brazil. In general, LEK on fishes corroborates the ichthyology literature, bringing original information in a local scale. Neighbor fishermen communities can develop different local species nomenclature and different LEK for fishery resources at the same area. We have verified that the fishing ban legislation on Epinephelus itajara in Brazil does not consider local species denominations, turning impossible its interpretation by local fishermen and generating conflicts on the law’s applicability. The main environmental changes registered were: decreasing abundance of fishery resources in general (and in particular that of the “Parambiju” (Cobia) Rachycentron canadum ), and the effects of the anthropogenic interruption of the “Linguado Channel” on the hydrological and sedimentological characteristics of the Babitonga Bay (channel-bed shallowing and increased water turbidity).

Local ecological knowledge on the goliath grouper epinephelus itajara (teleostei: serranidae) in southern Brazil

The goliath grouper Epinephelus itajara is a large sized (> 400 kg) and critically endangered marine fish, which is protected in many countries, including Brazil. Through the application of semi-structured interviews, we investigated the local ecological knowledge of seven fishermen specialist on catching E. itajara from the Babitonga bay, Santa Catarina, Brazil. Local long-line fisheries for E. itajara seemed to be a disappearing tradition in the studied site, with a detailed inherent local ecological knowledge system, which is also being lost. Our study also showed that fishermen engaged in recent fisheries, such as spear-fishing, can also possess a detailed local ecological knowledge system. Through the analysis of fishermen local ecological knowledge, several aspects of E. itajara life history were registered. This species is found in the inner and outer Babitonga bay, from saline waters to areas with a large input of freshwater, and inhabits submerged wooden substrates and artificial reefs such as shipwrecks, mooring pillars and cargo containers. It is known to spawn in December and subsequent summer months in the studied area. Spawning aggregations are usually seen in December (during full moon), being also eventually observed in January and February by our informants. While lobsters, spadefishes and octopuses seem to constitute the most important food items of inner bay E. itajara, outer bay individuals may feed on catfishes, crustaceans and other fish species. The goliath grouper is regarded as pacific and curious fish, but frequently display agonistic behavior in the presence of divers. Based on the perception of well experienced spear fishermen, we hypothesize that E. itajara undertakes seasonal migrations from the inner to the outer bay during summer, and that the studied population is suffering from growth over-fishing. Our data provides a practical evidence of how joining scientific and local ecological knowledge will likely benefit E. itajara local conservation and management practices by adding important new biological data into the decision-making process.

The occurrence of Pontoporia blainvillei (Gervais & d'Orbigny) (Cetacea, Pontoporiidae) in an estuarine area in southern Brazil

The toninha, or franciscana, Pontoporia blainvillei (Gervais & D'Orbigny, 1844), is an endemic species of cetacean of the southwestern Atlantic Ocean. There is little information on the occurrence of this species in its natural environment due to the great difficulty in sighting it. Systematized and non-systematized observations of franciscanas were made from December 1996 through November 2001 at Babitonga Bay, on the northern coast of Santa Catarina State, southern Brazil. The observations were made from small motorboats. A total of 79 observations were made, totaling 561 individuals. Up to 59.5% of the groups consisted of over four individuals and the average group size was seven. Calves were present in 30.4% of the observations. The species was found throughout the year within the bay and preferential areas were identified. Calves were registered during all seasons. Data are presented on the behavior (feeding, traveling, aerial behavior and behavior relating to the boats) and on inter-specific interactions with terns, cormorants [Phalacrocorax brasilianus (Gmelin, 1789)] and brown boobies [Sula leucogaster (Boddaert, 1783)]. The species is sympatric with the estuarine dolphin Sotalia guianensis (P. J. Van Bénéden, 1864) in the bay, but there was no record of interaction between them. The area of the bay represents an important refuge for the franciscana species.