Rosa Souza

The Path towards Endangered Species: Prehistoric Fisheries in Southeastern Brazil.

Brazilian shellmounds are archaeological sites with a high concentration of marine faunal remains. There are more than 2000 sites along the coast of Brazil that range in age from 8,720 to 985 cal BP. Here, we studied the ichthyoarchaeological remains (i.e., cranial/postcranial bones, otoliths, and teeth, among others) at 13 shellmounds on the southern coast of the state of Rio de Janeiro, which are located in coastal landscapes, including a sandy plain with coastal lagoons, rocky islands, islets and rocky bays. We identified patterns of similarity between shellmounds based on fish diversity, the ages of the assemblages, littoral geomorphology and prehistoric fisheries. Our new radiocarbon dating, based on otolith samples, was used for fishery characterization over time. A taxonomical study of the ichthyoarchaeological remains includes a diversity of 97 marine species, representing 37% of all modern species (i.e., 265 spp.) that have been documented along the coast of Rio de Janeiro state. This high fish diversity recovered from the shellmounds is clear evidence of well-developed prehistoric fishery activity that targeted sharks, rays and finfishes in a productive area influenced by coastal marine upwelling. The presence of adult and neonate shark, especially oceanic species, is here interpreted as evidence of prehistoric fisheries capacity for exploitation and possibly overexploitation in nursery areas. Various tools and strategies were used to capture finfish in seasonal fisheries, over rocky reef bottoms and in sandy littoral environments. Massive catches of whitemouth croaker, main target dermersal species of South Atlantic coast, show evidence of a reduction in body size of approximately 28% compared with modern fisheries. Fishery activity involving vulnerable species, especially in nursery areas, could mark the beginning of fish depletion along the southeastern Brazilian coast and the collapse of natural fish populations.

Marine reservoir effect on the Southeastern coast of Brazil: results from the Tarioba shellmound paired samples.

On the Southeastern coast of Brazil the presence of many archaeological shellmounds offers a great potential for studying the radiocarbon marine reservoir effect (MRE). However, very few such studies are available for this region. These archaeological settlements, mostly dating from 5 to 2 kyr cal BP, include both terrestrial and marine remains in good stratigraphic context and secure association, enabling the comparison of different carbon reservoirs. In a previous study the chronology of the Sambaqui da Tarioba, located in Rio de Janeiro state, Brazil, was established based on marine mollusc shells and charcoal samples from hearths, from several layers in two excavated sectors. We now compare the different materials with the aim of studying the MRE in this region. Calibration was performed with Oxford software OxCal v4.2.3 using the marine curve Marine13 with an undetermined offset to account for local corrections for shell samples, and the atmospheric curve SHCal13 for charcoal samples. The distribution of results considering a phase model indicates a ΔR value of -127 ± 67 (14)C yr in the 1 sigma range and the multi-paired approach leads to a mean value of -110 ± 94 (14)C yr.

Archaeozoology of marine mollusks from Sambaqui da Tarioba, Rio das Ostras, Rio de Janeiro, Brazil

A reference inventory of prehistoric marine mollusks from the Rio das Ostras region was created based on an excavation carried out at the Sambaqui da Tarioba shellmound. Patterns of richness and biogeography were studied, and the representativeness of bivalve and gastropod diversities found at this archaeological site were inferred. A total of 47 taxa belonging to 28 families, most of which from unconsolidated substrates, was identified. The shellmound species composition does not differ from the present-day composition. All recorded species are characteristic of a wide transition zone between the south of the states of Espirito Santo (21°S) and Rio Grande do Sul (32°S). Thus, the data show little evidence of evolution in the composition, richness,and biodiversity distribution patterns of mollusks in the Rio das Ostras region. Likewise, a reconstitution of the paleoenvironment from the functional characteristics of the shellmound species indicates that the localitys geomorphology and climate remained largely unchanged in the last 4,000 years BP.

Holocene molluscs from Rio de Janeiro state coast, Brazil

A list of marine species of bivalves and gastropods found in seventy archeological sites of the shellmound type from Rio de Janeiro state was produced, based on the archeological material deposited in the collections of Museu Nacional (Rio de Janeiro, RJ), Instituto de Arqueologia Brasileira (Belford Roxo, RJ) and Museu do Sambaqui da Tarioba (Rio das Ostras, RJ). A total of 124 taxa were identified, of which 65 bivalves and 59 gastropods. The data retrieved from the shellmounds indicate stability of the composition patterns of mollusc biodiversity on the Rio de Janeiro state coast, at least in the period between 8,000 and 2,000 years B.P. The listing presented may be useful as a reference inventory for research pertaining to biological invasions, biogeography, conservation and management.

Chronological Model of a Brazilian Holocene Shellmound (Sambaqui da Tarioba, Rio de Janeiro, Brazil)

Since the beginning of the Holocene, hunter-gatherers have occupied the central-south Brazilian coast, as it was a very productive estuarine environment. Living as fishers and mollusk gatherers, they built prehistoric shellmounds, known as sambaqui, up to 30 m high, which can still be found today from the Espirito Santo (21°S) to Rio Grande do Sul (32°S) states, constituting an important testimony of paleodiversity and Brazilian prehistory. The chronology of the Sambaqui da Tarioba, situated in Rio das Ostras, Rio de Janeiro, is discussed herein. Selected well-preserved shells of Iphigenia brasiliana and charcoal from fireplaces in sequential layers were used for radiocarbon dating analysis. Based on a statistical model developed using OxCal software, the results indicate that the settlement occupation begun most probably around 3800 cal BP and lasted for up to 5 centuries.

POTENTIAL USE OF ARCHAEOLOGICAL SNAIL SHELLS FOR THE CALCULATION OF LOCAL MARINE RESERVOIR EFFECT

Shellmounds are archaeological sites found across the Brazilian coast and form an important record of the human occupation of this area during the Holocene. The presence of both terrestrial and marine remains within the same archaeological context enables the comparison of different carbon reservoirs. There is only a small number of similar studies for the coast of south-southeastern Brazil. Previous work was based on the analysis of pre-bomb shells from museum collections and paired charcoal/marine shells from archaeological sites. This article assesses the potential use of terrestrial shells as representative of atmospheric carbon reservoir in the calculation of the marine reservoir effect (MRE) of the southeastern Brazilian coast. The presence of both terrestrial and marine shells over several archaeological layers represents a great potential for calculating reservoir corrections and their temporal variation. DOI: 10.2458/azu_rc.57.18365

The use of the terrestrial snails of the genera Megalobulimus and Thaumastus as representatives of the atmospheric carbon reservoir

In Brazilian archaeological shellmounds, many species of land snails are found abundantly distributed throughout the occupational layers, forming a contextualized set of samples within the sites and offering a potential alternative to the use of charcoal for radiocarbon dating analyses. In order to confirm the effectiveness of this alternative, one needs to prove that the mollusk shells reflect the atmospheric carbon isotopic concentration in the same way charcoal does. In this study, 18 terrestrial mollusk shells with known collection dates from 1948 to 2004 AD, around the nuclear bombs period, were radiocarbon dated. The obtained dates fit the SH1-2 bomb curve within less than 15 years range, showing that certain species from the Thaumastus and Megalobulimus genera are reliable representatives of the atmospheric carbon isotopic ratio and can, therefore, be used to date archaeological sites in South America.

Holocene crustaceans from the Tarioba shell mound, Rio das Ostras, Rio de Janeiro, Brazil

Crustacean remains from the Tarioba shell mound (Sambaqui da Tarioba) archaeological site were investigated in order to produce a reference inventory of this taxonomic group. Information on past crustacean diversity is important for establishing baselines on biodiversity, as well as recovering paleoenvironmental information and comprehension of evolutionary change patterns for the Brazilian coast. The archaeological site was excavated by delayering the soil by artificial 10 cm sections which revealed five archaeological stratigraphic layers. A sample of mollusk shells for each of these layers was used for dating based on the C 14 method. The results show an occupation period of 550 yr for the Tarioba shell mound, with dates ranging between 4,070 cal BP (beginning of occupation) and 3,520 cal BP (occupation ending) and record nine species of crustaceans from the shell mound. However, a reduction of biodiversity over time was found that was not statically significant. Therefore, it seems that patterns of composition, richness and distribution of crustaceans have been stable in the last 4,070 years BP.

Shell Mounds of the Southeast Coast of Brazil: Recovering Information on Past Malacological Biodiversity

Brazilian classical studies on archaeology have attempted to explain human settlement and cultural trajectories in different geographical regions. However, zoological remains found in archaeological sites can also provide important information on biological diversity. Shell mounds (or sambaquis, the Brazilian term for them derived from the Tupi language) are acknowledged as artificial constructions made under cultural aims. These deliberated accumulations enclose a sample of the fauna existing between at least 6500 years BP and the start of the Common Era. In this chapter studies dedicated to use archaeozoological remains as surrogates for Late Holocene malacological biodiversity of the Central-South Brazilian coast are reviewed. Important issues such as the establishment of baselines and the problem of bioinvasion are addressed. In pursuance, raw data from the reviewed publications are used to test the main assumption lying under all inferences done by them, namely that shell mounds can be used as samplers of the past mollusk fauna. In conclusion it is sustained that shell mounds can be useful proxies for Late Holocene biodiversity.

Taxonomic status of two morphotypes of Coryphaena hippurus (Perciformes: Coryphaenidae)

Dois morfotipos de Coryphaena hippurus (dourado e palombeta) encontrados ao longo da costa brasileira sao considerados especies diferentes por pescadores e mercadores das regioes de desembarque do estado do Rio de Janeiro. Alem disso, esses morfotipos sao comercializados por valores diferentes e sofrem diferentes pressoes de pesca. Desta forma, a definicao do status taxonomico desses morfotipos e importante, tanto em termos economicos quanto biologicos. A fim de investigar esse problema foi utilizado o metodo de eletroforese de aloenzimas com a amostragem de dezessete loci para 117 individuos dos dois morfotipos de C. hippurus obtidos em desembarques pesqueiros na regiao de Cabo Frio/RJ (Brasil). Os dados indicaram uma homogeneidade entre os conjuntos genicos dos morfotipos. A despeito disso, diferencas entre os conjuntos genicos de dourado e palombeta foram encontradas, devido, especialmente, ao locus alcool desidrogenase. A hipotese de selecao natural e discutida como possivel explicacao para esses resultados.