INDICADORES POPULACIONAIS E ECOLÓGICOS DE PEIXES-BOIS-MARINHOS (Trichechus manatus manatus) EM DUAS ÁREAS DE MANGUEZAIS E MARISMAS NO MARANHÃO / POPULATION AND ECOLOGICAL INDEX FOR MANATEES (Trichechus manatus manatus) IN TWO MANGROVES AND SALT-MARSHES AREAS OF MARANHÃO

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The Brazilian north coast has the largest continuous area of mangroves on the planet and hosts large groups of manatees, aquatic mammal critically endangered. This research examines the efforts of fix point methodology of observation of manatees on relevant sites of occurrence, from data collected while on the beach in Guarapiranga (GUA), São José de Ribamar and on Ilha do Gato (IGA), Baía do Tubarão. This article discusses the application of population index for manatees in a ecological-environmental study on IGA (0231 09, 81"S, 4337 09,13" W), Mapari estuary, serving as a methodological basis to be replicated in other parts of the coast. From the application of index developed with data from fixed point and the characterization of the environmental area, the study provides evidence to infer the relative abundance of the population and it trends over the years, discussing aspects of spatial and temporal use of estuary. Was characterized: temperature, salinity, pH, conductivity, depth, current speed, tides fluctuations, rainfall, biomass of salt-marsh (Spartina alterniflora), and density of plants/seedlings of mangrove. The region showed a seasonal variation marked by two regimes of water, rain (January-July) and dry (August-December), with annual rainfall of 1,704mm. The oceanographic parameters ranged from tides: salinity (FLOOD=14.8; EBB=1.5), conductivity (FLOOD=27.1; EBB=6.3mS/cm), speed of current (FLOOD=46; EBB=88m/s). The tide height ranged from 0.0-5.4m. Biomass of S. alterniflora ranged from 860g/m2(RAIN) to 430g/m2(DRY) and density of plants/seedlings of 74ind/m2(RAIN) to 21ind/m2(DRY). Variations between rain/dry seasons influenced the availability of fresh water and food resources, important factors in the choice of areas for manatees. The estuary was shown with strong influence of daily tide fluctuations, reflecting changes in salinity, current speed, depth and access to plant resources by manatees. Between 2004/2007, manatees were monitored in 1241 days (GUA = 625, IGA = 616). The population analysis carried out in two sites of Maranhão indicated a trend of reducing population between 2004 and 2006, with stabilization between 2006 and 2007. The IGA had the highest relative abundance and showed to be important site of occurrence of manatees, which used as an area of reproduction, parental care, food and rest. IGA in the number of manatees seems to have relation with the seasons, being sighted in greater numbers in the rainy season. Variations during the tides also shown to influence the pattern of use of the IGA, and the manatees were more frequent in the tides ebb and flood. The main type of human activity in the IGA was not motorized boat and it had no negative influence on the occurrence of fish-horse. Knowledge about characteristics of coastal ecosystems is essential for development of appropriate conservation strategies for manatees in the Brazilian north coast.

ASSUNTO(S)

mangroves peixe-boi manatees population and ecology index maranhão conservacao da natureza indicadores populacionais e ecológicos salt-marshes maranhão state manguezais trichechus manatus manatus marismas trichechus manatus manatus

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