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A batimetria de um corpo d'água pode ser medida em campo, a partir de sondas batimétricas; no entanto, é um processo oneroso e que demanda tempo. Com isso, o objetivo principal deste estudo foi ajustar modelos de estimativa de batimetria de um lago a partir de dados orbitais. O trabalho foi realizado no açude do Saco, localizado na bacia hidrográfica do Rio Pajeú, na cidade de Serra Talhada - PE. Foram ajustados modelos de regressão entre os valores batimétricos, coletados com auxílio de uma sonda, as bandas espectrais verde e infravermelho próximo do satélite Landsat 5 TM e o índice da diferença normalizada da água. A avaliação dos modelos ajustados foi realizada pela análise do coeficiente de determinação, do erro quadrado médio e da eficiência do modelo. A batimetria do açude variou entre 0,3 e 10 metros de profundidade. Os melhores ajustes foram encontrados com a utilização dos modelos potencial e exponencial, com valores de coeficiente de determinação superiores a 0,46 e de eficiência do modelo próximos da unidade. Pode-se concluir que os modelos de batimetria, ajustados a partir de dados de sensoriamento remoto, estimaram com satisfatória exatidão os valores de batimetria do açude do Saco, principalmente nas partes mais rasas do lago. The bathymetry of a water body can be measured in the field using bathymetric probes; however this process is costly and time-consuming. Thus, the main objective of this study was to fit bathymetry estimation models of a lake from satellite data. The study was conducted in the Saco reservoir, located in the Pajeu river basin near the city of Serra Talhada - PE, Brazil. Regression models were adjusted between the bathymetry values collected with a probe, the green and near infrared spectral bands of the Landsat 5 TM satellite and the normalized difference water index. Evaluation of the adjusted models was performed by analysis of the coefficient of determination, mean squared error and model efficiency. The bathymetry of the reservoir varied between 0.3 and 10 meters deep. The best fits were found when using the power and exponential models, with coefficients of determination greater than 0.46 and model efficiency close to one. It can be concluded that the bathymetry models adjusted to the remote sensing data provided a satisfactory accuracy for estimating bathymetry values of the Saco reservoir, especially in the shallow regions of the lake.

The reproductive cycle of Cardisoma guanhumi was described from the analysis of seasonal variation of the gonadal maturation stages. The first maturity for both sexes was determined based on three different tests: inflexion point on the curve; relevant character (morphometry); and histological analysis (physiology). In addition, some aspects of sexual dimorphism for the population were studied. A total of 353 individuals caught in north-eastern Brazil between December 2006 and November 2007 were analysed. The sex-ratio was statistically equal (P ≥ 0.05) and the carapace width (CW) of the females ranged from 4.34 to 8.56 cm and of the males from 2.84 to 9.22 cm. Mature females with fully developed gonads begin to appear in the dry season (August) and ovigerous females occurred from November to February, suggesting that spawning occurs mainly during the rainy season. The CW of first sexual maturity for females ranged from 5.87 cm to 6.70 cm and males from 6.22 cm to 7.20 cm. The highest percentage of individuals caught were juveniles, indicating the need for a targeted effort to preserve the species.

The reproductive tract of female Cardisoma guanhumi was macroscopically and microscopically described. The stages of sexual maturation were defined and related to gonad coloration and to the degree of development of the germ cells, including oogonia (diameter 14.17 0.97 mm), forming nests in the germ zone; pre-vitellogenic oocytes (PVO, 51.02 2.90 mm) of a basophilic nature, with one or two nucleoli; vitellogenic oocytes (VO, 110.93 7.04 mm) of acidophilic nature; mature oocytes (MO, 237.52 13.54 mm), revealing the chorion; and atretic oocytes (AO). Follicular cells were found close to germ cells. The following gonad development stages were identified: immature (translucent color, germ zone containing oogonia, and peripheral maturation zone with PVO); maturing (color ranging from yellow to dark brown; maturation zone with VO); mature (dark brown color; predominance of MO in maturation zone); spawning (dark brown or yellow color, containing oocytes in early atresia, stage observed in ovigerous females); and resting (translucent to yellow color, thick gonad wall, and residual AO).