Antonio Carlos Leal de Castro

Biologia reprodutiva de Hexanematichthys proops (Siluriformes, Ariidae) no litoral ocidental maranhense

The aim of this study was to investigate the influence of gonadal and nutritional indexes on the reproductive biology of Hexanematichthys proops (Valenciennes, 1840) (Siluriformes, Ariidae) in the western coast of Maranhao, between July 2001 and July 2002. A significant female dominance was observed during the study period. The weight/length relationship showed a significant difference between sexes in relation to the alometric coefficient, although both sexes showed positive alometric growth. Analysis of the maturation curve based on the monthly variation of the gonadosomatic and hepatosomatic index suggests that the reproductive period occurs between October and May. The month variation of the condition factor reveals that females presented general conditions poorer than males during all the study period. It was observed that the loss of liver weight occurs during gonadal maturation and reproductive processes. Analysis of the mean repletion index showed that the fishes exhibited better feeding conditions before and after the reproductive season.

Histological and Genotoxic Biomarkers in Prochilodus lacustris (Pisces, Prochilodontidae) for Environmental Assessment in a Protected Area in the Northeast of Brazil

The quality of aquatic environments all around the world is being altered by different human activities that represent direct threat to the ecological system and the aquatic biota. This study aimed to evaluate the occurrence of histological and genotoxic alterations in Prochilodus lacustris as indicators of anthropic impacts in a lacustrine environment in northeast Brazil. The histological alterations were evaluated using the histological alteration index, and the genotoxic alterations were detected using the micronuclei test, at three sampling stations (S1, S2 and S3). The gills presented lesions with three stages of severity, with mild lesions more frequent in the specimens collected at station S1. Mild hepatic tissue lesions were the most frequent type in both areas. Micronucleus analysis showed that station S3 was the most affected. The biological responses observed indicated that the fish are under influence of environmental changes. It is important to highlight that the organisms collected at station S3 had a more compromised health status.

Mineral content in fishes in the lower course of the itapecuru river in the state of Maranhão, Brazil

Concentrations of calcium, iron, potassium, magnesium, phosphorus, zinc, copper, selenium and nickel were determined in the muscle tissue of seven species of fish (Plagioscion squamosissimus, Geophagus surinamensis, Prochilodus lacustres, Curimata sp., Schizodon dissimilis, Ageneiosus ucayalensis and Hypostomus plecostomus) collected from the lower course of the Itapecuru River in the state of Maranhão, Brazil. The samples were digested in a nitricperchloric solution and analyzed using an inductively coupled plasma atomic emission spectrometer, with the construction of specific calibration curves for each element. The highest concentrations of constituent minerals were found for phosphorus, potassium, nickel and magnesium (399.83, 144.60, 90.20 and 29.49 mg 100 g−1, respectively) in G. surinamensi, P. lacustres and Curimata sp. The lowest concentrations were found for copper, zinc, iron and selenium (0.12, 0.51, 1.05 and 8.31 mg 100 g−1, respectively) in Curimata sp., S. dissimilis, A. ucayalensis and P. squamosissimus. The concentrations of all minerals can be considered low and are below the maximum limit established by Brazilian legislation for the human ingestion of fish meat. A comparison of the seven species of fish investigated revealed no statistically significant differences regarding the concentrations of minerals, suggesting that size and different dietary habits do not exert an influence on absorption. The low concentrations of metals, such as Fe, Cu, Zn and Ni, may be related to the environmental conditions of the mouth of the river, which receives ocean inputs that produce particular tide cycles with a strong dispersion capacity, thereby diminishing residence time in the water column and reducing the availability of these metals to species of fish.

Siltation rate and main anthropic impacts on sedimentation of the São Luís tidal inlet - State of Maranhão, Brazil

In recent decades, intense human intervention in the coastal zone has given rise to severe siltation and erosion problems. This scenario is located the Sao Luis tidal inlet, formed by the mouths of the Anil and Bacanga rivers which due to various kinds of interference have been changing their sediment transport and deposition processes. With these changes in mind, this study sought to evaluate the evolution of the siltation and sedimentation rates in this area, as well as the main anthropogenic influences associated with this process. The methodology consisted in verifying the morphological evolution on the basis of the scanning and vectorization of nautical charts of 1947 and 1966, bathymetric surveys conducted in 2006, and aerial photos dating from 2011. The results show a silting up process coincident with interventions that occurred in the Anil and Bacanga river basins, with a volume of silt estimated at 8.5x106 m3, over the period from 1944 to 2011 (64 years), at a rate of 1.6 cm.yr-1. These processes are associated mainly with the construction of the Bacanga dam and land reclamation projects undertaken for the purpose of providing new areas for urban expansion. The evaluation of the results showed intense and advanced silting up of the Sao Luis tidal inlet, at rates proportionally greater than those of other estuaries, calling for corrective actions and the implementation of coastal management policies for this area.