A participação dos metais pesados nas reações químicas do metabolismo dos peixes tornou esses elementos um dos principais focos nos estudos de contaminação. O objetivo deste estudo foi determinar as concentrações dos metais Cd, Cr, Cu, Pb, Zn e Hg no tecido muscular de peixes da bacia do rio Cassiporé (Estado do Amapá) e ambiente, visando avaliar os riscos de contaminação. As concentrações de Cd em Plagioscion squamosissimus (1,061 µg g ), Hoplias malabaricus (0.570 µg g -1 e Serrasalmus rhombeus (0.548 µg g -1 ) were above the legal limit. The water column showed high concentrations of heavy metals in all analyzed points, showing a contamination of this river basin. Therefore, the high concentrations of heavy metals in the environment and muscle tissue of fish indicate a high degree of contamination in the Cassiporé river basin and risk to human health.

RESUMO. A biologia populacional de M. jelskii foi investigada com ênfase na distribuição de frequência de comprimento, razão sexual, período reprodutivo e relação peso comprimento. A amostragem foi realizada durante o período de abril/2008 a maio/2009 junto às macrófitas, em um transecto de 50 m. As coletas foram obtidas com peneiras de 55 cm de diâmetro e malha de 2 mm, a cada 2 m, totalizando 25 amostras em todo o período de estudo. No laboratório, os exemplares de M. jelskii foram medidos, pesados, sexados e as fêmeas classificadas macroscopicamente quanto ao grau de maturação. Foram encontrados 910 exemplares, 505 machos e 405 fêmeas. O comprimento total variou de 9,7 a 50,3 mm e a maior frequência relativa de indivíduos ocorreu entre as classes de 19,7 a 21,7 mm e 37,7 a 39,7 mm. Os machos apresentaram tamanhos superiores e a proporção sexual foi instável entre os meses. A reprodução incidiu no período mais chuvoso. As fêmeas obtiveram crescimento isométrico e os machos alométrico negativo, demonstrando dimorfismo nas relações peso total/comprimento total de ambos os sexos.Palavras-chave: área inundável, área de ressaca, camarão.ABSTRACT: Aspects of the population biology of Macrobrachium jelskii (MIERS, 1778) (Crustacea, Decapoda, Palaemonidae) in a flood plain in eastern Amazonia, Brazil.The population biology of M. jelskii was investigated with emphasis on the length frequency distribution, sex ratio, breeding season and length and weight ratio. Sampling was conducted during the April/2008 May/2009 along with macrophytes in a transect of 50 m. The samples were obtained using sieves of 55 cm diameter and a 2 mm mesh, on a 2 m space interval, totaling 25 samples throughout the study period. In the laboratory, specimens of M. jelskii were measured, weighed, sexed and females classified macroscopically as to the degree of maturation. There were found 910 specimens, 505 males and 405 females. The total length ranged from 9.7 to 50.3 mm, and a higher frequency of subjects on the classes occurred between 19.7 to 21.7 mm and from 37.7 to 39.7 mm. The males showed greater sizes and sex ratio was stable between months. Reproduction occurred in the rainy season. Females had isometric growth and male allometric negative, showing dimorphism in relations total weight/total length of both sexes.

This study analyzes the effects of three aspects of artisanal fishing that occurred due to the construction of the Cachoeira Caldeirão dam in a community in the middle stretch of the Araguari River. Interviews were carried out with fishermen, questionnaires were applied, and field observations were made. According to fishermen, subsistence artisanal fishing for family consumption and commercial sale in Porto Grande suffered negatively after the dam, especially with the reduction of its fishing territory, limited between physical barriers and legal barriers. This scenario is aggravated by the reduction of active fishermen in fishing activities and an alteration in the fishing dynamics which poses an imminent risk to artisanal fishing, and this may cause fishing activities to disappear in a few years in the municipality of Porto Grande.

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