Abstract Macrobrachium rosenbergii (De Man, 1879) is a freshwater prawn from Malaysia and in 1977 it was introduced in Brazil for development of carciniculture. However, this species is currently found in various natural environments in the Brazilian states. The present study aimed at conducting a survey of M. rosenbergii sites in the natural environment, and shrimp farming ponds using this species. To do so, a search was conducted in scientific articles and databases on the occurrence of the species in Brazil. We found reports in 80 different sites in Brazil. Macrobrachium rosenbergii was found in the natural environment in eight states and 43 cities, with the largest amount of reports being from the states of Pará and Maranhão. In addition, we found 28 reports in 13 states of shrimp farming ponds. Macrobrachium rosenbergii was not reported in natural environments in the Center-West region (except in state of Goiás) and North region (except in state of Pará). Moreover, we found that most of the M. rosenbergii reports were in temperature equal to or greater than 25 °C. Therefore, this species has expanded its area of occurrence throughout various Brazilian states, and we believe that this expansion may be greater than that reported in the current study.

Resumo Ceratium furcoides é uma espécie invasora que tem causado desequilíbrio ecológico em vários reservatórios no Brasil. Este estudo investiga os principais fatores que podem favorecer a ocorrência de florações de C. furcoides em um reservatório tropical do Nordeste do Brasil, durante um período de seca extrema. Amostras contendo fitoplâncton foram coletadas mensalmente de fevereiro a setembro de 2017. Análises quantitativas de C. furcoides foram realizadas e o volume celular estimado por meio de fórmulas geométricas. O biovolume médio de C. furcoides apresentou diferenças significativas, variando de 0,78 mm3 L-1 a 11,29 mm3 L-1 relatado em março e setembro, respectivamente. Os parâmetros ambientais apresentaram baixa oscilação ao longo do estudo, exceto a condutividade. Relações significativas entre o biovolume de C. furcoides, temperatura da água e fosfato reativo solúvel foram observadas. Os resultados relatados aqui sugerem que as condições adversas causadas por uma estação de seca não afetam negativamente esta espécie.

Abstract Ceratium furcoides is an invasive species that has caused ecological imbalance in several reservoirs in Brazil. This study investigates the main factors that may favor the occurrence of Ceratium furcoides blooms in a tropical reservoir from the Northeast Brazil, during an extreme drought season. Samples containing phytoplankton were collected monthly from February to September 2017. Quantitative analysis of C. furcoides was performed and the cell volume was estimated using geometric formulas. Mean biovolume of C. furcoides showed significant differences, ranging from 0.78 mm3 L-1 to 11.29 mm3 L-1 reported in March and September, respectively. Environmental parameters presented low oscillation throughout the study, except the conductivity. Significant relationships among the C. furcoides biovolume, water temperature and soluble reactive phosphate were observed. The findings reported here suggest that adverse conditions caused by a drought season did not negatively affect this species.

Resumo: Obietivo O presente estudo teve como objetivo estimar a maturidade sexual, o crescimento e as taxas de mortalidade do peixe introduzido na região do semiárido brasileiro, o jaguar guapote, Parachromis managuensis. Métodos Os exemplares foram coletados entre os meses de Dezembro de 2015 e Novembro de 2016, em um açude do município de Serra Talhada, Pernambuco, onde a espécie é abundante. Resultados Um total de 520 indivíduos foram analisados, com comprimentos totais (CT) que variaram entre 23 e 240 mm. O comprimento de maturação sexual variou entre 130,87 e 140,68 mm CT (Média = 135,78 cm CT). Através da progressão modal das distribuições de frequência mensais, foram obtidos os seguintes parâmetros de crescimento segundo o modelo de von Bertalanffy: L∞ = 341,40 mm, k = 0,840 e t0 = -0,035 ano-1. As idades variaram entre 0,05 a 1,41 ano, com uma idade de primeira maturação entre 0,48 e 0,53 ano (Média = 0,51 ano), sendo a maior parte da amostra (72,64%) formada por indivíduos adultos. Taxas de mortalidade natural (M) foram estimadas à partir de três diferentes métodos, e variaram entre 1,53 e 3,04, com uma média de 2,27. Conclusão P. managuensis possui crescimento e maturação rápida e altas mortalidades naturais, o que lhe dá vantagens biológicas em relação a espécies nativas do mesmo nível trófico na área.

Abstract: Aim The present study aimed to estimate the sexual maturity, growth and mortality rates of the jaguar guapote, Parachromis managuensis, an introduced fish species in the Brazilian semiarid region. Methods Specimens were collected between December 2015 and November 2016, in a dam at Serra Talhada municipality, Pernambuco, where the species was abundant. Results In total, 520 individuals were analyzed, with total lengths (TL) varying between 23 and 240 mm. Length at sexual maturity varied between 130.87 and 140.68 mm TL (Mean = 135.78 mm TL). Through the modal progression of monthly frequency distributions, the following growth parameters were obtained according to the von Bertalanffy model: L∞ = 341.40 mm, k = 0.840 and t0 = -0.035 year-1. Ages varied from 0.05 to 1.41 year, and an age at first maturity between 0.48 and 0.53 year (Mean = 0.51 year), with the largest part of the sample (72.64%) made of adult individuals. Natural mortality rates (M) were estimated from three different methods, varying between 1.53 and 3.04, with a mean of 2.27. Conclusions P. managuensis shows fast growth and maturation and high natural mortalities, which grants it biological advantages when compared to native species from the same trophic level in the area.