Dinâmica populacional da matrinxã Brycon amazonicus (Characidae) na Amazônia Central Population dynamics of matrinxã Brycon amazonicus (Characidae) in Central Amazon

<abstract language="eng">The matrinxã, Brycon amazonicus (Spix & Agassiz, 1829) is one of the most important fishery resources of the Amazonas state. Its population dynamics in Central Amazon was analyzed based on total landing and biometry data registered in the main landing port of Manaus, between 1994 and 2002. Growth and mortality rates were estimated separately for the rivers Purus, Madeira and Solimões. Differences in size structure and growth curves suggest that different population units exist among these rivers, requiring individualized evaluation and fisheries management strategies. The analysis of the yield per recruit does not indicate overexploitation. However, the highest relative exploitation rate was observed in the Madeira river. The suggested management strategies are related to restrictions to the fishery in the main fishing grounds during the migratory dispersal period, instead of restrictions during reproductive periods

Biodiversity underpins fisheries resilience to exploitation in the Amazon river basin

Inland fisheries feed greater than 150 million people globally, yet their status is rarely assessed due to their socio-ecological complexity and pervasive lack of data. Here, we leverage an unprecedented landings time series from the Amazon, Earth's largest river basin, together with theoretical food web models to examine (i) taxonomic and trait-based signatures of exploitation in inland fish landings and (ii) implications of changing biodiversity for fisheries resilience. In both landings time series and theory, we find that multi-species exploitation of diverse inland fisheries results in a hump-shaped landings evenness curve. Along this trajectory, abundant and large species are sequentially replaced with faster growing and smaller species. Further theoretical analysis indicates that harvests can be maintained for a period of time but that continued biodiversity depletion reduces the pool of compensating species and consequently diminishes fisheries resilience. Critically, higher fisheries biodiversity can delay fishery collapse. Although existing landings data provide an incomplete snapshot of long-term dynamics, our results suggest that multi-species exploitation is affecting freshwater biodiversity and eroding fisheries resilience in the Amazon. More broadly, we conclude that trends in landings evenness could characterize multi-species fisheries development and aid in assessing their sustainability

Determinação de idade e crescimento do mapará (Hypophthalmus marginatus) na Amazônia Central Age and growth of mapará (Hypophthalmus marginatus) in the Central Amazon

O presente trabalho visa contribuir para a conservação e manejo do mapará (Hypophthalmus marginatus), um importante recurso pesqueiro de exportação do Amazonas para o qual é necessário conhecer informações essenciais de sua dinâmica de populações. Para contribuir à esta finalidade, o presente trabalho estabeleceu como objetivo identificar o par de otólito mais adequado para leitura de anéis etários, determinar os parâmetros de crescimento do mapará (H. marginatus), Amazônia Central, Amazonas - Brasil. O trabalho foi efetuado através da análise de otólitos coletados no período de dezembro de 1996 á agosto de 1997. Os otólitos escolhidos foram os asteriscus, sendo a leitura efetuada em lupa estereoscópica com monitor acoplado. As marcas de crescimento foram validadas por meio da análise do incremento marginal relativo, sendo encontrado dois anéis/ano. Os valores estimados para os parâmetros no período foram L<FONT FACE=Symbol>&yen;</FONT> = 52,63 cm; k = 0,555 ano; to = -0,029 e M = 0,552. O ciclo hidrológico e comportamento reprodutivo estão relacionados com a marcação de anéis etários.<br>The present work seeks to contribute for the conservation and management of the mapará(Hypophthalmus marginatus), an important export fishing resource of Amazonas for which is necessary to know essential information of its population dynamics. To contribute to this purpose, the present work established as objective to identify a structure for reading of age rings, to determine the parameters of growth of the mapará (H. marginatus), Central Amazon, Amazonas - Brazil. The work was made through the otoliths analysis collected in the period of December of 1996 to August of 1997. The otolith chosen for reading was the asteriscus, being the reading made in a stereomicroscope with coupled monitor. The mark structures were validated by means of the analysis of the relative marginal increment, being found two rings. The values estimated for the parameters in the period were L <FONT FACE=Symbol>&yen;</FONT> = 52,63 cm; k = 0,555 year; to = -0,029 and M = 0,552. The hydrologic cycle and reproductive behavior were the responsible factors for age rings