Abstract The present study was based on the analysis of 10,467 trawls of the industrial piramutaba (Brachyplatystoma vaillantii) fishing fleet of the Brazilian state of Pará, which were mapped by onboard GPS loggers (between February 2008 and September 2011) and the PREPS data from 40 vessels which were tracked by this system between 2008 and 2011. The variation in the mean monthly CPUE, based on Lomb’s periodogram, revealed a well-defined and constant cycle with a duration of approximately one year. Three environmental factors influenced this cycle. The El Niño 3.4 index had a negative correlation with the CPUE of the piramutaba fishery, with a time lag of 15 months, while monthly rainfall and the mean discharge of the Amazon River correlated strongly (r=0.89 and 0.87, respectively; p<0.001) with the CPUE, with time lags of 12 and 11 months, respectively. The spatiotemporal analysis of the distribution of the activity of the piramutaba fishing fleet indicated that the most intense area of operation of the fleet lies between latitudes 00º N and 02° N, and longitudes 047º40’ W and 049º40’ W. This area was divided into four geographic quadrants, although fishery operations were concentrated in only three of these quadrants. The study proposed a quadrimester fishing cycle with zoning in three of the quadrants, where fishing would be permitted for four months (occupation period), followed by an 8-month rest period for the recuperation of stocks, aiming at the sustainability of this fishing exploration.

O uso de sulfitos é uma prática utilizada a bordo para prevenir a melanose (manchas pretas) em crustáceos. No entanto, este composto, além de causar reações alérgicas em pessoas sensíveis ao SO2 quando usado em excesso, proporciona a decomposição do óxido de trimetilamina (OTMA) em dimetilamina (DMA) e formaldeído (FA), comprometendo assim a qualidade do pescado, principalmente no que se refere ao endurecimento da carne após cozimento. O presente trabalho foi desenvolvido com a finalidade de se verificar o aumento dos níveis de DMA e FA pelo uso em excesso de metabissulfito de sódio em camarão branco, Penaeus schmitti . Em laboratório, os exemplares foram descabeçados, lavados e imersos em solução de metabissulfito de sódio a 2% por 10 minutos. Uma parte foi acondicionada em gelo e mantida por 48 horas em refrigerador; outra foi congelada em salmoura e estocada em freezer por 48 horas. Foram determinados SO2 residual, OTMA, TMA, DMA e FA em amostras coletadas com 0, 24 e 48 horas. A prática de imersão dos camarões em solução de metabissulfito de sódio a 2% por 10 minutos favoreceu a decomposição do OTMA ocasionando acentuado aumento nos níveis de DMA e FA; verificou-se em camarões recém mortos um pequeno conteúdo de FA e DMA; o acondicionamento das caudas de camarão em gelo proporcionou uma redução sensivelmente maior nos níveis de TMA, DMA, FA e SO2, do que quando estocadas congeladas.

Currently, sulfites are employed on board to inhibit melanosis (blackspot) on crustaceans. However, when used in excess this chemical compound not only can cause adverse reactions in SO2-sensitive individuals, but also favors the decomposition of trimethylamine oxide (TMAO) into dimethylamine (DMA) and formaldehyde (FA), thus compromising the quality of the product, which can be observed mainly through the texture change of the meat after cooking. This study was conducted to verify the increase of the contents of DMA and FA by the excessive use of sodium metabisulfite in white shrimp (Penaeus schmitti). For laboratory trials, shrimp were beheaded, washed and immersed in a 2% sodium metabisulfite solution for 10 minutes. Specimens were stored either on ice and maintained for 48 hours in refrigeration, or stored in a freezer for 48 hours. Samples were collected at intervals of 0, 24 and 48 hours, and analyzed for residual SO2, TMAO, TMA, DMA and FA. The immersion of shrimp in a 2% sodium metabisulfite for 10 minutes favored the decomposition of TMAO which greatly increased the contents of DMA and FA. The FA and DMA measured in fresh shrimp was low. Moreover, the storage of shrimp tails on ice resulted in a significant reduction of the TMA, DMA, FA and residual SO2 contents compared to the specimens under frozen storage.