Abstract
Macrobrachium amazonicum is an indigenous prawn vastly distributed in basins of South America, widely exploited by artisanal fisheries in northern and northeastern Brazil and, with great potential for aquaculture. The recruitment pattern of Macrobrachium amazonicum at the Amazon River mouth, State of Amapa was studied for a period of twelve months from January to December of 2009. In this work, 5092 specimens were captured at the two selected sites. The sex ratios obtained in both sites were similar with 1 male to 1.46 females and 1 male to 1.31 females, respectively. The smallest captured specimens measured 10.07 mm. About 91% of juveniles, between 23.00 mm and 33.00 mm of standard length, integrated for the first time the exploitable stock. Ovigerous females of M. amazonicum were found during the entire year; however, the peak reproductive period was December to April when 18 to 34% of the females were ovigerous, coinciding with higher rainfall. The presence of ovigerous females and juvenile shrimps throughout the year observed in the Amazon River suggests that recruitment of M. amazonicum was continuous and that breeding activity is all year round. The recruitment pattern of M. amazonicum occurred throughout the year, showing a major peak in the month of July. The growth parameters obtained for the recruited prawns were L∞ = 95 mm of standard length, K = 0.83 cm.month -1 , C = 1.0, WP = 0.6 and t0 = 0. The size and number of juvenile shrimps caught in this study indicates that the traps in use has very closed cracks and can be affecting the local structure of M. amazonicum populations, given the considerably decreased volume and size of shrimps caught reported by local fishermen. The size at first maturity and number of juvenile prawns caught for M. amazonicum in the present study, suggested that the minimum size of capture is is between 60.0 and 70.0 mm. Keywords : Amazon Region; prawns fishing; reproduction; juvenile prawns .
Highlights
The genus Macrobrachium Bate, 1868 has a worldwide distribution that includes the Americas, with more than 55 recognized species, 17 of which are distributed in Brazil on basins of the inland, the coast and in Amazonia (MANTELATTO et al, 2008; PILEGGI; MANTELATTO, 2010)
Ovigerous females of M. amazonicum were found during the entire year; the peak reproductive period was December to April when 18 to 34% of the females were ovigerous, coinciding with higher rainfall
The presence of ovigerous females and juvenile shrimps throughout the year observed in the Amazon River suggests that recruitment of M. amazonicum was continuous and that breeding activity is all year round
Summary
The genus Macrobrachium Bate, 1868 has a worldwide distribution that includes the Americas, with more than 55 recognized species, 17 of which are distributed in Brazil on basins of the inland, the coast and in Amazonia (MANTELATTO et al, 2008; PILEGGI; MANTELATTO, 2010). The reproductive period of Macrobrachium species is closely associated with the rainy period, thermal variations and photoperiod of the region where it happens (LIMA et al, 2014). This shrimps are known to exhibit differentiated breeding strategies adapted to the most diverse environments. According Pitcher (1982), the recruitment occurs when an age group integrates itself for the first time into the exploitable stock. It is more or less a function of age (or size) when the juveniles grow large enough to stay with the main body of adults. Recruitment depends on where prawns of catchable sizes are located and to some extent this
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