Effect of density on population development in the Amazon River prawn Macrobrachium amazonicum

Abstract

The Amazon River prawn Macrobrachium amazonicum is widely distributed in lentic and lotic environments of South America, and shows different male morphotypes. In the present study, the effect of crowding on the general population structure of this species and its variation over time were evaluated. Prawns were reared in mesocosms consisting of 12 rectangular ~100 m 2 earthen ponds for ~160 d at densities of 10, 20, 40, and 80 prawns m -2 . Prawn density affected both individual and population development. Increased density reduced the size and frequency of the largest male morphotypes and reproductive females, delayed female maturation, and enhanced the asymmetry of the size distribution of individuals, increasing the frequency of smaller prawns. Although mortality was not affected up to 80 ind. m ). Therefore, the ontogeny and population development after metamorphosis are density-dependent processes. In conclusion, M. amazonicum has a dynamic and densitydependent population structure. This may be due to intrinsic regulatory mechanisms of the species and/or intraspecific competition. It seems that shifts in the sex ratio and the development pattern of male morphotypes are traits which evolved as part of the life strategy to decrease intraspecific competition in crowded conditions and to maintain a large population size. KEY WORDS: Intraspecific competition · Density-dependent factors · Sex ratio · Crustacean · Mesocosm · Macrobrachium amazonicum Resale or republication not permitted without written consent of the publisherAquat Biol 9: [291][292][293][294][295][296][297][298][299][300][301] 2010 ment plans for fisheries in order to guarantee longterm sustainability. M. amazonicum also has a high potential for aquaculture (Kutty 2005, New 2005. During the current decade, an intense research effort has been directed toward developing the technology for its commercial culture (Moraes-Valenti & Valenti 2010).Despite the high biological and economic importance of Macrobrachium amazonicum, its population biology is poorly understood. Natural populations inhabiting coastal areas show great variability in size, due to heterogeneous growth caused by the existence of 4 male morphotypes (Moraes- Riodades & Valenti 2004, Santos et al. 2006, da Silva et al. 2009). Some population studies have been performed in the eastern (KCA Silva et al. 2002a,b, 2005, MCN Silva et al. 2007) and central (Odinetz-Collart 1991a,b) Amazon basin. These studies suggest that reproduction, recruitment, and the size distribution of the prawn are site-dependent. However, the data presented did not cover other important ecological aspects, such as the population density, structure of the male morphotypes, mortality rates, reproductive capacity, intraspecific competition, and density-dependent processes. Therefore, more research is needed to fully understand the population biology of the Amazon River prawn.The aim of the present study was to evaluate the effect of density on population development of Macrobrachium amazonicum reare...

Stocking density for freshwater prawn Macrobrachium rosenbergii (Decapoda, Palaemonidae) in biofloc system

“…Several researchers also found decreased survival rate with increasing stocking density in the production of freshwater prawn (El-Sherif & Mervat, 2009;Paul et al, 2016) and marine shrimp (Krummenauer et al, 2011;Fróes et al, 2013;Wasielesky et al, 2013) in different farming systems. The increase in stocking density interferes with hierarchical competition and disputes for space and food, resulting in higher cannibalism (Sampaio & Valenti, 1996;Arnold et al, 2006;Moraes-Valenti et al, 2010). According to David et al (2015), M. rosenbergii shows higher performance at lower stocking densities.…”

Composition of shrimp populations (Crustacea: Decapoda) in non-vegetated areas of two river islands in a Brazilian Amazon estuary

“…Shrimps may be shorter when they occur in high densities, because the energy allocated for growth is used for social interactions such as territory disputes and defense, which occurs more intensively when the number of individuals increases (MORAES-RIODADES et al 2010). This fact deserves attention because, according to FONTELES-FILHO (1989), the species exploited by fisheries are susceptible to large changes in size and need to be monitored.…”

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