Abstract

MADRID, Fernando. Relation between prey (shrimp, Macrobrachium amazonicum) and size of predator (peacock bass, Cichla orinocensis). Bioagro [online]. 2009, vol.21, n.1, pp.69-74. ISSN 1316-3361.

The relation predator-prey between the river shrimp Macrobrachium amazonicum (Crustacea:Decapoda:Palaemonidae) and the peacock bass Cichla orinocensis ( Pisces:Perciformes: Cichlidae) were evaluated at laboratory level, with the aim of using this fish as a biological controller. The river shrimp is considered a plague by the “cachama” fish farmers of the central-western and high plains regions of Venezuela, due to its high rate of reproduction in cultured ponds. The high number of river shrimps affects dissolved oxygen concentration in the water, partially consumes fish feed, and  hampers the mobilization of networks in ponds. The equation that correlates the peacock bass mouth opening (MO, mm) with its weight (Wp, g) and standard length (SL, mm) was expressed as MO = -48.2060 + 2.0544 SL + 2.0505 Wp. Also, the following equations that express some morphometric relations were established:  Wp = 1.131 · 10 ^-5 · SL^3.217, and  Ws = 7.8311 x 10^-3 TL ^2.9737, where TL is the total length for shrimp and Ws its weight. A positive correlation between sizes of predator and prey was observed, but with no preferences for any particular size. In function of the oral cavity capacity, the peacock bass can consume river shrimp up to 80 % of its own size.

Keywords : Prey-predator relations; oral cavity capacity; standard length.