Behavior activities of Macrobrachium rosenbergii (De Man, 1879) in monosex and mixed populations, in the laboratory

ABSTRACT

Monosex all-male populations for the commercial breeding of the freshwater prawn Macrobrachium rosenbergii have been used to lessen the specimens´ aggressiveness and size heterogeneousness. The species´s behavioral variation in mixed, monosex all-male and monosex all-female populations, during the 24-h light-dark period, is assessed. The focal method, with instantaneous report, was employed, featuring a 15-m window for each aquarium, distributed in 12 time shifts throughout the light-dark phase. Eight aquariums contained four prawns each (10 prawns/m2), totaling 96 prawns, monitored for 160 h, during 30 days. Exploring, burrowing, covering with earth, feeding, cleaning, inactivity, crawling, swimming, change and agonistic activity were analyzed. The animals showed a high rate of autogrooming and exploitation during the light and dark phases in three culture modalities, whereas burrowing occurred more frequently during the light period. Agonism was more frequent during the dark phase in all populations, although rates of monosex all-female culture were higher during the light and dark phases when compared to mixed and monosex all-male cultures. The authors recommend shelters and substrates for protection and improvement of the animals´ welfare, especially during the dark shift. Since agonism was more frequent for monosex all-female culture when compared to that in mixed or monosex all-male culture, such population composition is not recommended.