Effect of stocking density on growth, maturity, fecundity, reproductive behaviour and fry production in the mouth brooding cichlid Oreochromis mossambicus (Peters)

Abstract

Growth and reproductive performance of Oreochromis mossambicus (Peters) in relation to stocking density was evaluated in indoor aquaria. Juveniles weighing 978 ± 370 mg were held in densities of 10, 20, 30 and 40 aquarium-¹ (429, 858, 1287 and 1716 juveniles/m³) in aquaria (size: 46 × 23 × 23 cm) each containing 12 L freshwater. They reared on dry Tubifex tubifex worms and dry fish pellets for over 25 weeks. Growth and specific growth rates were inversely proportional to stocking density (P=0.0555, r=0.944; P=0.0395, r=0.960 respectively). At the highest stocking density (40 juveniles aquarium-¹), magnitude of decrease in daily growth was 51.21%. Increase in stocking density resulted in reduction in size at maturity in both the sexes (male: 2 to 7.5%; female: 1.37 to 5.57%), reduction in fecundity (25 to 31%), fry production (18.58 to 28.58%) and inter-spawning interval (25 to 40%). At a living space of 597 cm3/fish (40 fish aquarium-¹), though males constructed the nest, females failed to spawn as post vitellogenic oocytes had become atretic and/or resorbed.

Key words: Oreochromis mossambicus, stocking density, size at maturity, fecundity, spawning, fry production.