Energy utilization during ovarian development of the cichlid fish Oreochromis mossambicus (Peters) inhabiting a perennial lentic water body in Bangalore, India.

Abstract

Mozambique tilapia Oreochromis mossambicus (Peters) is an invasive fish and a continuous breeder in inland waters of India. Present investigation highlights the distinct developmental stages of developing ovary and associated changes in the energy content. This investigation helps to understand the allocation of energy for development of eggs, prespawn and also oral brooding by the female. Although it is a continuous breeder, based on size of the ovary, number of eggs, their size and energy content, immature, early maturing, developing, prespawning and spawning stages are clearly noticed. Egg diameter during development of ovary varied between 0.31 mm (immature) and 2.21 mm (spawning). Energy content of ovary from immature to spawning stage ranged from 20.7515 kJ g-1 dry ovary to 31.1560 kJ g-1 dry ovary. Nearly 28.73% of energy content of ovary is expended for spawning. Similarly, yolk-sac fry utilized nearly 25.85% of energy of the fertilized egg for its development. Energy content of ovary of mouth-brooding female averaged 22.9528 kJ g-1 dry ovary, which is comparable to energy content of early maturing stage of ovary (24.5558 kJ g-1 dry ovary). A strong correlation between body weight and energy content of the developing ovary (P < 0.01), and between ovary weight and energy content of ovary (P < 0.01), was evident. During mouth-brooding, the fish continues to allocate energy to its developing ovary. Energy investment by the fish is the result of simultaneous processes associated with gonadal and somatic energy. As body size growth and gonadal development are interconnected, information on energy utilization by an iteroparous mouth-brooding fish could provide the pattern of energy allocation during ovarian developmental phase. Further details of energy utilization, as explained in this paper, could be used as one of the factors to predict the efficiency of fish production.