Physiological bases for the continuous and controlled production of pirarucu fry in captivity, to sustain volumes of meat production at industrial levels

Abstract

Aquaculture is growing rapidly in Brazilian agribusiness. Despite promising prospects, it is still a young activity and faces a number of difficulties at various levels. Production is centralized in a few species, notably tilapia, due to the difficulty of having technological packages defined for native species of great potential. The pirarucu is one of them, both for the productive performance as in product quality, with insertion in several consumer markets. The main obstacle to the cultivation of pirarucu is the lack of a technological package that allows the continuous and controlled production of fingerlings to sustain an equally continuous and even growing production. Captive production has been carried out with low yield and low technological level, with production of fingerlings when the natural period of reproduction of the species occurs and not following a commercial schedule of entry and exit of significant volumes for slaughter / commercialization. Several initiatives have been carried out by SEBRAE and EMBRAPA, research is ongoing but the reality is that the commercial production of pirarucu is not developed mainly by the lack of continuous, programmable and low-cost fingerlings. The difficulty in obtaining fingerlings is due in large part to the anatomical and physiological peculiarities of the pirarucu which, being a phylogenetically basal fish, is quite different from the fish most used in fish farming, which compromises the adaptation of technologies developed for other species. These peculiarities are still little known and only in the last years have been intensified the academic studies directed to these questions. Working in the last 20 years with research, production and conservation of pirarucu, we have identified some important issues that we intend to address in this research, whose knowledge will be fundamental to establish the basis for a continuous production of fingerlings. They are: 1) Definition of the time interval in which an immature gonad reaches the mature state, under natural or induced conditions. 2) Susceptibility of pirarucu to the action of inductors agents of maturation and / or spawning. 3) Physiological changes in larvae and / or fingerlings associated with the transition between the obligatory aquatic and obligatory air breathing phases. The innovative objective of this project is establishing the physiological bases to maintain batches of animals with mature gonads all year round and to intervene in the induction of maturation of animals outside the natural reproductive period (questions 1 and 2). In addition, to understand what happens in the respiratory phase change, (moment that entails significant mortality of fingerlings) to increase the survival of the larvae / fingerlings (question 3). Question (1) will be studied from samples of oocytes taken at regular intervals for 4 months, analyzed fresh and on histological slides, associated with plasma steroids and environmental parameters. Question (2) will be studied from hormonal induction experiments, with the use of hypothalamic, pituitary and gonadal hormones. Question (3) will be studied focusing on the development of organs from samples of larvae and fingerlings, analyzed fresh and in histological preparations. The results of the research are expected to provide the basic elements for the controlled production of fingerlings, maintenance of mature animals throughout the year, increased survival of larvae and fingerlings, significant reduction in the need for breeding stock and production costs of fingerlings. Consequently, these results establish a reliable production base for the continuity of the project, which provides commercial production at industrial levels in the subsequent stages, making the business viable. The main innovation of this project is the development of a technology of production that does not yet exist, and that will be made from scientific research on the physiology of pirarucu. (AU)