Comparative research on growth and development of populations of african sharptooth catfish, reproduced in different seasons
The aim of the research was a comparative assessment of growth and development dynamics of sharptooth catfish generations, obtained in different seasons. The object of the study was African sharptooth catfish populations bred in industrial aquaculture of pool type. The size and weight parameters and their variability were studied at different stages of ontogenesis of commercial fish growing, stating from the larval stage to the stage of commercial fish. The tendency of faster growth of spring generation, compared with the autumnal one, at all stages of ontogeny was established in the course of the studies. At the age of 23 weeks the catfish of spring generation increased the necessary commercial mass in accordance with the technology requirement (926.6 ± 33.4 g), and the fish breeding cycle was completed on schedule. At the age of 23 weeks, the biomass of catfish of autumn generation was 625 ± 37.8 g, which is 300400 g lower than that shown by spring generation. The population of catfish of autumn generation reached the parametres of spring generation three weeks later, which reduces the profitability of production. Significant intrapopulation competition for food resources was revealed at the larval stage. During this period, 30% of the individuals demonstrated a high growth rate, whereas 50% showed an average growth rate. The remaining 20% of the population lagged to a different extent in growth rate from the average rate. The decrease in the level of plastic metabolism of catfish population reproduced in the autumn period is preconditioned by a short light period, as all other abiotic environmental factors under artificial breeding conditions have been stabilized. Classification by height and weight characteristics and usage of the adaptogen “Irkutin" in feed and in fish habitat allowed to weaken the intrapopulation stress at all stages of breeding.