Growth and reproduction of the annual Austrolebias wolterstorffi fish (Cyprinodontiformes: Rivulidae) at different salinities
Temperature is especially important for the dynamics of biotic factors in poikilothermic animals. Life cycle of annual fish is affected by temperature. These fish inhabit fragile environments, susceptible to antropic actions, and as such some species are threatened with extinction. They are also important as biological models, but information on their bio-ecology is scarce. The aim of this work was to investigate the influence of temperature on growth and reproduction of Astrolebias wolterstorffi. Soon after hatching fish were exposed to 16, 20, 24 and 28°C, and their growth was followed for 67 days. Until 18 d.a.h (days after hatching) the growth is hampered at 16°C and do not show difference at 20, 24 and 28°C. Thereafter, the intermediate temperatures favor growth of juveniles, while extremes temperatures are prejudicial. After sexual differentiation, growth was improved for fish reared at 16°C, and reduced at 28°C. There is evidence suggestin that optimal growth temperature decrease with fish age. Juveniles grow faster at high temperature (23,8°C), whereas intermediate ones optimize the growth adults females (20,7°C) and males (20,1°C). Growth of males is higher at slightly lower temperatures than that optimal for growth of females. Maturation onset is defined by length rather than age, and at high temperatures maturation is observed earlier. Also, males mature earlier than females. For the reproduction study, 12 couples (150 d.a.h.) were distributed in 12 tanks at the same temperatures of the growth experiment. Reproduction output was favored when A. wolterstorffi were kept at 24°C. Furthermore, fish kept at 28°C presented the worst reproductive parameters, including condition factor, fertility, fecundity, gonadosomatic index, and also histological evidence. The results of the present studies suggest that A. wolterstorffi should be reared at 24°C during the whole cycle in captivity.