Water level and local rainfall predicting the reproductive synchronism of Amazonian floodplain fishes

Abstract

In seasonal environments, organisms evolved to respond to environmental cues that indicate the better moment to complete phenological cycles such as reproduction. In strongly seasonally regulated ecosystems, such as tropical floodplains, the annual cycle of rainfall and river flooding have been suggested as the synchronizing triggers of fish reproduction, responsible to signalize the end of vitellogenesis and gonadal maturation. However, the role of such variables as synchronizing triggers is not completely understood in tropical environments, partially because most studies are from subtropical latitudes or very close to. Studies on triggers of fish reproduction in ecosystems of low latitudes are very scarce. Also, most studies were based on short time series, most with of one or two years. This gap in knowledge limits the application of correct reservoir management to reduce the impact on fish reproduction downstream as well as evaluate the impact of hydroclimatic flow changes in not regulated rivers and abnormal hydroclimatic events which occurs repeatedly. This project is focused on the role of rainfall and water level change during river flooding in floodplain Amazon fishes. We hypothesized that the water level change is the best predictor for reproductive synchronism In this portion of the tropical region and that there is a window in the water level change (when is occurring the larger increase in water) that indicates the environmental reliability to conclude reproduction. To test these hypotheses two large datasets from independent studies with similar methodologies will be used. One from Madeira river, with 11 sampling sites with one year of sampling and one site with three years of sampling, and from a floodplain lake at the confluence of Negro and Solimões rivers with 20 years of monitoring. Both datasets wit monthly information for fish reproduction. This data will be correlated with monthly and annual data for river water level and local precipitation, such data will be taken from different repositories. Such data will be analyzed to understand the role of these variables as cues for environmental reliability for fish reproduction independent of the sampled site and if of the interannual hydrological variability promoted by hydroclimatic events which modify the flooding. The results from this study will allow the role of climatic variability and dam constructions among other rivers' flow control anthropogenic activities on Amazonian fish reproduction as well as give directions to better management.