Effects of warming on the reproduction of the three-spined stickleback: behavioural responses and fitness consequences

Abstract

Climate change is changing the Baltic Sea. Eutrophication and rising temperatures are threatening its unique ecosystem. The three-spined stickleback (Gasterosteus aculeatus), a common model species helps us to understand the processes happening in the Baltic Sea. The main question is: are there changes in the parental behaviour and early development of the stickleback due to the warming environment? The goal of my work was to observe the effects of elevated temperature on the reproductive success of sticklebacks: behavioural differences of parental care and the general condition of males, changes in the hatching success of the offspring and their survival probability throughout the first two weeks of their life. Sticklebacks were caught and transported to the laboratory to reproduce. The behavioural responses of 32 males divided into two groups were observed during two reproductive cycles in two different temperatures. Videos of their parental behaviour were made daily. The weight of the males and eggs, plus the fry mortality and growth was measured. In elevated temperature the males were forced to invest more energy in parental care, causing greater weight loss. Although hatching was more successful and faster at higher temperatures, the survival rate appeared to be lower. Early growth rate seems to be faster in the lower temperature. The changes in parental behaviour and trends in survival are likely to have consequences for the Baltic Sea three-spined stickleback population.