Data for Body size matters for mate choice of the paradise fish

In nature, animals of varying body sizes exhibit differences in genetics, growth rates, and resource-holding capacities. Numerous species display size-assortative mating patterns, which, according to matching theory, stem from mutual preferences for larger partners among both sexes. Although mate choice has been extensively studied in various animals (e.g., mammals and reptiles), some knowledge gaps remain regarding the role of morphological traits such as body size and the underlying behavioral mechanisms in fish. Here, our study investigates mate choice and same-sex behavior in the paradise fish (Macropodus opercularis). we have employed a male-male behavioural preference testing as a control measure to verify whether the outcome of this binary choice is associated with social preference Our findings indicate that female paradise fish consistently prefer larger individuals in both same-sex and opposite-sex encounters, regardless of their own body size. In contrast, male paradise fish exhibit a preference for smaller individuals in both types of encounters. Furthermore, the general activity levels of paradise fish, including swimming speed and percentage time spent on moving, do not appear to influence mate choice outcomes. These results provide evidence that larger body size may confer an advantage in mate choice for female paradise fish.