From the laboratory to the wild: Comprehending the reproductive dynamics of the Peloponnese Killifish Valencia robertae for its effective conservation

In depth knowledge of the reproductive ecology and ethology of a threatened fish species is needed for the design and implementation of successful conservation interventions, such as ex situ breeding and in situ translocation. In this ex situ study, we describe the critical parameters for successful reproduction of the threatened, endemic Peloponnese killifish Valencia robertae (Greece) and provide a full reproductive ethogram of the species that can guide successful captive propagation, appropriate habitat restoration and informed selection of suitable release habitats, and optimal release period. The Peloponnese killifish reproductive period is prolonged, lasting from early spring to early autumn, with spawning occurring mostly at night and mostly on gravel, with one egg per spawning event. Males exhibit breeding colouration and there are multiple behavioural interactions of males with females, as well as between males. In the Peloponnese killifish there is aggression in male-male interactions and no evidence of territoriality or parental care, through nest building or egg-guarding. These indicate male-male competition (mate monopolisation) with high levels of kleptogamy, mainly through sneaking (“parasitic spawning”), i.e., when other males try to fertilise the egg at the same time and, secondarily, through cannibalism, i.e., post-mating egg consumption by other males of different sizes. Although females are not selective about the size of males, there is a selectivity determined by the interaction of males, with the larger males driving off the smaller ones, which often act as satellites trying to mate secretly from the spawning male. We compare the reproductive behaviour of the killifish with other related genera with similar characteristics such as sexual dimorphism, male-female approach, and female substrate choice for egg deposition. Finally, we discuss future challenges to the killifish’s reproduction within the frame of climate change and alien species’ invasion, as well as the use of the ethogram in future conservation initiatives.