Where to place your eggs: The effects of conspecific eggs and water depth on oviposition decisions in bluefin killifish

In species with external development, egg placement is expected to impact the fitness of females and males via offspring survival. Both environmental and social cues influence the placement of eggs. In nest building fishes with male parental care, females frequently prefer to lay eggs in areas where eggs are already present. Most studies on female oviposition strategies have focused on species where males build nests and care for the eggs. However, few studies have examined oviposition strategies in species lacking parental care. This study tested whether female bluefin killifish Lucania goodei prefer to lay eggs in spawning substrates that already contain eggs from other females. The unique aspect of this study is that L. goodei is a non-nest building species with no parental care and high levels of iteroparity. Females preferred to lay eggs in areas where eggs were already present but these effects decreased with increasing clutch size. We suggest that females prefer to lay small bouts of eggs in areas already containing eggs of other females, but that in nature, they distribute these eggs across multiple males and locations. By doing so, females may increase the probability of offspring survival via either the dilution effect (reduced individual probability of predation due to increased group size) or the selection of 'good locations' for offspring development.