Age/Size Related Changes in Gulf Killifish Salinity Tolerance

Gulf killifish Fundulus grandis are a euryhaline baitfish species that could diversify aquaculture production in the southeastern US, however, little is known regarding low salinity or freshwater inland culture for any life history stage. Therefore, this research focused on physiological tolerance and performance in hypo-osmotic conditions during early life stages. In the first experiment, embryo and larval survival and two week larval length and weight were recorded for embryos air incubated in either 0ppt or 7ppt and hatched at the same or opposite salinity. Both the embryos and larvae survived and grew better in 7ppt conditions leading to the conclusion that the hypo-osmotic tolerance may improve with age or size. In the second experiment, killifish are currently being exposed to salinities of 0, 2.5, 5, and 7.5 ppt at 2, 7, and 12 weeks post-hatch in order to understand how hypo-osmotic tolerance changes with development. It is hypothesized that killifish gain hypo-osmotic tolerance with age and size. Growth, survival, Na⁺-K⁺-ATPase enzyme activity, and whole body ion content will be measured weekly for 4 weeks within each treatment. Results will be discussed in the context of age/size-related changes in physiological performance with application to aquaculture practices.