Alabama Cavefish

The Alabama cavefish is one of the rarest cavefish species in North America. While the specific habitat requirements of the fish are unknown, it is known that the Alabama cavefish is a cave obligate, restricted to Key Cave in Lauderdale County, Alabama. Key Cave is the critical habitat of the Alabama cavefish. Cave habitats tend to be stable, with drastic changes mainly being associated with the inflow of water. Annual rainfall and flooding in the cave produce changes in water level, temperature, and food availability for the fish. Researchers speculate that the flooding may trigger a hormonal change in the cavefish for growth and reproduction. Since the discovery of the cavefish, only nine specimens have been collected (all before 1983). Because very few individuals have been collected and observed, and the population is confined to Key Cave, the Alabama cavefish is believed to be the rarest of the American cavefish and the rarest of all freshwater fish. Since the underground water system in the area is so widespread, researchers had hoped that the cavefish had dispersed to other sites. However, studies of the 120 other caves in the area, conducted since 1977, have failed to locate any other Alabama cavefish populations. …

The diet of the Alabama cavefish, which consists of copepods, isopods, amphipods, and smaller cavefish, is supported by the nutrient-filled bat guano. It also can survive on other small organisms such as mites, spiders, millipedes, beetles, and other insects.

There is little information available on both the life history and reproductive cycle of the Alabama cavefish. It is hypothesized that, because of the jugular position of the vent and the size of the branchial chamber, the Alabama cavefish practices branchial incubation, or mouth-brooding. The Alabama cavefish, like most fish, utilizes seasonal cues to trigger hormonal changes that lead to its growth and reproduction. While most fish rely on a large change in water temperature or photoperiod, the Alabama cavefish mainly relies on the flooding of the cave in the winter and spring. This flooding results in an increased inflow of water into the cave and a small temperature change, signaling to the cavefish to begin reproduction. Even with these cues, reproduction does not occur every year for the Alabama cavefish. In years when reproduction does occur, only a few eggs are produced per female. Assumptions about the life history of the Alabama cavefish are largely based on information from the Northern cavefish, which sees only about 20% of the females spawn in a given year. It is hypothesized that the population growth for the Alabama cavefish is less than half of that of the Northern cavefish. Furthermore, the maximum longevity of the Alabama cavefish is estimated to be around 5–10 years; however, this estimate could be off by a factor of 3 or 4.