Friday, 13 July 2012

Alabama Cave Fish



The Alabama cavefish, Speoplatyrhinus poulsoni, is a critically endangered type of cavefish which lives in underground pools in Key Cave, located in northwestern Alabama, United States in the Key Cave National Wildlife Refuge. This is the only known location of the fish, and was discovered underneath a colony of Gray Bats in 1974 by Cooper and Kuehne.
Only nine specimens of the cavefish have been observed and scientists estimate that fewer than 100 are left on the planet. It is believed that this fish is the rarest of American cavefish and one of the rarest of all freshwater fish. It is the most specialized cavefish known, and exists in a fragile ecosystem based on nutrient rich guano of the gray bat. Researchers have failed to find the fish living in any other location.
The Alabama cavefish is a typical troglobite.


Habitat and distribution

 

The Alabama cavefish is one of the rarest troglobitic fish species in North America. When this species was discovered in 1970, it was so unusual that a new genus was created for its description (Cooper and Kuehne, 1974). The species is restricted to Key Cave in Lauderdale County, Alabama with only nine specimens having been collected. Because the underground water system in the area is so widespread, it was hoped that the cavefish had dispersed to other sites. However, studies of 120 other caves in the area, conducted since 1977, have failed to locate any other cavefish populations. The number of individuals in the Key Cave population is estimated to be less than 100. In 1988 the Alabama cavefish was reclassified from "threatened" to "endangered". There are two unconfirmed reports that these fish have also been seen in nearby Collier Cave. Both caves are protected and inaccessible to the public.
Its longevity ranges from 5 to 10 years, but it reproduces slower than all other cave dwellers. Because its known range is limited to a single cave, the Alabama cavefish has an uncertain future, being threatened by changes in groundwater quality and level, changes in aquifer characteristics, diminished organic input. It also may compete with the syntopic southern cavefish, Typhlichthys subterraneus.

Physiology

 

The average Alabama cavefish is about 3 inches (7.6 cm) long and has no eyes or discernible pigmentation, appearing semi-transparent with a slight pink hue. Its large head makes up more than one-third of its length. It is the only species in its genus, and can be distinguished from other cavefish with its very elongated, flattened head with a laterally constricted snout and a terminal mouth. The cavefish lacks pelvic fins, and its fin rays are unbranched with the fin membranes deeply incised between the rays. It has an elaborate system of sensory papillae, arranged in ridges on the head and sides, that is an adaptation to the dark environment.

Diet

 

Its diet of copepods, isopods, amphipods, and other fish is supported by the nutrient-filled bat guano. It can also survive off of other small organisms such as mites, spiders, beetles, millipedes, and other insects.

Reproduction

 

It is believed that they may reproduce like Northern Cavefish, by carrying its young inside its mouth to be incubated. Since its reproductive cycle appears to be based on various environmental triggers, it does not reproduce every year. Its reproduction could be caused by seasonal flooding in the cave, which causes hormonal changes in the species.

Behavior

 

Although little is known about the Alabama cave-fish, it probably incubates eggs within a chamber underneath the gills. There's some evidence to suggest that it matures late and reproduces until the end of its life. It feeds on small aquatic invertebrates and smaller cavefish and has a life span of five to 10 years.

  

Threats


The quality of the groundwater directly affects the fragile ecology of the cave. When water is degraded by fertilizers, pesticides, or sewage run-off, the food supply for the cavefish diminishes, which Alabama Cavefish, illustration. Cimmaron Trading Co. in turn reduces its longevity and reproductive capabilities. The U. S. Fish and Wildlife Service (FWS) is working with the Environmental Protection Agency to control sources of groundwater pollution in the area and to advise about the impact of any construction on the runoff patterns. The population level of the gray bat within the cave also affects the Alabama cavefish. In recent years, bat numbers have declined, reducing guano, and lessening habitat viability. Food availability is the primary limiting factor on population, which is directly related to the viability of the bat inhabitants of the cave. In Key Cave the bat population diminished by half over a 10-year period.


Conservations And Recovery

 

FWS personnel are currently exploring management techniques for stabilizing the population of the Endangered gray bat (Myotis grisescens; see separate entry). As the Gray Bat Recovery Plan is implemented, it will also benefit the cavefish. Further research is needed to plan the recovery of the Alabama cavefish. The little that is currently known, however, is not encouraging. Captive breeding of cave-dwelling species has invariably failed in the past, and it is not considered a viable recovery strategy for the Alabama cavefish. Transplanting the fish to other sites is not considered feasible, and biologists' options are limited.

The Recovery Plan calls for determining the recharge requirements of Key Cave; monitoring the Key Cave aquifer and water quality; determining the impact of the loss of bats in Shelta Cave; prohibiting human disturbance of the caves; and controling agricultural practices in the recharge area.