Alabama cavefish

Speoplatyrhinus poulsoni

 

SPECIES CODE: E011 V01

 

STATUS:

First listed threatened with critical habitat September 9, 1977 (42 FR 45526 45530);  reclassified as Endangered (53 FR 37968 37970, September 28, 1988).  Recovery Plan completed on October 10, 1990.

 

SPECIES DESCRIPTION:

The Alabama cavefish is a member of the Amblyopsidae family.  The Alabama cavefish is an eyeless, pinkish-white (almost transparent) cave dweller distinguishable from other cavefish by its long, anteriorly-depressed head, flat snout, absence of branching fin rays, notably incised fin membranes, and other features. The maximum known size is 58.3 millimeters.

 

In the cave habitat there is a lack of primary producers, resulting in dependency of the primary consumers on the import of organic matter.  Although flooding is responsible for organic import in most caves, in Key Cave the gray bat colony is likely the primary source of organic matter (Poulson 1961).  The cavefish’s diet most likely includes copepods, isopods, amphipods, and small cavefish.

 

REPRODUCTION AND DEVELOPMENT:

Little information is available on the reproductive cycle of the Alabama cavefish. As their range becomes more restricted, most cavefish show a concurrent decrease in reproductive potential and population growth.  However, the longevity of adult cavefish may increase.  Cavefish do not reproduce every year, numbers of reproductive females are few and those that do spawn lay very few eggs.  Because the Alabama cavefish is endemic to only one cave, all of these life history features are probably more extreme in the Alabama cavefish than in some other ablyopsids.

 

Environmental triggers result in growth and reproductive cycles.  Surface species are affected by photoperiod and temperature changes.  Since temperatures stay relatively constant and there’s no light in caves, seasonal flooding of caves may be the trigger.   Seasonal flooding may motivate hormonal and other changes in cavefish, thus stimulating growth and reproduction (Poulson, 1961).

 

The Alabama cavefish likely incubates its eggs and protects fry in branchial chambers similar to the northern cavefish Amblyopsis spelaea.  Using data on northern cavefish reproduction and development, it is estimated that the maximum lifespan of the Alabama cavefish is 5-10 years (Poulson 1961).

 


RANGE AND POPULATION LEVEL:

This species is apparently restricted to Key Cave, Lauderdale County, Alabama (Tennessee River drainage). Extensive surveys have been conducted in other area caves with no results. It is unknown whether this species has ever had a wider range.  This species appears to be the rarest of all American cavefish and one of the rarest freshwater fish. Cooper (1985) estimated the Alabama cavefish population in Key Cave to be fewer than 100 individuals. No more than 10 cavefish have ever been observed on a single visit.

 

HABITAT:

Key Cave is a large multi-level cave with over 10,000 feet of mapped passage (Dept. of Interior 1988). Water depths may rise to about 20 feet in late spring (U.S. Fish and Wildlife Service 1985). This cave has a stable environment with low temperature and a lack of visible incident radiation. An underwater species, the Alabama cavefish is less affected by photoperiod and temperature changes within the cave than are surface species. However, seasonal flooding is necessary to trigger hormonal changes within the cavefish for growth and reproduction. Gray bat guano contributes essential nourishment for all species involved in Key Cave's food chain.

 

PAST THREATS:

Factors most likely to have influenced the decline of the Alabama cavefish include unsuccessful reproduction, groundwater degradation, alteration in drainage and hydrologic patterns, lower ground water levels, collecting and diminished organic matter inputs.

 

There is little information on the reproduction of the Alabama cavefish.  However, comparisons have been made between the northern cavefish Amblyopsis spelaea and the Alabama cavefish, and conclusions have been made as to the reproductive characteristics of the Alabama cavefish.  Cavefish show an increase in longevity and a decrease in population growth rate with increasing restriction to caves (Poulson 1961).  Only about 55 percent of the northern cavefish population is mature and only 20 percent of the females spawn in a given year (Poulson 1961).  The northern cavefish rate of population growth is likely more than twice that of the Alabama cavefish.  This probability is based upon the Alabama cavefish being the most cave adapted of the amblyopsis.

 

A sewage sludge disposal operation is within the recharge area of Key Cave. Land  immediately above and around Key Cave have numerous sinkholes and water collecting depressions and is in agricultural row-crops.  The application of pesticides to these crops may impact the fauna in Key Cave.  These practices lower water levels, degrade groundwater quality and decrease food sources for the Alabama cavefish, as well as allow for bioaccumulation of toxins within the Alabama cavefish, all leading to a likely reduction in longevity and reproductive capability.

 

Steady sources of organic matter is essential for aquatic food bases in caves.  In Key Cave, the guano, supplied by the gray bat colony, is the source of organic matter.  Consequently, the well-being of the Alabama cavefish in Key Cave is directly related to the survival of the gray bat (Tuttle 1979).

 


CURRENT THREATS:

One of the primary threats is interference with the associated bat populations which indirectly contribute to the fish's food chain. Another serious threat is groundwater contamination from agricultural operations and a sewage disposal project for the City of Florence, Alabama. Most of Key Cave's recharge area is in row crops, and a sludge disposal project is also within the recharge area. Natural factors contributing to the vulnerability of this species are its small population size and low reproductive potential. Competition with the more numerous and aggressive southern cavefish for food and space is also a problem. Cave crayfish, a known predator of this species, are also abundant in Key Cave.

 

CONSERVATION MEASURES:

 

LITERATURE CITED:

·          Cooper, John E. and R.A. Kuehne. 1974. Speoplatyrhinus poulsoni, a New Genus and Species of Subterranean Fish from Alabama. Copeia, No. 2, pp. 486-493.

·     Department of the Interior. U.S. Fish and Wildlife Service. September 28, 1988. Endangered and Threatened Wildlife and Plants: Reclassification of the Alabama Cavefish from Threatened to Endangered. Federal Register, 53:188. pp. 37968-3797O

·          Federal Register, Vol. 42, No. 175. September 9, 1977.

·          Tuttle, Merlin D. 1979. Status, causes of decline, and management of endangered Gray bats. J. Wildl. Manage. 43(1):1-17.

·          U.S. Fish and Wildlife Service. 1985. Revised Recovery Plan for the Alabama Cavefish, Speolatyrhinus poulsoni Cooper and Kuehne 1974. Prepared by John E. Cooper, North Carolina Museum of Natural History. U.S. Fish and Wildlife Service, Atlanta, Georgia. 66 pp.