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Ozark Cavefish
Amblyopsis rosae
Family: Amblyopsidae
Description: The Ozark cavefish is a small colorless fish about 2.2 inches (5.5 centimeters) long. It has a flattened head, a slightly protruding lower jaw, and a rounded tail fin. Adapted to life in complete darkness, the Ozark cavefish has rudimentary eyes and no optic nerve, but possesses specialized sensory organs on the sides of its head, body, and tail.
| Status: |
Federally Listed Threatened (November 1, 1984) Global Rank: G2G3 State Rank: S1 |
Distribution: The Ozark cavefish occurs in the Springfield Plateau of the Ozark Mountains in southwestern Missouri, northwestern Arkansas, and northeastern Oklahoma. Currently, 15 caves in this area have verified cavefish populations. In Arkansas, the cavefish is known from a number of cave sites in Benton County. It occurs nowhere else in Arkansas. Nearly two-thirds of the range-wide population is thought to inhabit the Arkansas Natural Heritage Commission's Cave Springs Cave Natural Area in Benton County.
Habitat: The Ozark cavefish is one of many karst-dependent species in northern Arkansas. Karst habitats form in regions with limestone bedrock. Over thousands of years, water seeping into the ground dissolves limestone and forms sinkholes, underground streams, and caves. Ozark cavefish are found in cave streams and springs with a gravel bottom, or occasionally in pools over silt and sand bottoms. The water source for these caves is almost always an upwelling from the groundwater table. The land area that replenishes the cave's system with water through draining, percolation, and seepage is known as the "recharge zone." Due to the absence of light in cave settings, nutrient input into these systems are typically derived from bat guano and leaf litter. Optimum Ozark cavefish habitat consists of caves occupied by large colonies of gray bats (Myotis grisescens). The gray bat is listed as a federally endangered species.
Diet: The Ozark cavefish's diet consists of plankton, crustaceans, salamander larvae, and occasionally bat guano.
Reproduction: The Ozark cavefish matures very slowly, reaching adulthood at 4 or more years of age, and has a life expectancy of 7 to 10 years. Only about 20% of the female population breeds each year, with each female producing 20 to 25 eggs per spawn. Breeding may take place in the spring, after which the eggs and then young are probably held in the gill chamber for 4 to 5 months until June or July. With such a low reproductive capacity, most populations consist of relatively small numbers of individuals.
Cause of Decline: Groundwater contamination and human disturbance are thought to be factors responsible for the decline of the Ozark cavefish. The cavefish lives its entire life in cave streams and is dependent upon high water quality. In karst regions, water drains and seeps through sinkholes and losing streams into caves or springs, ultimately replenishing groundwater supplies. The presence of interconnected channels allows groundwater to move long distances quickly. Unfortunately, that also means that pesticides, eroded soil, and animal waste miles away can enter into these systems relatively fast. As the Ozarks have developed, pollutants have entered these systems resulting in declining water quality. Flooding by reservoirs and lowering water tables have also been implicated in the demise of some cavefish populations.
Human intrusion into caves containing Ozark cavefish can damage populations directly and indirectly. In the past, collecting of cavefish has damaged some populations. Bat colonies may also abandon caves frequently visited by humans. The loss of bats from a cave removes a vital source of nutrients, in the form on guano, that cavefish and other cave inhabitants depend on.
Conservation Status: Groundwater contamination and habitat degradation still represent threats to Ozark cavefish today. Arkansas populations of this species are located in one of the fastest developing regions in the United States. With large-scale development comes the increased risk of groundwater contamination from street/lawn runoff, chemical spills, and municipal sewage treatment plants. The close proximity of some developments also increases the risk of human disturbance. Protection of caves, and cave recharge zones, is critical if the Ozark cavefish is to survive. This includes monitoring the quality of water that flows into caves and erecting fences or gates that limit access by humans, but that do not interfere with bat populations.
