The Spring Cavefish (Forbesichthys agassizii) is one of six species in the family Amblyopsidae and only member of the genus Forbesichthys. This species is listed as state endangered in Missouri, but has been listed on the International Union for Conservation of Nature’s (IUCN) Red List as data deficient due to the lack of population studies. The spring cavefish inhabits caves, springs, spring runs, and spring seeps. It is subterranean, emerging at dusk and retreating underground an hour or two before dawn.
The plan for this particular species covers its geographic distribution, ecology, life history, current species management, and future management recommendations. For its geographic distribution, the species is located within areas of the central and southeastern United States. The spring cavefish stay underground after dawn, but then emerge into surface waters at dusk. They are a carnivorous fish and are well adapted to their environment. For life history, it is known that the species breeding behavior is rarely documented. Spawning occurs underground and in darkness between January and April. The status and distribution of cave-obligate species is incomplete or lacking entirely, which makes conservation and management decisions difficult. Kentucky and Missouri are the two main states that have their agencies managing this species in some way. There are many studies, management practices, and recommendations that are being done or could be done to help preserve and conserve this species for future generations.
Geographic distribution of species
Originally found in a deep well in Lebanon, Tennessee, the spring cavefish has a distribution within the central and south eastern United States. It inhabits select springs, spring runs/seeps, and caves from central and western Kentucky, west towards the Tennessee River, to south central Tennessee. It also is located in areas west across southern Illinois to southeastern Missouri.
The spring cavefish’s distribution has decreased from within its original streams and springs. This species is affected by the activities on the surface of the ground. Any activity that reduces water quality or quantity affects the spring cavefish. This species is vulnerable to pollution from many different sources. Some of these sources include nearby agricultural fields, pastures, septic tanks, sewage lagoons, urban runoff, mines, and livestock waste. Other issues with its distribution are some of the springs are intermittent. This means they fluctuate drastically in flow and turbidity, as a result of direct connections with surface drainage or they were enclosed as water supplies or otherwise modified by man.
Spring cavefish stay underground after dawn, but then emerge into surface waters at dusk. They are dark brown dorsally and fade to a creamy brown towards the pelvis and reach a maximum length of three and a half inches (90 mm). The head is sloped, and it has a protruding lower jaw. The fish has no pelvic fin or adipose fin. Their dorsal fin is set further back. This species is susceptible to developing retinoblastomas.
The spring cavefish is well adapted to its environment, as it has a well-developed sensory system. This system occurs in clusters on the head. Most fish detect food by sight, taste, touch, or smell, or by a combination of these senses. Sight is important in the detection of food by most species, but this is presumably excluded with the slightly blind spring cavefish. They use their underdeveloped eyes to distinguish between light and darkness. However, spring cavefish cannot readily distinguish between edible and non-edible substances by touch alone, but once in contact with the lips, the sense of taste enables the fish to distinguish among these items.
Another hurdle for this species is that food is often lacking in their habitats, so they compensate for this scarcity of food with cannibalistic behavior. Cannibalism in the spring cavefish presumably serves two purposes: it enables the adults to survive in an environment where food is the principal limiting factor, and it serves as a means of population control. The spring cavefish can be considered its own predator, because of the cannibalism behavior and the lack of natural predators within the caves. However, they are also known to eat a wide range of insects, small crustaceans, smaller fish, and some detritus.
Cave environments are known to provide a relatively stable habitat in terms of temperature fluctuations. However, the different species living in caves are reliant on food being brought to them by underground streams. This makes spring cavefish highly vulnerable to external factors as subterranean aquifers are becoming increasingly tapped for irrigation purposes, and many sites may be at risk from drying out either temporarily or permanently ).
The breeding behavior of spring cavefish is sparsely documented. Spawning occurs underground and in darkness between January and April. Spring cavefish are oviparous, meaning that they reproduce by means of eggs that develop and hatch outside the mother's body; however the eggs are carried in gill chambers of the females. Females produce roughly 100 young per female ). The average spring cavefish lives for about three years and they typically reach a length of about 1.8 to 2.6 inches ).
The status and distribution of cave-obligate species is incomplete or lacking entirely, which makes conservation and management decisions difficult. It is known that this species is listed as state endangered in Missouri. It has also been listed on the International Union for Conservation of Nature’s (IUCN) Red List as data deficient due to the lack of population studies. This species is declining, but many of the reasons are unknown. Therefore, a need exists to document the subterranean diversity, as well as the threats that impose upon the continued survival of this species. The Kentucky Department of Fish and Wildlife Resources is proposing to investigate the status, distribution, ecology, phylogenetic relationships, and threats to populations of three cave-associated fishes in the family Amblyopsidae in Kentucky (Kentucky Department of Fish and Wildlife Resources 2008). Kentucky and Missouri are the 2 main states that have their agencies managing this species in some way. Missouri has purchased Cape LaCroix Bluffs Conservation Area (CA) to provide habitat for the state endangered spring cavefish. The Cape LaCroix Bluffs CA is a 63.21 acre area that supports natural wetlands, limestone bluffs, and beech mesophytic forests unique to eastern Missouri. These are good examples of states acting to protect this species, however there are not many others currently.
Species like the spring cavefish are considered indicators of a clean, healthy aquatic system. Following these suggested recommendations will avoid or minimize impacts to cave systems and the spring cavefish. First, it is suggested minimizing the sedimentation runoff into streams, sinkholes, caves, and springs. This can be done by monitoring the erosion and sedimentation. Secondly, establish and maintain forest buffers of at least 100 foot wide along streams, around sinkhole, and cave entrances. These are also called streamside management zones or SMZ’s. Thirdly, try to dispose of all chemicals, toxins, garbage, and wash water in areas designated for such wastes. Lastly, if temporary roadways must be built, try to ensure that they are of low gradient with adequate roadbeds and storm water runoff drains/outlets. All of these suggestions are being implemented in the state of Missouri to help protect their spring cavefish.
Kentucky Department of Fish and Wildlife Resources have suggested the following sampling methods and actions to adequately monitor the spring cavefish species. The first recommendation is to conduct baseline surveys and status assessments for the species to determine the distribution of each species within the target state. It is also suggested to conduct baseline surveys for non-target cave-dwelling fauna to determine distribution and community associations and collect/preserve specimens and tissue samples of non-target cave-dwelling fauna for future genetic analyses. Secondly, they recommend conducting life history studies to obtain basic information. This includes habitat requirements, ecology, and population dynamics of the species and the area. Thirdly, it is recommended to identify potential threats to existing populations. Fourthly, it is recommended to develop management steps for each status evaluation and monitoring for this particular species. Kentucky also suggests collecting and preserving specimens with tissue samples of the species for genetic analyses to resolve any taxonomic statuses of questionable populations. This will allow one to examine the extent of gene flow among populations both within and between hydrologic drainages in the future. Both sets of recommendations are being used and experimented with in Kentucky and Missouri that currently have good spring programs.
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