Aquatic Animals and Their Habitats

Chapter 23: Aquatic Animals and their Habitats 537 Chapter 23: What are the history, status, and likely future of aquatic habitats and Aquatic Animals species in the South? and their Habitats Jim Herrig and Peggy Shute Southern Region, USDA Forest Service, and Tennessee Valley Authority ■ Gaps in our scientific knowledge insects (mayflies, stoneflies, caddisflies, Key Findings about southern aquatic species are and dragonflies and damselflies). They monumental. Research of many made many of the same observations ■ Sediments, introduced into aquatic types is urgently needed. about the importance of the Southeast systems above natural, background ■ In the South, much of the for these insects. Of the more than levels, have adverse impacts on animal habitat for rare aquatic species is 11,000 species known from North species in all seven taxonomic groups not controlled by Federal or State America north of Mexico, nearly considered in this Assessment. governments. The burden for half are in the Southeast (Morse and others 1997). Like crayfish, mussels, ■ The aquatic communities of protecting these habitats falls mainly on private landowners. and snails, the aquatic stages of these Southeastern United States are insects are found in all types of aquatic globally significant. Many are very habitats. Although some are predators narrow endemics and subject to Introduction (dragonflies), these aquatic insects are extinction from relatively minor also important components of aquatic habitat losses. communities because they shred leaves ■ Master and others (1998) ranked Habitat barriers created by dams the United States as first in terms of and other organic matter and serve as on major rivers have produced diversity of known aquatic species important food sources for many fish. isolated populations of many southern worldwide. Native taxa include cray- They are also useful indicators of water aquatic animals. Some species occupy fish, freshwater mussels, freshwater quality (Harris and others 1991). so little of their former range that snails, stoneflies, mayflies, caddisflies, Of the World’s freshwater mussels, they are vulnerable to extinction as and stygobites (cave-dwelling crusta- 91 percent occur in this region. In A described for the narrowly endemic cean invertebrates). The Southeastern addition, more than half of the known species. Some others, mainly larger United States accounts for much of fingernail clams and snails are found river animals, have become extinct the globally significant diversity. For in the Southeastern United States Q because of habitat alterations. example, many of the approximately (Neves and others 1997). Mollusks Current programs have improved 340 species of the freshwater crusta- are found in a wide variety of habitats, UATI conditions in some of the tailwaters. ceans (crayfish, shrimps, scuds, etc.) but more occur in riverine systems ■ In some areas aquatic habitats known from North America north than other habitat types (Neves and have improved, and reintroduction of Mexico occur here (Hobbs 1981, others 1997). Mussels have been or augmentation supported by captive Schuster 1997), and new species are described as important indicators of breeding programs may improve the still being discovered and described water quality because they are filter recovery potential for some species. from the region (see Thoma 2000, feeders and highly susceptible to poor C ■ Some ground-water systems are for example). Crustaceans occur in all water quality. They are also major food being dewatered, threatening unique habitat types. They are cave dwellers sources for many fish, reptiles, and aquatic communities. Careful aquifer and surface-water dwellers, and some some terrestrial animals. Mussels have management will be necessary for build burrows in damp areas. Crusta- also been important commercially, as these aquatic communities. ceans are important members of the the raw materials for the pearl button food web as they process leaves and industry of the early 20th century and ■ Certain aquatic species, for other organic matter, and they provide “blanks” for the Asian cultured pearl example, the flatwoods salamander, food for fish and other animals, industry (Jenkinson and Todd 1997). require ephemeral ponds to complete including humans (Pfieger 1996). their life cycles. Restoration and Of the approximately 850 species of protection of ephemeral ponds Insects also contribute tremendously freshwater mollusks in North America, is essential to the conservation of to the diversity of aquatic animals in 516 are snails, and more than half of these animals. the Southeast. Morse and others (1997) these are found in the Southeastern discussed four important groups of United States (Neves and others 1997). 538 Southern Forest Resource Assessment Little is known of the taxonomy of this About one-fourth of the approx- swamps, bogs, and some wetland areas) group of mollusks, with many species imately 200 aquatic reptiles known and flowing water (rivers and streams). still being described. Little is known from North America north of Mexico These two divisions are, obviously, gen- of the ecology and life history of most are found in the Southeastern United eralizations of the immense diversity of snails, and they are difficult to identify. States (Buhlmann and Gibbons 1997). aquatic habitats that exist in the South, Distributions (especially historical The Southeast is especially known for and grade from one to another (see, for versus current) are poorly known. its diversity of aquatic turtles, many of example, discussions by Vannote and Therefore, it is difficult to accurately which are commercially important as others 1980, Mishall and others 1983). assign conservation status (Neves food or for the pet trade (Buhlmann Aquatic systems are not only connected and others 1997). The list included and Gibbons 1997). but are also completely intergraded here is probably only a representative Unfortunately, the globally important between what is typically referred sample of snails at risk in the Southern southeastern aquatic fauna described to as an aquifer to a lake or a river. United States. earlier are under extreme threats By defining these broad categories Of the over 800 freshwater fish because of past and present human and attempting to determine a primary known from North America north of activities in the water and on land habitat and in some cases a secondary Mexico, the Southeastern United States (Benz and Collins 1997, Stein and habitat for each species considered is home to about half, many of which others 2000). In fact, Ricciardi and in this Assessment, we were able to are found nowhere else in the World Rasmussen (1999) projected extinction more thoroughly discuss the biological (Sheldon 1988; Warren and others rates for North American freshwater significance of these habitats and 1997, 2000). In comparison with the animals at about five times that of the factors threatening the species invertebrates briefly mentioned above, North American terrestrial animals, found there. much more documentation exists and within the range of that estimated Because they are generally threatened about North American freshwater for tropical rainforests. Richter and by the same factors, permanently fish. Even so, new species are still others (1997) summarized a survey flooded ponds were not distinguished being discovered and described of experts on freshwater fauna in from ephemeral ponds in this in the scientific literature (see Skelton the United States, which included discussion. Rivers were defined 2001). Obviously, fish are important the same animal groups we include as flowing waters exclusive of to humans for food. Their existence in this Assessment (except reptiles, headwater tributaries. Headwater in the aquatic assemblage is important which we include and they did not). tributaries include both perennial to freshwater mussels, as specific fish They showed variation in stressors and intermittent streams. hosts are needed for the mussel to among the groups of aquatic animals complete its larval stage and disperse considered; differences between the Aquatic Species (Neves and others 1997, and references top listed stressors in the Eastern and Several agencies and conservation therein). In addition, madtom catfish, Western United States; and differences organizations track the distribution many of which are found only in the between historic threats and those and conservation status of species in the Southeastern United States, could also currently threatening these animals. United States. The U.S. Fish and be indicators of water quality. They In the East, sediment from agricultural Wildlife Service (USFWS) maintains rely on “tasting” the water to know nonpoint pollution was listed as the a list of species that have officially AQUATIC what’s around them. Their intolerance major stressor affecting the ability been proposed or listed threatened of even minute amounts of pollutants of aquatic animals to recover from or endangered under the Endangered is a suggested explanation of why declines. Wilcove and Bean (1994) Species Act of 1976, as amended. They these small catfish are not found in made several recommendations for also track species, called candidates, areas where they were historically aquatic animal conservation. Master for which insufficient information exists known (Etnier and Jenkins 1980). and others (1998) and Wilcove and to warrant formal listing. Before species In comparison with the aquatic Bean (1994) provided several

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