W. L. Minckley & Craddock, 1962
Phenacobius crassilabrum, the fatlips minnow, is a species of suckermouth minnow that was first described in the upper Tennessee River system.
No fewer than 20 specimens were used for description, and the epithet crassilabrum (from the Latin crassus meaning thick or fat and labrum, or lip) was assigned to the species, separating it from Phenacobius catostomus, with which it had previously been identified. Because there is inadequate scientific information concerning P. crassilabrum as a specific species, this monitoring plan will consider sister species within the genus Phenacobius as precedent cases. Basic protocol for a monitoring effort include consistent annual sampling at key times during the breeding season, proper public awareness of watershed conservation, and scientific support in the form of research to back the efforts of wildlife managers.
Geographic Distribution of Species
P. crassilabrum is a species of suckermouth minnow that was first described in the upper Tennessee River system. The first holotype specimem collected in 1947 was 8mm-long adult female from the Elk River. Its distribution is restricted to North America, where it occurs in the upper Tennessee River drainage in western Virginia, western North Carolina, eastern Tennessee and northeastern Georgia. Its habitat is gravel and riffles in small to medium creeks. The fatlips minnow is believed to have arisen from a P. catostomus -like stock population that re-invaded the upper Tennessee River via reciprocal stream piracy. A genetic sister relationship between P. crassilabrum and P. uranops has been consistently resolved. The ranges of P. crassilabrum and P. uranops complement one another in the Tennessee river system, with the former opting for higher elevations. In Virginia, P. crassilabrum occupies the lower free-flowing portion of the South Fork of Holston River and Laurel Creek.
Changes in the populations of these fish are due in part to natural fluctuations in distribution, but a good deal of the observed declines are the result of human encroachment and anthropogenic factors affecting the environment at the local ecosystem scale. These fish are becoming unable to escape ecological threats by expanding their range, as they have simply run out of acceptable habitat area, and therefore out of acclimating options. There are documented instances of nonindigenous (out-of-range) occurrences of Phenacobius species; these are believed to be a result of fishermen releasing their unused baitfish into local bodies of water. The current population of P. crassilabrum is presumed to be about 10,000 individuals.
Insufficient data exists concerning the frequency of occurrence of P. crassilabrum, however data does exist for the frequency of occurrence of Phenacobius uranops. This figure is 81 - 300. P. crassilabrum is known to favor gravel riffles in in the warm clear waters of small to medium sized streams and rivers. Species of the genus Phenacobius remain near the bottom of streams, rooting in the ground for their prey of detritus and aquatic insects such as mayfly and caddisfly larvae. The palate of Phenacobius teretulus is also known to include small tubeworms and water snails. P. uranops has been found to feed in groups of ten to twenty individual fish, in daylight and into the winter months. By contrast, P. teretulus seems to feed just before, during, and just after nightfall. This feeding behavior is presumed to allow P. teretulus to remain incognito during the daylight to avert predation by larger fish or piscivorous birds. P. crassilabrum's habitat preferences of warm clear water suggest that it might exhibit a similar feeding strategy to decrease its visibility during the daytime. Anthropogenic factors such as urbanization, runoff from construction and agriculture, loss of watersheds, and pollution place restrictions on the habitat available to these fishes, resulting in decline.
Breeding activity has not been observed in P. crassilabrum; fortunately, the pattern within the genus is somewhat consistent. Spawning for Phenacobius species occurs in the spring and summer (April to August). Reproductive maturity in these fish can vary from one (P. uranops) to two (P. mirabilis) years of age. As a mark of the breeding season, males of the species P. mirabilis develop tubercles from May to July in Tennessee, so it would be interesting to find out whether P. crassilabrum exhibits similar breeding behavior. The average clutch size data available within the genus is for P. mirabilis, with females depositing one to five eggs at a time. Interestingly, despite this modest clutch size, females actually hold between 200 and 500 eggs. Spawning events take place in the preferred gravelly riffles, allowing the released eggs to seek out nooks and crannies within the substrate. The maximum life span described in the genus is three years.
Human impact on the species could be significantly eased with the promotion of watershed protection in areas supporting P. crassilabrum subpopulations. Other means of conservation include enforcement of environmental laws regarding clean water and responsible construction and agricultural techniques to reduce erosion and the resulting siltation of P. crassilabrum's home streams. P. crassilabrum, while existing in small numbers in comparison to other species sharing its ecosystem, is considered to be of the least concern in terms of conservation status (IUCN) and its population is considered stable. The main sources of human-induced decline are changes to water courses, such as dam construction. This slows the flow of water, increasing turbidity. An additional factor to consider is the movement of non-native fish into the range of P. crassilabrum, threatening habitat and resource availability.
The most obvious and important step in devising a monitoring plan for this species is to conduct thorough scientific observations of the species in the wild. Insufficient data makes it nearly impossible to propose an effective monitoring plan, as this leaves little room to tailor the plan to a species’ unique and specific needs, like habitat requirements and behavioral patterns. One method of attempting to better understand the distribution and life history of this species would be to seine in predetermined locations within the native range, to obtain a more accurate representation of density and distribution within the species’ described territory. Samples taken at a consistent interval during key times in the breeding season from year to year would be useful in determining population growth, decline, or other fluctuations. It should go without saying that environmental conditions in the watersheds and surrounding land that harbor this species should be carefully managed to avoid disrupting the species, as its native range has already been significantly reduced by the influences of man. Studies should also be conducted to assess the direct impact of invasive fish species on the success of P. crassilabrum in its native range, the results of which would allow wildlife managers to justify reduction or removal of these nonnative species. Any method of exotic removal would be a precarious undertaking considering P. crassilabrum also inhabiting the area of interest, but could be accomplished presuming adequate studies were published to create a more complete representation of P. crassilabrum's habits and needs.
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