THREATS TO THE SPECIES. The limited range and historical loss of suitable habitat are the primary factors affecting the Yadkin River goldenrod. The construction of the Narrows Dam in 1917, the Falls Dam in 1919, and Lake Xxxxxxx in 1928 possibly reduced available habitat and altered flow regimes. There are two other potential factors that may affect the viability of the only known extant population. The first potential factor is competition from the introduction and proliferation of non-native plants. Albizia julibrissin (Mimosa) is a non-native under story tree that also grows in the crevices at the Narrows Dam site. Mimosa may reduce suitable habitat and limit sunlight to Yadkin River goldenrod. The hybrid Xxxx Honeysuckle (Lonicera x bella) occurs nearby in dense understory colonies and could pose a potential threat in the future. The other potential threat to Yadkin River goldenrod is trampling from foot traffic associated with recreational users. Neither of these threats has been documented or has impacted the population to date based on available scientific data collected since 1999. However, the objective of establishing a second population or additional clumps within the current population of Yadkin River goldenrod is to help ensure the species survival, in case these potential threats or an unanticipated catastrophic event should impact the extant population. In summary, the limited amount of suitable habitat is the most serious threat to Yadkin River goldenrod. Additionally, trampling by human foot traffic and invasive species may further threaten Yadkin River goldenrod.
THREATS TO THE SPECIES. White River springfish Crenichthys baileyi baileyi: Threats to White River springfish include small population size, competition and predation by introduced nonnative aquatic species including mosquitofish, convict cichlids, mollies Poecilia sp., bullfrogs Rana catesbeiana and crayfish Procambaris sp.; unregulated recreational use in occupied habitats; water level regulation and alteration; and modifications and alterations to occupied aquatic habitats. Hiko White River springfish Crenichthys baileyi grandis: Threats to Hiko White River springfish include small population size, competition and predation by introduced nonnative aquatic species including mosquitofish, convict cichlids, mollies, bullfrogs and crayfish; unregulated recreational use in occupied habitats; livestock grazing practices; the presence of invasive plant species; water level regulation and alteration; and modifications and alterations to occupied aquatic habitats including the permanent loss and modification of spring outflow habitats. Pahranagat roundtail chub Gila robusta jordani: Threats to the Pahranagat roundtail chub include small population size, competition and predation by introduced nonnative aquatic species including common carp Cyprinus xxxxxx, convict cichlids, mollies., bullfrogs, crayfish and the snail Melanoides sp.; livestock grazing practices; the presence of invasive plant species; water level regulation and alteration including seasonal diversion of flows for irrigation; and modifications and alterations to occupied aquatic habitats including the permanent loss and modification of spring outflow and lotic riparian and stream habitats. Specific reasons for recent observed declines in numbers of chub in occupied habitats are unclear, but may be partially related to changes in seasonal irrigation practices which have had an effect on warm-season thermal characteristics of those occupied habitats. Southwestern willow flycatcher Empidonax traillii extimus: On a range-wide basis, principal threats to the southwestern willow flycatcher include: loss and modification of riparian nesting habitat, reductions in water flow, interruptions in natural hydrological events and cycles, physical modifications to streams, and direct removal of riparian vegetation; surface water diversions and groundwater pumping for agricultural, industrial, and municipal uses; physical manipulation of stream courses including channelization, bank stabilization, and removal of riparian vegetation; ove...
THREATS TO THE SPECIES. Water demands are expected to increase in the future, posing a threat in the form of decreases in river flows, decreases in reservoir water level management flexibility, and/or increases in domestic wastewater effluent and construction of new impoundments. Dam operations can result in incompatible habitat and water quality for these freshwater mollusk species, as well as fragmentation of populations. Non-native, invasive species, such as the introduced Flathead Catfish (Pylodictus olivaris) and Blue Catfish (Ictalurus furcatus), may be reducing native mussel populations through direct consumption of mussels or consumption of their host fishes. Hybridization of the Savannah Lilliput with the Lilliput (Toxolasma parvum), which is invasive, could also be a possible threat. Impactful activities in riparian zones adjacent to mollusk habitats can negatively affect mollusks and their associated aquatic community. These impacts/threats can result from poorly maintained riparian buffers, direct impacts to riparian vegetation and soil stability such as unregulated use of all-terrain vehicles (ATVs), and erosion from poorly controlled excess point source run-off or soils impacted by cattle use. A variety of land- uses including poorly managed agriculture and silviculture can lead to excess sedimentation as well as introduction of herbicides and pesticides into aquatic systems. Riparian management and protection can help mitigate these threats. In addition, increased bacteria, pathogens, nutrient loads, and other pollutants in water systems can originate from animal waste and domestic wastewater systems. Because of these threats, increasing the understanding of the species’ ranges, habitat requirements, taxonomy, and life histories of imperiled mollusk species in the Altamaha Basin is important. Protecting riparian buffer zones on GPC properties, educating landowners regarding the importance of riparian buffer zones, property runoff effects to water quality, and the ecosystem services provided by freshwater mussels, as well as suitably managing GPC reservoir water levels for freshwater mussels, generally, are measures in best management practices (BMP) that can be undertaken to alleviate threats to these imperiled species.
THREATS TO THE SPECIES. Razorback sucker: Principal threats to the razorback sucker include predation on early life stages by and competition from nonnative fish species, the alteration of mainstem and tributary historic flow regimes and loss of seasonal variability, the alteration of habitats through impoundment and channelization including thermal alteration and physical attributes, fragmentation of habitats and loss of connectivity, isolation and modification of connected backwaters essential for rearing and nursery habitat, and the small population sizes of remaining relict adult populations even where wild recruitment has been identified. Although reproduction is well documented in a variety of occupied habitats through the presence of early-stage razorback sucker larvae, there is almost invariably an absence of recruitment due to the loss of post-larval early life stages because of the absence of suitable nursery habitats, predation, and other factors. Bonytail: Principal threats to the bonytail are the same as for razorback sucker. In addition, the continued existence of wild adult stocks is unclear, and recovery is dependent on production of fish for release to the wild from very limited numbers of adult refugium stock held at Dexter NFH and other facilities.
THREATS TO THE SPECIES. The principle threat to the species in Illinois is habitat degradation/alteration. Developing commercial and residential areas, quarrying, landfills, construction of pipelines, roadways, and filling of wetlands could decrease the area of suitable habitat available to the species and fragment populations (USFWS 2001). Changes in surface and sub-surface hydrology could be detrimental to the HED. Alteration of hydrologic regimes could adversely affect the larval and breeding habitat of the species by changing water temperature, flow, chemistry, and volume. Road construction, municipal and private xxxxx, addition of impervious surfaces, and alteration of surface drainage patterns could all cause reductions in the suitability of habitat or the outright loss of suitable larval and breeding habitat. Changes in groundwater quality and quantity from various development related activities are a major cause of habitat degradation and loss in Illinois. A study to predict hydrologic changes to a spring near Black Xxxxxxxxx Creek caused by the construction of I-355 predicted an 8 to 35% loss in spring discharge from the spring (Xxxxxx et al. 1992, USFWS 2001). Soluk (2004a) has suggested that a reduction in groundwater flows to the rivulets and seeps at Lockport Prairie may have contributed to the decline in larval numbers observed there. Due to this ongoing concern regarding the hydrology at Lockport Prairie, Graef, Anhalt, Xxxxxxxxx & Associates (GASAI) has conducted investigations of the surface hydrology and hydrogeology of the preserve (GASAI 2004a, 2004b). A land use analysis for the estimated recharge area for Lockport Prairie has also been completed to aid agencies in identifying potential threats to the groundwater (GASAI 2005a). More recently, an estimate has also been made of the recharge area for HMS’s River South parcel (GASAI 2005b). The identification of these recharge areas is critical to efforts to maintain adequate groundwater hydrology at HED habitat. The other HED sites in Illinois are also fed by groundwater aquifers that have not been defined or estimated, however, they have not had any noted drying of the habitat other than that anticipated given natural drought conditions in 2005. Mining is also a threat to this species. Two of the sites in Illinois are owned by an aggregate mining company (HMS) and the smaller of those sites (Middle Parcel) has been proposed for mining the dolomite bedrock. This would result in a direct loss of habitat. Expansio...
THREATS TO THE SPECIES. The nene was listed as a federally endangered species in 1967 (32 FR 4001) and is considered one of the most endangered goose species in the world (Black 1998). A nene restoration program was initiated in 1949 and captive-bred birds have been released into the wild since 1960 (Xxxx and Xxxxxx 1980, USFWS 1999). The Zoological Society of San Diego currently manages the nene captive propagation program in Hawaii. Populations of nene on all the islands are partly maintained through releases of captive-bred birds (Black and Xxxxx 1994). Human activity has impacted nene since settlers first landed on the Hawaiian Islands. Hunting probably caused a substantial decline of birds in lowland habitats (Xxxxxxx 1945, Xxxxx and Xxxxx 1990, Xxxxxxx 1902, Xxxxxx and Xxxxx 1893), extensive burning and agricultural activities changed habitat conditions for nene, introduced plants and non-native ungulates altered and often degraded habitats, and introduced mammalian predators (mongooses, dogs, cats, rats, and pigs) preyed on nene, their eggs or goslings. These activities also had indirect effects including driving nene to marginal upland areas and changing migration patterns, flocking behaviors, and utilization of food items. Currently, the primary threats to nene are predation by introduced predators, lack of lowland habitats, and degraded habitat.
