7 minute read
Species
The Platte River Recovery Implementation Program (PRRIP) was formed in 1997 by Colorado, Wyoming, Nebraska, and the U.S. Department of the Interior (USDOI), with the goal of developing a shared approach to improved management of the Platte River (PRRIP undated-a). The PRRIP is described in detail in Section 5.3.3.5. The goals of the PRRIP include enhancing, restoring, and protecting habitat lands for four target species: the interior least tern, pallid sturgeon, piping plover, and whooping crane (PRRIP undated-b). These target species are described below.
Interior Least Tern
The interior least tern (Sternula antillarum athalassos) was ESA-listed as endangered on June 27, 1985, primarily due to the loss of nesting habitat as a result of dramatic alterations (channelization and impoundment) of important river systems. However, a recently completed five-year review resulted in a February 12, 2021, delisting of the interior least tern due to recovery. The USFWS is now in the process of putting in place a post-delisting monitoring plan to encourage and guide voluntary efforts to track species recovery. As described above, the interior least tern is a Platte River target conservation species and the PRRIP manages for the interior least tern along the central Platte River in a manner consistent with ongoing piping plover management on habitat used by both species (PRRIP undated-d).
Least terns are long-distance migrants that breed in North America and winter in Central and South America. The interior least tern historically nested along the Colorado (in Texas), Red, Rio Grande, Arkansas, Missouri, Ohio, and Mississippi River systems. It currently nests in the Mississippi and Rio Grande River basins from Montana south to Texas and from eastern New Mexico and Colorado to Indiana and Louisiana (PRRIP undated-d).
Least terns are viewed as opportunistic feeders, exploiting any fish within a certain size range. Foraging habitat for least terns includes side channels, sloughs, tributaries, shallowwater habitats adjacent to sand islands and the main channel (USFWS 2006). Least terns forage on small fish they capture by diving into shallow riverine habitats and freshwater ponds. Along the central Platte River, these birds usually feed within the river which is generally a short distance from their nesting colony. Throughout its range, least terns breed and nest on barren to sparsely vegetated riverine sandbars, sand and gravel pits, lake and reservoir shorelines, rooftops, ash pits, and salt flats from mid-May to early August. Along the central Platte River, least terns generally nest on managed off-channel nesting habitat created by sand and gravel mining operations or through excavation activities of the PRRIP (PRRIP undated-d).
A recovery plan for the interior least tern was issued on September 19, 1990 (USFWS 1990). The greatest threat to recovery of the interior least tern is the loss of nesting habitat attributable to channelization and impoundments of rivers where the species occurs, although disturbance of nesting areas by recreationists can reduce reproductive success.
Pallid Sturgeon
Pallid sturgeon (Scaphirhynchus albus) was listed as endangered under the ESA on September 6, 1990 (55 FR 36641-36647) (USFWS 2014). The pallid sturgeon is one of the largest freshwater fish species in North America. The pallid sturgeon's historical range spanned the entire Missouri River and into the Mississippi River. Pallid sturgeon prefer moderate to swift river currents, turbid waterways, and water depths between three and 25 feet. The species is more commonly found where sandy substrates are plentiful, but also lives in predominately rocky waterways. Though pallid sturgeon prefer more turbulent and deeper rivers than the Platte River, several pallid sturgeon, including some from hatcheries, have been captured from the Platte River. The lower reaches of the Platte River, a more than 30-mile stretch from the Elkhorn River to its confluence with the Missouri River, is believed to have suitable spawning habitat for pallid sturgeon, although no conclusive evidence has been found that successful spawning is occurring in this region (PRRIP undated-e).
Pallid sturgeon are generally bottom feeders, skimming the sandy reaches of the various rivers and streams in their habitat. Lacking teeth, pallid sturgeon use their extendable mouths to suck up small fish, mollusks, and other food sources from river bottoms. Though little is known about the precise eating habits of the species, they are thought to be opportunistic feeders (PRRIP undated-e).
Pallid sturgeon have a long lifespan, living in excess of 50 years and perhaps as long as 100 years. As is true for many long-lived species, pallid sturgeon reach reproductive maturity relatively late. Males reach sexual maturity between the ages of five and seven years, while females are believed to become capable of reproduction when they are at least 15 years old. Reproduction does not take place every year; the average interval between spawning is three years, although other studies suggest an interval as long as 10 years. Spawning usually takes place May to July (PRRIP undated-e).
The USFWS (2014) identified the following limiting factors affecting the species: 1) activities which affect in-river connectivity and the natural form, function, and hydrologic processes of rivers; 2) illegal harvest; 3) impaired water quality and quantity; 4) entrainment; and 5) life history attributes of the species (i.e., delayed sexual maturity, females not spawning every year, and larval drift requirements). The degree to which these factors affect the species varied among river reaches. There is currently no critical habitat designated for the pallid sturgeon (USFWS undated).
Piping Plover
Piping plovers (Charadrius melodus) were listed under the provisions of the ESA on January 10, 1986. Piping plovers breed in North America and Canada and winter along the Atlantic and Gulf coast and in the Bahamas and West Indies. Three breeding populations of piping plovers are recognized; however, this discussion focuses on the threatened Northern Great Plains population. This population breeds in alkaline wetlands and along lake shorelines of the northern Great Plains and on the Missouri River and its tributaries in North Dakota, South Dakota, and Nebraska (PRRIP undated-f).
Critical habitat was designated for the Northern Great Plains population of the piping plover on September 11, 2002 (USFWS 2001 as cited in USFWS 2015). Nineteen critical habitat units originally contained approximately 183,422 acres of prairie alkaline wetlands, inland and reservoir lakes, and portions of four rivers totaling approximately 1,207.5 river miles in Montana, Nebraska, South Dakota, North Dakota, and Minnesota. The affected areas include: the portion of the Missouri River adjacent to Nebraska counties; Loup; Niobrara, Elkhorn, and Platte Rivers (USFWS 2015). In response to a lawsuit brought by a consortium of water users in Nebraska (the Nebraska Habitat Conservation Coalition), an October 13, 2005, court ruling vacated the Nebraska portion of the piping plover critical habitat designation and remanded that portion to the USFWS for redesignation (USFWS 2006).
Piping plovers feed along the water's edge on small insects, spiders, crustaceans, and mollusks. Along the central Platte River, piping plovers usually feed along the shoreline of off-channel nesting habitats or on low sandbars within the river which is generally only a short distance from their nesting site. Throughout its range, this species nests from April to early August. Nests are generally located on barren to sparsely vegetated sand and gravel found on riverine sandbars, sand and gravel mines, lake and reservoir shorelines, and sand, gravel or pebbly mud found at alkali wetlands. Along the central Platte River, piping plovers generally nest on managed off-channel nesting habitat created by sand and gravel mining operations or through other PRRIP excavation activities. Piping plovers generally only produce a single brood of fledglings; however, re-nesting after fledging a brood has been observed (PRRIP undated-f).
The USFWS (2015) identified changes in the quality and quantity of riverine habitat due primarily to damming and water withdrawals as a primary threat to the species in the northern Great Plains. The USFWS (2015) also noted that habitat destruction and degradation has reduced suitable habitat. Human disturbance, predation, and invasive plants were also noted as further reducing breeding and wintering habitat quality and affecting survival.
Whooping Crane
In the United States, the whooping crane (Grus americana) was listed as threatened with extinction in 1967 (32 FR 4001) and endangered in 1970 (35 FR 16047) (both listings were grandfathered into the ESA). The USFWS has designated the Cheyenne Bottoms State Waterfowl Management Area and Quivira National Wildlife Refuge, Kansas; the Platte River bottoms between Lexington and Denman, Nebraska; and Salt Plains National Wildlife Refuge, Oklahoma, as critical migration habitat to the conservation of the species (Canadian Wildlife Service and USFWS 2005). These areas have geographic importance and are observed to have the highest frequency of crane use of any areas in the species’ migrational path (USFWS 2006).
Whooping cranes occur only in North America. According to the Canadian Wildlife Service and USFWS (2005), whooping crane currently exist in the wild at three locations and in captivity at nine sites. The February 2006 total wild population was estimated at 338 and includes: 215 individuals in the only self-sustaining Aransas-Wood Buffalo National Park Population that nests in Wood Buffalo National Park and adjacent areas in Canada, and
