Interstate Stream Commission

Threatened and Endangered Species in the Pecos River Basin

Pecos bluntnose shiner (Notropis simus pecosensis)

Species Status and Distribution: The Pecos bluntnose shiner (Notropis simus pecosensis) was listed by the U. S. Fish and Wildlife Service (USFWS) as a federally threatened species, with designated critical habitat, on February 20, 1987 (52 FR 5295) Historically, the fish was known to occur in about 320 miles (515 km) of the Pecos River in New Mexico, from near the town of Santa Rosa downstream to the vicinity of Major Johnson Springs near Carlsbad. Currently, the shiner remains in approximately 200 miles (322 km) of the Pecos River from near the town of Fort Sumner, downstream to the inflow of Brantley Reservoir (Platania 1995a). Two sections of the Pecos River are designated as critical habitat. The upper section extends 64 miles (103 km) from approximately one half mile above the confluence of Taiban Creek, downstream to near the confluence with Crocket Draw. The lower section extends 37 miles (60 km) from approximately U. S. Highway 31, downstream to U. S. Highway 82 bridge near Artesia.

Species Description:(from Propst, 1999). The Pecos bluntnose shiner is a relatively small, moderately deep-bodied minnow, rarely exceeding 80 mm total. It has a pallid gray to green-brown back, and is whitish to silvery on its underside. The shiner has a faint silvery broad band on its side, extending from the tail fin towards the head. Scales are outlined with pigment, giving a diamond-grid appearance from the side. The snout is bluntly rounded and overhangs the mouth, the characteristic for which the fish was named.

Ecology: The PBNS is one of a specialized guild of pelagic spawning cyprinids that have evolved to spawn in the hydrologically variable and geomorphically dynamic sand-bed rivers characteristic of the southwestern U.S. (Hatch et al. 1985, Moore 1944, Johnston and Page 1992). Females release ~1-mm diameter, non-adhesive, semi-buoyant eggs into the water column during increasing flows associated with spring runoff, summer thunderstorms events, or reservoir releases (Platania and Altenbach 1998). The eggs are immediately fertilized by accompanying males and quickly water-harden to 3-4 mm becoming almost neutrally buoyant. Eggs are kept suspended by turbulent flows and drift passively until they are entrained in low velocity habitats. The eggs hatch in 24–48 hours and larvae may continue to drift passively for 2–3 days post-hatching or until their air bladders develop and they actively seek suitable rearing habitats. This reproductive strategy is hypothesized to be an advantage over substrate spawning by reducing the probability of egg and larval suffocation when sediment is actively transported during high flow events (Moore 1944, Johnston and Page 1992). The Pecos bluntnose shiner inhabits primarily low velocity habitats including plunge pools at the leading and lateral margins of sand bars, slackwaters, pools, and some runs.

The Pecos bluntnose shiner has a carnivorous-omnivorous diet (Sublette et al. 1990) consisting of terrestrial invertebrates (ants and wasps), aquatic invertebrates, larval fish, and plant seeds Platania (1993).

Threats to the Pecos bluntnose shiner, as identified in the Final Rule (52 FR 5295), include water diversion and impoundment, habitat modification and destruction, water pollutants, non-native fish predation, inadequate protection of habitat and instream flow, and reduced numbers of individuals.

For more information: U.S. Fish & Wildlife Service Species Profile - Pecos bluntnose shiner

Interior Least Tern (Sterna antillarum athalassos)

Species Status and Distribution: The Interior least tern (Sterna antillarum athalassos) was listed as federally endangered on May 28, 1985 (50 FR 21784-21792). Historically, the interior least tern was common, and widespread within the Mississippi Basin and the interior of the western United States. Although still widespread, its range and numbers are much reduced. A breeding colony is known to exist on Bitter Lakes National Wildlife Refuge, east of Roswell, and a small colony successfully fledged chicks on an exposed sand bar within the conservation pool of Brantley Reservoir, during summer 2004.Census data indicate that about 5,000 interior least terns summer in the interior U.S. (USFWS 1990). At this time, no critical habitat has been designated.

Species Description: Least terns are characterized by a black-capped crown, white forehead, grayish back and upper wing surfaces and snowy white under surfaces. The legs are variously orange and yellow depending on the sex. The tern has a black-tipped bill whose color also varies depending on sex. Immature birds have darker plumage than adults, a dark bill, and dark eye stripes on their white foreheads (Watson 1966, Davis 1968, Boyd and Thompson 1985).

Ecology: Interior least terns were formally found in riverine, shoreline, and beach environments where highly dynamic flood events or wave actions maintained expansive beach habitats with little vegetative cover. In such habitats, terns nest on sparsely vegetated sand and gravel bars with wide unobstructed views so that they may easily detect predators. Nesting locations usually are at the higher elevations and away from the water's edge because nesting starts when the river flows are high and small amounts of sand are exposed. The nest is a simple unlined scrape usually containing three brown spotted buffy eggs. Breeding colonies or terneries are usually small (up to 20 nests) with nests spaced far apart. Egg-laying and incubation occur from late May to early August, depending on the geographical location and availability of habitat. To reduce the risk of nest inundation during summer rainstorm events, least terns have very short nesting periods. Typically, after a 20-day incubation period, eggs hatch, and chicks will fledge within another 20 days

The interior least tern primarily eats small fish, feeding in shallow waters of rivers, streams, and lakes. Terns usually feed close to their nesting sites but may fly up to 3.2 km to fish if necessary.

Historically, the primary threat to the tern was excessive harvest for their feathers which were extensively used in the millenary trade. The current primary threat to the species is the alteration of natural river dynamics due to reservoir impoundment and operations. This has lead to the inundation of historically used habitats and has caused unfavorable vegetation succession on now permanently exposed sand bars, that were formally maintained by seasonal high flows. Other threats to the species include river channelization projects, and recreational use of sand bar and shoreline habitats.

Note: All tern descriptions are abstracted and cited from the Recovery Plan (1990) and the Federal Register (1985).

For more information: U.S. Fish & Wildlife Service Species Profile - Least Tern