Big Hole River Grayling: "Warranted but Precluded" for ESA Listing

The US Fish & Wildlife Service has declared that Big Hole River grayling (i.e. fluvial Arctic grayling in Montana) are warranted but precluded for listing & protection under the Endangered Species Act. Montana grayling are warranted for listing because (1) they are a genetically distinct population that meets the agency's "Distinct Population Segment" criteria and (2) they are in imminent danger of extinction. They are precluded because as a population and not a species per se, Big Hole River grayling cannot be listed higher than Priority 3. Taking precedence are: higher priority listings, a backlog of cases from the anti-environment Bush II administration, and required actions in lawsuits FWS has lost.

In its decision document, FWS admits that Montana grayling are on the verge of extinction and that dewatering by ranchers (for hay irrigation) is the cause. As I have consistently pointed out on this blog, dewatering is especially a problem during the critical spring spawning & emergence period. Note that lake dwelling populations (i.e. the adfluvial life form) are now also included as a candidate.

See the Center for Biological Diversity press release here.

Here are a few quotations from the FWS document:

Grayling FWS decision Aug 2010

p. 13: “In Montana, Arctic grayling generally spawn from late April to mid-May by depositing adhesive eggs over gravel substrate without excavating a nest (Kaya 1990, p. 13; Northcote 1995, p. 151).

p. 13: “In the upper Missouri River basin, development from embryo to fry averages about 3 weeks (Kaya 1990, pp. 1617).”
p. 13: “In the Big Hole River, Montana, similar downstream and long-distance movement to overwintering habitat has been observed in Arctic grayling (Shepard and Oswald 1989, pp. 1821, 27). In addition, Arctic grayling in the Big Hole River may move downstream in proximity to colder tributary streams in summer when thermal conditions in the mainstem river become stressful (Lamothe and Magee 2003, p. 17).”

p. 13: “Fry from river populations typically seek feeding and rearing habitats in the vicinity where they were spawned (Armstrong 1986, pp. 67; Northcote 1995, p. 156)…”
p. 25: “We define the current range of the DPS to consist of extant native populations in the Big Hole River, Miner Lake, Mussigbrod Lake, Madison RiverEnnis Reservoir, and Red Rock Lakes. We refer to this DPS as the native Arctic grayling of the upper Missouri River.”
p. 25: “We identified a DPS for Arctic grayling in the upper Missouri River basin that includes five extant populations: (1) Big Hole River, (2) Miner Lake, (3) Mussigbrod Lake, (4) Madison River-Ennis Reservoir, and (5) Red Rock Lakes.”

p. 27: “general lack of monitoring data for the Big Hole River fluvial Arctic grayling population prior to the late 1970s, but data collected since that time indicate the overall range has contracted over the last 2 decades.

p. 27: “More recently, Arctic grayling have become less abundant in historical spawning and rearing locations in the upper watershed near Wisdom, Montana, and also in downstream river segments with deep pool habitats considered important for overwintering (Magee and Lamothe 2003, pp. 1821; MFWP unpublished data).”

p. 27: “Based on the best available data, the adult population declined by one half between the early 1990s and the early 2000s (see Figure 3, USFWS unpublished data), which is equivalent to a decline of 7 percent per year, on average.”

p. 31: “the largest population, Mussigbrod Lake,having a very low probability of extinction (less than 1 percent) in the foreseeable future, even given a population decline. The other four populations have comparatively greater probabilities of extinction in the foreseeable future with all being roughly similar in magnitude (13-55 percent across populations) when considering only stochastic (random or chance) processes. The Madison River has the greatest probability of extinction by stochastic processes (36- 55 percent), followed by Big Hole (33-42 percent), Red Rocks (31-40 percent), and Miner (13-37 percent).

p. 36 “Summer water temperatures exceeding 21 °C (70 °F) are considered to be physiologically stressful for cold-water fish species, such as Arctic grayling (Hubert et al. 1985, pp. 7, 9). Summer water temperatures consistently exceed 21 °C (70 °F) in the mainstem of Big Hole River (Magee and Lamothe 2003, pp. 1314; Magee et al. 2005, p. 15; Rens and Magee 2007, p. 11). Recently, summer water temperatures have consistently exceeded the upper incipient lethal temperature (UILT) for Arctic grayling (e.g., 25 °C or 77 °F) (Lohr et al. 1996) at a number of monitoring stations throughout the Big Hole River (Magee and Lamothe 2003, pp. 1314; Magee et al. 2005, p. 15; Rens and Magee 2007, p. 11). The UILT is the temperature that is survivable indefinitely (for periods longer than 1 week) by 50 percent of the test population in an experimental setting. Fish kills are a clear result of high water temperature and have been documented in the Big Hole River (Lohr et al. 1996, p. 934). Consequently, water temperatures that are high enough to cause mortality of fish in the Big Hole River represent a clear threat to Arctic grayling because of the potential to directly and quickly reduce the size of the population.

Water temperatures below that which can lead to instant mortality also can affect individual fish.”

p. 37 “we can infer effects from observations that the abundance and distribution of Arctic grayling has declined concurrent with reduced streamflows (MFWP et al. 2006, pp. 3940) and increased water temperatures associated with low streamflows.”

p. 38 “Removal of willows and riparian clearing concurrent with livestock and water management along the Big Hole River has apparently accelerated in recent decades, and, in conjunction with streamside cattle grazing, has led to localized bank erosion, channel instability, and channel widening (Confluence Consulting et al. 2003, pp. 2426; Petersen and Lamothe 2006, pp. 1617; Bureau of Land Management (BLM) 2009a, pp. 1421).”

p. 66 “As a result of our analysis of the best available scientific and commercial information, we assigned the native Arctic grayling of the upper Missouri River a Listing Priority Number (LPN) of 3 based on our finding that the DPS faces threats that are of high magnitude and are imminent.”