The Arctic grayling (Thymallus arcticus) is a circumpolar species, the distribution of which historically included two disjunct populations in Michigan and Montana. Arctic grayling became extinct in Michigan in the late 19th Century. Although the species still occurs in Montana, the fluvial (permanently stream dwelling) form has been extirpated from about 95 percent of its historic range. The last remaining reproductively-viable population of this grayling life-history type is limited to the upper 130 kilometers of Big Hole River and its tributaries.

In 1994, fluvial Arctic grayling in the Big Hole and Madison Rivers were identified by the US Fish and Wildlife Service as a Distinct Population Segment under the Endangered Species Act. Following subsequent review in 2004, this stock was elevated to the highest listing priority that can be given to a Distinct Population Segment. Furthermore, grayling in the Big Hole River have been identified as a "species of special concern" by the Endangered Species Committee of the American Fisheries Society, the Montana Chapter of the American Fisheries Society, Montana Fish, Wildlife and Parks, and the Montana Natural Heritage Program of the Nature Conservancy.

Because most of the habitat occupied by grayling in the Big Hole River watershed is on, or adjacent to, private land, a close relationship between private landowners and regulatory agencies has been developing since the 1980s. The prior potential for listing under the Endangered Species Act and the critical need to engage the majority of landowners in watershed-scale solutions to conserve and restore grayling have resulted in variety of integrated conservation programs (including one of the largest Candidate Conservation Agreement with Assurances in the United States). Specifically, these programs are attempting to increase instream flow, lower summer water temperatures, and improve riparian habitat conditions throughout the upper Big Hole River Watershed.

Our primary goal is to investigate relationships between stream habitat conditions, fish community composition, and Arctic grayling distribution, abundance, and movement patterns in the upper Big Hole River.  By gaining further knowledge about the basic population ecology and movement patterns of Artic grayling and other fish species in the Big Hole River and its tributaries, we aim to provide essential information for grayling conservation planning and ongoing habitat restoration efforts.

Objectives:

1. To consolidate and analyze past sampling data on Arctic grayling in the upper Big Hole River.
2. To determine seasonal distribution and movement patterns of grayling in the upper Big Hole River.
3. To determine the frequency and timing of fish movement between mainstem and tributary habitats in the upper Big Hole River.
4. To investigate the relationship between fish movement, habitat use patterns, and stream habitat conditions.
   

Future Activities:

We will continue to analyze the historic grayling tagging-recapture database for patterns of movement, trends in abundance, survival, habitat covariates, and fish species composition. This data will be presented in a poster at the 2007 American Fisheries Society Meeting in September and in an oral presentation at the 2007 Wild Trout Symposium in October.

Field sampling will continue through October 2007. We will complete continuous snorkel and habitat surveys of Fish Trap and LaMarche Creeks in July-August, and Sept-October. In addition, we will conduct extensive, spatially-continuous temperature surveys in July and August in these tributaries and in the adjacent mainstem Big Hole River. These data will allow us to compare seasonal trends in the fish assemblage of tributaries with fine-resolution water temperature and flow data.

In late August, installation of eight PIT monitoring stations will be completed (at mouths of tributaries and in main-stem sections upstream of Wisdom, MT) to further evaluate fish movement and habitat use. In September and October, fish will be captured by electrofishing throughout the upper Big Hole River watershed. These efforts will be coordinated with the annual MFWP fish monitoring surveys. All Artic grayling and most other fish will be PIT tagged to facilitate movement monitoring at the stationary antenna stations and portable antennae. Capture information will provide information on the movement, habitat use, growth, and demography of captured fish species. As a pilot study, fish locations will be monitored with one fixed PIT antenna and one portable antenna during the winter.

A lab experiment will be implemented at the Wild Trout Laboratory (MSU Water Center) to evaluate the effects of PIT tag implantation on Artic grayling growth, survival, and swimming performance. The timeline of this experiment is still tentative, because the source of fish and duration of acclimation prior to treatment are still being determined.

Progress to Date:

Through a series of ongoing planning meetings and communications, we are collaborating with biologists from the Montana Fish, Wildlife and Parks (MFWP) and other scientists involved in the Arctic Grayling Recovery Program (AGRP). As a result of these efforts, AGRP has purchased approximately $10,500 in passive integrated transponder (PIT) equipment for our use during this research project.

We have compiled a database of over 6,500 individually marked Artic grayling in the Big Hole River from 1986-2005. Preliminary analyses of mark-recapture locations suggest that Artic grayling exhibited strong interannual fidelity to seasonal habitat. Among-season movement patterns varied, and fish tended to move upstream in the spring, downstream in the fall, or remain in the same area of the watershed in spring and fall. Smaller fish (≤250 mm) tended to occupy the same locations, independent of season, but larger fish (>250 mm) exhibited much broader differences in movement among seasons (0-80 km). We presented these preliminary findings and our future research plans at the annual AGRP meeting in February 2007.

Passive integrated transponder (PIT) technology provides us with a robust tool to assess the research goals and objectives outlined above. In a riverine system, such as the upper Big Hole, where opportunities for snorkel and electrofishing surveys are limited, PIT-tagging allows for passive monitoring at a fine temporal scale (nearly continuous) with fixed antenna and at a fine spatial scale with portable PIT antenna. Compared to traditional mark-recapture approaches that require physical handling at each recapture event, this approach greatly reduces the amount of handling necessary to collect information from individual fish.

MFWP has requested that experimental evidence concerning the effects of PIT-tagging (specific to Artic grayling) be available prior to PIT-tagging any wild Artic grayling in the Big Hole River. Accordingly, we initiated an experiment investigating the effects of PIT tags on Artic grayling growth, survival, and swimming performance in April at the Wild Trout Laboratory. Unfortunately, these grayling suffered from a parasitic infection of the gastrointestinal tract, and we were unable to complete the experiment. We are planning to repeat the experiment this fall and/or winter (see Future Activities). In addition to the laboratory experiment, a short-term mortality experiment was conducted at the Green Hollow Artic grayling brood pond on Turner Enterprise’s Flying D Ranch. A total of 41 fish were held for 5 days, and 100 percent of control and PIT tagged fish survived (excluding one individual killed by an avian predator). We also observed 100 percent retention of PIT tags, and implantation wounds were healing well on day 5. We are currently preparing a report of these results for MFWP personnel.

In preparation for monitoring PIT-tagged grayling in the Big Hole River and its tributaries, three antenna stations were installed in May (with two channel-spanning antennas at each station to detect direction of movement). We also assembled five additional monitoring stations, complete with solar power supplies that will be installed prior to tagging operations. Permission to access private land has been acquired for most of the proposed antenna locations.

While awaiting permission to proceed with PIT-tagging, we have focused on the timing and extent of fluvial Artic grayling activity in tributaries to the upper Big Hole River. To identify factors influencing this potential mainstem-tributary dynamic, we are currently conducting continuous snorkel and habitat surveys of two tributaries, Fish Trap Creek and LaMarche Creek. These tributaries were selected because: 1) in the past few years, the relative abundance of grayling, as measured by fall electrofishing catch per unit effort (CPUE), was higher in these reaches than in other sampled portions of the Big Hole River watershed; 2) visibility in these two tributaries provides the opportunity for quantitative snorkel surveys.

Deliverables:

A final report on the Artic grayling movement and habitat use project will be submitted by December 31, 2007. This report will detail the past and present information gathered on Artic grayling movement and habitat use in the upper Big Hole River basin. In addition, the results of our PIT-tag experiments will be included.

Partners:

Montana Fish Wildlife and Parks, US Fish and Wildlife Service, US Forest Service, Big Hole River Watershed Committee, and local landowners.

Robert E. Gresswell, Affiliate Proffessor
USGS, Northern Rocky Mountain Science Center
Department of Ecology, Montana State University-Bozeman
Bozeman, Montana 59717