Montana Fishery Project
Adaptive monitoring for salmonids in Yellowstone River
August 2021 - June 2023
- Montana Fish, Wildlife & Parks
The Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri), rainbow trout (Oncorhynchus mykiss), and brown trout (Salmo trutta) fisheries in the upper Yellowstone River, Montana are important recreational fisheries that are highly valued by Montana Fish, Wildlife & Parks and anglers within and outside Montana. Though the Yellowstone River trout fishery is predominantly catch-and-release, fish populations are still susceptible to stressors including increases in angling pressure (i.e., mortality does occur from catch and release angling), increased susceptibility to disease due to elevated water temperatures, and changes in the seasonal hydrograph pattern (as a consequence of a changing climate). Maintaining a monitoring program for salmonid populations in the Yellowstone River can provide important information to natural resource agencies regarding population structure, vital rates, abundance, and distribution in response to environmental stressors. Moreover, identifying and understanding trends in the fishery can provide natural resource agencies with information necessary to adapt management strategies to mitigate for stressors and ensure the salmonid fisheries in the Yellowstone River are available for future generations to enjoy.
Montana Fish, Wildlife & Parks has been sampling Yellowstone cutthroat, rainbow, and brown trout in the Yellowstone River in Region 3 from Corwin Springs, Montana to Springdale, Montana since the early 1980s (Montana Fish, Wildlife & Parks 2018). In 1981, Montana Fish, Wildlife & Parks established a standardized monitoring program to evaluate the abundance, size structure, and geographic distributions of Yellowstone cutthroat trout, brown trout, and rainbow trout in the upper Yellowstone River using batch mark-recapture techniques. These data have been used to monitor the trout populations and inform management decisions. However, fisheries biologists have recently found that standardized sampling events are becoming less effective or cannot be completed due to changing snowmelt patterns, resulting in an altered hydrograph and turbidity regime. Consequently, fisheries biologists have considered implementing novel analytical methods that could account for the logistical challenges and would continue to provide time-series abundance data. Such analytical methods would be especially pertinent for native Yellowstone cutthroat trout, a species of Special Concern for the state of Montana. The objectives for the upper Yellowstone River monitoring program include providing robust estimates of abundance and survival under the changing hydrological and turbidity regime. The estimates would continue the historical time series of estimates but be more flexible for changing environmental conditions. In addition, the proposed new analytical methods would provide estimates of survival that could be useful in managing the fisheries.
The goal of this project is to determine if the current Yellowstone River trout mark-recapture database contains the appropriate data structure to estimate abundance and survival using more robust methods (e.g., N-mixture). In addition, we will determine if the current sampling plan could be improved to provide more efficient and effective sampling. Given the changing abiotic conditions, an improved sampling plan could be of value so that mark-recapture based abundance or occupancy models can be implemented.