Geology topics

Ryan A. Vosbigian

Publications and source records attributed to Ryan A. Vosbigian.

3 recordsLinked to original sources

USGS2026

Integrating data on a mixed stock anadromous fishery to estimate stock-specific escapement and mortalities

Objective Anadromous fisheries can affect stocks with differing management objectives. Understanding the effects of fisheries on individual stocks by quantifying final dispositions, including escapement and mortalities, is important for sustainable fishery management. Our objectives were to extend an existing management model that is used to evaluate final stock dispositions to estimate confidence intervals and to generalize the model so that it could be applied in other systems. Methods An annual run reconstruction model for estimating final dispositions of Snake River steelhead Oncorhynchus mykiss was previously developed to evaluate mortalities and escapement for each stock. We extended and generalized this model in two ways: (1) to propagate uncertainty using Monte Carlo simulation and (2) to fit the model using maximum likelihood methods. We generated confidence intervals and conducted sensitivity analyses to evaluate sources of uncertainty. Results The Monte Carlo version of the model explicitly propagates uncertainty in inputs through to model predictions, whereas the maximum likelihood version includes additional data sources, such as catch composition and escapement. We estimated disposition metrics for Snake River steelhead using the original formulation, Monte Carlo version, and the maximum likelihood version for the 2018–2019 season, and we found that the results were similar but that the maximum likelihood version provided a better fit to the observed data. Conclusions We demonstrate how to account for uncertainty when synthesizing several kinds of monitoring data. Improved characterizations of uncertainty facilitate better decision making about future data collection and fisheries management.

North American Journal of Fisheries Management↗

USGS2025

Elevation mediates juvenile steelhead demographic response to stream temperature and flow

Climate change alters streams by modifying flow dynamics, temperature, and biotic communities, changing the habitat where stream dwelling fish have evolved. We used snorkel survey data spanning four decades to investigate how juvenile steelhead (anadromous Oncorhynchus mykiss ) counts and size structure were influenced by stream temperature and flow. Warmer temperatures were associated with lower abundance and larger fish at low elevations and with higher abundance and smaller fish at higher elevations. Low flows were related to increased abundance and smaller fish at low elevations but to decreased abundance at high elevations, suggesting that lower elevation streams, which tend to be larger, provided additional habitat during low flows. High flows were negatively related to abundance and positively related to average size, suggesting emigration of fish in younger age-classes. Overall, steelhead exhibited greater resilience to warm temperatures at high elevations and, conversely, greater resilience to low and high flows at lower elevations. Understanding how streamflow and temperature affect juvenile steelhead abundance and size structure provides insight into how climate change can affect juvenile steelhead production.

Idaho↗

USGS2024

Cycles in adult steelhead length suggest interspecific competition in the North Pacific Ocean

Anadromous fishes rely on abundant prey in the ocean to grow large quickly, but prey limitation leads to interspecific competition. When species interactions are difficult to observe, growth can be studied to detect otherwise cryptic signals of competition. We describe a previously undocumented two-year cycle in the lengths of adult natural-origin steelhead ( Oncorhynchus mykiss ) returning to spawn in the Snake River Basin. Returning steelhead were 38 mm shorter on odd return years, not accounting for sex, stock, and years of ocean residence. The well-known cycle in abundance of Pink Salmon from eastern Kamchatka and North America had statistically significant negative effects on returning steelhead lengths that depended on sex and the number of years of ocean residence. These results suggest that competition for limited resources occurs well after initial ocean entry and that interactions during later stages of ocean residence can be influential. Interspecific competition has implications for future returns of steelhead from the ocean, especially as metabolic demands for steelhead increase as the ocean warms.

North Pacific Ocean↗