Geology topics

Brock M. Huntsman

Publications and source records attributed to Brock M. Huntsman.

27 records · Page 2Linked to original sources

USGS2021

Interagency Ecological Program long-term monitoring element review: Pilot approach and methods development (2020)

This report describes the first-year, pilot-phase of what is intended to be a larger, multiple-year review of all IEP core long-term monitoring elements (LTMEs). Here we hope to provide evidence that the review team arrangement and communication schedule was effective at developing a framework to objectively evaluate a suite of LTMEs. We focused on developing methods for an effective review, documenting the process of methods development, and compiling recommendations for applications of these methods to future reviews. We also gathered recommendations to improve data collection, catchability-adjustment, and record keeping processes which will be useful for all LTMEs regardless of when they are to be reviewed. Although we did not complete a comprehensive review of the long-term monitoring elements due to our short timeline, we believe this report represents a substantial effort towards that review and will serve as an invaluable guide for subsequent IEP LTME reviews.

Report↗

USGS2020

Intrinsic and extrinsic drivers of life-history variability for a south-western cutthroat trout

The impacts of climate change on cold-water fishes will likely negatively manifest in populations at the trailing edge of their distributions. Rio Grande cutthroat trout ( Oncorhynchus clarkii virginalis , RGCT) occupy arid south-western U.S. streams at the southern-most edge of all cutthroat trout distributions, making RGCT particularly vulnerable to the anticipated warming and drying in this region. We hypothesised that RGCT possess a portfolio of life-history traits that aid in their persistence within streams of varying temperature and stream drying conditions. We used otolith and multistate capture–mark–recapture data to determine how these environmental constraints influence life-history trait expression (length- and age-at-maturity) and demography in RGCT populations from northern New Mexico, United States. We found evidence that RGCT reached maturity fastest at sites with warm stream temperatures and low densities. We did not find a strong relationship between discharge and any demographic rate, although apparent survival of mature RGCT decreased as stream temperature increased. Our study suggests plasticity in trait expression may be a life-history characteristic which can assist trailing edge populations like RGCT persist in a changing climate.

New Mexico↗

USGS2020

Use of the smeltCam as an efficient fish sampling alternative within the San Francisco Estuary

Resource managers often rely on long-term monitoring surveys to detect trends in biological data. However, no survey gear is 100% efficient, and many sources of bias can be responsible for detecting or not detecting biological trends. The SmeltCam is an imaging apparatus developed as a potential sampling alternative to long-term trawling gear surveys within the San Francisco Estuary, California, to reduce handling stress on sensitive species like the Delta Smelt ( Hypomesus transpacificus ). Although believed to be a reliable alternative to closed cod-end trawling surveys, no formal test of sampling efficiency has been implemented using the SmeltCam. We used a paired deployment of the SmeltCam and a conventional closed cod-end trawl within the Napa River and San Pablo Bay, a Bayesian binomial N -mixture model, and data simulations to determine the sampling efficiency of both deployed gear types to capture a Delta Smelt surrogate (Northern Anchovy, Engraulis mordax ) and to test potential bias in our modeling framework. We found that retention efficiency—a component of detection efficiency that estimates the probability a fish is retained by the gear, conditional on gear contact—was slightly higher using the SmeltCam (mean = 0.58) than the conventional trawl (mean = 0.47, Probability SmeltCam retention efficiency > trawl retention efficiency = 94%). We also found turbidity did not affect the SmeltCam’s retention efficiency, although total fish density during an individual tow improved the trawl’s retention efficiency. Simulations also showed the binomial model was accurate when model assumptions were met. Collectively, our results suggest the SmeltCam to be a reliable alternative to sampling with conventional trawling gear, but future tests are needed to confirm whether the SmeltCam is as reliable when applied to taxa other than Northern Anchovy over a greater range of conditions.

California↗

USGS2019

Main stem and off-channel habitat use by juvenile Chinook salmon in a sub-Arctic riverscape

Poor growth and survival in freshwater and marine environments have been implicated as responsible for Chinook salmon ( Oncorhynchus tshawytscha ) declines across Alaska. Lateral connectivity of river main stems with off-channel habitats may play an integral role in sustaining Alaskan salmonid populations because off-channel habitats commonly provide greater growth opportunities than main stem habitats through greater macroinvertebrate productivity and warmer water temperatures. However, off-channel habitats may impose greater mortality risks to juvenile salmonids, as these habitats are typically more susceptible to drying and are often occupied by potential predators. We used a hierarchical Bayesian count model to describe juvenile Chinook salmon distributions throughout the Chena River, Alaska in main stem and off-channel habitats and employed diet, prey availability, and bioenergetic analyses to explain these habitat selection decisions from data collected in the summer of 2015. We found salmon to be most abundant in off-channel habitats as summer temperature increased, which suggested that salmon dispersed to off-channel habitats to take advantage of energetically favourable growth conditions as indicated by the higher prey biomass in benthic and diet samples collected within off-channel habitats. Our results could have significant implications for juvenile salmon under a warming Alaskan climate as access to productive off-channel habitats may be important to offset increased energetic costs as temperature warms.

Alaska↗

USGS2019

Climatic variation drives growth potential of juvenile Chinook Salmon (Oncorhynchus tshawytscha) along a sub-Arctic boreal riverscape

Climatic variation is a key driver of freshwater physical processes that in turn control stream fish growth and population dynamics at fine spatial scales and species distributions across broad landscapes. A recent downturn in Chinook Salmon returns across the Yukon River basin, Alaska, USA, and Yukon Territories, Canada, has led to hardship among user groups and increased interest in understanding how freshwater processes affect population persistence within this important commercial, recreational, and subsistence fishery. Here we present results for the Chena River basin, interior Alaska, where we used field observations and riverscape-scale spatially-explicit models to assess the influence of stream temperature on juvenile Chinook Salmon growth potential among years (2003 2015) and across 438 stream-km. We ran bioenergetic simulations for warm and cool year scenarios and contrasted temperature model precision and growth among different habitat types (small and large tributaries, main stem, side channels) based on field estimates of growth, size, and diet, and measured stream temperatures. Stream temperature regimes predicted from remotely-sensed land surface temperature were precise during the open water season (R2 > 0.87; RMSE < 1.1 C) although the relationship was weakest in groundwater-mediated tributary habitats. Field observations revealed salmon were 67% larger by mass (g) in September during a warm year versus a cool year from main stem sites. Bioenergetic simulations predicted that, on average, growth potential was 42% higher in warm years, although growth potential varied across the riverscape as much as 60% between cool upstream and warm downstream habitats. Climate variability is clearly an important driver of freshwater habitat conditions and has a large role in controlling freshwater growth of juvenile salmon. A better understanding of how climate influences growth conditions in different habitat types and across broad landscapes will be critical for conservation and management of Alaskan Chinook Salmon stocks under an expected warmer and more variable climate.

Alaska, Yukon↗

USGS2017

A mechanistic assessment of seasonal microhabitat selection by drift-feeding rainbow trout Oncorhynchus mykiss in a southwestern headwater stream

The positioning of fishes within a riverscape is dependent on the proximity of complementary habitats. In this study, foraging and non-foraging habitat were quantified monthly over an entire year for a rainbow trout ( Oncorhynchus mykiss ) population in an isolated, headwater stream in southcentral New Mexico. The stream follows a seasonal thermal and hydrologic pattern typical for a Southwestern stream and was deemed suitable for re-introduction of the native and close relative, Rio Grande cutthroat trout ( O. clarkii virginalis ). However, uncertainty associated with limited habitat needed to be resolved if repatriation of the native fish was to be successful. Habitat was evaluated using resource selection functions with a mechanistic drift-foraging model to explain trout distributions. Macroinvertebrate drift was strongly season- and temperature-dependent (lower in winter and spring, higher in summer and fall). Models identified stream depth as the most limiting factor for habitat selection across seasons and size-classes. Additionally, positions closer to cover were selected during the winter by smaller size-classes (0, 1, 2), while net energy intake was important during the spring for most size-classes (0, 1, 2, 3). Drift-foraging models identified that 81% of observed trout selected positions that could meet maintenance levels throughout the year. Moreover, 40% of selected habitats could sustain maximum growth. Stream positions occupied by rainbow trout were more energetically profitable than random sites regardless of season or size-class. Larger size-classes (3, 4+) were energetically more limited throughout the year than were smaller size-classes. This research suggests that habitat in the form of deep pools is of paramount importance for rainbow trout or native cutthroat trout.

New Mexico↗

USGS2017

The role of density-dependent and –independent processes in spawning habitat selection by salmon in an Arctic riverscape

Density-dependent (DD) and density-independent (DI) habitat selection is strongly linked to a species’ evolutionary history. Determining the relative importance of each is necessary because declining populations are not always the result of altered DI mechanisms but can often be the result of DD via a reduced carrying capacity. We developed spatially and temporally explicit models throughout the Chena River, Alaska to predict important DI mechanisms that influence Chinook salmon spawning success. We used resource-selection functions to predict suitable spawning habitat based on geomorphic characteristics, a semi-distributed water-and-energy balance hydrologic model to generate stream flow metrics, and modeled stream temperature as a function of climatic variables. Spawner counts were predicted throughout the core and periphery spawning sections of the Chena River from escapement estimates (DD) and DI variables. Additionally, we used isodar analysis to identify whether spawners actively defend spawning habitat or follow an ideal free distribution along the riverscape. Aerial counts were best explained by escapement and reference to the core or periphery, while no models with DI variables were supported in the candidate set. Furthermore, isodar plots indicated habitat selection was best explained by ideal free distributions, although there was strong evidence for active defense of core spawning habitat. Our results are surprising, given salmon commonly defend spawning resources, and are likely due to competition occurring at finer spatial scales than addressed in this study.

Alaska↗

USGS2013

The temperature-productivity squeeze: Constraints on brook trout growth along an Appalachian river continuum

We tested the hypothesis that brook trout growth rates are controlled by a complex interaction of food availability, water temperature, and competitor density. We quantified trout diet, growth, and consumption in small headwater tributaries characterized as cold with low food and high trout density, larger tributaries characterized as cold with moderate food and moderate trout density, and large main stems characterized as warm with high food and low trout density. Brook trout consumption was highest in the main stem where diets shifted from insects in headwaters to fishes and crayfish in larger streams. Despite high water temperatures, trout growth rates also were consistently highest in the main stem, likely due to competitively dominant trout monopolizing thermal refugia. Temporal changes in trout density had a direct negative effect on brook trout growth rates. Our results suggest that competition for food constrains brook trout growth in small streams, but access to thermal refugia in productive main stem habitats enables dominant trout to supplement growth at a watershed scale. Brook trout conservation in this region should seek to relieve the “temperature-productivity squeeze,” whereby brook trout productivity is constrained by access to habitats that provide both suitable water temperature and sufficient prey.

West Virginia↗

USGS2012

Brook trout movement in response to temperature, flow, and thermal refugia within a complex Appalachian riverscape

We quantified movements of brook trout Salvelinus fontinalis and brown trout Salmo trutta in a complex riverscape characterized by a large, open-canopy main stem and a small, closed-canopy tributary in eastern West Virginia, USA. Our objectives were to quantify the overall rate of trout movement and relate movement behaviors to variation in streamflow, water temperature, and access to coldwater refugia. The study area experienced extremely high seasonal, yearly, and among-stream variability in water temperature and flow. The relative mobility of brook trout within the upper Shavers Fork watershed varied significantly depending on whether individuals resided within the larger main stem or the smaller tributary. The movement rate of trout inhabiting the main stem during summer months (50 m/d) was an order of magnitude higher than that of tributary fish (2 m/d). Movement rates of main-stem-resident brook trout during summer were correlated with the maximum water temperature experienced by the fish and with the fish's initial distance from a known coldwater source. For main-stem trout, use of microhabitats closer to cover was higher during extremely warm periods than during cooler periods; use of microhabitats closer to cover during warm periods was also greater for main-stem trout than for tributary inhabitants. Main-stem-resident trout were never observed in water exceeding 19.5°C. Our study provides some of the first data on brook trout movements in a large Appalachian river system and underscores the importance of managing trout fisheries in a riverscape context. Brook trout conservation in this region will depend on restoration and protection of coldwater refugia in larger river main stems as well as removal of barriers to trout movement near tributary and main-stem confluences.

West Virginia↗