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Scott A. Bonar

Publications and source records attributed to Scott A. Bonar.

At least 19 recordsLinked to original sources
USGS2024

Estimating age and growth of Largemouth Bass in southwestern reservoirs using otoliths and scales

Age and growth data are frequently used to monitor and manage important North American sport fishes such as Largemouth Bass Micropterus salmoides . Continental and regional growth standards have been developed for this species to assess fish growth over time and across space. However, Largemouth Bass age and growth data are infrequently collected in Arizona and the reliability of age estimates derived from typical structures (e.g., scales, otoliths) in the Southwest is uncertain. Our objectives were to 1) compare precision and bias of age estimates from scales with those from otoliths and 2) estimate Largemouth Bass growth in several southwestern warmwater reservoirs by using otoliths. We collected Largemouth Bass from three Arizona reservoirs—Alamo, Peña Blanca, and Roosevelt—by boat electrofishing in spring 2021. We removed scales and sagittal otoliths from fish and then prepared and independently aged them three times. We compared differences in precision and bias between scales and otoliths using reader agreement percentages, confidence ratings, average coefficients of variation, and age-bias plots. We used age estimates from Largemouth Bass otoliths to calculate mean lengths-at-age at capture and relative growth indices based on published growth standards in each reservoir. Largemouth Bass scale age estimates were less precise, overestimated ages of younger fish, and underestimated age of older fish compared with those of otoliths. Growth was lower in Peña Blanca Lake than in the other two reservoirs according to mean length-at-age estimates, and relative growth indices suggested that Largemouth Bass growth in all three reservoirs was above average at younger ages, but less so at older ages. The results from this study add to a growing body of literature supporting the use of otoliths for estimating age and growth of Largemouth Bass.

Arizona↗
USGS2024

An introduction to standardized sampling

In 2009, the first edition of Standard Methods for Sampling North American Freshwater Fishes was published. This was the first time in the history of fisheries science that standardization of methods and equipment had taken place on such a large geographic scale. Since its publication, the methods have been used extensively across North America by local, state, and federal agencies, organizations, and universities who have seen the advantages of large-scale data comparison. Authors have been invited to present these methods in other locations around the world to help with standard sampling programs on other continents. Now, with large-scale issues such as human-caused climate change, effects of landscape-scale regulations, and effects of habitat degradation continuing to increase in importance, the ability to compare data across wide regions and political boundaries, compare data over time, and collect data with improved accuracy and precision is more important than ever. This new edition of Standard Methods is sponsored by the American Fisheries Society (AFS), the U.S. Fish and Wildlife Service, and the Association of Fish and Wildlife Agencies (AFWA), with contributions by numerous state, provincial and federal agencies, and numerous academic institutions and nongovernmental organizations (NGOs). It is authored by over 100 experts in fisheries sampling from across Canada, Mexico, and the United States. Most techniques for water body types addressed in the first edition have been kept the same-in the interest of standardization over time; however, many important additions have been made. Like the first edition, these methods are designed for fish community assessments in North American aquatic systems (e.g., for this edition, lakes, ponds, rivers, and streams containing warmwater and coldwater species; the Great Lakes, wetlands, and cenotes). Although other methods may be available that better target a more specific size-group or species, these techniques were selected as most effective for general surveys of these systems and typically are the most effective for capturing the common fishes found in these waters.

Book chapter↗
USGS2024

Indices for common North American fishes

One of the greatest advantages to the standardization of fisheries sampling methods is the comparable data they produce (Bonar et al. 2017). Following American Fisheries Society (AFS) standardized sampling methods, fisheries professionals can more easily compare their data with standardized data collected across North America to address both small- and large-scale fisheries questions. For example, access to standardized data can allow fisheries managers to evaluate if a fish species is within an expected range for weight or length in a particular water body, providing them with valuable information about the baseline health of their fish population. Additionally, given that fish can take years to respond to certain management actions (Meals et al. 2010), access to standardized data over time can be used to assess the effectiveness of these actions. Finally, standardized fisheries data can be analyzed over large geographic regions and provide increased sample sizes to evaluate management actions that cross local or state borders, such as habitat improvements or regulations, as well as the effects of large-scale transformations such as climate change on fish growth or body condition. Ultimately, the use of standardized data enhances the ability of fisheries professionals to address both small- and large-scale threats currently facing freshwater ecosystems and the fishes they support.

Book chapter↗
USGS2023

The effects of estradiol-17β on the sex reversal, survival, and growth of Red Shiner and its use in the development of YY individuals

Objective The Red Shiner Cyprinella lutrensis is one of the most prolific and ecologically destructive invasive fish species in the southwestern United States. The production and release of YY individuals as Trojan sex chromosome carriers can theoretically eradicate invasive fish populations by eventually eliminating phenotypic females. Methods The YY individuals are typically produced through hormonally induced sex reversals and selective breeding of subsequently feminized males. We tested three dosages of estradiol-17β (E2)-treated diets (50, 100, and 150 mg of E2 per kg of diet) administered to sexually immature Red Shiner for various durations to determine their effectiveness at feminizing Red Shiner cohorts. Survival, growth, and gonadal development were assessed for each treatment. Result All E2 treatments had minimal, if any, detrimental effects on the growth and gonadal development of Red Shiner. The 50-mg dosage lasting from 2 to 120 days posthatch achieved a 100% feminization rate while using the lowest amount of E2; therefore, this dosage and treatment interval are recommended when attempting Red Shiner feminization under these rearing conditions. Feminization of males allowed for the spawning of neofemales (F XY ) with wild-type males (M XY ), which resulted in the first putative YY Red Shiner. The YY verification crosses ( n = 20) resulted in predominately male offspring (189 males/191 offspring) except for (1) an intersex individual from an M YY × F XX cross with two previtellogenic oocytes in its testis and (2) a single female that may have resulted from an inbred cross between an XY male and a YY female or from an unknown autosomal or environmental effect on sexual phenotype. Conclusion More progeny tests with inbred and outbred crosses should be conducted to determine the prevalence of female offspring from YY individuals and how this may impact an eradication strategy featuring releases of YY Red Shiner.

North American Journal of Aquaculture↗
USGS2023

Native fish abundance and habitat selection changes in the presence of nonnative piscivores

We compared abundance patterns and developed resource selection models for imperilled native southwestern (USA) fishes in the presence and absence of Black Bass ( Micropterus spp.) to evaluate how fishes alter their selection for habitats when sympatric with a nonnative piscivore. We collected data using snorkel surveys and in-stream habitat sampling in Fossil Creek (AZ), upstream (native fish only) and downstream (native and nonnative fish) of a fish barrier. The abundance of all Roundtail Chub ( Gila robusta ), small (≤127 mm total length [TL]; vulnerable to predation) Sonora Sucker ( Catostomus insignis ) and Speckled Dace ( Rhinichthys osculus ) was significantly reduced, but the abundance of both small and large (>127 mm TL; invulnerable to predation) Desert Sucker ( Catostomus clarkii ) was similar in sampling reaches with and without Black Bass. When sympatric with Black Bass, small Roundtail Chub increased their selection for riffles by 2.57 times and small Desert Sucker reduce their selection for pools by 6.90 times while also selecting for faster flow velocity and finer substrates in lotic mesohabitats. Large native fishes altered selection least, notwithstanding an increased selection for canopy cover in sampling reaches with Black Bass. Observed shifts in resource selection are consistent with predator avoidance strategies. Our study highlights the behavioural consequences of nonnative piscivores on native fish communities and stresses the importance of maintaining lotic mesohabitats as potential refugia for vulnerable native fishes when nonnative piscivores are present.

Arizona↗
USGS2023

Influence of electrofishing boat operation and driving techniques on reservoir fish catches

We compared three methods of boat driving and pedal operation using 600-s transects: these were the parallel continuous (PC), parallel intermittent (PI), and arc-intermittent (AI) methods for surveying warmwater fishes in reservoirs. We tested differences in total time and distance per transect, CPUE (fish/h, fish/m), and length frequencies of captured fish among methods. The PC method took the least amount of time, while the AI method took the least amount of distance to complete a transect. The AI method provided slightly higher CPUE (fish/h, fish/m) for Bluegill Lepomis macrochirus and Yellow Bass Morone mississippiensis and higher CPUE (fish/m) for Common Carp Cyprinus carpio , Green Sunfish L. cyanellus , and Largemouth Bass Micropterus salmoides . Each method caught similar size ranges of fish; however, there were slight differences in proportions of sizes for Gizzard Shad Dorosoma cepedianum , Largemouth Bass, and Bluegill. Overall, the AI method performed slightly better for a few species; however, difference in the methods were minor. Any technique should work well for monitoring reservoir fish populations when fish/h is the effort metric.

Fisheries Magazine↗
USGS2023

The effects of estradiol-17β on the sex reversal, survival, and growth of green sunfish Lepomis cyanellus

The feminization of green sunfish Lepomis cyanellus could expand their utility as a game fish or aquacultured species by preventing overcrowding and precocious reproduction in stocked systems. Feminization of green sunfish could also help elucidate information on their sex determination system. We report the feminization of green sunfish cohorts via oral administration of estradiol-17β (E2) during early development. A low-dose (100 E2 mg per kg of diet) and a high-dose (150 E2 mg per kg of diet) experimental E2 treatment were fed to juvenile green sunfish from 30 to 90 days post-hatch. Fish were subsequently evaluated for any treatment effect on gonadal development, survival, and growth. Both E2 treatments resulted in 100% feminization, with no morphological or histological differences detected between E2 treated ovaries and those from a control group. The control group was composed mostly of males (82.61%). Overall, there was no effect of E2 on survival ( P = 0.310) and growth rate data suggested no statistical differences ( P = 0.0805). However, the growth rate of the high-dose group increased slightly higher after the treatment ended than the other treatments ( P = 0.042), suggesting that E2 might suppress growth in green sunfish. In addition, the control group did not exhibit a higher survival rate after the treatment period ended ( P = 0.266), whereas both E2 treated groups did ( P = 0.0003–0.0050). We found that the low dose, 100 E2 mg per kg of diet, was sufficient for fully feminizing green sunfish if administered during development from 30 to 90 days post-hatch and E2 dosages may result in deleterious effects on green sunfish's health and growth.

Aquaculture↗
USGS2022

The development of genetic sex identification markers and evidence of a male heterogametic sex determination system in Red Shiner

The Red Shiner Cyprinella lutrensis is of increasing management interest as an invasive species that negatively impacts many native fishes throughout North America. Trojan sex chromosome (TSC)-carrying individuals could theoretically control invasive fish populations by skewing the sex ratio to 100% male. The efficacy of TSC-based control programs requires an understanding of a population's sex determination system, yet such information is lacking for Red Shiner. We used single-digest restriction site-associated DNA sequencing to discover sex-linked single-nucleotide polymorphisms (SNPs), and we conducted a series of breeding experiments to uncover the sex determination system. All candidate sex-linked SNPs that fit our selection criteria exhibited a pattern of male heterogamety. We developed two sex-identification (sex-ID) marker assays, XY_248 and XY_170, which showed phenotype–genotype concordance scores of 77.00% and 84.35%, respectively. These sex-ID markers exhibited relatively high phenotype–genotype concordance in females (XY_248 = 96.30%; XY_170 = 98.61%), which allowed for selective breeding of phenotypically feminized genetic males. We observed a 3:1 male : female sex ratio in spawns from feminized males crossed with wild-type males, indicative of a male heterogametic sex determination system (i.e., XY male/XX female). The discovery of a male heterogametic sex determination system, in combination with our two markers, increases the likelihood of developing an effective TSC eradication strategy for invasive Red Shiner populations.

North American Journal of Aquaculture↗
USGS2022

Increased juvenile native fish abundance following a major flood in an Arizona river

Spring floods trigger spawning in many native fishes of the desert Southwest (USA), but less is known about fish community response when native fishes are rare. Here, we document change to native and nonnative fish captures and instream habitat features following a decade-high flooding event (2019) in the Verde River (AZ) where native fish captures were rare in the years pre-flood. Using prepositioned areal electrofishing devices (PAEDs), we sampled the fish community at 90 sampling units pre-flood (2017) and resampled those same units post-flood (2019) to compare and identify changes to catch and habitat features. Relative abundance of native fishes increased from 0.6% pre-flood (0.01 fish/PAED) to 53.0% post-flood (1.66 fish/PAED) and was largely attributable to the presence of juvenile Roundtail Chub Gila robusta (≤ 70 mm total length (TL)) and juvenile Sonora Sucker Catostomus insignis (≤ 100 mm TL). Juvenile Desert Sucker Catostomus clarkii experienced a lesser increase. One adult native fish was captured in 2017 and adult native fishes were absent from 2019 sampling. The catch of adult/subadult Common Carp Cyprinus carpio (> 100 mm TL) declined; however, this could be related to reservoir management and not the flood. The abundance of all size-classes of Black Bass Micropterus spp., Red Shiner Cyprinella lutrensis and other nonnative fishes did not change. The majority (97%) of juvenile native fishes were captured at the uppermost sampling reach. A 54% reduction to canopy cover across all sampling reaches and an increase of fine sediments at the most downstream reach demonstrates how floods can restructure the river environment. This case-study adds evidence that protection of spring floods is vital to the persistence and recolonization of fishes native to the desert Southwest, especially where they are rare. The continued presence of nonnative species may preclude juvenile native fishes from recruiting to adults.

Arizona↗
USGS2022

Development of aquaculture protocols and gonadal differentiation of green sunfish (Lepomis cyanellus)

We provide detailed rearing methods and describe green sunfish ( Lepomis cyanellus ) gonadal development and histological differentiation for both sexes. Developing in-depth aquaculture protocols and describing the gonadal differentiation of green sunfish could facilitate strategies to control nuisance populations, enhance stocking programs, and provide information for this species' use in bioassay trials or toxicology studies. Our methods resulted in consistent year-round production of green sunfish and allowed us to identify the timing of their gonadal differentiation through histological assessment. Our spawning methods provided year-round volitional spawns from green sunfish broodstock. Our rearing methods involved weaning larval green sunfish off live nauplii and onto only artificial diets by 37 days post-hatch (dph). Most of the offspring generation reached sexual maturity by 213 dph. Green sunfish are gonochoristic, with testes and ovaries differentiating directly from undifferentiated gonads. Ovaries begin to differentiate by 39 dph and testes begin to differentiate by 69 dph. This information can provide biologists consistent means to produce this Centrachid and understand their gonadal development.

Aquaculture↗
USGS2021

The impact of COVID-19 on freshwater fisheries fieldwork and data collection

COVID-19 has affected almost every aspect of society including freshwater fisheries fieldwork. Our study quantified the effects of the pandemic on fisheries fieldwork in the United States. We administered a survey to fisheries chiefs in all 50 states to assess the pandemic’s impact on fisheries fieldwork. Of the 37 participants, 91% reported the pandemic affected their fieldwork and 92% adapted their sampling methods in response to the pandemic. Common adaptation strategies included using Personal Protective Equipment (PPE; 100%), practicing social distancing (97%), using smaller crews (82%), and developing contingency plans (51%). Based on the survey results, we identified potential challenges to adaptations and offered strategies to improve them. Strategies we identified include adopting novel data collection techniques, finding new positions for temporary employees, and publicly sharing contingency plans. Ultimately, this paper offers novel guidance on how fisheries professionals can best move forward with fieldwork during a time of crisis.

Fisheries Magazine↗
USGS2021

Development of aquaculture protocols and gonadal differentiation of red shiner

Developing detailed rearing methods and describing the onset of gonadal differentiation in Red Shiners Cyprinella lutrensis could facilitate the development of novel techniques to control or enhance populations, enable toxicology studies, and help construct bioassays. In this study, we develop and report aquaculture practices for Red Shiner that ensure consistent year-round production in laboratory settings and evaluate the timing of sexual differentiation via histological gonad examinations. Our methods resulted in a mean of 56.00% (SD = 8.98%) survival through the larval stages of development, and we obtained spawns from captive-reared Red Shiners 138 d posthatch. Red Shiners are gonochoristic, and both ovaries and testes differentiate directly from undifferentiated gonads. Ovaries begin to differentiate in females 45 d posthatch, while testes begin differentiating in males 105 d posthatch. This study provides in-depth protocols for the closed-cycle aquaculture of Red Shiners and describes the gonadal differentiation and development of both sexes.

Arizona↗
USGS2021

Development and evaluation of habitat suitability criteria for native fishes in three Arizona streams

Habitat loss is a main contributor to fish fauna declines in the southwestern USA. Several studies have defined stream-specific habitat conditions that support the growth and survival of native fish in Arizona to inform stream restoration efforts, yet general habitat use of most individual species across the region is not established. Therefore, we evaluated habitat use of four native fishes, Speckled Dace Rhinichthys osculus , Sonora Sucker Catostomus insignis , Desert Sucker Catostomus clarkii , and Longfin Dace Agosia chrysogaster , across three Arizona streams through the development of habitat suitability criteria (HSC). We developed both stream-specific and generalized HSC for each species. Generalized HSC were calculated as the combination of stream-specific HSC for each species. We then assessed the utility of generalized HSC through transferability among study streams. Also, past HSC studies have not considered the occurrence of nonnative species, so we tested whether the presence of nonnative fishes influenced native fish habitat use through logistic regression models. Fish and habitat data were collected along the Mogollon Rim in Arizona during the 2017 summer field season at base flow conditions. We established minimum microhabitat use for four native Arizona fish species through developing HSC. Most generalized criteria did not transfer among study streams due to variation in habitat availability and fish community structure. Logistic regression analysis showed that the presence of nonnative fishes was inversely related to the presence of two native fish species, which could have influenced habitat use of both species. The lack of transferability across streams as demonstrated in this study confirms that only HSC developed in the stream of interest or in similar undegraded streams with comparable fish communities should be used for restoration efforts. For projects to restore native fishes in streams where nonnative competitors will not dominate, the least degraded similar streams without coexisting nonnative fishes can guide restoration efforts.

Arizona↗
USGS2020

Inexpensive, underwater filming of rare fishes in high definition

Generating public interest in fish and their biology is often challenging. Many aquatic species are cryptic and largely invisible to the public. Therefore, increasing public awareness of cryptic fishes and elevating their visibility to broad audiences requires innovation. Inexpensive technological advancements now provide fisheries biologists, managers, and researchers with means never before possible for documenting fish in their natural habitat via underwater videography. We investigated cost efficient and simple methods for capturing and creating high quality, high definition, and informative underwater videos that could be used by people with little or no previous experience in videography. We tested 1) a variety of filming equipment including cameras and camera recording settings, lenses, batteries, and memory cards; 2) active and passive camera deployment techniques; and 3) a variety of free and paid postproduction software and compared them for ease of use, expense, and quality of output. Highest quality footage, i.e., highest resolution, clearest, and most stable, was obtained using a GoPro action camera deployed underwater in a stationary position mounted to a metal base plate using a combination of stock and macro lenses, and filming in 4K resolution at 30 frames per second. Final production videos were created using Adobe Premiere Pro.

Fisheries Magazine↗
USGS2020

Use of underwater videography to quantify conditions utilized by endangered Moapa Dace While spawning

Advances in underwater camera technology provide an affordable means to quantify the environmental conditions under which fish spawn. This information is important for investigating spawning ecology, managing habitat, or providing information for captive breeding programs. We deployed 12 modified security cameras underwater to identify environmental conditions related to the spawning behavior of the critically endangered Moapa Dace Moapa coriacea , a Mojave Desert stream-dwelling cyprinid that had never been observed spawning and that had fallen to a low of 459 individual fish 4 years prior to this study. Camera sites were selected systematically along the stream to represent the variety of conditions available. We divided the field of view in front of each camera into a grid, and we estimated both the available environment and the habitat over which Moapa Dace showed spawning behavior. From over 4,000 10-min video clips that were randomly selected for analysis, 13 spawning events were identified. Using nonparametric contingency table analyses, we found that Moapa Dace selected depths between 30 and 34 cm, water velocities between 0.11 and 0.17 m/s, cobble substrate, and overhead instream cover. Although the recorded sample size of spawning events was small (13), our sample represents a large proportion of events given that the world's entire population of Moapa Dace at the time was approximately 650 fish distributed over multiple kilometers of stream length. Environmental conditions identified by this study were replicated in laboratory facilities to successfully propagate Moapa Dace for the first time in captivity. These propagation methods are now used in a management setting by the Nevada Department of Wildlife to maintain a captive population of this rare fish. Camera methods can be effective in helping to identify spawning conditions where water clarity is sufficient.

Nevada↗
USGS2019

Using a mechanistic model to develop management strategies to cool Apache Trout streams under the threat of climate change

User‐friendly stream temperature models populated with on‐site data may help in developing strategies to manage temperatures of individual stream reaches that are subject to climate change. We used the field‐tested Stream Segment Temperature model (U.S. Geological Survey) to simulate how altering discharge, groundwater input, channel wetted width, and shade prevents the temperatures of White Mountain, Arizona, stream reaches from exceeding the thermal tolerance of Apache Trout Oncorhynchus apache , both under existing conditions and under a climate change scenario. Simulations suggested increasing shade, either through streamside planting of specific numbers and species of plants or by other means, would be most effective and feasible for cooling the stream reaches we studied. Ponderosa pine Pinus ponderosa and Douglas fir Pseudotsuga menziesii provided the most shade followed in order by Engelman spruce Picea engelmannii , Bebb's willow Salix bebbiana , Arizona alder Alnus oblongifolia , and finally coyote willow Salix exigua . Vegetation survival depends on the appropriateness of site conditions at present and under climate change, and planting in buffer strips minimizes additional water removal from the watershed through evapotranspiration. Alternative shading options, including thick sedge growth, shade cloth, or felled woody vegetation, may be considered when environmental conditions do not support plantings. Increasing groundwater input can cool streams, but additional sources are scarce in the region. Decreasing the width‐to‐depth ratio would succeed best on reaches with widths greater than 2.0 m. Increasing discharge from upstream may lower water temperature on reaches with an initial discharge greater than 0.5 m 3 /s. Existing models provide suggestions to cool stream reaches. Further development of accessible software packages that incorporate evaporation, fragmentation, and other projected climate change effects into their routines will provide additional tools to help manage climate change effects.

Arizona↗
USGS2019

Opportunities and barriers for endangered species conservation using payments for ecosystem services

Endangered species laws seek to prevent extinction by outlawing actions that may cause harm or lead to extinction. In doing so, these laws are sometimes criticized for limiting management flexibility and subjecting landowners to regulatory burdens. One proposed solution to this challenge is development of payment for ecosystem service (PES) programs. These programs provide an economic incentive to conserve endangered species by compensating landowners for the costs of conservation or forgoing other profitable uses of land and resources. To assess the utility of PES as a means of overcoming opposition to endangered species regulations, we surveyed ranch operators in Arizona and New Mexico facing new regulations related to endangered jaguars ( Panthera onca ). Our findings suggest that PES cannot overcome the perceived burdens of species protection regulations and are unlikely to increase collaboration between landowners and government agencies. PES approaches are only likely to succeed where there is strong fit between institutional design and resource manager preferences. In the context of endangered species, PES proponents must pay particular attention to institutional arrangements that reduce concerns about regulatory risk. To this end, to effectively meet endangered species conservation goals, we recommend: 1) framing PES programs as voluntary conservation incentives, 2) focusing incentives on healthy ecosystems rather than a single species, and 3) using private funding to support incentives. Under these circumstances, PES may be an effective endangered species conservation tool.

Biological Conservation↗