Geology topics

Richard A. Snow

Publications and source records attributed to Richard A. Snow.

13 recordsLinked to original sources

USGS2025

Summary of first daily ring formation in otoliths of freshwater fishes in the continental United States

Daily ring counts in young-of-the-year fishes are important for estimating important vital rates, such as growth, mortality, and timing of hatch. To accurately estimate some of these rates, the timing of the first daily ring must be estimated accurately. Variation in the timing of the first daily ring can be attributed to many factors, including biology of the species and experience of laboratory personnel. The amount of variation and the degree of differences, however, have not been quantified, hindering the utility of daily ring information to provide accurate estimates of spawning and hatching times. We conducted a review of studies for freshwater fishes in the continental United States to quantify variation in daily ring validation studies as it relates to timing of the first ring. We found 40 studies representing 12 orders, 15 families, and 35 species. Most studies investigated rings in the sagittae, although the lapilli and asterisci were also used for a few species. Variation in the timing of the first ring formation was evident, but not consistent among otolith types or groups of fishes. The first daily ring in sagittae varied from 31 d before hatch to 150 d after hatch. First daily ring formation in lapilli was consistent within families but formed before hatch in some families of fish and after hatch in other families. The first daily ring in asterisci were near universally formed after hatch, with the exception of one species of sturgeon (family Acipenseridae). Only three of the nine species where replicate studies existed were found to exhibit consistent first ring formation timing. Such findings suggest that differences among laboratories and personnel may play a larger role than differences among species or populations when inconsistent first ring formation timing results occur. For most species, error surrounding differences in timing formation is about 1 week, except for Salmoniformes, where error was up to a 150-d difference. Incorporating species biology along with uncertainty in temporal estimates based on otolith chronology would aid interpretation of results in field situations.

continental United States↗

USGS2023

Validation and comparison of age estimates for Smallmouth Buffalo in Oklahoma based on otoliths, pectoral fin rays, and opercula

With an increased interest in nongame fishes such as buffalofishes (Catostomidae, Ictiobus ), there is a need for better foundational data on their life history. Bigmouth Buffalo I. cyprinellus , for example, have been found to live for more than a century. Age estimates for other sucker species have similarly suggested long life spans, but validation studies as reference points are often lacking. We conducted a 3-year study on Smallmouth Buffalo I. bubalus in Oklahoma to validate annual increments on three hard part structures (otoliths [lapilli], pectoral fin rays, and opercula) typically used for age estimation. We marked wild fish with oxytetracycline (OTC) injection and stocked those fish into a hatchery pond to create a population of fish with known times since marking. Furthermore, reproduction in the pond allowed us to validate annulus formation in young fish. We analyzed 117 fish and found that otoliths were more reliable, precise, and accurate than the other two structures for detecting OTC marks and counting annuli. Age estimates, from 1 to 61 years, were greatest when otoliths were used, with 99% of estimates corresponding to known time since marking or known age. Otoliths appear to be the only reliable structure for accurately estimating the age of Smallmouth Buffalo within 1 year of actual age, and their use indicates that this species can live for more than six decades in Oklahoma.

North American Journal of Fisheries Management↗

USGS2023

Viability of side-scan sonar to enumerate Paddlefish, a large pelagic freshwater fish, in rivers and reservoirs

Recreational-grade side-scan sonar (SSS) has become an invaluable tool for inland fisheries, particularly when characterizing underwater habitat, but it is being increasingly used for enumerating large-bodied (> 1 m total length [TL]) aquatic fauna. We used SSS in river and reservoir environments to evaluate methods for identifying and counting Paddlefish Polyodon spathula , a large pelagic planktivore of recreational and economic importance that can exceed 2 m in length and weigh over 70 kg. We assessed accuracy and precision among readers to identify Paddlefish by assigning confidence scores (1–3; with 3 being more confident) to sonar images of a ballistics-gel filled fiberglass replica Paddlefish. Readers varied in their confidence scores for the replica Paddlefish and no reader could identify the target beyond 25 m from the transducer. Afterwards, we used SSS to survey several kilometers of a reservoir during summer residency and a large river during springtime spawning migrations. Two readers counted Paddlefish images in the SSS recordings and we estimated population size in the surveyed area with distance sampling. In the reservoir, the number of Paddlefish counted ranged from 172 to 184. In the river, the number of Paddlefish counted ranged from 165 to 617. The exponential model of distance was most-supported for detection in both environments, except there was support for a half-norm distribution for one reader in the river. In the reservoir, abundance estimates were statistically similar between readers at approximately 1500 (7/ha) in the total scanned area. In the river, similar abundance estimates were obtained with the half-norm model from one reader compared to the exponential model of the other reader, resulting in approximately 1500 individuals (30/ha) in the surveyed area. The application of SSS to count Paddlefish has some clear advantages to traditional methods, such as gill netting, and can be done at multiple times of the year. Distance sampling methods compensated for differences in counts among readers, indicating distance sampling can produce similar abundance estimates even when variation in counts exists among readers.

Oklahoma↗

USGS2021

Morphology and composition of Goldeye (Hiodontidae; Hiodon alosoides) otoliths

We provide up-to-date morphological and compositional data on otoliths of the osteoglossomorph Goldeye ( Hiodon alosoides ). Using computed tomography (CT) X-ray, we documented the location of each of the three pairs of otoliths (lapilli, sagittae, and asterisci) in relation to the swim bladder, which extended forward in close proximity to the sagittae and asterisci. The lappili were the largest otoliths in terms of surface area and volume, but the sagittae were highly modified, appearing spiral in shape when viewed dorsally, with a surface area to volume ratio more than double that of the lapilli. Using scanning electron microscopy, the surface of each otolith was viewable in great detail, and small otoconia (~10.5 μm diameter) were observed on each, but were most numerous on the sagittae. On scanning electron micrographs, the sagittae appeared to be bi-lobed, with asymmetrical lobes each oriented in the same general direction. Using neutron and X-ray diffraction methods, we found three polymorphs of calcium carbonate crystals (aragonite, vaterite, and calcite), sometimes all within the same otolith. However, in general, lapilli and sagittae were composed predominately of aragonite whereas asterisci were composed chiefly of vaterite. With these results, we provide information on a unique species, whose inclusion in future studies would benefit our understanding of fish hearing, fish evolution, and fisheries ecology.

Journal of Morphology↗

USGS2020

Feeding ecology of age-0 gar at Lake Texoma inferred from analysis of stable isotopes

Conservation and restoration of gar (Lepisosteidae) populations in North America are increasingly of interest to fisheries managers. Alligator Gar Atractosteus spatula are being stocked as age-0 fish in efforts to re-establish extirpated populations. However, gars are known to be highly cannibalistic in hatcheries, suggesting that age-0 Alligator Gar introduced into natural habitats may face predation pressures from other gar species, limiting the likelihood of released fish recruiting to the population. Furthermore, introduced age-0 gar may not have the proper prey resources for rapid growth that would facilitate recruitment to adulthood. Texoma Reservoir, located on the Oklahoma–Texas border, hosts four native gar species, including the Alligator Gar, whose population is supported by supplemental stocking of age-0 fingerlings. We investigated feeding by age-0 gar to obtain a baseline level of trophic ecology for this group of fishes, including the potential for poststocking cannibalism. Food webs were reconstructed via analysis of carbon (δ 13 C) and nitrogen (δ 15 N) isotopes using Bayesian mixing model approaches. Isotopic values for age-0 fish of all four gar species were similar. Invertebrates represented a large fraction of the diet for all gars, followed by Common Carp Cyprinus carpio and Grass Carp Ctenopharyngodon idella . Competitive interactions among Bluegill Lepomis macrochirus , White Bass Morone chrysops , White Crappie Pomoxis annularis , and young gar may occur for invertebrates, shads Dorosoma spp., and Western Mosquitofish Gambusia affinis but are likely short-lived due to the rapid growth of age-0 gar after their transition to piscivory. Trophic position of age-0 Alligator Gar, Longnose Gar Lepisosteus osseus , and Spotted Gar Lepisosteus oculatus was positively related to TL, but this relationship was not observed for Shortnose Gar Lepisosteus platostomus . In Texoma Reservoir, the four native gar species, including stocked Alligator Gar, appear to have adequate food resources for recruitment, with little indication of within-family or interspecific predation. This suggests that stocked Alligator Gar quickly acclimated to their new environment.

North American Journal of Fisheries Management↗

USGS2020

Effects of temperature on hatching rate and early development of alligator gar and spotted gar in a laboratory setting

Water temperature influences both morphological and physiological development in fishes. However, the effects of water temperature on the early development of Alligator Gar Atractosteus spatula and Spotted Gar Lepisosteus oculatus are not well understood. Both gar species were collected from natural environments and spawned in a hatchery setting. After spawning, fertilized embryos were collected and transferred to the Oklahoma Fishery Research Laboratory, where the embryos (50–72 embryos/treatment) were placed into one of five water temperature treatments (15.5, 20.0, 23.8, 27.5, and 32.2°C) and observed over time to estimate the time to hatch and the time to reach the free-swimming stage. Both species showed an inverse relationship between temperature and the timing of hatch and advancement to free-swimming fingerlings for all treatments. In addition, Alligator Gar embryos did not develop at the coldest water temperature tested, and Alligator Gar juveniles held at the warmest temperature tested were observed with developmental abnormalities, potentially affecting their survival. The same temperature extremes had no comparable negative effect on Spotted Gar. The results of this study are useful for understanding early life history dynamics of these two species in their natural environments and can also be used by hatchery managers who are seeking to optimize their production protocols.

North American Journal of Fisheries Management↗

USGS2019

Marking otoliths of Alligator Gar by immersion in oxytetracycline

Alligator Gar Atractosteus spatula are increasingly being stocked to restore populations, making the need to identify stocked individuals important for monitoring. Oxytetracycline (OTC) immersion allows for large numbers of fish to be marked simultaneously, thus eliminating the need to handle fish individually, but protocols for doing so have not been investigated fully for this species. In this study, we sought to identify dosages of OTC (concentration and duration of exposure) that would successfully mark juvenile Alligator Gar while minimizing mortality as a result of the marking procedures. Juvenile Alligator Gar (38 ± 4.4 mm [mean ± SE]) were collected from raceways at Tishomingo National Fish Hatchery 18–22 d after hatch and were marked during transport to the Oklahoma Fishery Research Laboratory. Ten individuals per treatment (360 total individuals) were randomly placed into one of three replicates containing one of four concentration × duration combinations of Pennox 343 OTC solution. Juvenile Alligator Gar were exposed to an OTC concentration of 0 (control), 500, 600, or 700 mg/L for a duration of 4, 5, or 6 h. Asteriscus, lapillus, and sagittal otoliths were examined for mark presence at 14 d postexposure by using fluorescent microscopy. The OTC concentration and duration both affected mean mark quality similarly among otolith types. Mortality increased with increasing OTC concentration, suggesting that a balance between concentration and duration is needed to achieve marking goals. Based on our findings, batch marking of Alligator Gar was successful at OTC concentrations from 500 to 700 mg/L for 4–6 h, although immersion at 500 mg/L for 6 h and 600 mg/L for 4–6 h produced the best balance between high mark quality and low associated mortality.

North American Journal of Fisheries Management↗

USGS2018

Posthatch development of otoliths and daily ring genesis in age-0 Spotted Gars

Gars (Lepisosteidae) are increasingly being managed as top-level predators that are important to overall ecosystem health. Given the paucity of information on early life history for many species, additional early life history data would aid in gar conservation and management. Daily rings in otoliths are useful for determining many early life history parameters, such as growth rates and the date of hatch, but properly interpreting these structures requires additional information on otolith formation. Gars represent an ancient lineage, and their otoliths are unlike those of most teleost fishes, having multiple nuclei and being covered on the surface with very small otoconia. We used computed tomography X-ray scanning and oxytetracycline (OTC) marking of a series of known-age fish from hatch through 10–12 d posthatch (dph) to understand the formation of otoliths in the Spotted Gar Lepisosteus oculatus , a species that is of management concern in several parts of its range in North America. The sagittae and lapilli each began as loose associations of otoconia at hatch; they fused and hardened into single crystals by 4 dph, in concert with the transition from attached larvae to free-swimming juveniles. Asteriscus otoliths were not observed in any of the individuals examined through 12 dph. The OTC marks were not observed on individuals treated at hatch, and variable marks were detected at 1–5 dph. By 6 dph, 100% of individuals exhibited OTC marks on sagittae and lapilli. Daily rings could not be discerned until fish were marked at 4 dph, after which daily age estimates increased linearly with fish age. Results of this study verify that in Spotted Gars, otoliths (sagittae and lapilli) and their daily rings form several days after hatch, in relation to the transition from sessile, attached larvae to free-swimming juveniles.

Oklahoma↗

USGS2018

Precision of four otolith techniques for estimating age of white perch from a thermally altered reservoir

The White Perch Morone americana is an invasive species in many Midwestern states and is widely distributed in reservoir systems, yet little is known about the species' age structure and population dynamics. White Perch were first observed in Sooner Reservoir, a thermally altered cooling reservoir in Oklahoma, by the Oklahoma Department of Wildlife Conservation in 2006. It is unknown how thermally altered systems like Sooner Reservoir may affect the precision of White Perch age estimates. Previous studies have found that age structures from Largemouth Bass Micropterus salmoides and Bluegills Lepomis macrochirus from thermally altered reservoirs had false annuli, which increased error when estimating ages. Our objective was to quantify the precision of White Perch age estimates using four sagittal otolith preparation techniques (whole, broken, browned, and stained). Because Sooner Reservoir is thermally altered, we also wanted to identify the best month to collect a White Perch age sample based on aging precision. Ages of 569 White Perch (20–308 mm TL) were estimated using the four techniques. Age estimates from broken, stained, and browned otoliths ranged from 0 to 8 years; whole‐view otolith age estimates ranged from 0 to 7 years. The lowest mean coefficient of variation (CV) was obtained using broken otoliths, whereas the highest CV was observed using browned otoliths. July was the most precise month (lowest mean CV) for estimating age of White Perch, whereas April was the least precise month (highest mean CV). These results underscore the importance of knowing the best method to prepare otoliths for achieving the most precise age estimates and the best time of year to obtain those samples, as these factors may affect other estimates of population dynamics.

Oklahoma↗

USGS2017

Otolith marking of juvenile shortnose gar by immersion in oxytetracycline

Oxytetracycline (OTC) has been used to mark a variety of fish species at multiple developmental stages; however, there is little information on batch-marking Lepisosteidae. Juvenile Shortnose Gar Lepisosteus platostomus (53 ± 3 mm TL) were seined from an Oklahoma State University research pond and transported to the Oklahoma Fishery Research Lab. Juvenile Shortnose Gar were exposed to a range of OTC concentrations—0, 500, 600, and 700 mg/L—for 4, 5, or 6 h. Lapillus and sagitta otoliths were examined 14 d postexposure for mark presence and evaluation using fluorescent microscopy. Overall, 93.3% of otoliths exposed to OTC exhibited a mark. Concentration of OTC affected the mean mark quality, whereas duration and otolith type examined did not. However, as concentration increased, so did mortality, suggesting a balance is needed to achieve marking goals. Based on our findings, batch marking of Shortnose Gar can be successful at OTC concentrations from 500 to 700 mg/L for 4–6 h, although mark quality may vary and mortality rates increase at the higher concentrations and longer durations.

North American Journal of Fisheries Management↗

USGS2017

Validation of daily increments periodicity in otoliths of spotted gar

Accurate age and growth information is essential in successful management of fish populations and for understanding early life history. We validated daily increment deposition, including the timing of first ring formation, for spotted gar (Lepisosteus oculatus) through 127 days post hatch. Fry were produced from hatchery-spawned specimens, and up to 10 individuals per week were sacrificed and their otoliths (sagitta, lapillus, and asteriscus) removed for daily age estimation. Daily age estimates for all three otolith pairs were significantly related to known age. The strongest relationships existed for measurements from the sagitta (r2 = 0.98) and the lapillus (r2 = 0.99) with asteriscus (r2 = 0.95) the lowest. All age prediction models resulted in a slope near unity, indicating that ring deposition occurred approximately daily. Initiation of ring formation varied among otolith types, with deposition beginning 3, 7, and 9 days for the sagitta, lapillus, and asteriscus, respectively. Results of this study suggested that otoliths are useful to estimate daily age of spotted gar juveniles; these data may be used to back calculate hatch dates, estimate early growth rates, and correlate with environmental factor that influence spawning in wild populations. is early life history information will be valuable in better understanding the ecology of this species.

Journal of the Southeastern Association of Fish an↗

USGS2016

Effects of a growth check on daily age estimates of age-0 alligator gar

Accurate age and growth information is essential for a complete knowledge of life history, growth rates, age at sexual maturity, and average life span in fishes. Alligator gar are becoming increasingly managed throughout their range and because this species spawns in backwater flooded areas, their offspring are prone to stranding in areas with limited prey, potentially affecting their growth. Because fish growth is tightly linked with otolith growth and annulus formation, the ability to discern marks not indicative of annuli (age checks) in alligator gar would give managers some insight when estimating ages. Previous studies have suggested that checks are often present prior to the first annulus in otoliths of alligator gar, affecting age estimates. We investigated check formation in otoliths of alligator gar in relation to growth and food availability. Sixteen age-0 alligator gar were marked with oxytetracycline (OTC) to give a reference point and divided equitably into two groups: a control group with abundant prey and an experimental group with limited prey. The experimental group was given 2 g of food per week for 20 days and then given the same prey availability as the control group for the next 20 days. After 40 days, the gar were measured, sacrificed, and their sagittae removed to determine if checks were present. Checks were visible on 14 of the 16 otoliths in the experimental group, associated with low growth during the first 20 days when prey was limited and accelerated growth after prey availability was increased. No checks were observed on otoliths of the control group, where growth and prey availability were consistent. Age estimates of fish in the control group were more accurate than those in the experimental group, showing that fish growth as a function of prey availability likely induced the checks by compressing daily ring formation.

Journal of the Southeastern Association of Fish an↗

USGS2016

A comparison of lead lengths for mini-fyke nets to sample age-0 gar species

Mini-fyke nets are often used to sample small-bodied fishes in shallow (<1 m depth) water, especially in vegetated shoreline habitats where seines are ineffective. Recent interest in gar (Lepisosteidae) ecology and conservation led us to explore the use of mini-fyke nets to capture age-0 gar and specifically how capture is affected by lead length of the fyke net. In the summers of 2012, 2013, and 2015, mini-fyke nets with two different lead lengths (4.57 m and 9.14 m) were set at random sites in backwaters and coves of the Red River arm of Lake Texoma, Oklahoma. Mean CPUE (catch-per-unit-effort; number per net night) was significantly lower for mini-fyke nets with short leads (0.52) compared to those with long leads (1.51). Additionally, Spotted Gar ( Lepisosteus oculatus ) were captured at a higher rate than the other three gar species present in Lake Texoma, although this could have been an artifact of sampling location. We found that differences in length-frequency of captured gar between gear types were nearly significant, with total length ranging from 47mm to 590mm. Mini-fyke nets with longer leads increased the efficiency of sampling for age-0 gar by increasing catch rate without affecting estimates of other population parameters and appear to be useful for this purpose.

Proceedings of the Oklahoma Academy of Science↗