Geology topics

James Candrl

Publications and source records attributed to James Candrl.

4 recordsLinked to original sources

USGS2026

Culturing emerging, imperiled, and poorly understood fishes

Most fish hatcheries and farms raise fish for food, to supply the bait and ornamental fish trades, or to create or enhance recreational and commercial fishing opportunities. Culture methods for these species are well established and are described in various chapters of this book. However, a growing number of facilities are responsible for cultivation of emerging, imperiled, or lesser-known species in support of rescue or recovery efforts. “Imperiled” may refer to species that have been formally listed as threatened or endangered under the U.S. Endangered Species Act (ESA) or analogous state regulations, or it may refer to populations or other groups that are considered at-risk for other reasons (e.g., fish living in drought-affected areas). The USFWS defines an endangered species as one that is in danger of extinction throughout all or a significant portion of its range, while a threatened species is one that is likely to become endangered in the foreseeable future (USFWS 2016b). There is often limited information available regarding the biology and propagation of these species. Many have never been propagated in captivity, and conventional hatchery techniques are not necessarily suited to their dietary needs, feeding habits, flow preferences, reproductive requirements, stress management, tank preferences, and use of structure (Rakes et al. 1999). To successfully maintain and propagate these fish, the fish culturist must identify the water quality, health and nutrition, spawning, and habitat needs of the species in question. Success often demands a painstaking process of mimicking natural conditions in the hatchery until suitable modifications can be developed or individuals can be habituated to more conventional rearing conditions. Rearing lesser-known species requires dedication and creativity as well as the application of new, sometimes experimental culture techniques to ensure a safe environment that provides for the well-being of imperiled species while in captivity.

Book chapter↗

USGS2022

Ontogenetic development of pallid sturgeon (Scaphirhynchus albus) and shovelnose sturgeon (Scaphirhynchus platorynchus) from hatch through yolk absorption

Sturgeons have a complex free-embryo period extending from hatch to the initiation of exogenous feeding. Although available for some sturgeon species of the genus Acipenser , descriptions of the developmental stages of free embryos of the genus Scaphirhynchus are lacking. We characterised the ontogenetic development of pallid sturgeon ( Scaphirhynchus albus ) and shovelnose sturgeon ( S . platorynchus ) free embryos from hatch through melanin plug expulsion. The rate of development was similar between Scaphirhynchus species among free embryos from 4 pallid sturgeon and 7 shovelnose sturgeon crosses reared separately in the laboratory at a mean temperature of 17.8°C. Free embryos required a mean of 18.2 days postfertilisation (DPF; 323.5 cumulative thermal units; CTU) to reach melanin plug expulsion for pallid sturgeon and 17.9 DPF (318.3 CTU) for shovelnose sturgeon. Free embryos of both species showed overlap in lengths among developmental stages indicating that length of free embryos alone is insufficient to estimate age. Description of pallid sturgeon and shovelnose sturgeon free-embryo development provides a template to develop more sophisticated models incorporating length and stage to estimate the age of field-collected specimens. Improved estimates of free-embryo developmental stage and age may aid in the identification of timing and location of spawning and better inform flow manipulation and habitat management actions tailored to increase survival of early life-stage pallid sturgeon.

Ecology of Freshwater Fish↗

USGS2020

Physical characteristics and simulated transport of pallid sturgeon and shovelnose sturgeon eggs

The imperiled pallid sturgeon (Scaphirhynchus albus) and closely related, but more common, shovelnose sturgeon (S. platorynchus) are believed to broadcast adhesive, demersal eggs in the current and over coarse substrate in turbid rivers of the North American midcontinent. It has been hypothesized that eggs settle immediately following fertilization, but ﬁeld conditions preclude direct observation. We conducted laboratory studies to characterize the diameter, shape, settling velocity, and speciﬁc gravity of pallid sturgeon and shovelnose sturgeon eggs. Based on these laboratory measurements, we then modeled the potential fate of pallid sturgeon eggs by considering these physical properties in the context of two ﬁeld sites where spawning has occurred. Although eggs of pallid sturgeon and shovelnose sturgeon were of a similar size and shape, shovelnose sturgeon eggs had slightly higher speciﬁc gravity and settling velocity. For representative hydraulic conditions at documented spawning sites in the mainstem Missouri and Lower Yellowstone Rivers, eggs of both species will likely be concentrated near the bed although some eggs may be distributed throughout the water column. Simulations of egg transport indicate that eggs may be transported up to several hundred meters downstream from spawning locations in the approximate length of time required for eggs to become adhesive. Estimates of egg transport presented here rely on simplifying assumptions about river hydraulics and limited understanding of how eggs interact with the complex substrates and ﬂow near the bed; results highlight the need for additional studies to evaluate the fate of eggs and fertilized embryos of both species.

Missouri River basin↗

USGS2016

Sensitivity of lake sturgeon ( Acipenser fulvescens ) early life stages to 2,3,7,8-tetrachlorodibenzo- P -dioxin and 3,3′,4,4′,5-pentachlorobiphenyl

The aquatic food web of the Great Lakes has been contaminated with polychlorinated biphenyls (PCBs) since the mid-20th century. Threats of PCB exposures to long-lived species of fish, such as lake sturgeon ( Acipenser fulvescens ), have been uncertain because of a lack of information on the relative sensitivity of the species. The objective of the present study was to evaluate the sensitivity of early–life stage lake sturgeon to 3,3′,4,4′,5-pentachlorobiphenyl (PCB-126) or 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD) exposure. Mortality, growth, morphological and tissue pathologies, swimming performance, and activity levels were used as assessment endpoints. Pericardial and yolk sac edema, tubular heart, yolk sac hemorrhaging, and small size were the most commonly observed pathologies in both TCDD and PCB-126 exposures, beginning as early as 4 d postfertilization, with many of these pathologies occurring in a dose-dependent manner. Median lethal doses for PCB-126 and TCDD in lake sturgeon were 5.4 ng/g egg (95% confidence interval, 3.9–7.4 ng/g egg) and 0.61 ng/g egg (0.47–0.82 ng/g egg), respectively. The resulting relative potency factor for PCB-126 (0.11) was greater than the World Health Organization estimate for fish (toxic equivalency factor = 0.005), suggesting that current risk assessments may underestimate PCB toxicity toward lake sturgeon. Swimming activity and endurance were reduced in lake sturgeon survivors from the median lethal doses at 60 d postfertilization. Threshold and median toxicity values indicate that lake sturgeon, like other Acipenser species, are more sensitive to PCB and TCDD than the other genus of sturgeon, Scaphirhynchus , found in North America. Indeed, lake sturgeon populations in the Great Lakes and elsewhere are susceptible to PCB/TCDD-induced developmental toxicity in embryos and reductions in swimming performance.

Environmental Toxicology and Chemistry↗