Leo G. Nico

Validation of eDNA surveillance sensitivity for detection of Asian carps in controlled and field experiments.

In many North American rivers, populations of multiple species of non-native cyprinid fishes are present, including black carp (Mylpharyngodon piceus), grass carp (Ctenopharyngodon idella), bighead carp (Hypophthalmichthys nobilis), silver carp (Hypophthalmichthys molitrix), common carp (Cyprinus carpio), and goldfish (Carassius auratus). All six of these species are found in the Mississippi River basin and tracking their invasion has proven difficult, particularly where abundance is low. Knowledge of the location of the invasion front is valuable to natural resource managers because future ecological and economic damages can be most effectively prevented when populations are low. To test the accuracy of environmental DNA (eDNA) as an early indicator of species occurrence and relative abundance, we applied eDNA technology to the six non-native cyprinid species putatively present in a 2.6 river mile stretch of the Chicago (IL, USA) canal system that was subsequently treated with piscicide. The proportion of water samples yielding positive detections increased with relative abundance of the six species, as indicated by the number of carcasses recovered after poisoning. New markers for black carp, grass carp, and a common carp/goldfish are reported and details of the marker testing to ensure specificity are provided.

Food habits of piranhas in the low llanos of Venezuela

Eight piranha species (Characidae: Serrasalminae) coexist in streams and pools of the western Orinoco River Basin Ilanos. The species differ in adult size, body form, and relative abundance. Examination of some 1300 specimens collected over a seven-year period (1979-1985) showed that food habits and diet diversity usually change with age. Small juveniles of the abundant and widespread Pygocentrus notatus eat microcrustaceans and aquatic insects. Above 40 mm standard length (SL), they take small fish and chunks of fish flesh. Small juveniles (20-80 mm SL) of six species (Serrasaimus altuvei, S. irritans, S. cf elongatus, S. rhombeus, S. caribe, and Pristobrycon cf striolatus) specialize in fins of other small fishes, but by 80 mm SL their diets shift to small fish, pieces of fish flesh, and fins. However, all sizes of Catoprion mento eat scales. Considerable diet overlap among different piranha species in the same size dasses suggests that plentiful food resources are not limiting. These savanna piranhas do not depend on fruits and seeds as has been reported for piranhas in flooded tropical rain forests.

Spatial and temporal patterns of nonindigenous fish introductions in the United States

Abstract In 1978 biologists in Gainesville, Florida, began compiling records on the distribution and status of nonindigenous fishes known in U.S. inland waters. The database, now in electronic format, currently contains approximately 17,000 records representing more than 500 nonindigenous fish taxa (i.e., species, hybrids, and unidentified forms). Of these taxa, 317 (61%) are native to the United States but have been introduced by humans into U.S. drainages outside their natural geographic ranges; 185 (35%) are fishes introduced from foreign countries; and 22 (4%) are hybrids. Of the introduced foreign fish taxa, 71 (38%) are species that have established (i.e., reproducing) or possibly established populations in open U.S. waters. The database is a useful tool for natural resource managers and other decision makers. Although we periodically revise records and constantly enter new ones, our database is fairly updated; thus, we are able to more thoroughly analyze patterns of introduction and the spread of n...

Detection limits of quantitative and digital PCR assays and their influence in presence‐absence surveys of environmental DNA

A set of universal guidelines is needed to determine the limit of detection (LOD) in PCR‐based analyses of low‐concentration DNA. In particular, environmental DNA (eDNA) studies require sensitive and reliable methods to detect rare and cryptic species through shed genetic material in environmental samples. Current strategies for assessing detection limits of eDNA are either too stringent or subjective, possibly resulting in biased estimates of species’ presence. Here, a conservative LOD analysis grounded in analytical chemistry is proposed to correct for overestimated DNA concentrations predominantly caused by the concentration plateau, a nonlinear relationship between expected and measured DNA concentrations. We have used statistical criteria to establish formal mathematical models for both quantitative and droplet digital PCR. To assess the method, a new Grass Carp (Ctenopharyngodon idella) TaqMan assay was developed and tested on both PCR platforms using eDNA in water samples. The LOD adjustment reduced Grass Carp occupancy and detection estimates while increasing uncertainty—indicating that caution needs to be applied to eDNA data without LOD correction. Compared to quantitative PCR, digital PCR had higher occurrence estimates due to increased sensitivity and dilution of inhibitors at low concentrations. Without accurate LOD correction, species occurrence and detection probabilities based on eDNA estimates are prone to a source of bias that cannot be reduced by an increase in sample size or PCR replicates. Other applications also could benefit from a standardized LOD such as GMO food analysis and forensic and clinical diagnostics.

Nests and Nest Habitats of the Invasive Catfish Hoplosternum littorale in Lake Tohopekaliga, Florida: A Novel Association with Non-native Hydrilla verticillata

Abstract Hoplosternum littorale is a South American catfish (Family Callichthyidae) first discovered in the United States in 1995 in Florida. The presence of H. littorale was documented from early 2002 to late 2003 in Lake Tohopekaliga (Kissimmee River Basin) in central Florida. In this paper, 22 H. littorale nests and nest sites are described. The characteristic bubble nests were present from late May to early September, with number of nests peaking in August when water stage and temperature were both high. Nest habitats (shallow, open marshes) and timing of nest construction (rainy season) were similar to what has been reported for H. littorale in its native range. Most nests (n = 14) were in areas dominated by Hydrilla verticillata and constructed largely from parts of this Asian aquatic plant, representing a unique association between two non-native species. Nevertheless, during August, as water levels increased, nesting shifted from H. verticillata-dominated communities to use of inshore grass zones dominated by Luziola fluitans. Knowledge of H. littorale nesting seasonality and habitat preferences may be useful for any efforts to control or manage this invasive fish.

Jamie Edward Thomerson (1935–2015)

J AMIE EDWARD THOMERSON, Ichthyologist and Professor Emeritus, Department of Biological Sciences, Southern Illinois University–Edwardsville (SIU-E), passed away quietly on 4 January 2015, in Austin, Texas, after a two-year battle with prostate cancer (Fig. 1). He is survived by his wife of 57 years, Kathleen Thomerson, his sons Austin and Eric Thomerson, his daughter Rachel Miller, a son-in-law Richard Miller, and a grandson Mason Miller. Jamie, or “Jim,” was a Texan and a country boy, and he was proud of both. He was born on 7 May 1935 in Menard, a small town in the Texas Hill Country. He grew up in that part of the world, as did his father and grandfather. Jim was the only child of Eula Lee (Martin) (1902–1998) and Roy Thomerson (1898–1976). Eula was a teacher until her marriage to Roy in 1926. In 1936, shortly after Jim’s birth, they purchased a ranch, the Old Walston Place, south of Menard and operated it as a goat and cattle ranch. In his adult life, Jim often amused students and friends by recounting stories about life on the ranch. One favorite tale described how his mother would regularly take the rifle out into their woods to hunt squirrels, which she then cleaned and fried, made gravy, and served as the family dinner. As a boy, Jim was tasked by his parents to complete a variety of ranch chores, for instance, burning the thorns off cacti so that the goats could more easily feed on the plants, and using a rifle to control ground squirrels and armadillos. The family ranch was also where Jim became fascinated with the natural world. He wandered the ranch and explored nearby streams and became enchanted with the native fish faunas. Young Jim was also an avid reader and was especially enthralled by the exploits of Edgar Rice Burroughs’ characters, Tarzan, John Carter, and Carson Napier. Jim graduated fromMenard High School in 1953 and then enrolled in the University of Texas where he majored in geology, earning a B.S. in 1957. While an undergraduate, Jim met fellow Texas student Kathleen Armstrong and the two married in Austin on 1 June 1957. Kathleen is a musician, having studied in Europe with the renowned composers and organists Jean Langlais in Paris and Flor Peeters in Antwerp. She subsequently distinguished herself professionally and academically as a church and concert organist, organ instructor, book author, and composer of widely played hymns. After military service in the National Guard, Jim taught biology and chemistry classes at Electra High School in Electra, Texas, for the 1958–59 school year. He then entered the graduate program at Texas Tech University in Lubbock where he conducted research in micropaleontology (Forminifera and Ostracoda), obtaining his M.S. in Geology in 1961. Still in his mid-20s, Jim decided to shift from geology to biology and was accepted into the graduate program at Tulane University. Jim’s wife Kathleen remembers their life in New Orleans with special fondness. At Tulane, Jim researched the hybridization, geographical variation, and distribution of the topminnows Fundulus notatus and F. olivaceus under the guidance of the legendary ichthyologist Royal D. Suttkus. Contemporary Suttkus students at Tulane during Jim’s tenure included Clyde Barbour, Glenn Clemmer, Salvador Contreras Balderas, and John Ramsey. Of course, being a Suttkus student involved intensive collection trips in the southeastern United States (Fig. 2). The Tulane Fish Collection houses specimens from 31 collections made by Jim in Fig. 1. Jamie E. Thomerson, 2011. Photo courtesy of Kathleen Thomerson.