Jan Jeffrey Hoover

Observations of Swimming Ability in Shovelnose Sturgeon (Scaphirhynchus platorynchus)

ABSTRACT Swimming performance and behavior of five adult (57—69 cm fork length) shovelnose sturgeon, Scaphirhynchus platorynchus, were studied in a 945-L swim tunnel at 16° C. Fifteen-minute critical swimming speeds ranged from 65 to 116 cm s−1. Sturgeon swam volitionally at low speeds (5—30 cm s−1), but at higher speeds (40—120 cm s−1) sturgeon alternated between active swimming and appressing themselves to the bottom of the tunnel. This second behavior is enhanced by sturgeon morphology—streamlined body shape, flat rostrum, and large pectoral fins. It allows shovelnose sturgeon to exploit river bottoms as a refugia from current and maintain position in high velocities.

Effect of Pectoral Fin Ray Removal on Station-Holding Ability of Shovelnose Sturgeon

Abstract The effect of fin ray removal on swimming performance was evaluated for shovelnose sturgeon Scaphirhynchus platorynchus from the lower Mississippi River. Immediately upon collection, the marginal pectoral fin ray was removed from some fish, and others were left unclipped as a control group. Fish were promptly returned to the laboratory and held in 1,300-L recirculating tanks at 21-26°C. After a minimum recovery time of 48 h, individual fish were placed in a 1,000-L, Brett-type swim tunnel, and their ability to maintain station in flowing water by swimming, skimming, or substrate appression was tested by subjecting fish to increasing speeds beginning at 10 cm/s. After a 60-min swimming bout, speed was increased by 10 cm/s. This was repeated until the fish could no longer maintain station. Fin ray removal had no significant effect on critical station-holding speed (CSHS). The CSHS (mean ± SE) of fin-ray clipped fish was 60.1 ± 4.2 cm/s, and that of unclipped fish was 59.2 ± 3.0 cm/s. Correlation an...

Stranding Potential of Young Fishes Subjected to Simulated Vessel-Induced Drawdown

Abstract During early life stages, fish in the Mississippi River system may become stranded by shoreline drawdowns induced by the passage of commercial vessels. We examined the stranding of larval shovelnose sturgeon Scaphirhynchus platorynchus, paddlefish Polyodon spathula, and bigmouth buffalo Ictiobus cyprinellus and of juvenile blue catfish Ictalurus furcatus, largemouth bass Micropterus salmoides, and bluegill Lepomis macrochirus in a laboratory flume. Stranding was measured at three vertical drawdown rates (0.76, 0.46, and 0.21 cm/s) and two bank slopes (1:5 and 1:10). Blue catfish, shovelnose sturgeon, and paddlefish were not tested at both bank slopes. Susceptibility to stranding varied among species and was independent of drawdown rate. At a slope of 1:5, shovelnose sturgeons had the highest stranding percentage (66.7%), followed by paddlefish (38.0%), bluegills (20.0%), bigmouth buffalo (2.2%), and largemouth bass (0.0%). At 1:10, blue catfish had the highest stranding percentage (26.7%), follow...

Swimming Performance of the Topeka Shiner (Notropis topeka) an Endangered Midwestern Minnow

Abstract The Topeka shiner (Notropis topeka) is imperiled by extensive changes in stream hydrology. Responses of shiners to changes or variation in stream hydraulics, however, have not been quantified, hampering conservation efforts. We quantified swimming endurance and behavior for Topeka shiners in a laboratory swim tunnel. Sustained swimming (>200 min) was observed at water velocities of 30–40 cm/s. Prolonged and burst swimming (approximately 10 min to less than 0.1 min) was observed at water velocities of 40–75 cm/s and endurance was negatively correlated with water velocity. Larger individuals (4.4–5.5 cm standard length) exhibited greater sustained swimming ability than smaller individuals (3.0–4.2 cm standard length). Oral grasping of wire mesh within the swim tunnel was frequently employed at moderate water velocities (35–50 cm/s); this behavior may limit downstream displacement of shiners during freshets. Topeka shiners are capable of swimming speeds faster than water velocities which they typically inhabit. Fishways and culverts, therefore, may be employed to facilitate dispersal and recolonization. Swimming endurance data are used to determine optimal size and water velocities for such structures.

Oral Grasping: A Distinctive Behavior of Cyprinids for Maintaining Station in Flowing Water

Abstract We examined oral grasping behavior, a unique and relatively unknown method of maintaining station against flow, in nine species of North American cyprinids to determine whether oral grasping was used by a range of cyprinid species and to further investigate the relationship between oral grasping and water velocity. Fish were subjected to a stepwise increasing velocity test in a 100-liter laboratory swim tunnel that had wire mesh (0.6-mm diameter) attached to a flow filter serving as the grasping substrate. Frequency and duration of oral grasping events were noted for a particular fish during each velocity increment. We observed 608 grasping events, and oral grasping behavior was exhibited by all nine species examined. Mean number of grasping events was high (28.4/trial) for Cyprinella venusta, intermediate (approximately 18/trial) for Cyprinella camura, and Notropis longirostris, and low (< 5/trial) for Notropis texanus, Notropis maculatus, and Notropis wickliffi. Although critical swimming speed varied among species, the water velocity at which oral grasping behavior initially appeared (threshold grasping velocity), expressed as a percentage of critical swimming speed, was approximately 70–80% for most species tested. Oral grasping may be triggered by the onset of muscular fatigue, and is an attempt by minnows to maintain position in water velocities exceeding aerobic swimming ability. We speculate that minnows in lotic environments use oral grasping when high, energetically demanding water velocities are unavoidable, such as during a flood.

Stranding of Spawning Run Green Sturgeon in the Sacramento River: Post-Rescue Movements and Potential Population-Level Effects

Abstract The lower portion of the Sacramento River, California, has been highly engineered to protect low-lying surrounding communities from annual flood events. While engineered floodplains have provided adequate protection for the surrounding communities, there remain unintended consequences to migratory fish that become stranded during high flow events. In April 2011, we rescued 24 threatened Green Sturgeon Acipenser medirostris that were stranded in two flood diversions along the Sacramento River. We tagged these 24 Green Sturgeon with acoustic tags and analyzed their survival and migration success to their spawning grounds. Additionally, we provided a population viability analysis to show the potential impacts of stranding and the benefits of conducting rescues at the population level. We found that 17 of these 24 individuals continued their upstream migration to the spawning grounds. Modeling suggests that recurrent stranding of a similar magnitude without rescue could affect the long-term viability...

Observations of silver carp (Hypophthalmichthys molitrix) planktivory in a floodplain lake of the Lower Mississippi River basin.

ABSTRACT The invasive silver carp (Hypophthalmichthys molitrix) has become pervasive in much of the Mississippi River, its tributaries, and in connected lakes and wetlands. As an increasingly abundant planktivore, it competes directly for food with native fishes. Its greatest impact may be in connected backwater lakes and wetlands, which due to their high primary production serve as critical sites for feeding and growth of many fishes. To assess the impact that silver carp may have on one such system, we examined the composition of plankton samples and of alimentary tract (gut) contents of collected from an oxbow lake in Mississippi, Forest Home Chute. Through an occasional connection to the Mississippi River, Forest Home Chute was invaded by silver in winter 2005, after which the river and lake became disconnected for about two years. In the water-column, the most common types of phytoplankton were euglenoid algae, cyanobacteria, and diatoms. The vast majority of zooplankton was rotifers with densities sometimes exceeding 7,000 organisms per liter. Very high concentrations of phytoplankton in the gut, relative to in the water-column, indicate substantial consumption of phytoplankton production. In October 2006, euglenoid phytoplankters were a much greater, and cyanobacteria a much lesser, proportion of prey in the fish gut compared to their proportions in the water-column. In December, however, there was no evidence of selective consumption by the silver carp population. Some of the phytoplankters observed in the lowest portion of the gut, including pinnate diatoms and euglenoid algae, were motile, indicating they had survived transit through the 5 to 7-m long gut tract. There was no evidence of rotifer survival of gut passage. By its high consumption of plankton, possible selective planktivory, and differential digestion of consumed phytoplankton and zooplankton, the silver may be altering the food web structure of these important connected lakes.

NONLETHAL ACQUISITION OF LARGE LIVER SAMPLES FROM FREE-RANGING RIVER STURGEON (SCAPHIRHYNCHUS) USING SINGLE-ENTRY ENDOSCOPIC BIOPSY FORCEPS

Harvesting of liver samples for toxicologic and other laboratory analyses is frequently undertaken in free-ranging fish to evaluate accumulations of various pollutants and chemicals. However, commonly used, lethal techniques for collecting liver tissues are unacceptable when dealing with protected species. We report the use of a nonlethal, single-entry, endoscopic technique using saline infusion to examine and collect large liver samples using optical biopsy forceps from 16 free-ranging sturgeon (Scaphirhynchus spp.) during 25 and 27 January 2010. Under tricaine methanesulfonate anesthesia and following the introduction of the optical biopsy forceps (with a 5-mm telescope) through a 1–2-cm ventral midline skin incision, liver examination and collection of biopsies averaging 0.9 g, ranging up to 1.4 g, and representing up to 12% of total liver tissue were successful. All fish made uneventful recoveries and necropsy examinations the following day failed to indicate any significant hemorrhage or iatrogenic trauma. We recommend the use of large optical biopsy forceps as a practical, nonlethal alternative for collection of large liver biopsies from sturgeon and other fish.

Rostrum Size of Paddlefish (Polyodon spathula)(Acipenseriformes: Polyodontidae) from the Mississippi Delta

Abstract Paddlefish rostra vary in size and shape suggesting existence of multiple morphotypes. Measurements for 118 adult paddlefish from a Mississippi delta river indicate that the rostrum becomes shorter, narrower, and straighter as a fish grows. Negative allometric growth of rostra, and high variation within size classes, may obscure existence of distinctive rostral morphotypes.

Maximum swim speed of migrating sea lamprey (Petromyzon marinus) : reanalysis of data from a prior study

BACKGROUND: Sea Lamprey (Petromyzon marinus) are predatory and destructive animals superficially similar to fish (Figure 1); however, Sea Lamprey lack a well-developed boney skeleton, jaws, and paired fins and, as a result, are classified separately from true fishes (Moyle and Cech 1982). History, impacts, and management of invasive populations in the Great Lakes are well documented (Cox 1999; Rapai 2016; Egan 2017). Construction of the Erie Canal in 1825 and the Welland Canal in 1831 connected, respectively, the Hudson River and the Lake Ontario-St. Lawrence River to Lake Erie, and provided Sea Lamprey in the North Atlantic access to the upper Great Lakes previously isolated by Niagara Falls. Lamprey were subsequently detected in Lake Erie in 1921, Lake Michigan in 1936, Lake Huron in 1937, and Lake Superior in 1938. By 1946, lamprey populations were abundant and stocks of native salmonids and whitefishes had declined due to predation. Control programs were initiated in the 1950s and continue at present. These programs use combinations of traps, pheromones, lampricides, reproductive sterilization of adults, and physical barriers to reduce or prevent successful migration, reproduction, and recruitment of lamprey in their natal tributary streams. Barriers may be electric fields, simple dams (or sieves), vertical drops, or areas of fast-flowing water.