Theresa M. Schreier

Efficacy of formalin, hydrogen peroxide, and sodium chloride on fungal-infected rainbow trout eggs

Abstract Antifungal agents are essential for the maintenance of healthy stocks of fish and their eggs in intensive aquaculture operations. In the USA, formalin is the only fungicide approved for use in fish culture. However, hydrogen peroxide and sodium chloride have been granted low regulatory priority drug status by the United States Food and Drug Administration (FDA) and their use is allowed. We evaluated the efficacy of these fungicides for controlling fungal infections on rainbow trout eggs. A pilot study was conducted to determine the minimum water flow rate required to administer test chemicals accurately in Heath incubators. A minimum water flow rate of 7.6 1 min −1 was necessary to maintain treatment concentrations during flow-through chemical exposures. The antifungal activity of formalin, hydrogen peroxide, and sodium chloride was evaluated by treating uninfected and 10% fungal-infected ( Saprolegnia parasitica ) rainbow trout eggs ( Oncorhynchus mykiss ) for 15 min every other day until hatch. There were no significant differences among treatments in percent hatch or final infection for uninfected eggs receiving prophylactic chemical treatments. Eggs of the negative control group (uninfected and untreated) had a mean hatch exceeding 86%. All chemical treatments conducted on the infected egg groups controlled the spread of fungus and improved hatching success compared with the positive control groups (infected and untreated). Formalin treatments of 1000 and 1500 μl l −1 and hydrogen peroxide treatments of 500 and 1000 μl l −1 were the most effective. Sodium chloride treatments of 30 000 mg l −1 improved fry hatch, but the compound was less effective at inhibiting fungal growths compared with hydrogen peroxide and formalin treatments.

Effect of Species, Life Stage, and Water Temperature on the Toxicity of Hydrogen Peroxide to Fish

Abstract Hydrogen peroxide is a drug of low regulatory priority status that is effective in treating fish and fish eggs infected by fungi. However, only limited information is available to guide fish culturists in administering hydrogen peroxide to diseased fish. Laboratory tests were conducted to determine (1) the sensitivity of brown trout Salmo trutta, lake trout Salvelinus namaycush, fathead minnow Pimephales promelas, walleye Stizostedion vitreum, channel catfish Ictalurus punctatus, and bluegill Lepomis machrochirus to hydrogen peroxide treatments; (2) the sensitivity of various life stages of rainbow trout Oncorhynchus mykiss to hydrogen peroxide treatments; and (3) the effect of water temperature on the acute toxicity of hydrogen peroxide to three fish species. Fish were exposed to hydrogen peroxide concentrations ranging from 100 to 5,000 μL/L (ppm) for 15-min or 45-min treatments every other day for four consecutive treatments to determine the sensitivity of various species and life stages of fi...

Safety of formalin treatments on warm- and coolwater fish eggs

Abstract Formalin is widely used for treating fungal infections of fish eggs in intensive aquaculture operations. The use of formalin in the United States is only allowed on salmonid and esocid eggs unless a special exemption is granted for use on other species. This study was conducted to determine the safety of formalin treatments on eggs of representative warm- and coolwater fish species and data was used to support a request to allow the use of formalin on the eggs of warmwater and additional coolwater fish species. Non-eyed eggs of walleye ( Stizostedion vitreum ), common carp ( Cyprinus carpio ), white sucker ( Catostomus commersoni ), channel catfish ( Ictalurus punctatus ), and lake sturgeon ( Acipenser fulvescens ) were cultured in miniature egg hatching jars and treated for 45 min every-other-day with 1500, 4500, or 7500 μL L −1 formalin up to hatch. For all species tested, the percent hatch was greater in 1500 μL L −1 treatment groups than in untreated controls. Walleye eggs were the least sensitive species and had a hatch of 87% in the 7500 μL L −1 treatment. Lake sturgeon were the most sensitive species with a mean hatch of 54% in 1500 μL L −1 treatments. Adequate margins of safety exist for standard treatments (1500 μL L −1 for 15 min) on eggs of all species tested except lake sturgeon. Fungal infections drastically reduced or eliminated hatch in most control groups whereas most treated groups were free of infections. This confirms the efficacy of formalin as an fungicide.

Effectiveness of Piscicides for Controlling Round Gobies (Neogobius melanostomus)

ABSTRACT Round gobies (Neogobius melanostomus) were introduced to the Great Lakes presumably as a result of ballast water releases from seagoing freighters returning from European water bodies. These unwelcome fish have become established in the Great Lakes region and are expanding their range to suitable portions of other interior drainage basins including the Mississippi River traversing the central United States and the Trent-Severn waterway spanning south-central Ontario. If the invasion continues, use of chemical toxicants as a control measure may be necessary. Toxicity tests of the currently registered piscicides antimycin, rotenone, 3-trifluoromethyl-4-nitrophenol (TFM), and Bayluscide® were conducted with three fish species native to the Great Lakes and round gobies collected from the Illinois Waterway. Tests indicated that round gobies are sensitive to all of the piscicides, however, the level of sensitivity is similar to that of the native fish species tested. Therefore, currently registered piscicides have limited potential to selectively remove round gobies. Bottom-release formulations of Bayluscide® and antimycin were also evaluated as control agents for the normally bottom-dwelling round goby. Avoidance behavior tests demonstrated that the round goby did not react to the presence of either chemical. Therefore, the bottom-release formulations may have some application for the selective removal of round gobies, and may be one of the few tools presently available to fishery managers to help limit the range expansion of this invasive fish.

Efficacy of Formalin and Hydrogen Peroxide to Increase Survival of Channel Catfish Infected with Saprolegniasis

Abstract The efficacy of formalin and hydrogen peroxide to increase survival associated with external saprolegniasis on fingerlings of channel catfish Ictalurus punctatus was evaluated in four laboratory trials. Fungal epizootics were initiated according to procedures developed in a fungal-disease model. Fish were abraded with a dremel tool and then placed in an aerated static infection tank containing fungal-infected hemp seeds held in teaballs that were suspended in 100 L of water for 24 h (trials 1–3) or 6 h (trial 4). In the formalin trials, treatment regimens of 0, 82, and 166 mg/L (trial 1) or 0 and 83 mg/L (trial 2) were administered to channel catfish for 60 min once every other day for a total of three treatments (trial 1) or once daily for a total of seven treatments (trial 2). In the hydrogen peroxide trials, treatment regimens of 0, 75, and 102 mg/L (trial 3) or 0 and 75 mg/L (trial 4) were administered to channel catfish for 60 min once every other day for a total of three treatments. Each tr...

Live Transport of Yellow Perch and Nile Tilapia in AQUI-S 20E (10% Eugenol) at High Loading Densities

AbstractFish transport costs are a substantial portion of the operational expenses for aquaculture facilities in the USA. Safely transporting higher loading densities of fish would benefit haulers by increasing efficiency and reducing costs, but research evaluating transport for individual species is generally lacking. In this study, Yellow Perch Perca flavescens and Nile Tilapia Oreochromis niloticus were transported for 6 h immersed in water containing AQUI-S 20E (10% eugenol) at fish loading densities of 240 g/L (2 lb/gal) for perch and 480 g/L (4 lb/gal) for tilapia. Survival was quantified for fish transported in AQUI-S 20E concentrations of (1) control or 0 mg/L of water, (2) 100 mg/L, or (3) 200 mg/L. Yellow Perch had 98–100% survival, and Nile Tilapia had 100% survival up to through 14 d after transport across all AQUI-S 20E levels, including the control. Eugenol concentrations decreased rapidly in transport tank water, and fish showed no signs of sedation by the end of transport. We conclude that...

Survival and Growth of Newly Transformed Lampsilis cardium and Lampsilis siliquoidea in a Flow-Through, Continuous Feeding Test System

Abstract: A test system was evaluated for assessing chronic toxicity of waterborne chemicals with early life stage mussels. To determine if the test system could result in ≥80% survival in a control (unexposed) group, fat mucket mussels (Lampsilis siliquoidea Barnes, 1823) and plain pocketbook mussels (L. cardium Rafinesque, 1820) 1 day post transformation were stocked into test chambers (250 mL beakers, water volume, 200 mL, 21 °C, 40 mussels of 1 species per chamber) within a test system constructed for conducting chronic, continuous exposure, flow-through toxicity tests. The test system contained 60 chambers containing silica sand, 30 chambers with L. siliquoidea, and 30 with L. cardium. Each chamber in the continuous feeding system received 1 of 6 food types prepared with concentrated algal products. After 28 days, mussels were harvested from chambers to assess survival and growth. For L. siliquoidea, mean survival ranged from 34 to 80% and mean shell length ranged from 464 to 643 µm. For L. cardium, mean survival ranged from 12 to 66% and mean shell length ranged from 437 to 612 µm. The maximum mean growth rate for L. siliquoidea was 12.7 µm/d and for L. cardium was 11.8 µm/d. When offered a continuous diet of Nannochloropsis, Tetraselmis, and Chlorella for 28 days in the test system, the survival of 1 day post transformation L. siliquoidea was 80%. The test system can be easily enhanced with a pumping system continuously delivering test chemical to the test systems flow stream allowing for chronic toxicity tests with 1 day post transformation mussels.

Uptake, Metabolism, and Elimination of Niclosamide by Fish

The lampricide 2’,5-dichloro-4’-nitrosalicylanilide (niclosamide) formulated as the 2-aminoethanol salt (Bayluscide) has been used in combination with 3-trifluoromethyl4-nitrophenol (TFM) to control sea lampreys (Petromyzon marinus) in streams tributary to the Great Lakes for over 30 years. In addition, a bottom release formulation of Bayluscide has been used extensively to assess populations of larval lampreys in lenitic areas. The nature and magnitude of niclosamide residues in rainbow trout (Onchorhynchus mykiss) tissues and rates of elimination have been evaluated under laboratory and field exposure conditions. The uptake of niclosamide from water by rainbow trout is rapid, and residues reach equilibrium after 3 days of exposure. Only about 9% of total body niclosamide residues are found in edible fillet tissues after 24 hours of exposure. Metabolism of niclosamide by hydrolysis, reduction, or conjugation with glucuronic acid has been reported in fish, rats, cestodes, nematodes, midge larvae, mouse and sheep liver homogenates, and aerobic and anaerobic pond sediments. Rainbow trout exposed to niclosamide recently have been reported to have residues of the glucuronide conjugate and the sulfate ester in muscle fillet tissue. Fish transferred to niclosamide-free water after 24 hours of exposure to 0.02 mg/L of the chemical eliminated residues to below the limit of detection within 2–3 days.