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The ability to effectively treat parasitic infestations of fish is of high importance for fish culture facilities. However, tools or approved therapies for treating infestations on fish are limited. This paper summarizes results from four separate clinical field studies that evaluated the efficacy of hydrogen peroxide (H2O2; 35% PEROX‐AID) for reducing Gyrodactylusspp. infestation density. Three species of Gyrodactyluswere studied (G. salmonis, hosts: Brook Trout Salvelinus fontinalisand Lake Trout S. namaycush; G. freemani, host: Yellow Perch Perca flavescens; G. hoffmani, host: Fathead Minnow Pimephales promelas) before and after the application of immersion H2O2therapy. Parasite density was significantly reduced for each parasite × host combination to which H2O2therapy was applied. Two clinical field studies in salmonids were found to demonstrate substantial effectiveness that enabled 35% PEROX‐AID approval. Further assessments of Gyrodactylusspp. could expand the use of H2O2for controlling these parasites in aquaculture. Specifically, H2O2was effective at all levels tested (50 or 75 mg H2O2/L for 60 min for the Yellow Perch and Fathead Minnow clinical field studies; 100 or 150 mg H2O2/L for 30 min regardless of salt pre‐treatment for the Brook Trout study; and 100 mg H2O2/L for 30 min or 50 mg H2O2/L for 60 min for the Lake Trout study). Impact statementThe external parasite species of Gyrodactyluscan be very problematic to fish raised in hatchery settings. Having approved and effective treatments to reduce parasite infestations can be helpful to hatcheries. The work summarized in this paper explored the use of hydrogen peroxide as a treatment option for hatcheries to use for reducing Gyrodactylusinfestation density on four different species of fish. Hydrogen peroxide was effective at reducing Gyrodactylusinfestation densities at all levels tested. The external parasite species of Gyrodactyluscan be very problematic to fish raised in hatchery settings. Having approved and effective treatments to reduce parasite infestations can be helpful to hatcheries. The work summarized in this paper explored the use of hydrogen peroxide as a treatment option for hatcheries to use for reducing Gyrodactylusinfestation density on four different species of fish. Hydrogen peroxide was effective at reducing Gyrodactylusinfestation densities at all levels tested.

Two medications (one with florfenicol and one with oxytetracycline) that are approved in the United States to control mortality due to furunculosis associated with Aeromonas salmonicidawere assessed to determine their efficacy in medicated feeds to treat A. salmonicida‐infected Cisco (also known as Lake Herring) Coregonus artedi. Cisco were subjected to static infection baths containing A. salmonicidaor a sham control and then were distributed to replicate test tanks within four treatment groups: (1) fish infected with A. salmonicidaand treated with 15 mg florfenicol·kg body weight (BW)−1·d−1, (2) fish infected with A. salmonicidaand treated with 83 mg oxytetracycline·kg BW−1·d−1, (3) fish infected with A. salmonicidaand treated with a nonmedicated control feed, and (4) uninfected fish treated with a nonmedicated control feed. Medicated and comparative nonmedicated feed rations were administered at 2% BW/d for 10 consecutive days in accordance with the U.S. Food and Drug Administration‐approved drug label, followed by a 7‐d postdosing observation period using only nonmedicated feed. Cisco that were infected with A. salmonicidaand treated with florfenicol (79% survival) and oxytetracycline (85% survival) had significantly higher survival than A. salmonicida‐infected fish that received no medicated treatment (3% survival). No statistical difference in Cisco survival between the two medicated feed types was found. Aeromonas salmonicidawas not detected in the kidney tissue of any surviving fish treated with medicated feeds at 7 d postdosing using quantitative PCR analysis. Overall, this study demonstrated that florfenicol‐ and oxytetracycline‐medicated feeds were effective A. salmonicidatreatments for Cisco. Outcomes may inform ongoing propagation efforts for Cisco restoration within the Great Lakes basin.

Bighead Carp Hypophthalmichthys nobilis, Silver Carp H. molitrix, and Grass Carp Ctenopharyngodon idella(collectively termed “Asian carp”) were introduced into North America during the 1960s and 1970s and have become established in the lower Mississippi River basin. Previously published evidence for spawning of these species in the upper Mississippi River has been limited to an area just downstream of Dam 22 (near Saverton, Missouri). In 2013 and 2014, we sampled ichthyoplankton at 18 locations in the upper Mississippi River main stem from Dam 9 through Dam 19 and in four tributaries of the Mississippi River (Des Moines, Skunk, Iowa, and Wisconsin rivers). We identified eggs and larvae by using morphological techniques and then used genetic tools to confirm species identity. The spawning events we observed often included more than one species of Asian carp and in a few cases included eggs that must have been derived from more than one upstream spawning event. The upstream extent of genetically confirmed Grass Carp ichthyoplankton was the Wisconsin River, while Bighead Carp and Silver Carp ichthyoplankton were observed in Pool 16. In all these cases, ichthyoplankton likely drifted downstream for several hours prior to collection. Higher water velocities (and, to a lesser extent, higher temperatures) were associated with an increased likelihood of observing eggs or larvae, although the temperature range we encountered was mostly above 17°C. Several major spawning events were detected in 2013, but no major spawning events were observed in 2014. The area between Dam 15 and Dam 19 appears to be the upstream edge of spawning activity for both Silver Carp and Bighead Carp, suggesting that this area could be a focal point for management efforts designed to limit further upstream movement of these species. Received July 18, 2016; accepted May 4, 2017Published online July 19, 2017

AbstractBighead Carp Hypophthalmichthys nobilis, Silver Carp H. molitrix, and Grass Carp Ctenopharyngodon idella(collectively termed “Asian carp”) were introduced into North America during the 1960s and 1970s and have become established in the lower Mississippi River basin. Previously published evidence for spawning of these species in the upper Mississippi River has been limited to an area just downstream of Dam 22 (near Saverton, Missouri). In 2013 and 2014, we sampled ichthyoplankton at 18 locations in the upper Mississippi River main stem from Dam 9 through Dam 19 and in four tributaries of the Mississippi River (Des Moines, Skunk, Iowa, and Wisconsin rivers). We identified eggs and larvae by using morphological techniques and then used genetic tools to confirm species identity. The spawning events we observed often included more than one species of Asian carp and in a few cases included eggs that must have been derived from more than one upstream spawning event. The upstream extent of genetically confirmed Grass Carp ichthyoplankton was the Wisconsin River, while Bighead Carp and Silver Carp ichthyoplankton were observed in Pool 16. In all these cases, ichthyoplankton likely drifted downstream for several hours prior to collection. Higher water velocities (and, to a lesser extent, higher temperatures) were associated with an increased likelihood of observing eggs or larvae, although the temperature range we encountered was mostly above 17°C. Several major spawning events were detected in 2013, but no major spawning events were observed in 2014. The area between Dam 15 and Dam 19 appears to be the upstream edge of spawning activity for both Silver Carp and Bighead Carp, suggesting that this area could be a focal point for management efforts designed to limit further upstream movement of these species.Received July 18, 2016; accepted May 4, 2017Published online July 19, 2017