SEARCH · USGS Science

Results for “North American Journal of Aquaculture”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

USGS2009

Maintaining the competitiveness of the American Fisheries Society journals: An assessment based on influence and cost-effectiveness

Recent changes in the landscape of scientific publishing prompted the Publications Overview Committee of the American Fisheries Society (AFS) to review the Society's portfolio of scientific journals. We evaluated journals based on metrics in two categories: (1) citation-based measures of the influence of a journal on the scientific literature, and (2) measures of the cost-effectiveness of a journal (citation rate adjusted for subscription cost). Over the long-term, we found that ecology journals had far stronger citation-based influence than fisheries and aquatic sciences journals, and that journals publishing primarily basic research had stronger influence than journals publishing applied research (including four AFS journals and Fisheries magazine). In evaluating the current status of fisheries and aquatic sciences journals, we found that metrics of influence and cost-effectiveness provided considerably different portrayals of journals relative to their peers. In terms of citation-based influence, we found that the AFS journal Transactions of the American Fisheries Society (TAFS) and Fisheries magazine were competitive with highly regarded peer fisheries journals, but that North American Journal of Aquaculture (NAJA) and Journal of Aquatic Animal Health (JAAH) were less influential than their peers. The citation-based influence of North American Journal of Fisheries Management (NAJFM) was intermediate between TAFS/Fisheries and NAJA/JAAH . For journals like NAJFM and NAJA , we expect that much of the scientific influence on policy and management is not captured by citations in the primary literature, and alternative methods of evaluation may be needed. All of the AFS journals ranked highly with regard to cost-effectiveness because their subscription costs are low, and these rankings are in accordance with membership needs and the strategic mission of AFS to provide broad and timely dissemination of scientific information. We conclude by suggesting ways to increase the influence of AFS journals without compromising their accessibility and affordability, and offer advice about methods and frequency for future journal evaluations.

Fisheries↗

USGS2022

Local populations of eastern oyster from Louisiana differ in low salinity tolerance

Eastern oysters Crassostrea virginica support a critical commercial industry and provide many ecosystem services to coastal estuaries yet are currently threatened by changing estuarine conditions. A changing climate and the effects of river and coastal management are altering freshwater inflows into productive oyster areas, causing more frequent and extreme salinity exposure. Although eastern oysters are tolerant to a wide range of salinity means and variations, more frequent and extreme exposure to low salinity (<5‰) impacts oyster populations and aquaculture operations. This study assessed four Louisiana eastern oyster stocks to explore population-specific responses to low-salinity exposure. Hatchery-produced progeny (10–25 mm) were deployed in baskets kept off-bottom on longline systems in a low-salinity (mean ± 1 standard error of the mean daily salinity = 8.7 ± 0.2‰; range = 1.2–19.0‰) and a moderate-salinity (16.8 ± 0.3‰; 4.8–30.0‰) environment for 1 year, beginning in December 2019, with growth and mortality determined monthly. Significant differences in cumulative mortality between stocks at the end of the study were found at the low-salinity site, with the greatest increase in cumulative mortality occurring mid-July to mid-August. Mortality differences between stocks suggest that some eastern oyster populations (i.e., stocks) may be better suited to low salinity or low-salinity events than others. This difference may be attributed to similarity between site of origin and grow-out site conditions and/or to greater salinity variability and therefore higher phenotypic plasticity in some eastern oyster populations compared with others. The identification of oyster stocks able to survive under extreme low-salinity conditions may facilitate the development of “low-salinity-tolerant” broodstock to support aquaculture in areas experiencing and predicted to experience low-salinity events.

Louisiana↗

USGS2021

Development of aquaculture protocols and gonadal differentiation of red shiner

Developing detailed rearing methods and describing the onset of gonadal differentiation in Red Shiners Cyprinella lutrensis could facilitate the development of novel techniques to control or enhance populations, enable toxicology studies, and help construct bioassays. In this study, we develop and report aquaculture practices for Red Shiner that ensure consistent year-round production in laboratory settings and evaluate the timing of sexual differentiation via histological gonad examinations. Our methods resulted in a mean of 56.00% (SD = 8.98%) survival through the larval stages of development, and we obtained spawns from captive-reared Red Shiners 138 d posthatch. Red Shiners are gonochoristic, and both ovaries and testes differentiate directly from undifferentiated gonads. Ovaries begin to differentiate in females 45 d posthatch, while testes begin differentiating in males 105 d posthatch. This study provides in-depth protocols for the closed-cycle aquaculture of Red Shiners and describes the gonadal differentiation and development of both sexes.

Arizona↗

USGS2006

Effects of increased feeding frequency on growth of hybrid bluegill in ponds

Increased feeding frequency has been used in aquaculture to increase growth and food conversion efficiency, and recent laboratory studies have indicated that feeding frequency could be used to reduce the size variation within groups of hybrid bluegills (F1: male bluegill Lepomis macrochirus x female green sunfish L. cyanellus). Our experiment evaluated the growth of pond-reared hybrid bluegills fed equal amounts of food either once or four times per day. We were particularly interested in reducing the size variation and increasing the percentage of harvestable-size fish (???110 g). After 194 d, there was no significant effect of feeding frequency on growth, food conversion efficiency, size variation, or percentage of harvestable-size fish.

North American Journal of Aquaculture↗

USGS2000

Analytical verification of waterborne chemical treatment regimens in hatchery raceways

Chemical therapy for control and prevention of fish diseases is a necessary and common practice in aquaculture. Many factors affect the accuracy of a chemical treatment application, such as the functioning of the chemical delivery system, calculation of chemical quantities to be delivered, water temperature, geometry of the culture unit, inlet-outlet structure, the influence of aerators, wind movement, and measurement of water volumes and flow rates. Three separate trials were conducted at the Osceola Fish Hatchery, a facility of the Wisconsin Department of Natural Resources, evaluating the accuracy of flow-through hydrogen peroxide treatments applied to 1, 3, or 9 raceways that were connected in series. Raceways were treated with 50 or 75 ??L/L of hydrogen peroxide for 30 min. Chemical concentrations were determined titrimetrically. The target treatment regimen was not realized in any of the applications. Chemical concentrations dropped and exposure times increased with each additional raceway treated in series. Single introduction of a therapeutant to more than three raceways in series is not recommended. Factors that interfered with the accuracy of the treatments were culture unit configuration, aeration, and flow rates. Several treatment modifications were identified that would result in more accurate chemical treatments.

North American Journal of Aquaculture↗

USGS2017

Live transport of Yellow Perch and Nile Tilapia in AQUI-S 20E (10% Eugenol) at high loading densities

Fish 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 live transport of Yellow Perch and Nile Tilapia at higher loading densities resulted in high survival regardless of the AQUI-S 20E concentrations we tested.

North American Journal of Aquaculture↗

USGS2018

Reproductive potential of captive Rio Grande Silvery Minnow

Captive propagation and augmentation of the Rio Grande Silvery Minnow Hybognathus amarus is necessary for continued persistence of the species until habitat can be restored. Augmentation occurs using captive fish within the first year (age 0) through age 2; however, older year‐classes (ages 3–4) have been released into the wild. We quantified fecundity and compared egg quality across four reproductive age‐classes (1–4) of hatchery‐reared Rio Grande Silvery Minnow. Batch fecundity (total number of spawned eggs) ranged from 2,029 eggs in age‐1 fish to 10,588 eggs in age‐4 fish. Standing stock of vitellogenic (i.e., yolked) oocytes remaining in ovaries after spawning increased from 988 oocytes at age 1 to 4,924 oocytes at age 4. Total fecundity (i.e., batch fecundity plus standing stock of yolked oocytes) increased from 3,017 eggs and yolked oocytes in age‐1 fish to 15,522 eggs and yolked oocytes in age‐4 fish. Of note, batch fecundity ranged from 57% to 68% across the four age‐classes indicating that over half of the total fecundity occurs in the first spawn. Average percent fertilization of eggs (63–82%) was not detectably different across the four age‐classes, while average egg diameter (4.1–5.5 mm) increased as age increased. Fecundity increased across all four reproductive age‐classes of Rio Grande Silvery Minnow, with the larger portion of total fecundity occurring in the first spawn across all age‐classes. The timing of spawning with optimal conditions in the Rio Grande is critical for survival and ultimately recruitment into the wild fish population.

North American Journal of Aquaculture↗

USGS2019

Growth disparity in sympatric kokanee breeding groups

Growth is arguably the most important dynamic rate function due to its interaction with survival and recruitment. As such, understanding the mechanisms underlying growth is a primary focus of fisheries research. Kokanee Oncorhynchus nerka in Lake Pend Oreille, Idaho, provide an interesting case study for investigating the factors that influence growth. Early‐run and late‐run kokanee occur in Lake Pend Oreille, but early‐run fish generally grow faster than late‐run fish. The observed growth disparity between early‐ and late‐run fish could be due to genetic differences between the two groups. Conversely, a common hatchery practice of slowing growth by reducing feed has been hypothesized to elicit a compensatory growth response in early‐run fish and to explain the size difference between breeding groups. Using two different experiments, we tested the hypotheses that (1) early‐run kokanee are genetically disposed to grow faster than late‐run kokanee at identical water temperatures; and (2) feed restriction elicits a compensatory growth response in early‐run kokanee that explains the observed size difference between breeding groups. Estimates of mean FL, weight, Fulton's condition factor ( K ), and specific growth rate (SGR) were not significantly different ( P ≥ 0.05) between early‐run and late‐run fish in the first experiment. However, water temperature was positively related to mean FL, weight, K , and SGR for both breeding groups. Fish that were subjected to food deprivation exhibited an increased growth rate and obtained weights similar to those of control fish. Overall, our results suggest that early‐ and late‐run fish have similar growth potential, but certain hatchery practices likely provide early‐run fish with an initial advantage in growth, size, or both.

Idaho↗

USGS2021

Effect of temperature on survival of Lost River Suckers with a natural infection of Ichthyobodo spp.

To compensate for low natural survival of endangered Lost River Suckers Deltistes luxatus , the U.S. Fish and Wildlife Service and the Klamath Tribes have initiated captive rearing programs. We conducted laboratory experiments intended to determine the temperature for optimum growth of juvenile Lost River Suckers; however, due to an unanticipated infection with Ichthyobodo spp., we instead estimated survival in conjunction with temperature and parasite loads. Ichthyobodo spp. are common parasites that infest fish skin and gills; they are known to be present in Upper Klamath Lake and have been found in fish at both the federal and tribal fish-rearing facilities. All fish held at mean temperatures of 16°C and 19°C survived the entire 65-d experiment, whereas the median time to death was 27 d at 22°C, 8 d at 24°C, and 7 d at 26°C. Gill samples from all Lost River Suckers tested positive for Ichthyobodo spp. DNA, with a trend toward higher copy numbers in suckers that were held at a mean temperature of 22°C or warmer compared to those held at 19°C or cooler. Fish kept at all temperatures grew slowly. These results suggest that survival of Lost River Suckers with a natural infection of Ichthyobodo spp. was significantly impacted by temperature.

North American Journal of Aquaculture↗

USGS2022

Quantitative method development to determine feed consumption using a dye

Although there are many methods to determine ingestion and absorption of aquafeeds, none exist that are simple, cost-effective, and quantitative and that can mark fish with a long-lasting, visible indicator. In addition to aquafeed development, selective baits are needed that can be used for aquatic invasive species removal efforts, including for Grass Carp Ctenopharyngodon idella . Bait incorporated with a pesticide would allow for selective removal of targeted species. A method to quickly assess multiple bait formulations was developed to expediate development for invasive species management. Incorporation of Sudan Black B (SBB) in aquafeeds at concentrations greater than 75 and 120 mg SBB/kg fish resulted in pigmented external soft tissues of Largemouth Bass Micropterus salmoides and Rainbow Trout Oncorhynchus mykiss , respectively, 24 h after consumption. Visual confirmation of consumption was detectable in the gastrointestinal tract at all concentrations tested (≥10 mg SBB/kg) and quantifiable by absorbance measured at 601 nm from extracted SBB in tissues at concentrations less than those required for visual pigmentation. Although SBB was detectable in multiple tissues, fin and mandible tissues yielded the greatest accuracy in estimating consumption from extracted SBB. Compared with other tissues tested, liver tissue accumulated the highest level of SBB but had the greatest variability, while muscle tissue accumulated little detectable SBB. We used the SBB analytical method to compare consumption of six novel baits that were in the initial developmental stages to produce a palatable bait formulation designed to attract Grass Carp for management control. Overwhelming preference of a rapeseed bait formulation was confirmed using SBB as a tracer of consumption in the laboratory; however, use of SBB under natural conditions may be valuable for answering additional questions. Baits incorporated with SBB allowed for the rapid, simultaneous assessment of multiple formulations and could allow for future refinement of management baits, with results available as quickly as 24–72 h after application.

North American Journal of Aquaculture↗

USGS2022

The development of genetic sex identification markers and evidence of a male heterogametic sex determination system in Red Shiner

The Red Shiner Cyprinella lutrensis is of increasing management interest as an invasive species that negatively impacts many native fishes throughout North America. Trojan sex chromosome (TSC)-carrying individuals could theoretically control invasive fish populations by skewing the sex ratio to 100% male. The efficacy of TSC-based control programs requires an understanding of a population's sex determination system, yet such information is lacking for Red Shiner. We used single-digest restriction site-associated DNA sequencing to discover sex-linked single-nucleotide polymorphisms (SNPs), and we conducted a series of breeding experiments to uncover the sex determination system. All candidate sex-linked SNPs that fit our selection criteria exhibited a pattern of male heterogamety. We developed two sex-identification (sex-ID) marker assays, XY_248 and XY_170, which showed phenotype–genotype concordance scores of 77.00% and 84.35%, respectively. These sex-ID markers exhibited relatively high phenotype–genotype concordance in females (XY_248 = 96.30%; XY_170 = 98.61%), which allowed for selective breeding of phenotypically feminized genetic males. We observed a 3:1 male : female sex ratio in spawns from feminized males crossed with wild-type males, indicative of a male heterogametic sex determination system (i.e., XY male/XX female). The discovery of a male heterogametic sex determination system, in combination with our two markers, increases the likelihood of developing an effective TSC eradication strategy for invasive Red Shiner populations.

North American Journal of Aquaculture↗

USGS2023

Efficacy of florfenicol and oxytetracycline administered in feed to control cisco mortality associated with Aeromonas salmonicida infections

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 salmonicida were 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. salmonicida or a sham control and then were distributed to replicate test tanks within four treatment groups: (1) fish infected with A. salmonicida and treated with 15 mg florfenicol·kg body weight (BW) −1 ·d −1 , (2) fish infected with A. salmonicida and treated with 83 mg oxytetracycline·kg BW −1 ·d −1 , (3) fish infected with A. salmonicida and 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. salmonicida and 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 salmonicida was 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. salmonicida treatments for Cisco. Outcomes may inform ongoing propagation efforts for Cisco restoration within the Great Lakes basin.

North American Journal of Aquaculture↗

USGS2023

Is chemical control for crayfish in hatchery fish shipments practical?

Invasive crayfish (family Cambaridae) displace native crayfish species and alter aquatic habitat, community structure, and ecosystem function. We evaluated whether chemical control can be a reliable control agent for crayfish to ensure that shipments from fish hatcheries did not result in new infestations of invasive crayfish. A series of acute (≤1 h) toxicity tests were conducted to evaluate the toxicity of cypermethrin and pyrethrin to crayfish, freshwater mussels, and fish; chemical concentrations in test organisms; effectiveness of carbon-block filters to remove cypermethrin from test waters; and the cost of chemical control relative to extra handling of fish. Cypermethrin dosed at 75 μg/L for 15 min resulted in 100% mortality of adult white river crawfish Procambarus acutus and virile crayfish Faxonius virilis but did not cause >20% mortality in adult pondmussel Ligumia subrostrata , juvenile fatmucket Lampsilis siliquoidea , fingerling Bluegill Lepomis macrochirus , hybrid sunfish (Bluegill × Green Sunfish L. cyanellus ), hybrid Striped Bass (White Bass Morone chrysops × Striped Bass M. saxatilis ), yearling Paddlefish Polyodon spathula, or ready-to-eat Bluegill, hybrid sunfish, and Channel Catfish Ictalurus punctatus . Behavioral effects, such as loss of equilibrium or head shaking, were generally limited to 1 h postexposure. Mean concentrations of cypermethrin increased in fish fillets (4–26 μg/g) and whole fish (5–1,770 μg/g); therefore, regulations limiting harvest for up to 7 d following stocking may be required. A carbon-block filtration system was effective in reducing (<90%) cypermethrin concentrations and thus reducing potential effects to nontarget species in receiving waters. Extra handling of fish was more cost-effective for all fish tested except for Paddlefish, where the cost of chemical control was half that for extra handling. For all other fish tested, chemical control was 4–10 times more expensive than extra handling. Special use permits or chemical registration are needed before chemical control for crayfish could be routinely used at fish hatcheries.

North American Journal of Aquaculture↗

USGS2023

The effects of estradiol-17β on the sex reversal, survival, and growth of Red Shiner and its use in the development of YY individuals

Objective The Red Shiner Cyprinella lutrensis is one of the most prolific and ecologically destructive invasive fish species in the southwestern United States. The production and release of YY individuals as Trojan sex chromosome carriers can theoretically eradicate invasive fish populations by eventually eliminating phenotypic females. Methods The YY individuals are typically produced through hormonally induced sex reversals and selective breeding of subsequently feminized males. We tested three dosages of estradiol-17β (E2)-treated diets (50, 100, and 150 mg of E2 per kg of diet) administered to sexually immature Red Shiner for various durations to determine their effectiveness at feminizing Red Shiner cohorts. Survival, growth, and gonadal development were assessed for each treatment. Result All E2 treatments had minimal, if any, detrimental effects on the growth and gonadal development of Red Shiner. The 50-mg dosage lasting from 2 to 120 days posthatch achieved a 100% feminization rate while using the lowest amount of E2; therefore, this dosage and treatment interval are recommended when attempting Red Shiner feminization under these rearing conditions. Feminization of males allowed for the spawning of neofemales (F XY ) with wild-type males (M XY ), which resulted in the first putative YY Red Shiner. The YY verification crosses ( n = 20) resulted in predominately male offspring (189 males/191 offspring) except for (1) an intersex individual from an M YY × F XX cross with two previtellogenic oocytes in its testis and (2) a single female that may have resulted from an inbred cross between an XY male and a YY female or from an unknown autosomal or environmental effect on sexual phenotype. Conclusion More progeny tests with inbred and outbred crosses should be conducted to determine the prevalence of female offspring from YY individuals and how this may impact an eradication strategy featuring releases of YY Red Shiner.

North American Journal of Aquaculture↗

USGS2024

Survival and growth of larval Pallid Sturgeon are improved by a live diet

Objective Conservation propagation facilities in the upper basin of the Missouri River are currently experiencing inconsistent survival of first-feeding larval Pallid Sturgeon Scaphirhynchus albus among genetic families (i.e., distinct male–female pairings). The inconsistent survival can have unintended negative consequences for genetic representation of Pallid Sturgeon that are returned to the Missouri and Yellowstone rivers. We conducted a laboratory study designed to determine whether a live diet improves survival and growth of first-feeding larval Pallid Sturgeon. Methods First-feeding larval Pallid Sturgeon from three distinct genetic families were assigned to one of the following diets: live first instar brine shrimp ( Artemia franciscana ) nauplii, an Otohime dry diet, a 50–50% combination of Otohime and live first instar brine shrimp nauplii, or food restricted (no food). Mortality was evaluated at the end of each day and at the end of the trial (21 days after the onset of exogenous feeding), and individual weight (g) was measured at the end of the trial. Result Pallid Sturgeon larvae that received a live diet (either solely live first instar brine shrimp nauplii or the combined diet) experienced higher survival than larvae that were fed solely Otohime. Furthermore, there was statistical evidence that larvae receiving solely live first instar brine shrimp nauplii were heavier at 21 days postexogenous feeding than larvae that were fed either solely Otohime or the combined diet. Conclusion Our results suggest that a live diet can improve survival and growth of first-feeding larval Pallid Sturgeon at conservation propagation facilities.

North American Journal of Aquaculture↗

USGS2011

Efficacy and toxicity of iodine disinfection of Atlantic salmon eggs

Recent interest in the restoration of Atlantic salmon Salmo salar in the Great Lakes has given rise to new culture techniques and management programs designed to reduce pathogen transmission while stabilizing and enhancing wild populations. We examined the toxicity of iodine to Atlantic salmon eggs and its effectiveness as a disinfectant against bacteria on egg surfaces. We spawned and fertilized eight gravid Atlantic salmon from Cayuga Lake, New York, and exposed their eggs to 10 concentrations of iodine (5, 10, 50, 75, 100, 500, 750, 1,000, 5,000, and 7,500 mg/L) for 30 min during water hardening. An additional subsample of unfertilized eggs was also exposed to some of the same concentrations of iodine (5, 10, 50, 75, and 100 mg/L) to determine the efficiency of disinfection. Viable eggs were only obtained from four females. Survival of eggs to the eyed stage and hatch tended to be reduced at iodine concentrations of 50 and 75 mg/L and was significantly reduced at concentrations of 100 mg/L iodine or more. We calculated the concentrations of iodine that killed 50% of the Atlantic salmon eggs at eye-up and hatch to be 175 and 85 mg/L, respectively. Aeromonas veronii, A. schubertii, A. hydrophila, A. caviae, Plesiomonas shiggeloides , and Citrobacter spp. were the predominant bacteria present on the surface of green eggs and were significantly reduced by an iodine immersion. The use of iodine as a disinfectant on Atlantic salmon eggs was effective at low concentrations (50–75 mg/L), for which toxicity to Atlantic salmon was minimal.

North American Journal of Aquaculture↗

USGS2012

Novel praziquantel treatment regime for controlling Asian tapeworm infections in pond-reared fish

The Asian tapeworm Bothriocephalus achelognathii is an intestinal fish parasite that is nonnative to but widespread throughout the southwestern United States. Praziquantel is an anthelminthic drug commonly used to treat fish for Asian tapeworm; however, it does not kill tapeworm eggs, so the water in ponds used for fish rearing must be exchanged after treatment. Our objective was to determine whether a system containing both an intermediate copepod host and a definitive fish host for Asian tapeworm could be treated without exchanging the water by using a follow-up treatment for any tapeworms that developed from eggs released before or during the first treatment. Here, we have described a new praziquantel treatment regimen to control Asian tapeworm infections in freshwater-reared fish. To evaluate the efficacy of this regimen, we stocked 50 red shiners Cyprinella lutrensis and an intermediate copepod host, Cyclops vernalis, into each of six pond mesocosms containing artificial macrophytes, sand, and gravel to simulate natural pools and provide suitable substrate for the copepod's life history. The test fish population had been naturally infected with B. achelognathii and had an initial infection prevalence of 14% and an infection intensity of 2.14 ± 2.19 (mean ± SD) worms per fish. Three mesocosms were treated twice, each with 2.5 mg/L praziquantel; 19 d passed between treatments to allow for possible reinfection to occur. After a 2.5-month posttreatment period to allow any remaining tapeworms to reestablish themselves, we killed and dissected all of the remaining fish. No worms were found in treated fish; however, the control group had an infection prevalence of 18 ± 6% and an infection intensity of 3.45 ± 2.1 worms per fish. Based on these results, we concluded that the praziquantel treatment regime administered was efficacious and suggest testing it on a larger scale. We caution that praziquantel has not been approved by the U.S. Food and Drug Administration for use on fish but can be used legally in some situations.

North American Journal of Aquaculture↗

USGS2013

Use of lethal short-term chlorine exposures to limit release of non-native freshwater organisms

Fish hatcheries and other types of aquatic facilities are potential sources for the introduction of nonnative species of fish or aquatic invertebrates into watersheds. Chlorine has been suggested for use to kill organisms that might be released from the effluent of a facility. While acute LC50s (concentrations lethal to 50% of organisms exposed for up to 96 h) for chlorine are available for some species, short-term LC100s for chlorine have not been determined. The objective of this study is to establish concentrations of chlorine that are lethal to 100% of organisms after brief (1-, 5-, or 15-min) exposures. A total of 22 species were exposed to total residual chlorine concentrations (TRC) of 1, 10, or 25 mg TRC/L for 1, 5, or 15 min under static conditions followed by a 24-h postexposure recovery period in water without the addition of chlorine. Concentrations of chlorine resulting in 100% lethality of organisms were established for all of the species tested except for four species of mollusks or for a beetle. Exposures for 5 to 15 min to 10–25 mg TRC/L were the lowest combined time–chlorine treatments under which all of the fish tested and the other invertebrates tested (17 species) exhibited 100% lethality by the end of the initial chlorine exposures or after the 24-h recovery period.

North American Journal of Aquaculture↗