Evaluation of short-term toxicity of ammonia and nitrite on the survival of whiteleg shrimp, Litopenaeus vannamei juveniles

The effects of short-term toxicity of total ammonia nitrogen (TAN) and nitrite were estimated in juveniles of Litopenaeus vannamei under laboratory conditions. In the first experiment, L. vannamei juveniles were exposed to different concentrations of ammonia (0, 5, 10, 15, 20, 30, and 40 mg of TAN L-1) or nitrite (0, 5, 10, 20, 30, 40, and 50 mg of NO2--N L-1), using the static renewal method at a salinity of 20 ppt and pH 8.2. The survival rates of juveniles significantly decreased when exposed to increased concentrations of ammonia or nitrite during the 96 h bioassays. The 24, 48, 72, and 96 h LC50 values of TAN in juveniles were 45.5, 30.1, 13.8, and 6.3 mg L-1, respectively, while the LC50 values of NO2--N at 24, 48, 72, and 96 h were 37.6, 16.7, 8.8, and 4.8 mg L-1, respectively. Experiment 2 evaluated the tolerance of L. vannamei juveniles at various salinities (5, 10, 15, and 20 ppt) under a high concentration of ammonia or nitrite (5 mg L-1). Results showed that the survival rates of L. vannamei at 5 ppt and 10 ppt were significantly lower than those at 20 ppt after 72 h and 96 h of exposure

Negative impacts of elevated nitrate on physiological performance are not exacerbated by low pH

Multiple environmental stressors, including nutrient effluents (i.e. nitrates []) and altered pH regimes, influence the persistence of freshwater species in anthropogenically disturbed habitats. Independently, nitrate and low pH affect energy allocation by increasing maintenance costs and disrupting oxygen uptake, which ultimately results in impacts upon whole animal performance. However, the interaction between these two stressors has not been characterised. To address this, the effects of nitrate and pH and their interaction on aerobic scope and physiological performance were investigated in the blueclaw crayfish, Cherax destructor. Crayfish were exposed to a 2 × 3 factorial combination, with two pH levels (pH 5.0 and 7.0) and three nitrate concentrations (0, 50 and 100 mg L−1). Crayfish were exposed to experimental conditions for 65 days and growth and survival were monitored. Aerobic scope (i.e. maximal – standard oxygen uptake) was measured at six time points (1, 3, 5, 7, 14, and 21 days) during exposure to experimental treatments. Crayfish performance was assessed after 28 days, by measuring chelae strength and whole animal activity capacity via the righting response. Survival was reduced in crayfish exposed to pH 5.0, but there was no exacerbation of this effect by exposure to high nitrate levels. Aerobic scope was compromised by the interaction between low pH and nitrate and resulted in prolonged elevations of standard oxygen uptake rates. Exposure to nitrate alone affected aerobic scope, causing a 59% reduction in maximum oxygen uptake. Reduced aerobic capacity translated to reduced chelae strength and righting capacity. Together, these data show that low pH and elevated nitrate levels reduce aerobic scope and translate to poorer performance in C. destructor, which may have the potential to affect organismal fitness in disturbed habitats

The Effects Of Oil-Contaminated Prey On The Feeding, Growth, And Related Energetics On Pink Salmon, Oncorhynchus Gorbuscha Walbaum, Fry

Thesis (Ph.D.) University of Alaska Fairbanks, 1984Pink salmon, Oncorhynchus gorbuscha Walbaum, fry were exposed to oil-contaminated prey (OCP) in a series of experiments to determine the effects of oil exposure via the diet on the ability of pink fry to survive. Brine shrimp, Artemia salina, nauplii were contaminated with petroleum hydrocarbons by exposure to the water-soluble fraction (WSF) of Cook Inlet crude oil and fed to the fish. Feeding rates were measured for 10 days using OCP and for 5 days using uncontaminated prey (post-exposure period). In a separate experiment, fry growth was measured over a 50 day period. In another experiment, fry oxygen consumption, food absorption and utilization, and ammonia excretion was measured to determine the effects of OCP on fry metabolic activity. Fry feeding rates were reduced by exposure to OCP, and remained suppressed during the post-exposure period. Chronic exposure to OCP for 50 days reduced fry growth. OCP were not lethal to the fry. There was no change in fry oxygen consumption or ammonia excretion from exposure to OCP, but the fish exposed to OCP absorbed less food than controls and continued to absorb less food for 7 days after exposure. Results indicate that exposure to OCP can reduce fry growth primarily by reducing food intake, but additional nutrition is lost from the non-absorption of ingested food. Reductions in growth could decrease fry survival, and thereby reduce the number of returning adult pink salmon

Study of natural and induced tissue response in Macrobrachium rosenbergii de Man

The tissue response of the giant freshwater prawn Macrobrachium rosenbergii de Man, was studied histologically by investigating clinical cases of natural infectious and non-infectious diseases which occurred in cultured prawns and by carrying out the following experimental intramuscular injection of alcian blue dye, intramuscular injection of BCG vaccine (also using TEM), intramuscular injection of complete Freund’s adjuvant, intramuscular and systemic injection of heat-killed Aeromonas hydrophila, intramuscular and systemic injection of heat-killed and live Vibrio parahaemolyticus and Vibrio anguillarum, grafting or insertion of pieces of cuticle into the muscle of the same or different prawns and by cuticular traumatization or wounding of slight, moderate and severe degrees (also using SEM). Results demonstrated histologically the presence of a unified system of haemocytic cells participating in a range of defensive activities in varying degrees of intensity; viz. infiltration, aggregation, coagulation, melanization, phagocytosis, encapsulation, nodule formation and fibroplasia. More pronounced haemocytic activity occurred in the gills, hepatopancreas, heart and antennal gland, in addition to locally at the site of injection, wounding or grafting. Electron microscopy revealed that the haemocytes which participate in the tissue inflammatory response consist of cell types belonging to all three main classes, namely agranular, semi-granular and granular haemocytes, although semi-granular and granular haemocytes appeared to predominate. Findings of the experimentally induced tissue response were comparable to observations in the natural infectious and non-infectious disease conditions in Macrobrachium and in general, similar to those reported in natural infections and experimental challenges of other important wild and cultured crustaceans including penaeid shrimps, crabs and crayfish. A routine study of the haemocytic tissue response in cultured prawns can be recommended as a useful means of monitoring their health status and identifying the early stages of a disease process. This can prove of assistance in developing disease control strategies

Life Cycle Exposure of Fathead Minnows to Complex Environmental Mixtures

More than one-third of the Earth’s freshwater is used for agricultural, industrial, and domestic purposes leading to the frequent co-occurrence of nitrate and mixtures of contaminants of emerging concerns in aquatic ecosystems. However, little is understood about the consequences of life-cycle exposure of fishes to these complex environmental mixtures. This project examined changes in physiology, performance, and reproduction in fathead minnows across three generations of exposure to agricultural and urban mixtures at environmentally relevant concentrations with an added stressor of nitrate. Exposure of adult fathead minnows in the first, but not second, generation to high nitrate concentrations resulted in a two-fold increase in egg production. In the second generation, the agricultural mixture enhanced fecundity in female fathead minnows above levels observed in EtOH control fish. Contrary to some published studies, neither nitrate nor estrogenic agricultural mixtures stimulated vitellogenin production in male fishes. In contrast, feminization (presence of the egg-yolk protein vitellogenin) was found in first generation males following exposure only to an urban chemical mixture independent of nitrate concentrations. Adult behavior does not appear to be affected regardless of treatment and generation. In contrast, larval behaviors, including predator avoidance performance and foraging efficiency, were both improved in higher nitrate treatments. Using an extended life-cycle fathead minnow exposure, we were able to improve our understanding of the consequences associated with long-term exposures to complex environmental mixtures. Overall, the observed effects of environmentally realistic mixtures were subtle and did neither follow a clear dose-response or matched effects observed in single compound exposures in the published literature. The complexity of interactions between multiple pollutant stressors observed in the current study highlight the need for additional such studies to ensure adequate assessment of environmental risk

Rock Lobster Autopsy Manual

The objective of this project was to publish an autopsy manual for use by the rock lobster industry. The manual was to include details of the approach to be used in conducting an autopsy of rock lobster, descriptions of assay methodology, normal ranges for selected immune and physiological functions and photographs of gross and microscopic lesions and descriptions of pathogens observed in lobsters. The publication was to be aimed primarily for use by fishers, processing factory staff and seafood business managers but was to also include information of relevance to veterinarians, fish health personnel and researchers

Sustainable Aquaculture Techniques

This book presents some innovative developments in sustainable aquaculture practices in the context of environmental protection and seafood production techniques. The chapters are written by experts in their respective areas, so that their contribution represents the progress of their research, which is intended to mark the current frontier in aquaculture practices. Every chapter presents techniques that contribute to good aquaculture practices, where direct and vital nutrition and food, as a source of energy and biomass generation, is fundamentally based. We hope this book supports producers and researchers in their activities and helps to maintain a spirit of environmental protection in the context of production of high quality, nutritional food