Mucosal organs exhibit distinct response signatures to hydrogen sulphide in Atlantic salmon (Salmo salar).

Hydrogen sulphide (HS) is considered an immunotoxicant, and its presence in the water can influence the mucosal barrier functions of fish. However, there is a significant knowledge gap on how fish mucosa responds to low environmental HS levels. The present study investigated the consequences of prolonged exposure to sub-lethal levels of HS on the mucosal defences of Atlantic salmon (Salmo salar).

Nile tilapia (Oreochromis niloticus) show high tolerance to acute ammonia exposure but lose metabolic scope during prolonged exposure at low concentration.

Ammonia is a respiratory gas that is produced during the process of protein deamination. In the unionised form (NH), it readily crosses biological membranes and is highly toxic to fish. In the present study we examined the effects of unionized ammonia (UIA), on the resting oxygen consumption (MO), ventilation frequency (f), heart rate (HR) and heart rate variability (HRV) in Nile tilapia (Oreochromis niloticus).

Relatedness of hypoxia and hyperthermia tolerances in the Nile tilapia (Oreochromis niloticus) and their relationships with cardiac and gill traits.

In fish, thermal and hypoxia tolerances may be functionally related, as suggested by the oxygen- and capacity-limited thermal tolerance (OCLTT) concept, which explains performance failure at high temperatures due to limitations in oxygen delivery. In this study the interrelatedness of hyperthermia and hypoxia tolerances in the Nile tilapia (Oreochromis niloticus), and their links to cardiorespiratory traits were examined. Different groups of O.

No additional stress of sublethal gas supersaturation in a landlocked population of Atlantic salmon (Salmo salar) exposed to environmental acidification.

The landlocked Atlantic salmon population "bleke" faces extinction due to environmental acidification (EA) and hydropower expansion in the Norwegian river Otra. Despite of restoration, unexpected mortality has been reported for this population, possibly due to gas bubble trauma (GBT) from gas supersaturation (GSS) downstream of hydroelectric plants, or EA induced aluminum toxicity. In this study, we applied the allostasis concept to investigate interactions between EA and GBT.

Mucosal and systemic physiological changes underscore the welfare risks of environmental hydrogen sulphide in post-smolt Atlantic salmon (Salmo salar).

Atlantic salmon (Salmo salar) might encounter toxic hydrogen sulphide (HS) gas during aquaculture production. Exposure to this gas can be acute or chronic, with heightened levels often linked to significant mortality rates. Despite its recognised toxicity, our understanding of the physiological implications of HS on salmon remains limited.

Air-breathing behavior in Heterotis niloticus fingerlings: Response to changes in oxygen, temperature, and exercise regimes.

Air-breathing in fish is believed to have arisen as an adaptation to aquatic hypoxia. Although air-breathing has been widely studied in numerous fish species, little is known about the obligate air-breathing African bonytongue, Heterotis niloticus. We evaluated if abiotic factors and physical activity affect air-breathing patterns in fingerlings.

A novel method to estimate biofilm activity based on enzymatic oxygen release from hydrogen peroxide decomposition.

Biofilm is central for biological water treatment processes in recirculating aquaculture systems (RAS). A lack of suitable methods for quantifying biofilm activity, however, makes it difficult to assess and compare the microbial status of biofilm. This type of information of the biofilm will be useful to assess the colonization status of nitrifying biocarriers or to evaluate the effect of disinfectants on the biofilm activity.

Removal of dissolved organic matter from the woodchip bioreactor start-up by foam fractionation.

Denitrifying woodchip bioreactors are passive, low-tech systems primarily designed to remove nitrate from shallow ground waters as well as point source discharges. Despite their capacity to achieve constant nitrate removal over several years, natural aquatic environments may be affected by the leaching of dissolved organic matter (DOM) from fresh woodchips during start-up. Simple on-site measures might reduce the woodchip leachate during start-up and thus add to the overall environmental sustainability of woodchip bioreactor installations.

Reducing phosphorus emissions from net cage fish farming by diet manipulation.

To alleviate the environmental impact of net cage fish farming in terms of phosphorous (P) emissions to the Baltic Sea, this study aimed at developing and documenting a diet concept for large rainbow trout (Oncorhynchus mykiss) in brackish water (∼15 ppt) that minimizes the excretion of dissolved P and reduces the excretion of particulate P without compromising fish performance and gonadal development. This was to be achieved by reducing the total dietary P content and matching dietary bioavailable P concentrations to fish requirements using whole-body P concentration and expected individual raw material digestibility as criteria. The diet concept was firstly tested in a laboratory mass-balance study with all female rainbow trout (∼1100 g fish) fed three commercial-like low-P diets with 0.

Environmental Enrichment for Rainbow Trout Fingerlings: A Case Study Using Shelters in an Organic Trout Farm.

Physical enrichment can improve the welfare of captive fish. Previous research has shown that fish often show preference for enriched environments, which can also result in improvements in growth performance. However, effects of enrichment are not always positive and the design and extent of the enrichment needs to be carefully considered.

Combined antagonist treatment of glucocorticoid and mineralocorticoid receptor does not affect weight loss of fasting rainbow trout but inhibits a fasting-induced elevation of cortisol secretion.

The gastrointestinal system of fish reacts rapidly to food deprivation. The relative masses of digestive organs and activities of digestive enzymes decrease within days of fasting. This is believed to be an energy-conserving strategy as the metabolic cost of maintaining digestive capacity is high.

Regulation of the molecular repertoires of oxidative stress response in the gills and olfactory organ of Atlantic salmon following infection and treatment of the parasite Neoparameoba perurans.

The present study investigated the involvement of key molecular regulators of oxidative stress in amoebic gill disease (AGD), a parasitic infestation in Atlantic salmon. In addition, the study evaluated how these molecular biomarkers responded when AGD-affected fish were exposed to a candidate chemotherapeutic peracetic acid (PAA). Atlantic salmon were experimentally infected with the parasite Neoparameoba perurans, the causative agent of AGD, by bath exposure and after 2 weeks, the fish were treated with three commercial PAA products (i.

Mucosal immune and stress responses of -infected Atlantic salmon () treated with peracetic acid shed light on the host-parasite-oxidant interactions.

Treatment development for parasitic infestation is often limited to disease resolution as an endpoint response, and physiological and immunological consequences are not thoroughly considered. Here, we report the impact of exposing Atlantic salmon affected with amoebic gill disease (AGD) to peracetic acid (PAA), an oxidative chemotherapeutic. AGD-affected fish were treated with PAA either by exposing them to 5 ppm for 30 min or 10 ppm for 15 min.

Escaping from multiple visual threats: modulation of escape responses in Pacific staghorn sculpin (Leptocottus armatus).

Fish perform rapid escape responses to avoid sudden predatory attacks. During escape responses, fish bend their bodies into a C-shape and quickly turn away from the predator and accelerate. The escape trajectory is determined by the initial turn (stage 1) and a contralateral bend (stage 2).

Replacement of Antarctic krill () by extruded feeds with different proximate compositions: effects on growth, nutritional condition and digestive capacity of juvenile European lobsters (, L.).

Extruded feeds are widely used for major aquatic animal production, particularly for finfish. However, the transition from fresh/frozen to extruded/pelleted feeds remains a major obstacle to progressing sustainable farming of European lobster (). The aim of the present study was to investigate the effects of using extruded feeds with different protein levels and lipid/carbohydrate ratios on growth, feed utilisation, nucleic acid derived indices (sRD) and digestive enzymatic activity of juveniles.

Prolonged cortisol elevation alters whole body and tissue metabolism in rainbow trout (Oncorhynchus mykiss).

Chronic elevation of circulating cortisol is known to have deleterious effects on fish, but information about the consequences of prolonged cortisol elevation on the metabolism of fish is scarce. To test the effects of chronic cortisol elevation on the aerobic performance of rainbow trout, we examined how two severities of chronically elevated plasma cortisol levels affected the oxygen uptake during rest and after exhaustive exercise using a high (HC) and a medium cortisol (MC) treatment. High cortisol doses significantly affected standard (SMR) and maximum metabolic rates (MMR) compared to control fish.

Microbial communities in full-scale woodchip bioreactors treating aquaculture effluents.

Woodchip bioreactors are being successfully applied to remove nitrate from commercial land-based recirculating aquaculture system (RAS) effluents. In order to understand and optimize the overall function of these bioreactors, knowledge on the microbial communities, especially on the microbes with potential for production or mitigation of harmful substances (e.g.

Interactions of temperature and dietary composition on juvenile European lobster (Homarus gammarus, L.) energy metabolism and performance.

Optimal rearing temperatures for European lobster Homarus gammarus in aquaculture differ from those prevalent in their aquatic ecosystems and acclimating juveniles to the prevailing temperatures before release may aid in the success of re-stocking programs. As the dietary nutritional composition is important for optimal performance of H. gammarus, in this study we aimed to investigate whether juvenile growth and energy metabolism responses to temperature variation could be modulated by the diet.

Hypoxia tolerance and metabolic coping strategies in Oreochromis niloticus.

The Nile tilapia (Oreochromis niloticus) is widely farmed in tropical and subtropical pond culture. O. niloticus is recognized as a species that is tolerant of hypoxic conditions, a trait that may largely be responsible for the success of this species in aquaculture.

Hurricane Disturbance Stimulated Nitrification and Altered Ammonia Oxidizer Community Structure in Lake Okeechobee and St. Lucie Estuary (Florida).

Nitrification is an important biological link between oxidized and reduced forms of nitrogen (N). The efficiency of nitrification plays a key role in mitigating excess N in eutrophic systems, including those with cyanobacterial harmful algal blooms (cyanoHABs), since it can be closely coupled with denitrification and removal of excess N. Recent work suggests that competition for ammonium (NH ) between ammonia oxidizers and cyanoHABs can help determine microbial community structure.

Growth, metabolism and respiration in Nile tilapia (Oreochromis niloticus) exposed to chronic or periodic hypoxia.

Tropical earthen ponds for extensive aquaculture are characterised by daily fluctuations in the availability of dissolved oxygen in the water. Primary production during the daytime ensures excess oxygen availability with oxygen partial pressures (pO) exceeding 220 mmHg, while nocturnal respiration of fish, plankton and bacteria leads to nightly episodes of severe hypoxia (pO < 20 mmHg), often persisting for several hours. To investigate how oxygen availability affects feeding, growth, digestive performance, metabolism and behaviour in Nile tilapia (Oreochromis niloticus), a series of experiments were conducted under different oxygen regimes.

Nitrate removal microbiology in woodchip bioreactors: A case-study with full-scale bioreactors treating aquaculture effluents.

Woodchip bioreactors are viable low-cost nitrate (NO) removal applications for treating agricultural and aquaculture discharges. The active microbial biofilms growing on woodchips are conducting nitrogen (N) removal, reducing NO while oxidizing the carbon (C) from woodchips. However, bioreactor age, and changes in the operating conditions or in the microbial community might affect the NO removal as well as potentially promote nitrous oxide (NO) production through either incomplete denitrification or dissimilatory NO reduction to ammonium (DNRA).

Key nutritional factors and interactions during larval development of pikeperch (Sander lucioperca).

The effects of 8 nutritional variables (Ca/P, Eicosapentaenoic acid (20:5n-3) + Docosahexaenoic acid (22:6n - 3) (EPA + DHA), Arachidonic acid (20:4n - 6) (ARA), Se, vitamins E, C, D and A) were investigated to identify their respective importance and interactions in pikeperch larval development. In this respect, two modalities (low and high levels) of each variable were tested through a fractional factorial experimental design allowing a reduction from 256 (2) to 16 (2) experimental units. Survival was significantly higher in larvae fed a high Ca/P diet while larval growth was significantly lower in larvae fed the same diet variant, associated with a higher incidence of kyphosis and pectoral anomalies in these larvae.

Are all bony fishes oxygen regulators? Evidence for oxygen regulation in a putative oxygen conformer, the swamp eel Synbranchus marmoratus.

This study investigated the oxygen consumption of the putative oxygen conformer marbled swamp eel Synbranchus marmoratus during progressive hypoxia. Earlier studies have not reached an agreement on whether S. marmoratus is a conformer or a regulator.