Oxygen Consumption Of Fish Research Articles

Changes of oxygen consumption rates in response to various environmental factors and different anesthetic methods in juvenile hybrid sturgeon, Acipenser baeri♀×Acipenser schrencki♂

Live fish transportation plays a crucial role in realizing the value of aquaculture in sturgeons. However, hypoxia and hypercapnia are the major issues during the high-density transportation of live fish. Therefore, monitoring the changing environmental factors (such as water temperature, salinity, and pH) or anesthesia methods (MS-222, dissolved CO2, or low-voltage direct electrical current), which can potentially alter the oxygen consumption of fish, are crucial for a better understanding of the necessary conditions for live fish transportation. A semi-open respirometry system was used to quantify the oxygen consumption and respiration frequency of hybrid sturgeon (Acipenser baeri♀×Acipenser schrencki♂). The results indicate that the oxygen consumption rate and respiration frequency of hybrid sturgeon increased linearly with water temperature from 1.4 °C to 25°C. The oxygen consumption rate of hybrid sturgeon increased with the increase of salinity in the range from 3 to 10 ‰ in 9 hours (P < 0.05). Respiration frequency decreased but did not affect the oxygen consumption rate when pH was from 8.1 to 9.8. Exposure to low-voltage direct electrical current ranging from 0.4 to 1.0 V/cm significantly increased the respiration frequency (P < 0.05). The oxygen consumption rate maintained below 1 mg/(g·h) when CO2 concentration ranges from 8.5 to 67.85 mg/L. Compared with the change of oxygen consumption rate and respiration frequency with MS-222 at the range from 5 to 30 mg/L, immersion of fish into more than 8.5–67.85 mg/L dissolved CO2 in water could as an alternative anesthetic method for hybrid sturgeon. These findings in the study may contribute to the culture, live fish transportation, and basic research in hybrid sturgeon.

Pectoral fin swimmers turn to save energy in coral reef waves

It takes all sorts to make a coral reef community. From elegant shimmering Hawaiian flagtails (Kuhlia xenura) to vivid kole tangs (Ctenochaetus strigosus) and stripy sergeant major fish (Abudefduf vaigiensis), these creatures all make their homes in the perpetual swell of the coral reef waters off Hawaii. ‘The waves over shallow reefs create constantly changing water flows that may help explain the great variety of fish body shapes and types of swimming we see among reef fishes’, says Keith Korsmeyer from Hawaii Pacific University, USA. Some fish swim sinuously, gently beating their tails from side to side, while others manoeuvre and hover deftly by wiggling their wing-like pectoral fins. But all must be able to withstand strong surges and remain in place, even when the turbulence of the strongest storms blows through. Yet it wasn't clear just how much of an effort it takes for fish with different builds and swimming styles to hold their own in turbulent coral reef waters. Korsmeyer teamed up with Mathias Schakmann (Hawaii Pacific University) and the pair recreated the wavey conditions on a reef to find how much effort it takes fish to stay in place and how much swimming style affects their exertions.‘I went fishing at the local pier and was lucky to catch fish with interesting differences in body shape and how they swim’, says Schakmann, who came back with Hawaiian flagtails, kole tangs, sergeant major fish and saddle wrasse (Thalassoma duperrey). He then set up a fish ‘treadmill’ in the lab with water flowing through a tube, where he could measure the fish's oxygen consumption to calculate the energy they used as they swam at different steady speeds, in addition to how hard they had to swim when the water washed to and fro as he simulated coral reef waves. ‘All the fish quickly adjusted to each wave surge and kept swimming into the flow’, says Korsmeyer.It was quickly clear that the fish switched direction each time a simulated wave washed through, speeding up and slowing down to remain in place as the waves surged past. Although all of the fish swam harder to stay put in the wavey conditions, when Schakmann compared the fish's swimming styles, it was evident that the pectoral fin wiggling swimmers were far more efficient than the tail-beating Hawaiian flagtails. The flagtail's energy use increasing 2.5-fold as the waves increased from one every 10 s to one every 3.3 s, while the fin-flapping saddle wrasse only increased their exertions by 1.5-fold and the disc-shaped fin-wiggling sergeant major fish barely made any additional effort (0.5-fold increase). ‘The fish that swam with flapping pectoral fins could deal with the increasing wave motion more easily, which would save energy while living in these wave-swept habitats’, says Korsmeyer.However, when Schakmann compared the exertions of the three pectoral fin swimmers, the deepest-bodied kole tangs and sergeant major fish swam more efficiently than the slimmer saddle wrasse as they switched back and forth. ‘Our results suggest that more rounded disc-shaped bodies seem to be the most efficient for dealing with staying put in a wave surge water flow’, says Schakmann.So disc-like fish that depend on their pectoral fins for manoeuvrability are best suited for life on wave-swept coral reefs, turning on a dime as each wave washes through, and it takes all sorts to make a community, although some are better suited to steady swimming in the calmer deep waters off coral reefs.

Media Oxygen Consumption Level for A Seed Brek Fish (Puntius Orphoides)

Disolved oxygen plays an important role for fish living in its life environment. Information on the ammount of oxygen consumption of a fish in certain volume of water is needed in order to give balancing between the ammount of disolved oxygen and fish in it. The objective of this research is obtaining oxygen consumption level of a juvenile of brek fish (Puntius orphoides) of 5-7 cm body length. Oxygen consumption of fish was measured using a tube that equiped with DO tool (dissolved oxygent, DO), and the tube was filled by fresh water. Measurement of oxygen consumption of juvenil was done by measuring the concentration of dissolved oxygen from fresh water in the respirometer tube, began when fish had entered into the respirometer tube up to two hours observation. The result showed that oxygen consumption rate a juvenile of brek fish (Puntius orphoides) of 5-7 cm length, is ranging between 0.816 and 1.734 mg/hour.

Larger Nile tilapia struggle in hot water

When your metabolism depends on the temperature of your surroundings, climate change represents a unique and alarming challenge. As temperatures increase, your metabolic rate rises too, requiring that you consume more oxygen to maintain your body at a faster pace. ‘At warmer temperatures, larger individuals may be prone to limitations in their capacity for oxygen uptake’, says David McKenzie, at the CNRS's Centre for Marine Biodiversity Exploitation and Conservation, Montpellier, France, with the consequence that larger fish may struggle to survive at higher temperatures. ‘If true, this would be important in projecting how global warming will affect fish populations’, says McKenzie; the size distribution of fish populations could become smaller as temperatures rise. ‘But evidence is lacking’, McKenzie admits. So, he and colleagues from the Federal University of São Carlos, Brazil, decided to find out how well Nile tilapia (Oreochromis niloticus), ranging in size from 21 to 313 g, managed to keep swimming at high speed as the temperature rose. First, the team tested how resilient the resting fish were as the water temperature rose. Initially, the fish began behaving erratically but eventually they toppled over when the temperature was too high. However, the largest fish were as resilient as the smallest; getting enough oxygen was not an issue when the fish were resting. ‘They may lose their balance for another reason when they are warmed up while resting in a tank’, McKenzie says.He and his colleagues then set the fish a challenge, encouraging them to swim at 85% of their top speed while the researchers gently increased the water temperature, and they found that the largest animals struggled most as the temperature rose. They gave up swimming at lower temperatures (around 37°C), while the smaller fish managed to keep going at temperatures up to 39.5°C. And when the team investigated the fish's oxygen consumption as the temperature increased, they found the largest fish got out of breath at far lower oxygen consumption rates (∼18 mmol O2 kg−1 h−1) than their smaller counterparts (41 mmol O2 kg−1 h−1).So, larger tilapia struggle to keep swimming as the temperature rises and they seem to find it difficult to get enough oxygen, which could have implications for the size of fish in future populations. McKenzie suspects that ‘Global warming may favour the small’, as smaller individuals may be able to take the heat while larger fish may have more trouble surviving in hot water.

Effects of dietary iron levels on growth performance, iron metabolism and antioxidant status in spotted seabass (Lateolabrax maculatus) reared at two temperatures

The increased ambient temperature is often accompanied by the enhanced metabolic rate and oxygen consumption of fish, which affects their nutritional requirements. Currently, no information compares the iron requirements of fish species under moderate and high temperatures. This study investigated the effects of dietary iron levels on growth performance, iron metabolism, and antioxidant status in spotted seabass (Lateolabrax maculatus) reared at two temperatures. Six diets were formulated to contain 63, 120, 188, 316, 425, and 554 mg/kg iron, each of which was fed to two groups of juveniles reared at 27°C (MT) and 33°C (HT) for 56 days. The results showed that the satisfied iron requirement for spotted seabass improved growth, feed utilization, and antioxidant capacity. Furthermore, fish fed with high‑iron diets prevented iron overload by repressing intestinal iron-regulatory proteins and inducing liver hepcidin production. Iron deficiency depressed erythropoiesis and worsened HT-induced hypoxic status. Moreover, the HT compromised fish growth, feed utilization and liver hepcidin expression, while inducing lipid deposition. Compared to 27°C, the iron demand of spotted seabass was increased at 33°C as more blood erythrocyte and tissue iron deposition were required. Based on the broken-line regression analysis of weight gain, the optimum dietary iron levels for spotted seabass reared at 27°C and 33°C were 178.5 and 209.0 mg/kg, respectively.

Determining Oxygen Consumption of Indonesian Mahseer (Tor soro) Fingerlings at Different Size and Stocking Density

Understanding oxygen consumption in fish is one of the essential factors in the survival performance of cultured fish. As this information is established, the appropriate size and optimum stocking density of cultured fish reared in an aquaculture system can be determined for successful larval rearing of mahseer in a hatchery. This study aimed to obtain information on the oxygen consumption rate and critical oxygen level of Indonesian mahseer fingerlings at different sizes and stocking densities. This study was conducted in the Laboratory of Fish Reproduction and Genetics, which belongs to the Research Institute for Freshwater Aquaculture and Fisheries Extension, Bogor. A factorial design with two factors (size and stocking density) and three replications were employed to run the experiments. Oxygen consumption rate was measured using a closed respirometer system (volume: 1.4 L) Parameters observed during the study are oxygen consumption rate and critical oxygen level. The results showed that the highest oxygen consumption rate was found at the size of 6-8 cm at 9.52 mg O2/g/minute with a stocking density of 7 fish/1.4 L. Oxygen consumption rate of mahseer was increased with the increase of size and stocking density. In this experiment, the critical oxygen level of mahseer fingerlings was observed at 1.44 mg/L. The obtained critical oxygen consumption could be used as a reference to determine the amount of dissolved oxygen that could support the survival rate of mahseer. In rearing practice, it would be important information used for designing early warning and mitigating culture systems to avoid deterioration of dissolved oxygen levels in the water. Therefore, this study can be recommended for improvement mahseer rearing practice for better hatchery production with providing an appropriate oxygenation system for fingerling growth.

Molecular and physiological responses predict acclimation limits in juvenile brook trout (Salvelinus fontinalis).

Understanding the resilience of ectotherms to high temperatures is essential because of the influence of climate change on aquatic ecosystems. The ability of species to acclimate to high temperatures may determine whether populations can persist in their native ranges. We examined physiological and molecular responses of juvenile brook trout (Salvelinus fontinalis) to six acclimation temperatures (5, 10, 15, 20, 23 and 25°C) that span the thermal distribution of the species to predict acclimation limits. Brook trout exhibited an upregulation of stress-related mRNA transcripts (heat shock protein 90-beta, heat shock cognate 71 kDa protein, glutathione peroxidase 1) and downregulation of transcription factors and osmoregulation-related transcripts (nuclear protein 1, Na+/K+/2Cl- co-transporter-1-a) at temperatures ≥20°C. We then examined the effects of acclimation temperature on metabolic rate (MR) and physiological parameters in fish exposed to an acute exhaustive exercise and air exposure stress. Fish acclimated to temperatures ≥20°C exhibited elevated plasma cortisol and glucose, and muscle lactate after exposure to the acute stress. Fish exhibited longer MR recovery times at 15 and 20°C compared with the 5 and 10°C groups; however, cortisol levels remained elevated at temperatures ≥20°C after 24 h. Oxygen consumption in fish acclimated to 23°C recovered quickest after exposure to acute stress. Standard MR was highest and factorial aerobic scope was lowest for fish held at temperatures ≥20°C. Our findings demonstrate how molecular and physiological responses predict acclimation limits in a freshwater fish as the brook trout in the present study had a limited ability to acclimate to temperatures beyond 20°C.

Estimating oxygen consumption of rainbow trout (Oncorhynchus mykiss) in a raceway: A Precision Fish Farming approach

The Precision Fish Farming (PFF) approach was applied to the estimation of fish oxygen consumption of rainbow trout in a raceway farm. A dynamic model, simulating the evolution of Dissolved Oxygen concentration, was identified: the daily oscillation of fish oxygen consumption rate was simulated by means of a sinusoidal function. The model was applied to the data set collected during a four-week field study, which was carried out in July 2019. Water temperature and Dissolved Oxygen concentration were measured with an hourly frequency in farm influent and effluent. Fish biomass was monitored on a daily basis by combining the data provided by a state-of-the art system for non-invasive estimation of fish weight distribution with mortality counting. The monitoring period was partitioned into two time-windows, as fish was not fed during the first two weeks. These windows were further partitioned into a calibration and validation set. Three model parameters, i.e. the average daily respiration rate, the amplitude of its daily oscillation, and its phase were estimated by fitting the model output to the time series of DO concentration in the effluent. The results of the calibration show that: 1) the daily average oxygen consumption rate is consistent with the literature; 2) the amplitude of the daily oscillation when fish is regularly fed is more than twice that estimated for fasting fish. The results of the validation suggest that the model could be used to implement a cost-effective automatic control of oxygen supply, based on the short-term prediction of oxygen demand.

A Study on Oxygen Consumption in Freshwater Fish Labeo Rohita Exposed to Lethal and Sub Lethal Concentrations of Ethion 50%Ec

The pesticide pollution different classes like organochlorines, organophosphates, carbamates and other newgeneration ones affect the fish oxygen consumption in sublethal concentrations. Respiratory responses tolethal concentrations increase the ventilation volume and symptoms of pesticide intoxication suggestingthat the effect on respiratory surface were high in fish. Hence, in the present study an attempt has beenmade to study the effect of lethal(1.2µg/l) and sub-lethal 1/10(0.12µg/l) LC50 and 96hrs of 50% mortalityconcentrations of Ethion 50% EC an Organophosphate effect on oxygen consumption for 24 h at each 2hours interval to the Indian major carp, Labeo rohita (Hamilton). Oxygen consumption of aquatic animals isa very sensitive physiological process and therefore, alteration in the respiratory activity is considered as anindicator of stress of animals exposed to pesticides. The significant drop in the rate of oxygen consumptionwas observed in the present study in lethal and sub-lethal concentrations.

Optimization of Anguilla bicolor oxygen consumption in alkalinity culture media

One potential aquaculture commodity that can be developed is Anguilla bicolor. One effort that can be conducted to maximize the life and growth of A. bicolor by manipulating water quality through alkalinity parameters. Alkalinity is a buffer capacity for changing in water pH, and osmotic pressure of water. Alkalinity levelss in culture media can be managed by the addition of calcium carbonate (CaCO3), calcium oxide (CaO), or calcium hydroxide (CaOH) with a certain dose to the culture media. This study aimed to determine the effect of alkalinity on aquaculture media based on the level of oxygen consumption (OC) that related to growth value. This research was conducted with an experimental design using a completely randomized design (CRD) with four treatments, namely the addition of CaCO3 to maintenance media with different doses (A, 0 mg/L; B, 50 mg/L; C, 100 mg/L; D, 150 mg/L). The results showed that the treatment B (50 mg / L) showed an OC value (0.15 mgO2/g/h) and an optimal Growth Rate (GR) (3.75 g/day), while the Survival Rate (SR) parameter, the treatment had no significant effect. The conclusion was 50 mg/L of calcium carbonate (CaCO3) having the optimum alkalinity level in A. bicolor culture media. At the additional dose of CaCO3, the growth value (GR), and the level of eel fish oxygen consumption were optimal.

Surfing behind rocks costs trout dear when feeding

Despite appearances, life in the fast lane may not be as tumultuous as it might seem at first. Many fish species choose to reside in fast-flowing sections of river as the turbulence provides them with an almost free ride when sheltering downstream of rocks in the flow. ‘Prevailing theory suggests that many species exploit hydrodynamic refuges to minimise the cost of locomotion while foraging’, says Jimmy Liao from the University of Florida, USA. But he was curious to find out how much exertion it takes for fish sheltering behind rocks to catch a snack. Explaining that a lifetime of reading fly-fishing magazines had convinced him that fish use less energy when foraging in choppy water than in more sluggish sections, Liao, with Jacob Johansen and Otar Akanyeti, put the anglers’ perceived wisdom to the test.Slowly increasing the water flow in an artificial stream in the lab to 68 cm s−1, Liao and Johansen provided individual trout with a D-shaped column to shelter behind while measuring how much oxygen they consumed. Then they tricked the hungry trout into nipping out from behind the obstacle to snap at a tasty treat drifting past on a line, before wrenching it from the surprised fish's lips; ‘They would sometimes chase it upstream’, he chuckles. However, when Liao compared the fish's oxygen consumption with that of fish swimming freely in an unobstructed flow, he realised that the fish that were ensconced behind the D-shaped obstacle had to work 65% harder when snapping at the lure than fish that were feeding in a freely flowing stream. And, when Liao and Johansen monitored the fish's reactions as tempting food pellets drifted toward the animals, the sheltering fish struggled to intercept their treats as the flow increased, barely capturing any pellets at the fastest flow (84 cm s−1), compared with the unobstructed fish, which still captured 60% of the pellets. Even though trout save energy when surfing in the wake of an obstacle, venturing out of the wake to feed requires more effort and their success rate plummets in faster flowing sections of water.Taking these lessons into account, Akanyeti and Liao built a computer model of the energetics of a fish feeding in a river to help them understand when it is best for fish to take advantage of shelter and when the benefits of refuging no longer outweigh the expense of foraging from behind a rock. Running the simulated river at flows ranging from still water up to 84 cm s–1, the team found that sheltering behind a rock was more beneficial in slower flows, while freely swimming fish appeared to have the upper hand in torrents of faster water; ‘Our model predicts that individuals living in flows greater than 50 cm s–1 should avoid refuges while foraging’, says Akanyeti. The simulation also suggested that toggling between hiding behind rocks for part of the day and venturing into faster smooth water at other times to feed benefits the fish most, allowing them to take advantage of both worlds.Although it seems that life is more costly for refuging trout than anglers had presumed, Liao suspects that the shrewd fish also make the most of other energy-saving shortcuts that we have yet to discover. He hopes that engineers designing slipways alongside dams for migrating fish and ecologists restoring river beds can learn from the life experiences of trout. ‘I'd like to see us more often asking the fish themselves what they want; which means ground-truthing designs based on fish behaviour’, he says.

Hot minnows could struggle to navigate as temperatures rise

Climate change is going to get uncomfortable for many, but for ectotherms (so-called ‘cold blooded’ animals), which depend on their surroundings to maintain a healthy body temperature, the consequences could be disastrous. For example, warmer temperatures raise the metabolic rate for basic life support, leaving less spare energy for animals to go about their daily activities, in addition to impacting the energy use of the brain. But no one knows how these changes might affect the ability of ectotherms to negotiate their surroundings. For example, could higher temperatures produce bold super-smart fish or timid dunderheads that struggle with the simplest task? Libor Závorka from Shaun Killen's lab at the University of Glasgow, UK, nipped to the nearby River Kelvin to catch young minnows (Phoxinus phoxinus) before raising them at different temperatures (14 and 20°C) for 8 months to find out how climate change might affect their ability to navigate their surroundings.Measuring the fish's oxygen consumption while they lazed about and after a chase in the tank (to get their heart racing) it was clear that the fish that had grown up in extreme heat (20°C) used more energy to keep their bodies ticking over. Yet, they were able to increase the amount of energy they consumed when exercising hard, so they had as much spare energy as fish currently residing at current River Kelvin temperatures (14°C) for day-to-day activities. But when the team tested the minnows’ ability to home in on a bloodworm snack secluded in a simple maze, they realised that the fish that had been raised at 20°C struggled to secure their tasty reward, despite having larger brains. The hot fish raised in conditions that could be more common in the future simply weren't as good at navigating as modern-day fish, even though their larger brains could have made them smarter.All in all, it seems probable that minnows will be able to keep active as temperatures rise in the future, but Killen and his colleagues are concerned that they may struggle to explore their surroundings successfully, ‘probably affecting fitness and ecological interactions’, says Závorka.

Algal oxygen boost could help hot rock pool dwellers on sunny days

If you're down on the beach poking around in a rock pool, it's often the start of a summer holiday, but for Tristan McArley, from the University of Auckland, New Zealand, it's just another day at the office. He collects fish from rock pools to learn how the animals cope as the temperatures soar and the water oxygen levels dwindle, usually impairing the ability of fish to go about their daily chores. However, on one particularly brilliant summer day, McArley noticed that the rock pools were literally fizzing. Algae trapped in the pools were photosynthesising and pumping out oxygen, boosting the gas in the stagnant water to the point where it could hold no more and the oxygen escaped as bubbles. It occurred to McArley that a surfeit of oxygen is just another situation that the fish encounter naturally when it is sunny, ‘[yet] very few studies had looked into the influence of higher than normal levels of oxygen in rock pool fish’, he says.Knowing that European perch are able to extend their metabolic capacity (the difference between their maximum and minimum metabolic rates, which permits them to perform routine activities) when oxygen levels are boosted, McArley and his colleagues Anthony Hickey and Neill Herbert, also from Auckland, wondered how local triplefin fish deal with an overabundance of oxygen on blistering summer days.‘These fish often occupy quite small rock pools so they are easily caught with hand nets’, says McArley, who transported 2 g mottled twisters (Bellapiscis medius) and common triplefins (Forsterygion lapillum) back to the Leigh Marine Laboratory. McArley then began measuring the fish's oxygen consumption – initially when swimming at their top speed in 21°C water at either normal (100% air saturation) or 200% air saturation (super oxygenated) to record their maximum oxygen consumption. Next, he allowed the fish to settle down gradually until they reached the minimum oxygen consumption necessary for survival. After that, McArley increased the temperature gradually from 21°C to 29°C to find out how the fish's oxygen consumption increased as the temperature rose. Finally, he logged when the fish toppled over as they were warmed in normal and super-oxygenated water, to find the highest temperature that they can tolerate.The metabolic capacity of the fish in 200% air saturated water increased, allowing them to continue going about their lives despite the higher temperatures, which usually impair fish activities. Considering the sunny conditions that cause oxygen levels to increase in rock pools, McArley says, ‘It may be that whenever these species face acutely high temperatures, they do so under super-oxygenated conditions’. At the highest temperatures, the super-oxygenated fish were barely more resilient than the fish in normally oxygenated water, toppling over at about 31°C, ‘pointing to factors other than the ability to supply oxygen to tissues as being responsible for setting the absolute thermal limits in these species’, says McArley. However, he was surprised when he measured the metabolic rates of the super-oxygenated twisters and triplefins at rest; the metabolic rates were higher than those of the fish in normal water. ‘This suggests there are also some additional metabolic costs of super-oxygenation to these fish’, he says.It seems that fish in hot rock pools on sunny days may not be as compromised as everyone had thought and McArley adds, ‘It is important to study the impacts of stressors such as acute heat stress under ecologically relevant conditions’. However, he warns that the algal oxygen boost is unlikely to protect sizzling rock pool species in the long run as climate change takes an unrelenting grip.

Economic values of growth rate, feed intake, feed conversion ratio, mortality and uniformity for Nile tilapia

The aim of the study was to derive the economic value (s) (EVs) of growth rate, feed intake, feed conversion ratio, mortality and uniformity for Nile tilapia (Oreochromis niloticus). A smallholder production system where fish are cultured in earthen ponds and oxygen is a limiting factor for production, was simulated using a deterministic bio-economic model. Traits of interest were: thermal growth coefficient (TGC), thermal feed intake coefficient (TFC), feed conversion ratio (FCR), mortality rate (M) and uniformity of harvest body weight (U). Two breeding objectives were considered: a breeding objective with TGC, TFC, M and U (H1model), and a breeding objective with TGC, FCR, M and U (H2model). Gross margin (GM) was simulated before and after one genetic standard deviation improvement (σa) on a trait while other breeding objective traits were kept unaltered. EVs (US$/kg/σa) were derived as: change in GM/(farm production before genetic improvement). Results show that EVs of TGC differ depending on the definition of the breeding objective. The EV of TGC was 1.19 when TFC was in the breeding objective. In contrast, EV was only 0.02 when FCR was in the breeding objective. This difference is caused by the way EVs are calculated: the increase in gross margin resulting from a marginal increase in TGC while keeping other traits (FCR or TFC) constant. EV of TFC was 1.25 and the EV for FCR was 0.41. EVs for M and U were 0.06 and 0.02, irrespective of the model used. Improving TGC reduced the overall grow-out period, increasing the number of production cycles in the farm. In H1 model, reduced grow-out period was accompanied by a decrease in the amount of feed used in the farm (−272.24kg/year) and in individual fish oxygen consumption (−1.67g/fish/year), resulting in an increase in gross margin. In H2 model, increasing TGC resulted in a reduced grow out period but also increased feed used in the farm (5.73kg/year) and increased individual fish oxygen consumption (0.57g/fish/year). We conclude that the EV of TGC depends on which breeding objective is used. Faster growing fish consume more oxygen, and unless faster growth is accompanied by improved FCR, this will lead to oxygen limitations, necessitating lower stocking densities. Our results thus strongly confirm the economic importance of reducing FCR, irrespective of the model used.Statement of relevanceThis is the first study that presents the economic values for breeding objective traits for Nile tilapia farmed in earthen ponds using a bio-economic model.

Oxygen consumption rate v. rate of energy utilization of fishes: a comparison and brief history of the two measurements.

Accounting for energy use by fishes has been taking place for over 200 years. The original, and continuing gold standard for measuring energy use in terrestrial animals, is to account for the waste heat produced by all reactions of metabolism, a process referred to as direct calorimetry. Direct calorimetry is not easy or convenient in terrestrial animals and is extremely difficult in aquatic animals. Thus, the original and most subsequent measurements of metabolic activity in fishes have been measured via indirect calorimetry. Indirect calorimetry takes advantage of the fact that oxygen is consumed and carbon dioxide is produced during the catabolic conversion of foodstuffs or energy reserves to useful ATP energy. As measuring [CO2 ] in water is more challenging than measuring [O2 ], most indirect calorimetric studies on fishes have used the rate of O2 consumption. To relate measurements of O2 consumption back to actual energy usage requires knowledge of the substrate being oxidized. Many contemporary studies of O2 consumption by fishes do not attempt to relate this measurement back to actual energy usage. Thus, the rate of oxygen consumption (M˙O2 ) has become a measurement in its own right that is not necessarily synonymous with metabolic rate. Because all extant fishes are obligate aerobes (many fishes engage in substantial net anaerobiosis, but all require oxygen to complete their life cycle), this discrepancy does not appear to be of great concern to the fish biology community, and reports of fish oxygen consumption, without being related to energy, have proliferated. Unfortunately, under some circumstances, these measures can be quite different from one another. A review of the methodological history of the two measurements and a look towards the future are included.

Paradoxical anaerobism in desert pupfish.

In order to estimate metabolic demands of desert pupfish for conservation purposes, we measured oxygen consumption in fish acclimated to the ecologically relevant temperatures of 28 or 33°C. For these experiments, we used fish derived from a refuge population of Devils Hole pupfish (Cyprinodon diabolis). Measurement of routine oxygen consumption (V̇O2,routine) revealed some 33°C-acclimated fish (10% of 295 assayed fish) periodically exhibited periods of no measurable oxygen consumption despite available ambient oxygen tensions that were above the critical PO2. We call this phenomenon paradoxical anaerobism. The longest observed continuous bout with no oxygen consumption was 149 min, although typical bouts were much shorter. Fish maintained normal posture and ventilation rate (>230 ventilations per minute) during paradoxical anaerobism. Fish rarely demonstrated a compensatory increase in oxygen use following a period of paradoxical anaerobism. In contrast, only one out of 262 sampled fish acclimated at 28°C spontaneously demonstrated paradoxical anaerobism. Muscle lactate concentration was not elevated during periods of paradoxical anaerobism. However, the amount of ethanol released by the 33°C-acclimated fish was 7.3 times greater than that released by the 28°C acclimation group, suggesting ethanol may be used as an alternative end product of anaerobic metabolism. Exposure to exogenous ethanol, in concentrations as low as 0.1%, produced periods of paradoxical anaerobism even in 28°C-acclimated fish.

Alcoholic pupfish kick breathing oxygen

Deep in a warm pool in a limestone cavern in the Mojave Desert lives one of the rarest species on earth: the Devils Hole pupfish (Cyprinodon diabolis). With a current population of just 131 adults, the race is on to secure the fish's future. ‘One possible cause for the small population size of C. diabolis is limited food availability’, says Frank van Breukelen from the University of Nevada Las Vegas, USA. Realising that the dark conditions dramatically limit the amount of food that grows in the cavern to support the fish, van Breukelen and his colleague, Stanley Hillyard, were curious to know how many pupfish the restricted ecosystem could sustain. However, before they could do the calculation, the duo needed to measure the scarce fish's metabolic rate. As the native Devils Hole pupfish population is too endangered to study directly, van Breukelen and Hillyard measured the metabolic rate of a refuge population of the fish that had been established as an insurance policy should the population ever be wiped out. But when they performed the measurement, the duo stumbled across an unexpected paradox.Recording the fish's oxygen consumption at temperatures ranging from 25 to 38°C, Matt Heuton found that they consumed oxygen at a stable rate of around 300 μl h−1 when they came from a population that had been raised at 28°C. However, when Heuton measured the oxygen consumption rate of fish raised at 33°C – the temperature in the Devils Hole spring – something went wrong. The fish appeared to stop consuming oxygen. ‘My initial reaction was that there was a malfunction of the electrode’, laughs van Breukelen. However, after testing 295 animals, van Breukelen and Hillyard had to concede that the phenomenon was real. The fish were somehow switching from aerobic metabolism to anaerobic metabolism, which was perplexing as anaerobic metabolism is nowhere near as effective as aerobic metabolism – only yielding 1/15 the amount of ATP per glucose molecule generated by aerobic metabolism. Why were the fish indulging in such a profligate practice?Intrigued, the team tested whether the phenomenon was the result of the refuge C. diabolis population breeding with another closely related species, Cyprinodon nevadensis mionectes. van Breukelen explains that it has been suggested that interbreeding with other pupfish could have compromised the function of the mitochondria that generate ATP. However, when the team measured the oxygen consumption patterns of the two species, they both performed paradoxical anaerobism, so there was no mitochondrial disruption. And when the team tested whether C. diabolis were switching to paradoxical anaerobism because they had depressed metabolism, they found that the fish were still wafting their gill covers to take in oxygen, so they weren't depressing their metabolism. Finally, the team checked whether C. diabolis were switching to paradoxical anaerobism because there simply was not enough oxygen to sustain aerobic metabolism in the warm conditions. However, even that theory did not hold water.‘We were going nuts trying to figure out what triggers paradoxical anaerobism’, admits van Breukelen, until he and Heuton embarked on an animated brain-storming session one night. It occurred to them that the fish may be switching to paradoxical anaerobism to avoid the toxic side-effects of aerobic metabolism, producing ethanol instead. They knew that the 33°C-acclimated fish naturally produced high levels of ethanol – 7.3 times more than the fish from cooler water: could the ethanol be switching off aerobic energy production and stalling oxygen consumption? ‘I said, “Let's get the fish drunk”’, recalls van Breukelen. And when the team added ethanol to the fish's water, even the fish that were adapted to cooler water switched to paradoxical anaerobism. So Devils Hole pupfish switch off aerobic metabolism to avoid the toxic side-effect of an aerobic lifestyle, despite the expense.

Growth, Oxygen Consumption, and Behavioral Responses of Danio rerio to Variation in Dietary Protein and Lipid Levels.

In recent years, there has been increasing interest in the welfare of ornamental fish. Diet can significantly impact the welfare of fish, which can manifest as changes in the fish's physical health and behavior. The zebrafish, Danio rerio, is a popular ornamental species; however, little is known about their nutritional requirements with possible implications for their welfare. Here, we investigated the effect of diets with increasing crude protein (iso-caloric diets) and lipid (iso-nitrogenous diets) on the growth performance, oxygen consumption, and behavior of zebrafish. We found no significant effects of crude protein (32%-75%) or lipid (8%-16%) on the specific growth rate or oxygen consumption of fish fed 5% of their body mass (BM)/day, although the highest crude protein and lipid diet resulted in an increase in condition factor. Furthermore, the crude protein diets did not affect zebrafish behavior when fed a 2% BM ration, once a day. This study has shown that a diet with 32% crude protein and a diet with 8% crude lipid, when fed at a 5% BM ration, were sufficient to meet the growth requirements of our zebrafish. These diets supported the fish's physical health and thus benefited their welfare.

Influence of tank hydrodynamics on vertical oxygen stratification in flatfish tanks

In sole (Solea spp.) culture, like in other flatfish culture, it is likely that a vertical gradient of dissolved oxygen (DO) occurs with the lower concentrations being at the tank bottom. This lower concentration at the tank bottom is a consequence of fish oxygen consumption and of the presence of the boundary layer. This fact generates lower DO concentrations in the near-bottom zone where soles are lying most of the time. The aim of this work was to study the hydrodynamic conditions that determine the oxygen gradient that occurs in the layer of water adjacent to flatfish.Three flow rates were tested in a circular tank and in a rectangular or raceway tank. For each flow rate, water velocities, boundary layer thickness and Reynolds number were calculated. Results showed that the vertical gradient of dissolved oxygen diminishes when water velocity and Reynolds numbers (Re) increase. At the fish density used in this work (11.6kgm−2), when Re decreased under 6000, a large increase in the DO gradient was observed. Guidelines are presented to determine in which situations, as defined by hydraulic parameters, Re>6000 is achieved and DO stratification avoided.The present work shows that in raceways, the flow rate required to avoid DO stratification is higher than that typically needed to maintain water quality (oxygen, ammonia-nitrogen, carbon dioxide and suspended solids). In circular tanks, it can be easier to achieve velocities that are high enough to avoid stratification with low water inlet flow rates, by adjusting the area of the water entry orifices.

Oxygen Consumption Constrains Food Intake in Fish Fed Diets Varying in Essential Amino Acid Composition

Compromisation of food intake when confronted with diets deficient in essential amino acids is a common response of fish and other animals, but the underlying physiological factors are poorly understood. We hypothesize that oxygen consumption of fish is a possible physiological factor constraining food intake. To verify, we assessed the food intake and oxygen consumption of rainbow trout fed to satiation with diets which differed in essential amino acid (methionine and lysine) compositions: a balanced vs. an imbalanced amino acid diet. Both diets were tested at two water oxygen levels: hypoxia vs. normoxia. Trout consumed 29% less food under hypoxia compared to normoxia (p<0.001). Under both hypoxia and normoxia trout significantly reduced food intake by 11% and 16% respectively when fed the imbalanced compared to the balanced amino acid diet. Oxygen consumption of the trout per unit body mass remained identical for both diet groups not only under hypoxia but also under normoxia (p>0.05). This difference in food intake between diets under normoxia together with the identical oxygen consumption supports the hypothesis that food intake in fish can be constrained by a set-point value of oxygen consumption, as seen here on a six-week time scale.