Effects of temperature on food consumption, growth and oxygen consumption of freshwater prawn Macrobrachium rosenbergii (de Man 1879) postlarvae

Effects of temperature on food consumption, growth and oxygen consumption were estimated for the freshwater prawn Macrobrachium rosenbergii postlarvae at 23 °C, 28 °C and 33 °C in the laboratory. The results showed that the animal's initial body weight had a close linear relationship with food consumption and growth. Food consumption increased directly with temperature. Consumption rates (C; mg day^?1 ind^?1 ) of the 28 °C and 33 °C groups were much higher than that of the 23 °C group (P < 0.001), and the 33 °C group's consumption rate was higher than that of the 28 °C group (P < 0.05). The relationship of food consumption with temperature and initial body weight (W; mg) could be described as: C = 0.0679W + 0.185t? 3.17. Growth increased significantly with increased temperature. The relationship among specific growth rate, temperature and initial body weight was as follows: SGR = ?0.110W + 0.213t + 0.176. However, temperature showed no effect on growth efficiency. Oxygen consumption increased significantly with temperature (P < 0.01). The weight‐specific oxygen consumption rates (mg O₂ g^?1 h^?1) at 23 °C, 28 °C and 33 °C were 0.83, 1.16 and 1.49 mg O₂ g^?1 h^?1 for 61.92 mg M. rosenbergii.     

Aquaculture development in less developed countries: Social,economic and political problems: Leah J. Smith and Susan Peterson. Bowker Publishing Company,Essex, U.K., 1982. 152 pp., US$ 29.50. ISBN 0-86531-235-4

Oxygen consumption and ammonia production in elvers of varying growth rates were studied. The allometric equation describing the relationship between oxygen consumption and weight is y =00.638 x^0,525, where y is the oxygen consumption (mg/h) and x is the mass (g). The weight specific allometric equation for the relationship between ammonia excretion and weight is $\text{y}\text{x}\text{= 0.0129 x}{}^{\mathrm{0,465}}$. Slow growing elvers were found to have higher respiratory rates (0.737 mg O₂ h^?1 g^?1) than would be expected for their size.     

Optimization of blue mussel (Mytilus edulis) seed culture using recirculation aquaculture systems

By introducing recirculation aquaculture systems (RAS) in the nursery phase of the blue mussel (Mytilus edulis) (17–18 mm), we aimed at a similar growth and survival and a similar water quality compared to the commonly used flow‐through systems (FTS). To calculate water flow and size of the biofilter, a series of experiments were done to determine clearance rate (9.26 mL min^?1), pseudo faeces threshold (60 000 cells Pavlova lutheri mL^?1), nitrogen production (0.00065 mg TAN h^?1 ind^?1 and 1.6 × 10^?5 mg NO₂–N h^?1 ind^?1) and oxygen consumption (0.03 ± 0.01 mg O₂ h^?1 ind^?1). RAS showed no significant differences in water quality (0.06 mg TAN L^?1; 7.7 mg O₂ L^?1) and growth performance of mussel seed specific growth rate (SGR = 5% day^?1) after the experimental period of 4 weeks compared with FTS. The low water refreshment, 10% per day, as well as the constant chlorophyll concentrations (9.76 ± 1.06 μg L^?1), suggests the potential of RAS as culture system for mussel seed.     

Sex differences in metabolic rate and swimming performance in pink salmon (Oncorhynchus gorbuscha): the effect of male secondary sexual traits

Do secondary sexual traits, such as large dorsal hump and hooked snout, decrease the swimming efficiency of male pink salmon during freshwater migration? This is the first study to address the effects of secondary sexual traits in pink salmon on oxygen uptake and swimming capacity. We conducted a laboratory experiment using a swimming respirometer and a field study using electromyogram (EMG) telemetry in the Shibetsu River, Hokkaido, Japan. We compared the relationship between MO₂ (mg O₂·kg^?1·h^?1) and swimming velocity U (m·s^?1) in male and female fish, and also investigated the effects of morphological traits (secondary sexual characters) on the relationship between MO₂ (mg O₂·kg^?1·h^?1) and swimming velocity U (m·s^?1). Additionally, we compared energy costs and swimming behaviour during upstream migration between male and female pink salmon. The laboratory experiment revealed that MO₂ exponentially increased with increasing U; this increase was described by MO₂ = 167.9e^1.23U for males and 144.9e^1.14U for females. Linear mixed models found that hump height and the upper jaw length in males significantly and positively affected the relationship between MO₂ and U; no effect was found in females. The field study found that swimming velocity for both sexes estimated from EMG calibration was lower than optimal swimming velocity (U_opt) calculated from the laboratory experiment. We suggest that pink salmon in the Shibetsu River do not swim at the optimal swimming velocity because of the short migration distance involved (20 km).     

Temperature‐dependent feed requirements in farmed blue mussels (Mytilus edulis L.) estimated from soft tissue growth and oxygen consumption and ammonia‐N excretion

Feed requirements were estimated from specific growth rates in standardized soft tissue dry weight (SGR_DW’) and atomic O:N ratios for mussels fed seven rations of microalgae (5–735 μg C h^?1 ind^?1) at 7 and 14°C respectively. The mean oxygen consumption and ammonia‐N excretion rates were significantly higher at 14°C (0.29 μg O² and 27.3 μg N ind^?1 h¹) compared with those at 7°C (0.16 μg O² and 11.4 μg N ind^?1 h^?1) (P < 0.05), resulting in O:N ratios between 3 and 45 at 7°C and 7 and 28 at 14°C. Low O:N ratios indicate protein catabolism and an unfavourable condition, whereas high ratios indicate that carbohydrate is the primary energy source. The measured SGR_DW’ suggests minimum feed requirements of ~240 and ~570 μg C ind^?1 h^?1 for weight maintenance at 7 and 14°C, with corresponding O:N ratios of 24 and 16, respectively, indicating a more stressed condition at 14°C. A 0.5% SGR_DW’ day^?1 was obtained by ~565 (O:N = 29) and ~680 (O:N = 23) μg C ind^?1 h^?1 at 7 and 14°C respectively. A positive and significantly higher SGR_DW’, with the lowest feed ration at 7°C compared with a negative SGR_DW’ at 14°C (P < 0.05), indicated that storage time can also possibly be prolonged at low temperatures if the mussels are not fed.     

Characterization of whitebait (Galaxias maculatus) respiratory rates to optimize intensive culture carrying capacities

Galaxias maculatus is an osmeriform native fish of the Southern Hemisphere, in which the crystalline larvae is considered as a luxury delicacy, for this reason, it has been commercially exploited in Chile, Argentina and New Zealand. However, the fisheries have been rapidly decreasing due to the overexploitation and the predation of introduced species. Because of these events, there is a need to determine a carrying capacity for an intensive fish culture. In order to optimize stocking densities for fish culture, this paper proposes objectives to determine oxygen consumption (OC) rates, dissolved oxygen concentrations that produce signs of hypoxia and the average time elapsed between food intake and peak OC in G. maculatus. In the oxygen experiments under routine metabolism conditions, we found that G. maculatus adults and whitebait showed signs of asphyxia at dissolved oxygen concentrations between 1.3 and 2.2 mg L^?1 and that adults tolerated dissolved oxygen levels as low as 1.3 mg L^?1. The results showed that G. maculatus individuals with an average weight of 0.04 g consumed 0.048 mg O₂ h^?1, whereas individuals with an average weight of 1.4 g consumed 0.345 mg O₂ h^?1. Galaxias maculatus increased the OC rate by 31%, from 0.39 to 0.51 mg O₂ h^?1 g^?1, occurring 14 min after food intake. The carrying capacities for industrial cultures of G. maculatus, were estimated using an allometric equation (OC=0.2363 ×W ^0.612 ), a water flow rate of 1 m³ h^?1 and an input oxygen concentration of 10 mg L^?1 at 12 °C. The density culture of whitebait (4 g) can be allowed to reach 8–11 kg m^?3; therefore, these stocking densities reduce the risk of hypoxia and mortality, ensuring the appropriate growth and feed conversion rates.     

Effect of chloride concentration on the acute toxicity of nitrite to common carp, Cyprinus carpio L., fry

Abstract. Duplicate static bioassays were conducted for 168 h each to determine the median lelhal concentration (LC50) of nitrite (NO^?₂) for common carp, Cyprinus carpio L., fry at five different chloride (Cl^?) levels. The acute toxicity of nilrite ceased towards the end of 96 h at all levels of chloride concentration. There was a highly significant positive correlation between the chloride concentration tested and the 96-h LC50. The 96-h LC50 values are 2·55, 5·77, 14·41 27·26 and 48·70 mgl^?1 NO^?₂-N at chloride concentration of 1·0. 5·0, 10·5, 27·3 and 45·0 mgl^?1 Cl^? respectively. The linear relationship between chloride concentration and 96-h LC50 is best described by the equation: y= 1·03x+ 1·49 (r=+ 0·996; d.f. = 3;P <0·001), where y= 96 h LC50 of NO^?₂-N and x= concentration of Cl^?. A NO^?₂-N to Cl^? ratio of about 1:1·5–3·0 prevented complete mortality over the 168-h experimental period. A NO^?₂-N to Cl^? ratio of 1:5 is recommended for protection of carp fry against nilrite mortality in fish farms.     

Standard oxygen consumption of seasonally acclimatized cownose rays, Rhinoptera bonasus (Mitchill 1815), in the northern Gulf of Mexico

Standard oxygen consumption rate (MO₂) was determined for 19 cownose rays (Rhinoptera bonasus) using flow-through respirometry. Rays ranged in size from 0.4 to 8.25 kg (350–790 mm DW). Respirometry experiments were conducted on seasonally acclimatized rays at temperatures from 19.0 to 28.8 °C. Estimates of mass-dependent MO₂ ranged from 55.88 mg O₂ kg⁻¹ h⁻¹ for an 8.25 kg ray to 332.75 mg O₂ kg⁻¹ h⁻¹ for a 2.2 kg animal at 22–25°C. Multiple regression analysis examining the effect of temperature, salinity, and mass on standard mass-independent MO₂ found temperature (P < 0.01), and mass (P < 0.0001) to have a significant effect on oxygen consumption, whereas salinity did not (P > 0.05). Q ₁₀ was calculated as 2.33 (19–28 °C), falling between the estimates determined for two other batoid species, the bull ray (Myliobatos aquila; Q ₁₀ = 1.87) and the bat ray (Myliobatis californica; Q ₁₀ = 3.00). The difference in the Q ₁₀ estimates may be attributed to the use of seasonally acclimatized as opposed to laboratory-acclimated animals.     

The effect of feeding on oxygen consumption and ammonia excretion of juvenile tench Tinca tinca (L.) reared in a water recirculating system

The effect of feeding frequency (one, three, and continuous feeding), feed ration (0.2, 0.5, 0.8% of total fish biomass), and feeding per se on the oxygen consumption (OC, mg O₂ kg⁻¹ h⁻¹) and ammonia excretion (AE, mg TAN kg⁻¹ h⁻¹) of juvenile tench (body weight 15–19 g) and variations in these parameters in daily cycles were examined. Fish metabolism was studied in a recirculating system (rearing tanks of 0.2 m³, water temperature 23 °C). It was found that oxygen consumption and ammonia excretion depended significantly on feed ration. An increase of feed ration from 0.2 to 0.8% of fish biomass caused an increase of OC and AE from 126.80 mg O₂ kg⁻¹ h⁻¹ and 1.95 mg TAN kg⁻¹ h⁻¹ to 187.35 mg O₂ kg⁻¹ h⁻¹ and 8.80 mg TAN kg⁻¹ h⁻¹ (p<0.05). There was no dependence between feeding frequency and the mean rate of oxygen consumption. However, the relationship between feeding frequency and ammonia excretion by juvenile tench was statistically significant (p<0.05). Feeding frequency significantly affected daily fluctuations of AE and OC. It was found that diurnal variations in metabolic rates were strictly related to tench feeding, and the daily variations of AE were significantly higher than OC.     

Rates of oxygen consumption and ammonia excretion of juvenile Eurasian perch Perca fluviatilis L.

The impact of feeding, fish size (body weight from 18.5 to 56.5 g) and water temperature (20 and 23 °C) on oxygen consumption (OC, mg O₂ kg^–1 h^–1) and ammonia excretion (AE, mg TAN kg^–1 h^–1) was studied in Eurasian perch held in recirculation systems. OC for both fed and feed-deprived (3 days) fish was higher at 23 °C (278.5 and 150.1 mg O₂ kg^–1 h^–1) than at 20 °C (249.3 and 135.0 mg O₂ kg^–1 h^–1; P < 0.01). AEs for both fed and feed-deprived fish were also significantly higher at 23 °C than at 20 °C (P < 0.001). Water temperature and fish size had a significant impact on the oxygen:feed ratio (OFR, kg O₂ kg^–1 feed fed day^–1) and ammonia:feed ratio (AFR, kg TAN kg^–1 feed fed day^–1; P < 0.001). Their average values at temperatures of 20 and 23 °C were 0.17 and 0.19 kg O₂ kg^–1 feed fed day^–1 and 0.009 and 0.011 kg TAN kg^–1 feed fed day^–1, respectively.     

Oxygen consumption and ammonia excretion of common wolffish Anarhichas lupus Linnaeus 1758 in an experimental-scale, seawater, land-based culture system

The oxygen consumption (0₂) and ammonia excretion (N) of juvenile and adult common wolffish was measured in culture tanks in the laboratory. The oxygen consumption and ammonia excretion were affected by temperature (C), fish size and feeding rate. For juveniles (0.5 kg; 7C) the diel oxygen consumption rate varied between 37 and 62 mg O₂ kg^-1 h^-1 and ammonia excretion between 2.3 and 5.7 mg N kg^-1 h^-1. The corresponding rates for adult fish (6.9 kg; 7C) were 29-44 mg O₂ kg^-1 h^-1 and 1.2–3.1 mg N kg^-1 h^-1. The weight-specific oxygen consumption (mg O₂ kg^-1 h^-1) was described by the following formulae: O₂ (7C) = 0.17* W^0.83 and O₂ (12C) = 0.39 * W^0.73 and the corresponding ammonia excretion (mg N kg^-1 h^-1) by: N(7C) = 0.024 W^0.75 and N(12C) = 0.073 W^0.60, where W is fish weight in g.     

Growth performance and tissue mineral content of juvenile grouper (Epinephelus coioides) fed diets supplemented with various levels of manganese

This study was conducted to investigate the effect of dietary manganese (Mn) on growth, vertebrae and whole‐body Mn content of juvenile grouper, and to examine the effect of dietary Mn on copper (Cu), iron (Fe), zinc (Zn), calcium (Ca), phosphorus (P) and magnesium (Mg) content of vertebrae and whole body. Seven casein‐gelatin‐based diets were supplemented with 0, 5, 10, 15, 20, 50 and 1000 mg kg^?1 of Mn from MnSO₄·H₂O. Grouper with an initial weight of 12.9 ± 0.4 g were fed to satiation with one of the seven diets for 8 weeks. Growth was not significantly affected by dietary Mn supplements. Vertebrae Mn increased from 31.7 to 118.1 mg kg^?1 dry weight with dietary Mn supplement increasing from 0 to 50 mg kg^?1 (y = ?0.0002x³ + 0.0162x² + 1.3903x + 26.27, R² = 0.9561, where y is the vertebrae Mn content and x is the dietary Mn content). Whole‐body Mn increased from 2.5 to 7.8 mg kg^?1 wet weight with dietary Mn supplement increasing from 0 to 50 mg kg^?1 (y = 0.00001x³ ? 0.00107x² + 0.11054x + 2.24615, R² = 0.9080, where y is the whole‐body Mn content and x is the dietary Mn content). Dietary Mn had no significant effect on vertebrae Fe, Ca, P and Mg content, and whole‐body Cu, Zn and Mg content. However, vertebrae Zn and whole body Ca, P were highest in fish fed diet supplemented with 15 mg kg^?1 of Mn. Based on this, Mn supplement of 15 mg kg^?1 might be the optimum when the basal diet contained 4 mg kg^?1 of Mn. Fish fed diet supplemented with 1000 mg kg^?1 of Mn did not show any gross abnormality or change in feeding behaviour, but Mn contents of vertebrae and whole body were as high as 695.1 mg kg^?1 dry weight and 42.5 mg kg^?1 wet weight, respectively. Also, whole body Fe decreased significantly when Mn supplement was up to 1000 mg kg^?1.     

Thermal tolerance, oxygen consumption and haemato-biochemical variables of Tor putitora juveniles acclimated to five temperatures

A 30-day acclimation trial was conducted using Tor putitora to elucidate its thermal tolerance, oxygen consumption, haemato-biochemical variables and selected enzymatic activities at five acclimation temperatures (AT). Juveniles of T. putitora were randomly distributed among five treatment groups (20, 23, 26, 29 and 32 ± 0.5 °C). There was a significant curvilinear increase in critical thermal maxima (CT_max) (y = ?0.0693x ² + 1.7927x + 34.628, R ² = 0.996) and lethal thermal maxima (LT_max) (y = ?0.1493x ² + 2.3407x + 35.092, R ² = 0.991) with increasing AT. The oxygen consumption rate increased significantly with increasing AT. The Q ₁₀ values were 1.16 between 20 and 23 °C, 3.09 between 23 and 26 °C, 1.31 between 26 and 29 °^C and 1.76 between 29 and 32 °C of AT. The acclimation response ratios were ranged between 0.37 and 0.59. Catalase, superoxide dismutase and ATPase activities were increased linearly in liver, gill and kidney, while brain acetylcholine esterase activity decreased linearly with increasing AT. Blood glucose remained unchanged up to AT of 26 °C and increased significantly at AT of 29 and 32 °C. Haemoglobin content was increased linearly with increasing AT. The highest WBC count was observed at 20 °C, and no significant changes found till AT of 26 °C and significantly decreased at 32 °C. Total serum protein and globulin were significantly decreased with increasing AT. Highest values were observed at 20 °C and remained consistent till 26 °C, then decreased significantly. There was no significant change in A/G ratio through the AT 20–29 °C and increased significantly at 32 °C. The increase in CT_max, LT_max and oxygen consumption rate with increasing AT may suggest that the thermal tolerance of T. putitora is dependent on its prior thermal exposure history, and it could adapt to higher AT by altering its haemato-biochemical variables.     

Effectiveness of eugenol sedation to reduce the metabolic rates of cool and warm water fish at high loading densities

Effects of eugenol (AQUI‐S^®20E, 10% active eugenol) sedation on cool water, yellow perch Perca flavescens (Mitchill), and warm water, Nile tilapia Oreochromis niloticus L. fish metabolic rates were assessed. Both species were exposed to 0, 10, 20 and 30 mg L^?1 eugenol using static respirometry. In 17°C water and loading densities of 60, 120 and 240 g L^?1, yellow perch controls (0 mg L^?1 eugenol) had metabolic rates of 329.6–400.0 mg O₂ kg^?1 h^?1, while yellow perch exposed to 20 and 30 mg L^?1 eugenol had significantly reduced metabolic rates of 258.4–325.6 and 189.1–271.0 mg O₂ kg^?1 h^?1 respectively. Nile tilapia exposed to 30 mg L^?1 eugenol had a significantly reduced metabolic rate (424.5 ± 42.3 mg O₂ kg^?1 h^?1) relative to the 0 mg L^?1 eugenol control (546.6 ± 53.5 mg O₂ kg^?1 h^?1) at a loading density of 120 g L^?1 in 22°C water. No significant differences in metabolic rates for Nile tilapia were found at 240 or 360 g L^?1 loading densities when exposed to eugenol. Results suggest that eugenol sedation may benefit yellow perch welfare at high densities (e.g. live transport) due to a reduction in metabolic rates, while further research is needed to assess the benefits of eugenol sedation on Nile tilapia at high loading densities.     

The effect of temperature on the resting and post-exercise metabolic rates and aerobic metabolic scope in shortnose sturgeon <Emphasis Type="Italic">Acipenser brevirostrum</Emphasis>

The effects of acclimation temperature (15, 20, 25 °C) on routine oxygen consumption and post-exercise maximal oxygen consumption rates (MO₂) were measured in juvenile shortnose sturgeon (Acipenser brevirostrum LeSueur, 1818). The routine MO₂ of shortnose sturgeon increased significantly from 126.75 mg O₂ h^?1 kg^?1 at 15 °C to 253.13 mg O₂ h^?1 kg^?1 at 25 °C. The temperature coefficient (Q ₁₀) values of the routine metabolic rates ranged between 1.61 and 2.46, with the largest Q ₁₀ values occurring between 15 and 20 °C. The average post-exercise MO₂ of all temperature groups increased to a peak value immediately following the exercise, with levels increasing about 2-fold among all temperature groups. The Q ₁₀ values for post-exercise MO₂ ranged from 1.21 to 2.12, with the highest difference occurring between 15 and 20 °C. Post-exercise MO₂ values of shortnose sturgeon in different temperature groups all decreased exponentially and statistically returned to pre-exercise (resting) levels by 30 min at 15 and 20 °C and by 60 min at 25 °C. The aerobic metabolic scope (post-exercise maximal MO₂-routine MO₂) increased to a maximum value ～156 mg O₂ h^?1 kg^?1 at intermediate experimental temperatures (i.e., 20 °C) and then decreased as the temperature increased to 25 °C. However, this trend was not significant. The results suggest that juvenile shortnose sturgeon show flexibility in their ability to adapt to various temperature environments and in their responses to exhaustive exercise.     

Oxygen consumption of the ascidian Styela clava in relation to body mass,temperature and salinity

The metabolic physiological response to body mass, temperature (12–28 °C) and salinity (20–36 g L^?1) was examined in this paper. Oxygen consumption rate, which is dependent on environmental conditions, was exponentially related to body mass and varied from 0.045 to 1.11 mg h^?1 g^?1. Oxygen consumption rate increased as salinity increased from 20 to 36 g L^?1, and increased with increasing temperature. The effect of temperature gradient between experimental treatments on oxygen consumption rate was evaluated by calculating Q₁₀ (the Arrehenius relationship for increase with temperature). The Q₁₀ value within the temperature range from 12 to 16 °C was much higher than the value within the temperature range from 16 to 20 °C, 20 to 24 °C and 24 to 28 °C, indicating a reduced temperature dependence of ascidian metabolism at a high temperature.     

Swimming activity and energetic expenditure of captive rainbow trout Oncorhynchus mykiss (Walbaum) estimated by electromyogram telemetry

Rainbow trout Oncorhynchus mykiss (Walbaum) are usually cultured at high densities to maximize production, but little is known about the physiological and behavioural consequences of high‐density fish culture. The purpose of this study was to develop quantitative correlates of activity for fish held under conditions of increasing density. Fifteen hatchery‐reared rainbow trout (mean fork length = 432.3 ± 9.2 mm) were implanted with activity (electromyogram; EMGi) transmitters and randomly assigned to each of three replicate tanks. Original tank densities (15 kg m^?3) were then increased to 30 and finally to 60 kg m^?3 at weekly intervals by adding additional fish. Remote telemetry signals indicated that activity increased with increasing stocking density. Fish were relatively inactive during the middle of the day, with diel activity patterns not differing among treatments. Fish were more active during periods of darkness, with activity increasing with increasing stocking density. Relationships between swimming speed, EMGi activity and oxygen consumption were developed using a respirometer and used to estimate oxygen consumption of the fish in the density treatments. Average oxygen consumption estimates increased with increasing density treatments as follows: low density = 75.6 mg kg^?1 h^?1; medium density = 90.0 mg kg^?1 h^?1; and high density = 102.6 mg kg^?1 h^?1. Telemetry permits quantification of the effects of increasing density on fish activity. Physiological telemetry devices may provide a useful tool for remotely monitoring animal welfare correlates under controlled conditions for fish exposed to different husbandry conditions and may prove a valuable tool for the aquaculture industry.     

Routine metabolism of larval green sturgeon (Acipenser medirostris Ayres)

Routine metabolic rates of green sturgeon (Acipenser medirostris) from hatching to 31 days post hatch (dph) were determined under normoxic conditions. During the endogenous feeding stage that comprised period from hatching to 15 dph, the oxygen consumption rate (MO₂, μg O₂ larva⁻¹ h⁻¹) increased 5-fold before yolk reserves became exhausted and MO₂ rates steady. The allometric relationships between MO₂ and body mass had mass exponents greater than 1.0 (b=1.64±0.21) and equal to 1.0 (b=1.04±0.07) during the endogenous and exogenous feeding phases, respectively. The magnitude and changes of MO₂ rates in green sturgeon larvae reflected their early ontogeny, especially during the endogenous feeding phase when the increase in metabolic rates was associated with organogenesis, acquisition of organ functions, and the conversion of yolk sac into new tissues. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of temperature on excess post-exercise oxygen consumption in juvenile southern catfish (<Emphasis Type="Italic">Silurus meridionalis</Emphasis> Chen) following exhaustive exercise

The effects of temperature on resting oxygen consumption rate (MO_2rest) and excess post-exercise oxygen consumption (EPOC) after exhaustive exercise (chasing) were measured in juvenile southern catfish (Silurus meridionalis) (8.40 ± 0.30 g, n = 40) to test whether temperature has a significant influence on MO_2rest, maximum post-exercise oxygen consumption rate (MO_2peak) and EPOC and to investigate how metabolic scope (MS: MO_2peak − MO_2rest) varies with acclimation temperature. The MO_2rest increased from 64.7 (10°C) to 160.3 mg O₂ h⁻¹ kg⁻¹ (25°C) (P < 0.05) and reached a plateau between 25 and 30°C. The post-exercise MO₂ in all temperature groups increased immediately to the peak values and then decreased slowly to a steady state that was higher than the pre-exercise MO₂. The MO_2peak did not significantly differ among the 20, 25 and 30°C groups, though these values were much higher than those of the lower temperature groups (10 and 15°C) (P < 0.05). The duration of EPOC varied from 32.9 min at 10°C to 345 min at 20°C, depending on the acclimation temperatures. The MS values of the lower temperature groups (10 and 15°C) were significantly smaller than those of the higher temperature groups (20, 25 and 30°C) (P < 0.05). The magnitude of EPOC varied ninefold among all of the temperature groups and was the largest for the 20°C temperature group (about 422.4 mg O₂ kg⁻¹). These results suggested that (1) the acclimation temperature had a significant effect on maintenance metabolism (as indicated by MO_2rest) and the post-exercise metabolic recovery process (as indicated by MO_2peak, duration and magnitude of EPOC), and (2) the change of the MS as a function of acclimation temperature in juvenile southern catfish might be related to their high degree of physiological flexibility, which allows them to adapt to changes in environmental conditions in their habitat in the Yangtze River and the Jialing River.     

Food consumption, growth and respiration of sole, Solea solea (L.), during early ontogeny in a hatchery environment

Three components of the energy budget, consumption (C), respiration (R) and growth (G). were measured in larval and early juvenile sole (77 μg to 7.2 mg dry weight) kept under controlled temperature (15^oC), light (photoperiod 18 h at 800 lux) and food (Artemici salina. 5 ind ml^-1) conditions. The increase in body weight with age is described by the growth function W_t= 51.9 e^0143t, where t is time in days from hatching. W_t is weight (ug dry wt) at time t, 51.9 is the estimate of larval weight at hatching (Wo) and 0.143 is the instantaneous growth coefficient. Daily food consumption (C, in ug dry wtday”¹ ind^-1) increased with body weight (W, in ug dry wt) according to the allometric function, C = 1.852W^0.852. Low routine oxygen consumption (R, in nl 0₂ h^-1 ind^-1) was best described in relation to body weight by the allometric equation R = 1.47W^0.975 By using the above growth and allometric functions and by converting G, C and R into their energetic equivalents (joules day^-1 ind^-1), the changes in assimilation efficiency (K₁) and gross growth efficiency (K₁) during ontogeny could be modelled.